Category Archives: Articles

Update: Bilateral chronic subdural hematoma

Data on bilateral chronic subdural hematomas (CSHs) are scant 1) , including information on the frequency of symptoms, response to various treatments, and postoperative complications, compared with data on unilateral CSH. Bilateral CSHs constitute a fair portion of CSHs, especially in patients older than 75 years and in those with coagulopathy.

Clinical features

The presenting symptoms are those of raised intracranial pressure and mass effect.

The frequency of focal neurological deficits was found to be lesser in patients with bilateral CSDH, and it may confound the diagnosis and delay treatment 2).

Diagnosis

Computed tomography

Bilateral hematomas may lead to medial compression of both ventricles resulting in a narrow, slit-like elongated ventricle (the anterior horns sharply pointed and approaching one another so called ‘squeezed ventricle,’ ‘hare’s ears sign, or ‘rabbit’s ears’) 3) 4)5) 6).

see also Bilateral isodense chronic subdural hematoma

Magnetic resonance imaging

Magnetic resonance imaging is a more sensitive modality.

Differential diagnosis

If the lesion is placed more anteriorly and medially, hyperdense in intensity and enclosed in thick capsule, it may look biconvex in shape and can mimic extradural hematoma. This location of the lesion will also displace the frontal horns of the lateral ventricles laterally than medially, as in the present case. To avoid this confusion, if available, magnetic resonance imaging (MRI) would be better than CT in identifying these lesions 7) 8) 9) 10) 11).

Treatment

Occasionally patients with bilateral CSDH undergo unilateral surgery because the contralateral hematoma is deemed to be asymptomatic, and in some of these patients the contralateral hematoma may subsequently enlarge, requiring additional surgery.

Treatment of bilateral CSHs presents its own unique set of problems. New hemorrhage on the contralateral side and shift of midline structures are concerns and can be avoided by simultaneous bilateral decompression 12) 13). and significantly lowers the risk of retreatment compared with unilateral intervention and should be considered when choosing a surgical procedure 14).

To prevent neurological deterioration resulting from the thicker hematomas, early surgical decompression for bilateral CSDH should be implemented 15).

Outcome

Mixed high and low intensity in T2WI or low intensity in T1WI is the most predictable factor to show rapid aggravation 16).

Clinicians must be aware of the higher recurrent rate of bilateral CSDH after burr hole craniostomy 17).

Case series

2017

Two hundred ninety-one patients with bCSDH were identified, and 264 of them underwent unilateral (136 patients) or bilateral (128 patients) surgery. The overall retreatment rate was 21.6% (57 of 264 patients). Cases treated with unilateral surgery had twice the risk of retreatment compared with cases undergoing bilateral surgery (28.7% vs 14.1%, respectively, p = 0.002). In accordance with previous studies, the data also showed that a separated hematoma density and the absence of postoperative drainage were independent predictors of retreatment.

In bCSDHs bilateral surgical intervention significantly lowers the risk of retreatment compared with unilateral intervention and should be considered when choosing a surgical procedure 18).


Ninety-three patients with bilateral CSDH who underwent unilateral bur hole surgery at Aizu Chuo Hospital were included in a retrospective analysis. Findings on preoperative MRI, preoperative thickness of the drained hematoma, and the influence of antiplatelet or anticoagulant drugs were considered and evaluated in univariate and multivariate analyses.

The overall growth rate was 19% (18 of 93 hematomas), and a significantly greater percentage of the hematomas that were iso- or hypointense on preoperative T1-weighted imaging showed growth compared with other hematomas (35.4% vs 2.3%, p < 0.001). Multivariate logistic regression analysis showed that findings on preoperative T1-weighted MRI were the sole significant predictor of hematoma growth, and other factors such as antiplatelet or anticoagulant drug use, patient age, patient sex, thickness of the treated hematoma, and T2-weighted MRI findings were not significantly related to hematoma growth. The adjusted odds ratio for hematoma growth in the T1 isointense/hypointense group relative to the T1 hyperintense group was 25.12 (95% CI 3.89-51.58, p < 0.01).

The findings of preoperative MRI, namely T1-weighted sequences, may be useful in predicting the growth of hematomas that did not undergo bur hole surgery in patients with bilateral CSDH 19).

2013

Huang et al., identified 25 of 98 CSDH (25.51%). The patients with bilateral lesions had a lower incidence of hemiparesis than those having unilateral lesions (p = 0.004). Analysis of the neuro-images revealed significant differences in the presence of a midline shift (p = 0.001) and thickness of the hematoma (p < 0.001).

The mean Markwalder grading score at admission was 1.89 ± 0.66 and 1.64 ± 0.49 in the unilateral and bilateral hematoma groups, respectively (p = 0.010). After a minimum follow-up period of 6 months, the mean Glasgow Outcome Scale was not significantly different (p = 0.060). The recurrence rate of up to 28.00% observed for the bilateral disease was found to be higher than 9.59% observed for the unilateral disease (p = 0.042) 20).

Case reports

2017

A 72-year-old man with bilateral chronic subdural hematomas was admitted and treated using a YL-1 type hematoma aspiration needle. The treatment was complicated by hemorrhage of the basal ganglia and brainstem. This patient had no history of hypertension. Chen et al evaluated the relevant literature to analyze the causes of cerebral hemorrhage in similar patients.

This case report illustrates that the stability of the intracranial pressure should be closely monitored during the surgical treatment of chronic subdural hematomas, and large fluctuations in the cerebral perfusion pressure should be avoided during the operation. They also propose improvements in the technical details of the operative treatment of chronic subdural hematomas 21).


Calcified chronic subdural hematomas are an occurrence rarely seen in neurosurgical clinical practice. And when they occur bilaterally, the radiologic image they present is fascinating, as is the clinical presentation, but their management may be challenging. They have been reported to present with a multitude of neurologic deficits but never with diabetes insipidus, which is described by Siddiqui et al.

Due to the rarity of this pathology, the management protocol is not well defined, though there have been quite a few papers on this condition. This review article gathers information published over the years on this rare entity to suggest a treatment protocol 22).

2006

An 81-year-old man suffered blunt trauma to his chest resulting from a road traffic accident. On admission a chest X-ray showed multiple rib fractures but a computerized tomography scan of the head ruled out any post-traumatic lesion. He had a background diagnosis of mild Alzheimer’s dementia for which he was being treated with galantamine. He lived a reasonably independent life with his wife and was driving the car himself when the accident occurred. After a fortnight he was discharged from hospital.

Two months later he developed progressive deterioration in mobility. His wife noted an increasing level of forgetfulness and intermittent episodes of confusion. His general practitioner noted a shuffling gait and rigidity affecting lower limbs and made a working diagnosis of parkinsonism. A trial of Madopar (Levodopa and benserazide: 62.5 mg three times a day for 2 weeks) was given by the GP but this failed to improve the situation and he became virtually bed-bound. He was referred back to the hospital for further investigation.

On admission he was confused and marked rigidity affecting upper and lower limbs was detected. No resting tremor was noted but gait could not be tested, as he was unable to get out of bed. In view of the clinical presentation a computerized tomography scan of the head was repeated which showed bilateral fronto-parietal chronic subdural haematoma (Figure 1a,b). He was referred to the regional neurosurgical centre where he underwent bilateral burrhole drainage. Postoperative recovery was unremarkable and on examination there was complete resolution of previous rigidity affecting upper and lower limbs. He was able to converse normally with his wife and began walking with the aid of a stick by third postoperative day. A week later he was discharged from the hospital having regained his previous level of mobility and independence with activities of daily living 23).

1)

Schaller B, Radziwill AJ, Wasner M, Gratzl O, Steck AJ. [Intermittent paraparesis as manifestation of a bilateral chronic subdural hematoma]. Schweiz Med Wochenschr. 1999 Jul 27;129(29-30):1067-72. German. PubMed PMID: 10464909.
2) , 15) , 17) , 20)

Huang YH, Yang KY, Lee TC, Liao CC. Bilateral chronic subdural hematoma: what is the clinical significance? Int J Surg. 2013;11(7):544-8. doi: 10.1016/j.ijsu.2013.05.007. Epub 2013 May 24. PubMed PMID: 23707986.
3)

Marcu H, Becker H. Computed-tomography of bilateral isodense chronic subdural hematomas. Neuroradiology. 1977;14:81–3.
4)

Ellis GL. Subdural haematoma in the elderly. Emerg Med Clin North Am. 1990;8:281–94.
5)

Karasawa H, Tomita S, Suzuki S. Chronic subdural haematomas: Time density curve and iodine concentrations in enhanced CT. Neuroradiology. 1987;29:36–9.
6)

Kim KS, Hemmati M, Weinberg P. Computed tomography in isodense subdural haematoma. Radiology. 1978;128:71–4.
7)

Fujisawa H, Nomura S, Kajiwara K, Kato S, Fujii M, Suzuki M. Various magnetic resonance imaging patterns of chronic subdural hematomas: indicators of the pathogenesis? Neurol Med Chir (Tokyo) 2006;46:333–9.
8)

Kelly AB, Zimmerman RD, Snow RB, Gandy SE, Heier LA, Deck MD. Head trauma: Comparison of MR and CT experience in 100 patients. AJNR Am J Neuroradiol. 1988;9:699–708.
9)

Guenot M. Chronic subdural haematoma: diagnostic imaging studies. Neurochirurgie. 2001;47:473–8.
10)

Hosoda K, Tamaki N, Masumura M, Matsumoto S, Maeda F. Magnetic resonance images of chronic subdural hematomas. J Neurosurg. 1987;67:677–83.
11)

Agrawal A. Bilateral biconvex frontal chronic subdural hematoma mimicking extradural hematoma. J Surg Tech Case Rep. 2010 Jul;2(2):90-1. doi: 10.4103/2006-8808.73625. PubMed PMID: 22091345; PubMed Central PMCID: PMC3214288.
12)

Sadrolhefazi A, Bloomfield SM. Interhemispheric and bilateral chronic subdural hematoma. Neurosurg Clin N Am. 2000 Jul;11(3):455-63. Review. PubMed PMID: 10918015.
13) , 16)

Kurokawa Y, Ishizaki E, Inaba K. Bilateral chronic subdural hematoma cases showing rapid and progressive aggravation. Surg Neurol. 2005 Nov;64(5):444-9; discussion 449. PubMed PMID: 16253697.
14) , 18)

Andersen-Ranberg NC, Poulsen FR, Bergholt B, Hundsholt T, Fugleholm K. Bilateral chronic subdural hematoma: unilateral or bilateral drainage? J Neurosurg. 2017 Jun;126(6):1905-1911. doi: 10.3171/2016.4.JNS152642. Epub 2016 Jul 8. PubMed PMID: 27392267.
19)

Fujitani S, Ishikawa O, Miura K, Takeda Y, Goto H, Maeda K. Factors predicting contralateral hematoma growth after unilateral drainage of bilateral chronic subdural hematoma. J Neurosurg. 2017 Mar;126(3):755-759. doi: 10.3171/2016.1.JNS152655. PubMed PMID: 27081904.
21)

Chen L, Dong L, Wang XD, Zhang HZ, Wei M, She L. Bilateral Chronic Subdural Hematoma Treated by YL-1 Type Hematoma Aspiration Needle Complicated by Hemorrhage of the Basal Ganglia and Brainstem. World Neurosurg. 2017 Jan;97:761.e11-761.e13. doi: 10.1016/j.wneu.2016.09.074. PubMed PMID: 27702707.
22)

Siddiqui SA, Singh PK, Sawarkar D, Singh M, Sharma BS. Bilateral Ossified Chronic Subdural Hematoma Presenting as Diabetes Insipidus-Case Report and Literature Review. World Neurosurg. 2017 Feb;98:520-524. doi: 10.1016/j.wneu.2016.11.031. Review. PubMed PMID: 27867130.
23)

Suman S, Meenakshisundaram S, Woodhouse P. Bilateral chronic subdural haematoma: a reversible cause of parkinsonism. J R Soc Med. 2006 Feb;99(2):91-2. PubMed PMID: 16449784; PubMed Central PMCID: PMC1360497.

