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Update Cerebellopontine angle epidermoid cyst

The cerebellopontine angle epidermoid cyst is a posterior fossa epidermoid cyst.

It account for 3-6% of cerebellopontine angle tumors. Comparatively, vestibular schwannomas, the most common CPA angle tumor, account for 85%.

Men and women are equally affected and the symptoms usually arise between the mid-20’s and early 50’s 1) with a mean age of 38.8 years at presentation 2).


Although several mechanisms for cranial nerve dysfunction due to these tumors have been proposed.

Hasegawa et al. report the first direct evidence of etiology of cranial nerve dysfunction caused by cerebellopontine angle epidermoid tumors. Young age and rapidly progressive neurological deficit might be the characteristics for strangulation of the affected nerves by the cyst capsule 3).

Clinical features

CPA epidermoid cysts can compress the surrounding cranial nerves, brainstem, and cerebellum. Ataxia and cranial nerve palsies often result 4).Thirty cases of cerebellopontine angle epidermoid cysts treated over a period of 20 years werw reviewed with regard to their clinical features, the pathophysiology of their symptoms and their management. The predominating symptoms were related to the 7th and 8th cranial nerves and headaches. The signs and symptoms were present for an average period of 4 months. It was not always possible to determine if the signs and symptoms were due to local involvement by the epidermoid, increased intracranial pressure, or both 5).


Diagnostic procedures evolved from angiography and ventriculography to non-invasive computed tomography and MRI 6).



The posterior cranial fossa approach was used in 27 cases in the case series of deSouza et al. Total excision of the epidermoid was the aim and was carried out in five (18%) patients but concern regarding the preservation of nearby important neurovascular structures forced partial removal in 22 patients. To minimise reformation, the residual epidermoid was carefully coagulated with the aid of the operating microscope and bipolar cautery without damaging surrounding neurovascular structures 7).

The characteristics of epidermoid cysts make them amenable to whole course neuroendoscopic resection. Use of physiologic/pathologic interspaces and neuroendoscopic angulations decreases traction on the brain, improves complete resection rates, and decreases postoperative complications 8).

Case series


Twenty-two cases with epidermoid cysts of CPA micro-neurosurgically treated since 2005 were reviewed. Clinical status of the patients before the surgery and post-operative functional outcome were recorded. Available data from the English literature