Mannitol for intraoperative brain relaxation

The risk of brain edema after dural opening is high in patients with midline shift undergoing supratentorial tumor surgery. Brain swelling may result in intracranial hypertension, impeded tumor exposure, and adverse outcomes. Mannitol is recommended as a first-line dehydration treatment to reduce brain edema and enable brain relaxation during neurosurgery. Research has indicated that mannitol enhanced brain relaxation in patients undergoing supratentorial tumor surgery; however, these results need further confirmation, and the optimal mannitol dose has not yet been established 1).

Some clinicians 2) 3) advocate high doses (>1.0 g/kg) of mannitol to effectively reduce intracranial pressure, while others recommend lower doses (<1.0 g/kg) 4) 5).

Treatment guidelines for using mannitol in patients with traumatic brain injury and stroke have been published and provide recommendations regarding the dose and timing of mannitol. However, there is still controversy concerning dehydration treatment with mannitol in patients with preoperatively increased intracranial pressure during brain tumor surgery.


Seo et al. sought to determine the dose of mannitol that provides adequate brain relaxation with the fewest adverse effects.

A total of 124 patients were randomized to receive mannitol at 0.25 g/kg (Group A), 0.5 g/kg (Group B), 1.0 g/kg (Group C), and 1.5 g/kg (Group D). The degree of brain relaxation was classified according to a 4-point scale (1, bulging; 2, firm; 3, adequate; and 4, perfectly relaxed) by neurosurgeons; Classes 3 and 4 were considered to indicate satisfactory brain relaxation. The osmolality gap (OG) and serum electrolytes were measured before and after mannitol administration.

The brain relaxation score showed an increasing trend in patients receiving higher doses of mannitol (p = 0.005). The incidence of satisfactory brain relaxation was higher in Groups C and D than in Group A (67.7% and 64.5% vs 32.2%, p = 0.011 and 0.022, respectively). The incidence of OG greater than 10 mOsm/kg was also higher in Groups C and D than in Group A (100.0% in both groups vs 77.4%, p = 0.011 for both). The incidence of moderate hyponatremia (125 mmol/L ≤ Na+ < 130 mmol/L) was significantly higher in Group D than in other groups (38.7% vs 0.0%, 9.7%, and 12.9% in Groups A, B, and C; p < 0.001, p = 0.008, and p = 0.020, respectively). Hyperkalemia (K+ > 5.0 mmol/L) was observed in 12.9% of patients in Group D only.

The higher doses of mannitol provided better brain relaxation but were associated with more adverse effects. Considering the balance between the benefits and risks of mannitol, the authors suggest the use of 1.0 g/kg of intraoperative mannitol for satisfactory brain relaxation with the fewest adverse effects. Clinical trial registration no.: NCT02168075 ( clinicaltrials.gov ) 6).

1)

Peng Y, Liu X, Wang A, Han R. The effect of mannitol on intraoperative brain relaxation in patients undergoing supratentorial tumor surgery: study protocol for a randomized controlled trial. Trials. 2014 May 10;15:165. doi: 10.1186/1745-6215-15-165. PubMed PMID: 24884731; PubMed Central PMCID: PMC4018619.
2)

Wise BL. High-dose mannitol. J Neurosurg. 2004;101:566–567.
3)

Cruz J, Minoja G, Okuchi K, Facco E. Successful use of the new high-dose mannitol treatment in patients with Glasgow Coma Scale scores of 3 and bilateral abnormal pupillary widening: a randomized trial. J Neurosurg. 2004 Mar;100(3):376-83. PubMed PMID: 15035271.
4)

Myburgh JA, Lewis SB. Mannitol for resuscitation in acute head injury: effects on cerebral perfusion and osmolality. Crit Care Resusc. 2000;2:14–18
5)

Sorani MD, Morabito D, Rosenthal G, Giacomini KM, Manley GT. Characterizing the dose–response relationship between mannitol and intracranial pressure in traumatic brain injury patients using a high-frequency physiological data collection system. J Neurotrauma. 2008;25:291–298. doi: 10.1089/neu.2007.0411.
6)

Seo H, Kim E, Jung H, Lim YJ, Kim JW, Park CK, Se YB, Jeon YT, Hwang JW, Park HP. A prospective randomized trial of the optimal dose of mannitol for intraoperative brain relaxation in patients undergoing craniotomy for supratentorial brain tumor resection. J Neurosurg. 2017 Jun;126(6):1839-1846. doi: 10.3171/2016.6.JNS16537. Epub 2016 Aug 19. PubMed PMID: 27540904.

Cystic glioblastoma

Cystic glioblastoma is a descriptive term to one form of glioblastoma that contains large cystic component, rather than being a pathological subtype.

Epidemiology

It is a rare disease whose exact prevalence is unknown. Glioblastoma is usually seen as a unilateral solid tumor more commonly in the supratentorial compartment. The presence of cyst in the GBM is rare. Bilateral large cystic GBM is still rarer 1).

Tumor cysts may be a nutrient reservoir for brain tumors, securing tumor energy metabolism and synthesis of cell constituents. Serum is one likely source of cyst fluid nutrients. Nutrient levels in tumor cyst fluid are highly variable, which could differentially stimulate tumor growth. Cyst fluid glutamate, lactate, and phosphate may act as tumor growth factors; these compounds have previously been shown to stimulate tumor growth at concentrations found in tumor cyst fluid.


GBM cysts contained glucose at 2.2 mmol/L (median value; range <0.8-3.5) and glutamine at 1.04 mmol/L (0.17-4.2). Lactate was 7.1 mmol/L (2.4-12.5) and correlated inversely with glucose level (r = -0.77; P < .001). Amino acids, including glutamate, varied greatly, but median values were similar to previously published serum values. Ammonia was 75 μmol/L (11-241). B vitamins were present at previously published serum values, and riboflavin, nicotinamide, pyridoxal 5΄-phosphate, and cobalamin were higher in cyst fluid than in cerebrospinal fluid. Inorganic phosphate was 1.25 mmol/L (0.34-3.44), which was >3 times higher than in ventricular cerebrospinal fluid: 0.35 mmol/L (0.22-0.66; P < .001). Tricarboxylic acid cycle intermediates were in the low micromolar range, except for citrate, which was 240 μmol/L (140-590). In cystic metastatic malignant melanomas and lung tumors values were similar to those in GBMs. 2).


Cystic GBM may be confused rarely on radiology with tuberculoma as both may show a mass lesion with hypodense centre surrounded by a ring of enhancement. Peroperative cytological examination of smears prepared from fluid aspirated from cysts by rapid Diff-Quik method may prove beneficial for immediate diagnosis in suspicious cases and appropriate patient management may be carried out 3).

Outcome

The presence of cystic features in glioblastoma (GBM) has been described as a favorable prognostic factor, possibly because cystic GBMs showed comparatively little infiltration of the peritumoral brain parenchyma 4).

Case series

 2011

A retrospective review of 354 consecutive patients treated with resection of primary GBM was performed using medical records and imaging information obtained at the University of California, San Francisco from 2005 to 2009. Within this cohort, 37 patients with large cysts (≥ 50% of tumor) were identified. Clinical presentations and surgical outcomes were statistically compared between the cystic and noncystic patients.

There were no statistically significant differences in clinical presentation between groups, including differences in age, sex, presenting symptoms, tumor location, or preoperative functional status, with the exception of tumor size, which was marginally larger in the cystic group. Surgical outcomes, including extent of resection and postoperative functional status, were equivalent. The median actuarial survival for the patients with cystic GBM was 17.0 months (95% CI 12.6-21.3 months), and the median survival for patients with noncystic GBM was 15.9 months (95% CI 14.6-17.2 months). There was no significant between-groups difference in survival (p = 0.99, log-rank test). A Cox multivariate regression model was constructed, which identified only age and extent of resection as independent predictors of survival. The presence of a cyst was not a statistically significant prognostic factor.

This study, comprising the largest series of cases of primary cystic GBM reported in the literature to date, demonstrates that the presence of a large cyst in patients with GBM does not significantly affect overall survival as compared with survival in patients without a cyst. Preoperative discussions with patients with GBM should focus on validated prognostic factors. The presence of cystic features does not confer a survival advantage 5).

2004

A retrospective analysis was conducted in 22 patients by using imaging information and chart reviews of operative reports of GBMs with large cysts (> or = 50% of tumor volume) at The University of Texas M. D. Anderson Cancer Center between 1993 and 2002. Clinical and neurosurgical outcomes and recurrence rates were studied. A statistical comparison was made with a matching cohort of 22 patients with noncystic GBMs. No significant differences in clinical variables were found between the cohort with cystic GBMs and the matched cohort with noncystic GBMs. To avoid bias in preoperative assessment of tumor volume, the tumor burden was compared in patients whose tumors had cysts (excluding the cystic mass) and in patients whose tumors did not contain cysts. There was no statistically significant difference between the two groups (p = 0.8). In patients with cystic GBMs the median survival time after surgery was 18.2 months (95% confidence interval [CI] 11.9-24.5 months) and at 2 years 43% of the patients were still alive. In comparison, in patients with noncystic GBMs, the median survival time was 14.3 months (95% CI 12.1-16.4 months) and only 16% of patients were alive at 2 years. The median time to tumor recurrence was 7.6 months (95% CI 0.01-18 months) in patients harboring cystic GBMs and 4.2 months (95% CI 1.8-6.6 months) in the matched cohort (log-rank test, p = 0.04). In the cystic GBM group, no recurrence was observed in 53% of patients at 6 months, 45% at 1 year, and 38% at 2 years after surgery, whereas the corresponding numbers for the noncystic group were 36, 14, and 9%, respectively.

The results indicate that patients harboring a GBM that contains a large cyst survive longer and have a longer time to recurrence than those who lack such a cyst. This is the first such observation in the literature 6).

1)

Kumar S, Handa A, Sinha R, Tiwari R. Bilateral cystic glioblastoma multiforme. J Neurosci Rural Pract. 2013 Oct;4(4):476-7. doi: 10.4103/0976-3147.120196. PubMed PMID: 24347967; PubMed Central PMCID: PMC3858779.
2)

Dahlberg D, Struys EA, Jansen EE, Mørkrid L, Midttun Ø, Hassel B. Cyst Fluid From Cystic, Malignant Brain Tumors: A Reservoir of Nutrients, Including Growth Factor-Like Nutrients, for Tumor Cells. Neurosurgery. 2017 Jun 1;80(6):917-924. doi: 10.1093/neuros/nyw101. PubMed PMID: 28327992.
3)

Hasan M, Siddiqui B, Qadri S, Faridi S. Cystic glioblastoma multiforme masquerading as a cerebral tuberculoma. BMJ Case Rep. 2014 Oct 17;2014. pii: bcr2014206832. doi: 10.1136/bcr-2014-206832. PubMed PMID: 25326570; PubMed Central PMCID: PMC4202055.
4)

Utsuki S, Oka H, Suzuki S, Shimizu S, Tanizaki Y, Kondo K, Tanaka S, Kawano N, Fujii K. Pathological and clinical features of cystic and noncystic glioblastomas. Brain Tumor Pathol. 2006 Apr;23(1):29-34. PubMed PMID: 18095116.
5)

Kaur G, Bloch O, Jian BJ, Kaur R, Sughrue ME, Aghi MK, McDermott MW, Berger MS, Chang SM, Parsa AT. A critical evaluation of cystic features in primary glioblastoma as a prognostic factor for survival. J Neurosurg. 2011 Oct;115(4):754-9. doi: 10.3171/2011.5.JNS11128. Epub 2011 Jul 15. PubMed PMID: 21761969.
6)

Maldaun MV, Suki D, Lang FF, Prabhu S, Shi W, Fuller GN, Wildrick DM, Sawaya R. Cystic glioblastoma multiforme: survival outcomes in 22 cases. J Neurosurg. 2004 Jan;100(1):61-7. PubMed PMID: 14743913.

Butterfly glioma

 

Butterfly glioma is a high grade astrocytoma, usually a glioblastoma (WHO grade IV), which crosses the midline via the corpus callosum. Other white matter commissures are also occasionally involved. The term butterfly refers to the symmetric wing like extensions across the midline.

Epidemiology

Most frequently butterfly gliomas occur in the frontal lobes, crossing via the genu of the corpus callosum, however posterior butterflies are also encountered.

Differential diagnosis

Primary central nervous system lymphoma: especially in AIDS patients

cerebral toxoplasmosis: especially in AIDS patients

tumefactive demyelination

cerebral metastases (rare)

occasionally a leptomeningeal process which fills the quadrigeminal and ambient cisterns can cause confusion.

A meningioma can mimic butterfly glioma when it arises from the falx cerebri and crosses the midline. Presence of a cerebrospinal fluid intensity cleft between the tumour and adjacent brain cortex is a useful sign to identify the extra-axial location of these lesions and differentiate them from butterfly gliomas 1).

Treatment

Gliomas invading the anterior corpus callosum are commonly deemed unresectable due to an unacceptable risk/benefit ratio, including the risk of abulia.

Burks et al. in a study presents evidence that anterior butterfly gliomas can be safely removed using a novel, attention-task based, awake brain surgery technique that focuses on preserving the anatomical connectivity of the cingulum and relevant aspects of the cingulate gyrus 2).

Current management options include biopsy only, followed by radiation and chemotherapy; surgical decompression followed by radiation and chemotherapy; or biopsy followed by palliative measures (comfort care). Management decisions are subjective, based upon physician experience and/or patient/family preferences in light of the prognosis of this disease.

Outcome

The prognosis of glioblastoma multiforme (GBM) is poor even with aggressive first-line therapy, which includes surgery, radiation therapy, and adjuvant chemotherapy. Although the ideal course of treatment for elderly patients with newly diagnosed GBM is still undecided and requires further studies, the new chemotherapeutic agents administered with or without concomitant radiation therapy have shown promising results. However, in our setting, where resources are limited and newer treatment options are expensive, it is often difficult to deliver the best care to the patient 3).

Case series

2017

Burks et al. reviewed clinical data on all patients undergoing glioma surgery performed by the senior author during a 4-year period at the University of Oklahoma Health Sciences Center. Forty patients were identified who underwent surgery for butterfly gliomas. Each patient was designated as having undergone surgery either with or without the use of awake subcortical mapping and preservation of the cingulum. Data recorded on these patients included the incidence of abulia/akinetic mutism. In the context of the study findings, the authors conducted a detailed anatomical study of the cingulum and its role within the DMN using postmortem fiber tract dissections of 10 cerebral hemispheres and in vivo diffusion tractography of 10 healthy subjects.

Forty patients with butterfly gliomas were treated, 25 (62%) with standard surgical methods and 15 (38%) with awake subcortical mapping and preservation of the cingulum. One patient (1/15, 7%) experienced postoperative abulia following surgery with the cingulum-sparing technique. Greater than 90% resection was achieved in 13/15 (87%) of these patients.

This study presents evidence that anterior butterfly gliomas can be safely removed using a novel, attention-task based, awake brain surgery technique that focuses on preserving the anatomical connectivity of the cingulum and relevant aspects of the cingulate gyrus 4).

2014

Of 336 patients with newly diagnosed GBM who were operated on, 48 (14 %) presented with bGBM, where 29 (60 %) and 19 (40 %) underwent surgical resection and biopsy, respectively. In multivariate analysis, a bGBM was independently associated with poorer survival [HR (95 % CI) 1.848 (1.250-2.685), p < 0.003]. In matched-pair analysis, patients who underwent surgical resection had improved median survival than biopsy patients (7.0 vs. 3.5 months, p = 0.03). In multivariate analysis, increasing percent resection [HR (95 % CI) 0.987 (0.977-0.997), p = 0.01], radiation [HR (95 % CI) 0.431 (0.225-0.812), p = 0.009], and temozolomide [HR (95 % CI) 0.413 (0.212-0. 784), p = 0.007] were each independently associated with prolonged survival among patients with bGBM. This present study shows that while patients with bGBM have poorer prognoses compared to non-bGBM, these patients can also benefit from aggressive treatments including debulking surgery, maximal safe surgical resection, temozolomide chemotherapy, and radiation therapy 5).

2011

Median age was 59 years; 52 % were female; median preoperative Karnofsky performance score (KPS) was 80. Twelve patients underwent biopsy and eleven underwent surgical decompression. The median tumor volume for the biopsy group was 60.6 cm(3) and for the surgically decompressed group 40.5 cm(3). In the biopsy group, five patients received adjuvant therapy but one died prior to its completion; two died prior to the initiation of adjuvant therapy and five were lost to follow up. In the surgical decompression group, seven patients received adjuvant therapy, one died prior to the initiation of adjuvant therapy, two were treated with palliative measures only, and one was lost to follow up. Kaplan-Meier estimates of overall median post surgical-survival of the whole group was 180 days, the biopsy group 48 days, and the surgically decompressed group 265 days (p = 0.14). Our results show that there was a higher median survival in the surgically decompressed group; but a direct correlation could not be established, and that the median KPS did not improve in either group after treatment. A larger multicenter review is required to quantitatively assess the factors, including tumor biomarkers that are associated with patient outcome 6).

Case reports

A 54-year-old man presented with change in behaviour, nocturnal enuresis, abnormal limb movement and headache of one week’s duration. The diagnosis of butterfly glioma (glioblastoma multiforme) was made based on imaging characteristics and was further confirmed by biopsy findings. As the corpus callosum is usually resistant to infiltration by tumours, a mass that involves and crosses the corpus callosum is suggestive of an aggressive neoplasm 7).

1)

Watts J, Box G, Galvin A, et al. Magnetic resonance imaging of meningiomas: a pictorial review. Insights Imaging. 2014;5:113–22.
2) , 4)

Burks JD, Bonney PA, Conner AK, Glenn CA, Briggs RG, Battiste JD, McCoy T, O’Donoghue DL, Wu DH, Sughrue ME. A method for safelyresecting anterior butterfly gliomas: the surgical anatomy of the default mode network and the relevance of its preservation. J Neurosurg. 2017 Jun;126(6):1795-1811. doi: 10.3171/2016.5.JNS153006. Epub 2016 Sep 16. PubMed PMID: 27636183.
3)

Agrawal A. Butterfly glioma of the corpus callosum. J Cancer Res Ther. 2009 Jan-Mar;5(1):43-5. PubMed PMID: 19293489.
5)

Chaichana KL, Jusue-Torres I, Lemos AM, Gokaslan A, Cabrera-Aldana EE, Ashary A, Olivi A, Quinones-Hinojosa A. The butterfly effect on glioblastoma: is volumetric extent of resection more effective than biopsy for these tumors? J Neurooncol. 2014 Dec;120(3):625-34. doi: 10.1007/s11060-014-1597-9. Epub 2014 Sep 6. PubMed PMID: 25193022; PubMed Central PMCID: PMC4313925.
6)

Dziurzynski K, Blas-Boria D, Suki D, Cahill DP, Prabhu SS, Puduvalli V, Levine N. Butterfly glioblastomas: a retrospective review and qualitative assessment of outcomes. J Neurooncol. 2012 Sep;109(3):555-63. doi: 10.1007/s11060-012-0926-0. Epub 2012 Jul 18. PubMed PMID: 22806339; PubMed Central PMCID: PMC3992290.
7)

Krishnan V, Lim TC, Ho FC, Peh WC. Clinics in diagnostic imaging (175). Corpus callosum glioblastoma multiforme (GBM): butterfly glioma. Singapore Med J. 2017 Mar;58(3):121-125. doi: 10.11622/smedj.2017017. PubMed PMID: 28361164; PubMed Central PMCID: PMC5360865.

Sphenoid wing meningioma

It is a type of anterior skull base meningioma.

These intracranial meningiomas may be associated with hyperostosis of the sphenoid ridge and may be very invasive, spreading to the dura of the frontal, temporal, orbital, and sphenoidal regions. Medially, this tumor may expand into the wall of the cavernous sinus, anteriorly into the orbit, and laterally into the temporal bone.

Epidemiology

The relative incidence of meningiomas of the sphenoid ridge is 17%. This tumor usually arises from the lesser wing of the sphenoid bone. Sphenoid wing meningiomas, or ridge meningiomas, are the most common of the basal meningiomas.

Types

Tumors found in the external third of the sphenoid are of two types: en-plaque and globoid meningiomas.

En plaque meningiomas characteristically lead to slowly increasing proptosis with the eye angled downward. Much of this is due to reactive orbital hyperostosis. With invasion of the tumor into the orbit, diplopia is common.

Patients with globoid meningiomas often present only with signs of increased intracranial pressure. This leads to various other symptoms including headache and a swollen optic disc.

see Medial sphenoid wing meningioma or clinoidal meningioma.

see Meningioma en plaque of the sphenoid ridge.

see Sphenoorbital meningioma

Clinical Features

Tumors growing in the inner wing (clinoidal) most often cause direct damage to the optic nerve leading especially to a decrease in visual acuity, progressive loss of color vision, defects in the field of vision (especially cecocentral), and an afferent pupillary defect.

If the tumor continues to grow and push on the optic nerve, all vision will be lost in that eye as the nerve atrophies.

Proptosis, or anterior displacement of the eye, and palpebral swelling may also occur when the tumor impinges on the cavernous sinus by blocking venous return and leading to congestion. Damage to cranial nerves in the cavernous sinus leads to diplopia.

The Ophthalmic nerve (is often the first affected, leading to diplopia with lateral gaze. The patient will have pain and altered sensation over the front and top of the head.

Horner syndrome may occur if nearby sympathetic fibers are involved.

Endocrine testing is important because pituitary insufficiency has been reported to occur in 22% of patients with anterior skull base meningiomas, including thyroid stimulating hormone (TSH), follicle stimulating hormone (FSH), and luteinizing hormone (LH).

Diagnosis

Following the physical exam, the diagnosis is confirmed with neuro-imaging. Either a head CT or MRI with contrast such as gadolinium is useful, as meningiomas often show homogenous enhancement. Angiography looking for signs like stretched arteries may be used to supplement evaluation of vascular involvement and to determine whether embolization would be helpful if surgery is being considered.

On MRI imaging, T1- and T2-weighted sequences have variable signal intensity, but they enhance intensely and homogeneously after injection of gadolinium. They also tend to exhibit hyperostosis and calcifications which can be seen on either CT or MRI imaging. Additionally, the presence of a dural extension (also known as a dural tail) is helpful in distinguishing a meningioma from fibrous dysplasia.

Differential diagnosis

The differential diagnosis for sphenoid wing meningioma includes other types of tumors such as optic nerve sheath meningioma, cranial osteosarcoma, metastases, and also sarcoidosis.

Treatment

Microsurgery may be the most effective method for the large and giant medial sphenoid wing meningiomas 1).

With the improved requirement of postoperative quality of life in patients, intentional incomplete resection should be considered as an acceptable treatment option. Multivariate analysis confirmed that incomplete resection, poor blood supply, lack of adhesion or encasement of adjacent structure were independent predictive factors for favorable postoperative quality of life. An individual treatment strategy could help improved quality of life 2).

Outcome

Large and giant medial sphenoid wing meningiomas that are located deeply in the skull base where they are closely bounded by cavernous sinus, optic nerve, and internal carotid artery make the gross resection hard to achieve. Also, this kind of meningiomas is often accompanied by a series of severe complications.

For medial sphenoid wing meningiomas, visual loss and abnormalities of cranial nerves III, IV, VI, V1, and V2 may occur because the meningioma may have some degree of encasement of these structures as they ride through the cavernous sinus.

Seizures, paresis, and sensory loss may result depending on potential damage to adjacent brain parenchyma for patients with lateral sphenoid wing meningiomas.

Sphenoid wing meningiomas (SWMs) can encase arteries of the circle of Willis, increasing their susceptibility to intraoperative vascular injury and severe ischemic complications.

Case series

2017

A retrospective review of 75 patients surgically treated for SWM from 2009 to 2015 was undertaken to determine the degree of circumferential vascular encasement (0°-360°) as assessed by preoperative magnetic resonance imaging (MRI). A novel grading system describing “maximum” and “total” arterial encasement scores was created. Postoperative MRIs were reviewed for total ischemia volume measured on sequential diffusion-weighted images.

Of the 75 patients, 89.3% had some degree of vascular involvement with a median maximum encasement score of 3.0 (2.0-3.0) in the internal carotid artery (ICA), M1, M2, and A1 segments; 76% of patients had some degree of ischemia with median infarct volume of 3.75 cm 3 (0.81-9.3 cm 3 ). Univariate analysis determined risk factors associated with larger infarction volume, which were encasement of the supraclinoid ICA ( P < .001), M1 segment ( P < .001), A1 segment ( P = .015), and diabetes ( P = .019). As the maximum encasement score increased from 1 to 5 in each of the significant arterial segments, so did mean and median infarction volume ( P < .001). Risk for devastating ischemic injury >62 cm 3 was found when the ICA, M1, and A1 vessels all had ≥360° involvement ( P = .001). Residual tumor was associated with smaller infarct volumes ( P = .022). As infarction volume increased, so did modified Rankin Score at discharge ( P = .025).

Subtotal resection should be considered in SWM with significant vascular encasement of proximal arteries to limit postoperative ischemic complications 3).

2015

The clinical materials of 53 patients with sphenoid wing meningiomas treated microsurgically between January 2008 and January 2012 were analyzed retrospectively. Follow-up period ranged from 6 to 62 months (median, 34 months). Clinical outcomes including postoperative quality of life and recurrence rate were evaluated. Univariate and multivariate statistical analysis were performed among factors that might influence postoperative quality of life.

The mean age of patients was 49 years. Mean tumor size was 3.9cm. Total tumor resection was achieved in 38 cases (71.7%), subtotal in 10 cases (18.9%) and partial resection in 5 cases (9.4%). Within the follow-up period, ten patients (18.9%) had recurrence and three patients (5.7%) died. In univariate analysis, we found the postoperative Karnofshky Performance Score (KPS) improvement was determined by various factors, including extent of tumor resection, peritumoral edema, tumor blood supply, size, adhesion, encasement and preoperative KPS. However, multivariate analysis showed that complete resection, rich blood supply, adhesion to adjacent structure, encasement of neurovascular were independent predictive factors for worse postoperative KPS.

With the improved requirement of postoperative quality of life in patients, intentional incomplete resection should be considered as an acceptable treatment option. Multivariate analysis confirmed that incomplete resection, poor blood supply, lack of adhesion or encasement of adjacent structure were independent predictive factors for favorable postoperative quality of life. An individual treatment strategy could help improved quality of life 4).

Case reports

2014

Endo et al. report the utility of a pulsed water jet device in meningioma surgery. The presented case is that of a 61-year-old woman with left visual disturbance. MRI demonstrated heterogeneously enhanced mass with intratumoral hemorrhage, indicating sphenoid ridge meningioma on her left side. The tumor invaded the cavernous sinus and left optic canal, engulfing the internal carotid artery in the carotid cistern and encased middle cerebral arteries. During the operation, the pulsed water jet device was useful for dissecting the tumor away from the arteries since it was safe in light of preserving parent arteries. The jet did not cause any vascular injury and did not induce vasospasm as shown by postoperative symptomatology and MRIs. With the aid of pulsed water jet, we could achieve total resection of the tumor except for the piece within the cavernous sinus. The patient had no new neurological deficits after the operation 5).

1)

Yang J, Ma SC, Liu YH, Wei L, Zhang CY, Qi JF, Yu CJ. Large and giant medial sphenoid wing meningiomas involving vascular structures: clinical features and management experience in 53 patients. Chin Med J (Engl). 2013 Dec;126(23):4470-6. PubMed PMID: 24286409.
2) , 4)

Ouyang T, Zhang N, Wang L, Li Z, Chen J. Sphenoid wing meningiomas: Surgical strategies and evaluation of prognostic factors influencing clinical outcomes. Clin Neurol Neurosurg. 2015 May 4;134:85-90. doi: 10.1016/j.clineuro.2015.04.016. [Epub ahead of print] PubMed PMID: 25974397.
3)

McCracken DJ, Higginbotham RA, Boulter JH, Liu Y, Wells JA, Halani SH, Saindane AM, Oyesiku NM, Barrow DL, Olson JJ. Degree of Vascular Encasement in Sphenoid Wing Meningiomas Predicts Postoperative Ischemic Complications. Neurosurgery. 2017 Jun 1;80(6):957-966. doi: 10.1093/neuros/nyw134. PubMed PMID: 28327941.
5)

Endo T, Nakagawa A, Fujimura M, Sonoda Y, Shimizu H, Tominaga T. [Usefulness of pulsed water jet in dissecting sphenoid ridge meningioma while preserving arteries]. No Shinkei Geka. 2014 Nov;42(11):1019-25. doi: 10.11477/mf.1436200025. Japanese. PubMed PMID: 25351797.

Update: Cervical laminoplasty

Cervical laminoplasty is an established treatment for cervical myelopathy.

Fields et al., 1) observed in their randomized study comparing the effects of cervical laminectomy and laminoplasty in the rabbit, that laminectomized animals had poorer clinical outcome at 3 months post-operatively, associated with statistically significant angular deformity.

Similarly, Baisden et al., 2) , using a goat model, concluded that laminoplasty is superior to laminectomy in maintaining sagittal cervical alignment and preventing spinal deformities. The removal of bony and ligamentous structures of the posterior cervical spine might alter the biomechanics of the vertebral column and predispose to instability.

History

The first laminoplasty technique was the modification of Kirita’s technique for laminectomy, in which the laminae were thinned and then partially removed in the midline using an air drill. The lateral edges of the laminae close to the pedicles were further thinned until the laminae could be bent and lifted up. It was considered important to lift multiple laminae expeditiously so that multiple segments of the cord could be simultaneously decompressed. The laminae were then removed with scissors 3)).

Based on this technique, Oyama et al. developed z-plasty method of laminoplasty. After thinning the laminae, z-shaped cuts were made in each laminae, which were lifted and then fixed with sutures to reconstruct the expanded spinal canal. They reported that all the 15 cases were neurologically improved after the operation 4)).

Tsuji reported a variation of en bloc laminectomy in which laminae were cut bilaterally along the imaginary line separating laminar arches and articular processes and made completely free from their bony attachments. The lamiae were reflected as a flap and then permitted to float on the cord without fixing sutures or bone grafting 5).

Expansive open-door laminoplasty was devised by Hirabayashi et al. in 1977, as relatively easier, safer, and better than the ordinary cervical laminectomy from the standpoint of structural mechanics of the cervical spine.

Operative results in the patients with cervical OPLL, spondylosis, and canal stenosis were satisfactory, and optimal widening of the AP diameter of the spinal canal is considered to be over 4 mm. From this procedure a bilateral, open-door laminoplasty has been devised for extensive exploration at the intradural space.

Cervical laminoplasty was devised to avoid problems associated with laminectomy such as postoperative segmental instability, kyphosis, perineural adhesions, and late neurological deterioration 6).

Kurokawa et al. developed spinous process splitting laminoplasty, in which the spinous processes and laminae are split in the midline and hinges are made bilaterally along the lateral borders of the laminae, which are lifted bilaterally 7)).

This is also called double-door laminoplasty 8), French-window 9) or French door laminoplasty 10)

There are multiple variations, many advocating the use of allograft, but for the best technique controversy persists.

Complications

Neck pain

Axial neck pain after C3-6 laminoplasty has been reported to be significantly lesser than that after C3-7 laminoplasty because of the preservation of the C-7 spinous process and the attachment of nuchal muscles such as the trapezius and rhomboideus minor, which are connected to the scapula. The C-6 spinous process is the second longest spinous process after that of C-7, and it serves as an attachment point for these muscles. The effect of preserving the C-6 spinous process and its muscular attachment, in addition to preservation of the C-7 spinous process, on the prevention of axial neck pain is not well understood. The purpose of the current study was to clarify whether preservation of the paraspinal muscles of the C-6 spinous process reduces postoperative axial neck pain compared to that after using nonpreservation techniques.

Montano et al. studied 60 patients who underwent C3-6 double-door laminoplasty for the treatment of cervical spondylotic myelopathy or cervical ossification of the posterior longitudinal ligament; the minimum follow-up period was 1 year. Twenty-five patients underwent a C-6 paraspinal muscle preservation technique, and 35 underwent a C-6 nonpreservation technique. A visual analog scale (VAS) and VAS grading (Grades I-IV) were used to assess axial neck pain 1-3 months after surgery and at the final follow-up examination. Axial neck pain was classified as being 1 of 5 types, and its location was divided into 5 areas. The potential correlation between the C-6/C-7 spinous process length ratio and axial neck pain was examined.

The mean VAS scores (± SD) for axial neck pain were comparable between the C6-preservation group and the C6-nonpreservation group in both the early and late postoperative stages (4.1 ± 3.1 vs 4.0 ± 3.2 and 3.8 ± 2.9 vs 3.6 ± 3.0, respectively). The distribution of VAS grades was comparable in the 2 groups in both postoperative stages. Stiffness was the most prevalent complaint in both groups (64.0% and 54.5%, respectively), and the suprascapular region was the most common site in both groups (60.0% and 57.1%, respectively). The types and locations of axial neck pain were also similar between the groups. The C-6/C-7 spinous process length ratios were similar in the groups, and they did not correlate with axial neck pain. The reductions of range of motion and changes in sagittal alignment after surgery were also similar.

The C-6 paraspinal muscle preservation technique was not superior to the C6-nonpreservation technique for preventing postoperative axial neck pain 11).

Case series

2017

Thirty-two consecutive patients (19 male, 13 female, average age 66 yr) from a prospective outcome registry that underwent cervical laminoplasty between 2009 and 2013 were reviewed. Computed tomography (CT) scan was performed immediately postoperatively and at 6-mo follow-up. Parameters included patient perception of outcome, Nurick score, Neck Disability Index (NDI), visual analog scale for neck pain, and SF-36.

On retrospective analysis, all patients felt improved at 3 mo postoperatively; at 2 yr, this rate was 91%. Improvements were seen in Nurick scores, from 3.16 ± 0.9 preoperatively to 1.94 ± 0.8 at 2 yr; NDI score from 28.7% ± 9% preoperatively to 20.8% ± 9.6% at 2 yr; visual analog scale from 2.8 ± 1.2 preoperatively to 1.7 ± 0.9 at 2 yr; and SF-36 physical component summary from 27.9 ± 10 preoperatively to 37.8 ± 11.9 at 2 yr. All values reached significance at all follow-up points ( P < .05) with the exception of 6-mo NDI values ( P = .062). No C5 palsy, graft complications, or reclosure was observed in any patient during the follow-up period.

Laminoplasty with autograft is a safe and effective method to treat cervical myelopathy, with good medium-term clinical outcome. No reclosures were observed. Bony fusion was seen in all cases on CT scan. The study found good outcomes in the performance of open door laminoplastywithout hardware, in the treatment of cervical stenosis 12).

2016

Sakaura et al., reported that the presence of chronic kidney disease (CKD) and/or extended abdominal aortic calcification was associated with significantly worse clinical outcomes after posterior lumbar interbody fusion. CKD is one of the highest risk factors for systemic atherosclerosis. Therefore, impaired blood flow due to atherosclerosis could exacerbate degeneration of the cervical spine and neural tissue. However, there has been no report of a study evaluating the deleterious effects of CKD and atherosclerosis on the outcomes after decompression surgery for cervical spondylotic myelopathy.

They analyzed data from 127 consecutive cases involving patients who underwent cervical laminoplasty for CSM and met their inclusion criteria. Stage 3-4 CKD was present as a preoperative comorbidity in 44 cases. Clinical status was assessed using the Japanese Orthopaedic Association (JOA) cervical myelopathy evaluation questionnaire before surgery and 2 years postoperatively. As a marker of systemic atherosclerosis, the presence of aortic arch calcification (AoAC) was assessed on preoperative chest radiographs.

AoAC was found on preoperative chest radiographs in 40 of 127 patients. Neither CKD nor AoAC had a statistically significant deleterious effect on preoperative JOA score. However, CKD and AoAC were significantly associated with reductions in both the JOA score recovery rate (mean 36.1% in patients with CKD vs 44.7% in those without CKD; 26.0% in patients with AoAC vs 48.9% in those without AoAC) and the change in JOA score at 2 years after surgery (mean 2.3 points in patients with CKD vs 3.1 points in those without CKD; 2.1 points for patients with AoAC vs 3.2 points for those without AoAC). A multivariate regression analysis showed that AoAC was a significant independent predictor of poor outcome with respect to both for the difference between follow-up and preoperative JOA scores and the JOA score recovery rate.

CKD and AoAC were associated with increased rates of poor neurological outcomes after laminoplasty for CSM, and AoAC was a significant independent predictive factor for poor outcome 13).

1)

Fields MF, Hoshijima K, Feng AHP, et al. A biomechanical, radiologic, and clinical comparison of outcome after multilevel cervical laminectomy or laminoplasty in the rabbit. Spine. 2000;25(22):2925–2931. doi: 10.1097/00007632-200011150-00015.
2)

Baisden J, Voo LM, Cusick JF, Pintar FA, Yoganandan N. Evaluation of cervical laminectomy and laminoplasty. A longitudinal study in the goat model. Spine (Phila Pa 1976). 1999 Jul 1;24(13):1283-8; discussion 1288-9. PubMed PMID: 10404568.
3)

Kirita Y, Miyazaki K, Hayashi T, Nosaka K, Shima M, Yamamura H, Tamaki S: [Ossification of posterior longitudinal ligament of the cervical spine]. Rinsho Seikeigeka 10: 1077– 1085, 1975. (Japanese
4)

Oyama M, Hattori S, Moriwaki N, Nitta S: [A new method of cervical laminectomy]. Chuubu Nippon Seikeigeka Gakkai Zasshi 16: 792– 794, 1973. (Japanese
5)

Tsuji H. Laminoplasty for patients with compressive myelopathy due to so-called spinal canal stenosis in cervical and thoracic regions. Spine (Phila Pa 1976). 1982 Jan-Feb;7(1):28-34. PubMed PMID: 7071659.
6)

Hirabayashi K, Watanabe K, Wakano K, Suzuki N, Satomi K, Ishii Y. Expansive open-door laminoplasty for cervical spinal stenotic myelopathy. Spine (Phila Pa 1976). 1983 Oct;8(7):693-9. PubMed PMID: 6420895.
7)

Kurokawa T, Tsuyama N, Tanaka H, Kobayashi M, Machida H, Nakamura K, Iizuka T, Hoshino Y: [Enlargement of spinal canal by the sagittal splitting of spinous processes]. Bessatsu Seikeigeka 2: 234– 240, 1982. (Japanese
8)

Seichi A, Takeshita K, Ohishi I, Kawaguchi H, Akune T, Anamizu Y, Kitagawa T, Nakamura K. Long-term results of double-door laminoplasty for cervical stenotic myelopathy. Spine (Phila Pa 1976). 2001 Mar 1;26(5):479-87. PubMed PMID: 11242374.
9)

Hukuda S, Ogata M, Mochizuki T, Shichikawa K. Laminectomy versus laminoplasty for cervical myelopathy: brief report. J Bone Joint Surg Br. 1988 Mar;70(2):325-6. PubMed PMID: 3346317.
10)

Nakama S, Nitanai K, Oohashi Y, Endo T, Hoshino Y. Cervical muscle strength after laminoplasty. J Orthop Sci. 2003;8(1):36-40. PubMed PMID: 12560884.
11)

Mori E, Ueta T, Maeda T, Yugué I, Kawano O, Shiba K. Effect of preservation of the C-6 spinous process and its paraspinal muscular attachment on the prevention of postoperative axial neck pain in C3-6 laminoplasty. J Neurosurg Spine. 2015 Mar;22(3):221-9. doi: 10.3171/2014.11.SPINE131153. Epub 2014 Dec 19. PubMed PMID: 25525962.
12)

Stamates MM, Cui MX, Roitberg BZ. Clinical Outcomes of Cervical Laminoplasty: Results at Two Years. Neurosurgery. 2017 Jun 1;80(6):934-941. doi: 10.1093/neuros/nyw058. PubMed PMID: 28329252.
13)

Sakaura H, Miwa T, Kuroda Y, Ohwada T. Surgical outcomes after laminoplasty for cervical spondylotic myelopathy in patients with renal dysfunction and/or aortic arch calcification. J Neurosurg Spine. 2016 Oct;25(4):444-447. PubMed PMID: 27231811.

Update: Chiari type 1 deformity

Chiari type 1 deformity is a hindbrain disorder associated with elongation of the cerebellar tonsils, which descend below the foramen magnum into the spinal canal.

The hindbrain is not malformed but deformed. Accordingly, “Chiari type 1 deformity,” not “Chiari type 1 malformation” is the correct term to characterize primary tonsillar herniation.

Defined as cerebellar tonsillar herniation ≥ 5 mm below the foramen magnum 1).

Classification

Chiari malformation Type 1.5 (CM 1.5) was defined as the association of Chiari malformation Type I (CM I) and brainstem herniation.

Although CM 1.5 patients presented with brainstem herniation and more severe tonsillar herniation, other clinical and imaging features and surgical outcomes were similar with CM I patients. Liu et al. think CM 1.5 is just a subtype of CM I, rather than a unique type of Chiari malformations 2).


Taylor et al. identifies two subtypes, crowded and spacious, that can be distinguished by MRI appearance without volumetric analysis. Earlier age at surgery and presence of syringomyelia are more common in the crowded subtype. The presence of the spacious subtype suggests that crowdedness alone cannot explain the pathogenesis of Chiari I malformation in many patients, supporting the need for further investigation 3).

Epidemiology

Chiari type 1 deformity is commonly seen in pediatric neurology, neuroradiology, and neurosurgery and may have various clinical presentations depending on patient age. In addition, Chiari type 1 deformity is increasingly found by neuroimaging studies as an incidental finding in asymptomatic children 4).

In the past, it was estimated that the condition occurs in about one in every 1,000 births. However, the increased use of diagnostic imaging has shown that CM may be much more common. Complicating this estimation is the fact that some children who are born with the condition may not show symptoms until adolescence or adulthood, if at all. CMs are more prevalent in certain groups, including people of Celtic descent.

A statistically significant (P = .03) female predominance of the malformation was observed, with a female: male ratio of approximately 3:2.

Associated skeletal anomalies were seen in 24% of patients.

Syringomyelia was detected in 40% of patients, most commonly between the C-4 and C-6 levels. Of the 25 patients who presented with spinal symptoms, 23 (92%) proved to have a syrinx at MR imaging. When the syrinx extended into the medulla (n = 3), however, brainstem symptoms predominated. Patients with objective brain stem or cerebellar syndrome had the largest mean tonsillar herniations. Patients with tonsillar herniations greater than 12 mm were invariably symptomatic, but approximately 30% of patients with tonsils herniating 5-10 mm below the foramen magnum were asymptomatic at MR imaging. “Incidental” Chiari I malformations are thus much more common than previously recognized, and careful clinical assessment remains the cornerstone for proper diagnosis and management 5).

Etiology

The innate bony dysontogenesis in patients with CMI contributes to tonsilar ectopia and exacerbates CSF flow obstruction. A pressure gradient that existed between syringomyelia(SM) and SAS supports the perivascular space theory that is used to explain SM formation. Our findings demonstrate that phase-contrast magnetic resonance imaging (PCMR) maybe a useful tool for predicting patient prognosis 6).

In adult CIM, most tonsillar herniations are asymmetrical and most syringomyelia is eccentrical. The dominant side of tonsillar herniation determines the side of syrinx deviation, which in turn determines the main side of clinical presentations and the convex side of scoliosis. The results suggest that the more the descended tonsil tilts to one side, the more the syrinx tilts to the same side 7).

Syndromic craniosynostosis

Chiari malformation Type I (CM-I) related to syndromic craniosynostosis in pediatric patients has been well-studied. The surgical management consists of cranial vault remodeling with or without posterior fossa decompression. There were also cases, in whom CM-I was diagnosed prior to the craniosynostosis in early childhood.

A 16-year-old boy who admitted with symptoms related to CM-I. With careful examination and further genetic investigations, a diagnosis of Crouzon syndrome was made, of which the patient and his family was unaware before. The patient underwent surgery for posterior fossa decompression and followed-up for Crouzon’s syndrome.

This is the only case report indicating a late adolescent diagnosis of Crouzon syndrome through clinical symptoms of an associated CM-I 8).

Familial clustering

A population-based genealogical resource with linked medical data was used to define the observed familial clustering of Chiari malformation Type I (CM-I). METHODS All patients with CM-I were identified from the 2 largest health care providers in Utah; those patients with linked genealogical data were used to test hypotheses regarding familial clustering. Relative risks (RRs) in first-, second-, and third-degree relatives were estimated using internal cohort-specific CM-I rates; the Genealogical Index of Familiality (GIF) test was used to test for an excess of relationships between all patients with CM-I compared with the expected distribution of relationships for matched control sets randomly selected from the resource. Pedigrees with significantly more patients with CM-I than expected (p < 0.05) based on internal rates were identified. RESULTS A total of 2871 patients with CM-I with at least 3 generations of genealogical data were identified. Significantly increased RRs were observed for first- and third-degree relatives (RR 4.54, p < 0.001, and RR 1.36, p < 0.001, respectively); the RR for second-degree relatives was elevated, but not significantly (RR 1.20, p = 0.13). Significant excess pairwise relatedness was observed among the patients with CM-I (p < 0.001), and borderline significant excess pairwise relatedness was observed when all relationships closer than first cousins were ignored (p = 0.051). Multiple extended high-risk CM-I pedigrees with closely and distantly related members were identified. CONCLUSIONS This population-based description of the familial clustering of 2871 patients with CM-I provided strong evidence for a genetic contribution to a predisposition to CM-I 9).

Pathophysiology

The pathophysiology of CMI is poorly understood and it remains unknown how ICP alterations relate to symptoms and radiological findings.

There is some evidence of impaired intracranial compliance as an important pathophysiological mechanism 10).

Magnetic resonance imaging measurement of transcranial CSF flow and blood flow may lead to a better understanding of the pathophysiology of Chiari malformations and may prove to be an important diagnostic tool for guiding for the treatment of patients with Chiari I malformation 11).

The pathogenesis of a Chiari I malformation of the cerebellar tonsils is grouped into 4 general mechanisms. 12).

It appears that the pathogenesis of Chiari malformation with or without associated basilar invagination and/or syringomyelia is primarily related to atlantoaxial instability. The data suggest that the surgical treatment in these cases should be directed toward atlantoaxial stabilization and segmental arthrodesis. Except in cases in which there is assimilation of the atlas, inclusion of the occipital bone is neither indicated nor provides optimum stability. Foramen magnum decompression is not necessary and may be counter-effective in the long run 13). It occurs in children and adults. Clinical symptoms mainly develop from alterations in CSF flow at the foramen magnum and the common subsequent development of syringomyelia.


Patients with Chiari malformation type 1 (CMI) often present with elevated pulsatile and static intracranial pressure (ICP).

Several lines of evidence suggest common pathophysiological mechanisms in Chiari malformation Type I (CMI) and idiopathic intracranial hypertension (IIH). It has been hypothesized that tonsillar ectopy, a typical finding in CMI, is the result of elevated intracranial pressure (ICP) combined with a developmentally small posterior cranial fossa (PCF).

The study of Frič and Eide showed comparable and elevated pulsatile intracranial pressure, indicative of impaired intracranial compliance, in both CMI and IIH cohorts, while static ICP was higher in the IIH cohort. The data did not support the hypothesis that reduced PCFV combined with increased ICP causes tonsillar ectopy in CMI. Even though impaired intracranial compliance seems to be a common pathophysiological mechanism behind both conditions, the mechanisms explaining the different clinical and radiological presentations of CMI and IIH remain undefined14).

Natural history

Chiari malformation Type I was incidentally detected on MR images in 11 of 22 patients. The remaining 11 patients had minimal clinical signs at presentation that were not regarded as necessitating immediate surgical treatment. Seventeen patients (77.3%) showed progressive improvement in their symptoms or remained asymptomatic at the last follow-up whereas 5 patients (22.7%) experienced worsening, which was mild in 2 cases and required surgical correction in the remaining 3 cases. On MR imaging a mild reduction in tonsillar herniation was appreciated in 4 patients (18.18%), with complete spontaneous resolution in 1 of these. In 16 patients, tonsillar herniation remained stable during follow-up.

Data confirm the common impression that in both asymptomatic and slightly symptomatic patients with CM-I, a conservative approach to treatment should be adopted with periodic clinical and radiological examinations 15).

Clinical Features

Although the most common presentation is occipital headache, the association of audio-vestibular symptoms is not rare.

The headache is commonly aggravated by Valsalva and sensory and motor deficits.

In a series of 71 patients, pain was the commonest symptom (69% of patients); other symptoms included weakness (56%), numbness (52%), and unsteadiness (40%). The presenting physical signs consisted of a foramen magnum syndrome (22%), central cord syndrome (65%), or a cerebellar syndrome (11%) 16).

Audio-vestibular manifestations

The appearance of audio-vestibular manifestations in CM-I makes it common to refer these patients to neurotologists. Unsteadiness, vertiginous syndromes and sensorineural hearing loss are frequent. Nystagmus, especially horizontal and down-beating, is not rare. It is important for neurotologists to familiarise themselves with CM-I symptoms to be able to consider it in differential diagnosis 17).


Feinberg et al present a case of Chiari malformation manifesting as isolated trismus, describe the typical symptoms associated with Chiari malformation, and discuss the potential anatomical causes for this unique presentation. A 3-year-old boy presented with inability to open his jaw for 6 weeks with associated significant weight loss. The results of medical and radiological evaluation were negative except for Chiari malformation type 1 with cerebellar tonsils 12 mm below the level of the foramen magnum. The patient underwent Chiari decompression surgery. Postoperatively, his ability to open his mouth was significantly improved, allowing resumption of a regular diet. Postoperative MRI revealed almost complete resolution of the syringobulbia. To the best of the authors’ knowledge, this is the first reported case of isolated trismus from Chiari malformation with syringobulbia 18).

Diagnosis

Along with tonsillar herniation, imaging studies have documented additional abnormalities, including smaller and overcrowded posterior cranial fossa 19) 20) 21) 22) 23).

MRI Findings After Surgery for Chiari Malformation Type I is important when evaluating postoperative changes 24).


Sagittal MRI overestimates the degree of tonsillar ectopia. Misdiagnosis may occur if sagittal imaging alone is used. The cerebellar tonsils are paramedian structures, and this should be kept in mind when interpreting midline sagittal MRI.

Treatment

An accurate and reliable selection of patients based on clinical and neuroimaging findings is paramount for the success of neurosurgical treatment25).

see Posterior fossa decompresion for Chiari type 1 deformity.

Outcome

Efforts to guide preoperative counseling and improve outcomes research are impeded by reliance on small, single-center studies.

Approximately 1 in 8 pediatric CM-I patients experienced a surgical complication, whereas medical complications were rare. Although complex chronic conditions (CCC) were common in pediatric CM-I patients, only hydrocephalus was independently associated with increased risk of surgical events. These results may inform patient counseling and guide future research efforts 26).

CM-I in children is not a radiologically static entity but rather is a dynamic one. Radiological changes were seen throughout the 7 years of follow-up. A reduction in tonsillar herniation was substantially more common than an increase. Radiological changes did not correlate with neurological examination finding changes, symptom development, or the need for future surgery. Follow-up imaging of asymptomatic children with CM-I did not alter treatment for any patient. It would be reasonable to follow these children with clinical examinations but without regular surveillance MRI 27).

Outcome assessment for the management of Chiari malformation type 1 is difficult because of the lack of a reliable and specific surgical outcome assessment scale. Such a scale could reliably correlate postoperative outcomes with preoperative symptoms.

Chicago Chiari Outcome Scale (CCOS)

Outcome is poor in approximately 3 in 10 patients 28).

The degree of tonsillar herniation has not been a reliable predictor of either symptom severity 29) or surgical outcome 30).

Arnautovic et al. identified 145 operative series of patients with CM-I, primarily from the United States and Europe, and divided patient ages into 1 of 3 categories: adult (> 18 years of age; 27% of the cases), pediatric (≤ 18 years of age; 30%), or unknown (43%). Most series (76%) were published in the previous 21 years. The median number of patients in the series was 31. The mean duration of the studies was 10 years, and the mean follow-up time was 43 months. The peak ages of presentation in the pediatric studies were 8 years, followed by 9 years, and in the adult series, 41 years, followed by 46 years. The incidence of syringomyelia was 65%. Most of the studies (99%) reported the use of posterior fossa/foramen magnum decompression. In 92%, the dura was opened, and in 65% of these cases, the arachnoid was opened and dissected; tonsillar resection was performed in 27% of these patients. Postoperatively, syringomyelia improved or resolved in 78% of the patients. Most series (80%) reported postoperative neurological outcomes as follows: 75% improved, 17% showed no change, and 9% experienced worsening. Postoperative headaches improved or resolved in 81% of the patients, with a statistical difference in favor of the pediatric series. Postoperative complications were reported for 41% of the series, most commonly with CSF leak, pseudomeningocele, aseptic meningitis, wound infection, meningitis, and neurological deficit, with a mean complication rate of 4.5%. Complications were reported for 37% of pediatric, 20% of adult, and 43% of combined series. Mortality was reported for 11% of the series. No difference in mortality rates was seen between the pediatric and adult series 31).

Complications

Patients treated for Chiari I malformation (CM-I) with posterior fossa decompression (PFD) may occasionally and unpredictably develop postoperative hydrocephalus. The clinical risk factors predictive of this type of Chiari-related hydrocephalus (CRH) are unknown.

Younger patients, those with extensive intraoperative blood loss, and those found during surgery to have a fourth ventricular web were at higher risk for the development of CRH. Clinicians should be alert to evidence of CRH in this patient population after PFD surgery 32).

Sports

There is currently no consensus on the safety of sports participation for patients with Chiari I malformation (CM-I).

A prospective survey was administered to 503 CM-I patients at 2 sites over a 46-month period. Data were gathered on imaging characteristics, treatment, sports participation, and any sport-related injuries. Additionally, 81 patients completed at least 1 subsequent survey following their initial entry into the registry and were included in a prospective group, with a mean prospective follow-up period of 11 months.

Of the 503 CM-I patients, 328 participated in sports for a cumulative duration of 4641 seasons; 205 of these patients participated in contact sports. There were no serious or catastrophic neurological injuries. One patient had temporary extremity paresthesias that resolved within hours, and this was not definitely considered to be related to the CM-I. In the prospective cohort, there were no permanent neurological injuries.

No permanent or catastrophic neurological injuries were observed in CM-I patients participating in athletic activities. The authors believe that the risk of such injuries is low and that, in most cases, sports participation by children with CM-I is safe 33).

Case series

2017

Brock et al., analyzed prospectively 49 patients with CM operated at the Hospital das Clinicas, College of Medicine, University of São Paulo. Patients underwent decompressive surgery with or without opening of the duramater after intraoperative ultrasonography measuring flow rate. A value of 3cm/s was considered a cut-off. Quality of life before and after surgery and the improvement of neck pain and headache were evaluated.

Among 49 patients enrolled, 36 patients (73%) had CSF flow above 3 cm/s and did not undergo duraplasty. In 13 (27%) patients with initial flow <3 cm/s, a dural opening was performed together with duraplasty. All patients improved comparing pre and post operative scores and all clinical parameters evaluated did not differ between both surgical groups. Patients submitted to bone decompression alone had fewer complication rate.

Intraoperative USG with measurement of CSF allows the proper selection of patients with CM that can have a less invasive surgery with bone decompression without duraplasty 34).

2015

A retrospective cohort study was performed for patients 0-18 years of age who underwent surgical correction for Chiari Type I malformation with syrinx between 1995 and 2013. Basic demographic information was collected as well as data for preoperative symptoms, prior surgical history, perioperative characteristics, and postsurgical outcomes. Descriptive statistics were performed in addition to bivariate analyses. Candidate predictor variables were identified based on an association with tonsillar cautery with p < 0.10. Forward stepwise likelihood ratio was used to select candidate predictors in a binary logistic regression model (Pin = 0.05, Pout = 0.10) most strongly associated with the outcome. RESULTS A total of 171 patients with Chiari Type I malformation with syrinx were identified, and 43 underwent tonsillar cautery. Patients who underwent tonsillar cautery had 6.11 times greater odds of improvement in their syrinx (95% CI 2.57-14.49, p < 0.001). There was no effect of tonsillar cautery on increased perioperative complications as well as the need for repeat decompressions. CONCLUSIONS Tonsillar cautery is safe and effective in the treatment of Chiari Type I malformation with syrinx and may decrease time to syrinx resolution after cervicomedullary decompression. Tonsillar cautery does not increase postoperative complications in pediatric Chiari Type I malformation patients 35)


156 consecutive pediatric patients in whom the senior authors performed PFD without dural opening from 2003 to 2013. Patient demographics, clinical symptoms and signs, radiographic findings, intraoperative ultrasound results, and neuromonitoring findings were reviewed. Univariate and multivariate regression analyses were performed to determine risk factors for recurrence of symptoms and the need for reoperation. RESULTS Over 90% of patients had a good clinical outcome, with improvement or resolution of their symptoms at last follow-up (mean 32 months). There were no major complications. The mean length of hospital stay was 2.0 days. In a multivariate regression model, partial C-2 laminectomy was an independent risk factor associated with reoperation (p = 0.037). Motor weakness on presentation was also associated with reoperation but only with trend-level significance (p = 0.075). No patient with < 8 mm of tonsillar herniation required reoperation.

The vast majority (> 90%) of children with symptomatic CM-I will have improvement or resolution of symptoms after a PFD without dural opening. A non-dural opening approach avoids major complications. While no patient with tonsillar herniation < 8 mm required reoperation, children with tonsillar herniation at or below C-2 have a higher risk for failure when this approach is used 36).


Thirty-nine cases of CM-1 with and without syringomyelia (SM) were included. There were 18 patients in the nonduraplasty and 21 in the duraplasty group. Syringomyelia, tonsillar herniation (TH), preoperative symptom duration, and postoperative SM size were compared.

No significant difference was found between improvement in the duraplasty group (81%) and the non-duraplasty group (61.1%). In cases whose symptom duration was 0-36 months, improvement in the duraplasty group (93%) was significantly better than in the nonduraplasty group (50%) (p < 0.01). The rate of syrinx regression was 92.3% in the duraplasty group and 12.5% in the non-duraplasty group (p < 0.05). In cases with SM, the improvement was 21.4% in the non-duraplasty group compared to 78.6% in the duraplasty group (p=0.056). In cases with TH greater than 10 mm, the improvement was 66.7% in the non-duraplasty group, whereas all six cases (100%) in the duraplasty group had improved.

In SM associated cases, cases with TH greater than 10 mm, and whose symptom duration is less than 36 months, duraplasty is a more reliable choice despite a slightly higher rate of complications 37).

2014

In 21 patients, 12 cases had osteo-compression on the cerebellar hemisphere, 18 cases had thickened adhered fabric ring that stretched from arachnoid membrane to cerebellar hemisphere, and 15 cases with syringomyelia. The patients were followed up for 6 months to 3 years after the surgery. All patients showed a remarkable recovery of syringomyelia. There were no morbidity or death related to the surgery. Most of ACM-1 patients, the osteo- and membrane compression on cerebellar hemisphere and tonsil were observed during the operation. Therefore, decompression of foramen magnum and posterior craniocervical combined with the removal of cerebellomedullary fissure arachnoid membrane and placement of an artificial dural graft should be considered as a comprehensive option of minimally invasive surgery and rational and radical treatment of ACM-1. Our experience showed that, by using our procedure, shunting becomes no longer necessary in the treatment of ACM-1-associated syringomyelia 38).

1992

Of the 25 patients who presented with spinal symptoms, 23 (92%) proved to have a syrinx at MR imaging. When the syrinx extended into the medulla (n = 3), however, brain stem symptoms predominated. Patients with objective brain stem or cerebellar signs had the largest mean tonsillar herniations. Patients with tonsillar herniations greater than 12 mm were invariably symptomatic, but approximately 30% of patients with tonsils herniating 5-10 mm below the foramen magnum were asymptomatic at MR imaging. “Incidental” Chiari I malformations are thus much more common than previously recognized, and careful clinical assessment remains the cornerstone for proper diagnosis and management 39).

1983

In a series of 71 patients, pain was the commonest symptom (69% of patients); other symptoms included weakness (56%), numbness (52%), and unsteadiness (40%). The presenting physical signs consisted of a foramen magnum compression syndrome (22%), central cord syndrome (65%), or a cerebellar syndrome (11%). Myelography was performed in 69 patients, and was the most useful investigation. Only 23% of plain radiographs were abnormal. In addition to tonsillar descent, the operative findings included arachnoid adhesions (41%) and syringomyelia (32%). All patients underwent suboccipital craniectomy and C1-3 laminectomy. Respiratory depression was the most frequent postoperative complication (14%), and one patient died from sleep apnea. Early postoperative improvement of both symptoms (82%) and signs (70%) was followed by later relapse in 21% of patients, showing an initial benefit following surgery. None of the patients with a cerebellar syndrome deteriorated, whereas 56% of patients with evidence of foramen magnum compression and 66% of those with a central cord syndrome maintained their initial improvement. The authors conclude that posterior fossa decompression appears to benefit some patients, although a significant proportion might be expected to relapse within 2 to 3 years after operation, depending upon the presenting syndrome 40).

Case reports

2007

A 13-year-old obese boy with a 3-week history of headaches, neck pain, torticollis and progressive visual deterioration was admitted. Bilateral chronic papilledema and decrease in visual acuity were found in the presence of a previously diagnosed CMI.

Intracranial pressure monitoring demonstrating increased pressure levels was followed by a suboccipital decompression, C1 laminectomy and duroplasty. Post-operatively, the boy improved markedly, the 6 months follow-up opthalmological examination demonstrated resolution of papilloedema, but consecutive bi-lateral optic nerve atrophy.

IH with progressive visual deterioration represents one of the varying clinical presentations of CMI and may be classified as a secondary form of idiopathic intracranial hypertension (IH). Neuro-ophthalmological examination in all patients with CMI is recommended to identify the real incidence of this presentation. Altered CSF dynamics, venous hypertension and obesity as co-factors may be causative pathophysiologic factors 41).

Books

ecx.images-amazon.com_images_i_4176qdt_2bynl._sl210_.jpg

References

1) , 5) , 39)

Elster AD, Chen MY. Chiari I malformations: clinical and radiologic reappraisal. Radiology. 1992 May;183(2):347-53. PubMed PMID: 1561334.
2)

Liu W, Wu H, Aikebaier Y, Wulabieke M, Paerhati R, Yang X. No significant difference between chiari malformation type 1.5 and type I. Clin Neurol Neurosurg. 2017 Mar 30;157:34-39. doi: 10.1016/j.clineuro.2017.03.024. [Epub ahead of print] PubMed PMID: 28384597.
3)

Taylor DG, Mastorakos P, Jane JA Jr, Oldfield EH. Two distinct populations of Chiari I malformation based on presence or absence of posterior fossa crowdedness on magnetic resonance imaging. J Neurosurg. 2017 Jun;126(6):1934-1940. doi: 10.3171/2016.6.JNS152998. Epub 2016 Sep 2. PubMed PMID: 27588590.
4) , 25)

Poretti A, Ashmawy R, Garzon-Muvdi T, Jallo GI, Huisman TA, Raybaud C. Chiari Type 1 Deformity in Children: Pathogenetic, Clinical, Neuroimaging, and Management Aspects. Neuropediatrics. 2016 Jun 23. [Epub ahead of print] PubMed PMID: 27337547.
6)

Wang CS, Wang X, Fu CH, Wei LQ, Zhou DQ, Lin JK. Analysis of cerebrospinal fluid flow dynamics and morphology in Chiari I malformation with cine phase-contrast magnetic resonance imaging. Acta Neurochir (Wien). 2014 Jan 7. [Epub ahead of print] PubMed PMID: 24395050.
7)

Deng X, Wang K, Wu L, Yang C, Yang T, Zhao L, Xu Y. Asymmetry of tonsillar ectopia, syringomyelia and clinical manifestations in adult Chiari I malformation. Acta Neurochir (Wien). 2014 Jan 22. [Epub ahead of print] PubMed PMID: 24449150.
8)

Canpolat A, Akçakaya MO, Altunrende E, Ozlü HM, Duman H, Ton T, Akdemir O. Chiari Type I malformation yielded to the diagnosis of Crouzon syndrome. J Neurosci Rural Pract. 2014 Jan;5(1):81-3. doi: 10.4103/0976-3147.127885. PubMed PMID: 24741262.
9)

Abbott D, Brockmeyer D, Neklason DW, Teerlink C, Cannon-Albright LA. Population-based description of familial clustering of Chiari malformation Type I. J Neurosurg. 2017 Feb 3:1-6. doi: 10.3171/2016.9.JNS161274. [Epub ahead of print] PubMed PMID: 28156254.
10)

Frič R, Eide PK. Comparison of pulsatile and static pressures within the intracranial and lumbar compartments in patients with Chiari malformation type 1: a prospective observational study. Acta Neurochir (Wien). 2015 Sep;157(8):1411-23; discussion 1423. doi: 10.1007/s00701-015-2465-x. Epub 2015 Jun 24. PubMed PMID: 26105759.
11)

Alperin N, Kulkarni K, Loth F, Roitberg B, Foroohar M, Mafee MF, Lichtor T. Analysis of magnetic resonance imaging-based blood and cerebrospinal fluid flow measurements in patients with Chiari I malformation: a system approach. Neurosurg Focus. 2001 Jul 15;11(1):E6. PubMed PMID: 16724816.
12)

Buell TJ, Heiss JD, Oldfield EH. Pathogenesis and Cerebrospinal Fluid Hydrodynamics of the Chiari I Malformation. Neurosurg Clin N Am. 2015 Oct;26(4):495-9. doi: 10.1016/j.nec.2015.06.003. Epub 2015 Aug 4. Review. PubMed PMID: 26408057.
13)

Goel A. Is atlantoaxial instability the cause of Chiari malformation? Outcome analysis of 65 patients treated by atlantoaxial fixation. J Neurosurg Spine. 2015 Feb;22(2):116-27. doi: 10.3171/2014.10.SPINE14176. Epub 2014 Nov 21. PubMed PMID: 25415487.
14)

Frič R, Eide PK. Comparative observational study on the clinical presentation, intracranial volume measurements, and intracranial pressure scores in patients with either Chiari malformation Type I or idiopathic intracranial hypertension. J Neurosurg. 2016 Jun 24:1-11. [Epub ahead of print] PubMed PMID: 27341045.
15)

Novegno F, Caldarelli M, Massa A, Chieffo D, Massimi L, Pettorini B, Tamburrini G, Di Rocco C. The natural history of the Chiari Type I anomaly. J Neurosurg Pediatr. 2008 Sep;2(3):179-87. doi: 10.3171/PED/2008/2/9/179. PubMed PMID: 18759599.
16) , 40)

Paul KS, Lye RH, Strang FA, Dutton J. Arnold-Chiari malformation. Review of 71 cases. J Neurosurg. 1983 Feb;58(2):183-7. PubMed PMID: 6848674.
17)

Guerra Jiménez G, Mazón Gutiérrez Á, Marco de Lucas E, Valle San Román N, Martín Laez R, Morales Angulo C. Audio-vestibular signs and symptoms in Chiari malformation type i. Case series and literature review. Acta Otorrinolaringol Esp. 2015 Jan-Feb;66(1):28-35. doi: 10.1016/j.otorri.2014.05.002. Epub 2014 Sep 4. English, Spanish. PubMed PMID: 25195076.
18)

Feinberg M, Babington P, Sood S, Keating R. Isolated unilateral trismus as a presentation of Chiari malformation: case report. J Neurosurg Pediatr. 2016 May;17(5):533-6. doi: 10.3171/2015.7.PEDS1592. Epub 2016 Jan 1. PubMed PMID: 26722762.
19)

Nishikawa M, Sakamoto H, Hakuba A, Nakanishi N, Inoue Y. Pathogenesis of Chiari malformation: a morphometric study of the posterior cranial fossa. J Neurosurg. 1997;86(1):40-47.
20)

Milhorat TH, Chou MW, Trinidad EM, et al. Chiari I malformation redefined: clinical and radiographic findings for 364 symptomatic patients. Neurosurgery. 1999;44(5):1005-1017.
21)

Karagöz F, Izgi N, Kapíjcíjo!glu Sencer S. Morphometric measurements of the cranium in patients with Chiari type I malformation and comparison with the normal population. Acta Neurochir (Wien). 2002;144(2):165-171; discussion 171.
22)

Milhorat TH, Nishikawa M, Kula RW, Dlugacz YD. Mechanisms of cerebellar tonsil herniation in patients with Chiari malformations as guide to clinical management. Acta Neurochir (Wien). 2010;152(7):1117-1127.
23)

Badie B, Mendoza D, Batzdorf U. Posterior fossa volume and response to suboccipital decompression in patients with Chiari I malformation. Neurosurgery. 1995;37(2):214-218.
24)

Rozenfeld M, Frim DM, Katzman GL, Ginat DT. MRI Findings After Surgery for Chiari Malformation Type I. AJR Am J Roentgenol. 2015 Nov;205(5):1086-93. doi: 10.2214/AJR.15.14314. PubMed PMID: 26496557.
26)

Greenberg JK, Olsen MA, Yarbrough CK, Ladner TR, Shannon CN, Piccirillo JF, Anderson RC, Wellons JC 3rd, Smyth MD, Park TS, Limbrick DD Jr. Chiari malformation Type I surgery in pediatric patients. Part 2: complications and the influence of comorbid disease in California, Florida, and New York. J Neurosurg Pediatr. 2016 May;17(5):525-32. doi: 10.3171/2015.10.PEDS15369. Epub 2016 Jan 22. PubMed PMID: 26799408.
27)

Whitson WJ, Lane JR, Bauer DF, Durham SR. A prospective natural history study of nonoperatively managed Chiari I malformation: does follow-up MRI surveillance alter surgical decision making? J Neurosurg Pediatr. 2015 Aug;16(2):159-66. doi: 10.3171/2014.12.PEDS14301. Epub 2015 May 1. PubMed PMID: 25932776.
28)

Aliaga L, Hekman KE, Yassari R, Straus D, Luther G, Chen J, Sampat A, Frim D. A novel scoring system for assessing Chiari malformation type I treatment outcomes. Neurosurgery. 2012 Mar;70(3):656-64; discussion 664-5. doi: 10.1227/NEU.0b013e31823200a6. PubMed PMID: 21849925.
29)

Khan AA, Bhatti SN, Khan G, et al. Clinical and radiological findings in Arnold Chiari malformation. J Ayub Med Coll Abbottabad. 2010;22(2):75-78.
30)

NoudelR,GomisP,SotoaresG,etal.Posteriorfossavolumeincreaseaftersurgery for Chiari malformation type I: a quantitative assessment using magnetic resonance imaging and correlations with the treatment response. J Neurosurg. 2011;115(3): 647-658.
31)

Arnautovic A, Splavski B, Boop FA, Arnautovic KI. Pediatric and adult Chiari malformation Type I surgical series 1965-2013: a review of demographics, operative treatment, and outcomes. J Neurosurg Pediatr. 2015 Feb;15(2):161-77. doi: 10.3171/2014.10.PEDS14295. Epub 2014 Dec 5. PubMed PMID: 25479580.
32)

Guan J, Riva-Cambrin J, Brockmeyer DL. Chiari-related hydrocephalus: assessment of clinical risk factors in a cohort of 297 consecutive patients. Neurosurg Focus. 2016 Nov;41(5):E2. PubMed PMID: 27798986.
33)

Strahle J, Geh N, Selzer BJ, Bower R, Himedan M, Strahle M, Wetjen NM, Muraszko KM, Garton HJ, Maher CO. Sports participation with Chiari I malformation. J Neurosurg Pediatr. 2016 Apr;17(4):403-9. doi: 10.3171/2015.8.PEDS15188. Epub 2015 Dec 4. PubMed PMID: 26636249.
34)

Brock RS, Taricco MA, de Oliveira MF, de Lima Oliveira M, Teixeira MJ, Bor-Seng-Shu E. Intra Operative Ultrasonography for Definition of Less Invasive Surgical Technique in Patients with Chiari Type I Malformation. World Neurosurg. 2017 Feb 9. pii: S1878-8750(17)30152-3. doi: 10.1016/j.wneu.2017.02.003. [Epub ahead of print] PubMed PMID: 28192262.
35)

Stanko KM, Lee YM, Rios J, Wu A, Sobrinho GW, Weingart JD, Jackson EM, Ahn ES, Chaichana KL, Jallo GI. Improvement of syrinx resolution after tonsillar cautery in pediatric patients with Chiari Type I malformation. J Neurosurg Pediatr. 2015 Oct 30:1-8. [Epub ahead of print] PubMed PMID: 26517059.
36)

Kennedy BC, Kelly KM, Phan MQ, Bruce SS, McDowell MM, Anderson RC, Feldstein NA. Outcomes after suboccipital decompression without dural opening in children with Chiari malformation Type I. J Neurosurg Pediatr. 2015 May 1:1-9. [Epub ahead of print] PubMed PMID: 25932779.
37)

Gurbuz MS, Karaaslan N, Caliskan T, Unal E, Berkman MZ. Comparison of the Surgical Results for Foramen Magnum Decompression with and without Duraplasty in Chiari Malformation Type 1. Turk Neurosurg. 2015;25(3):419-24. doi: 10.5137/1019-5149.JTN.11235-14.1. PubMed PMID: 26037182.
38)

Liang CJ, Dong QJ, Xing YH, Shan M, Wen LX, Qiang ZY, Ping ZQ, Tao PZ, Ping HX. Posterior fossa decompression combined with resection of the cerebellomedullary fissure membrane and expansile duraplasty: a radical and rational surgical treatment for Arnold-Chiari type I malformation. Cell Biochem Biophys. 2014 Dec;70(3):1817-21. doi: 10.1007/s12013-014-0135-x. PubMed PMID: 25018150.
41)

Kurschel S, Maier R, Gellner V, Eder HG. Chiari I malformation and intra-cranial hypertension:a case-based review. Childs Nerv Syst. 2007 Aug;23(8):901-5. Epub 2007 May 8. PubMed PMID: 17486353.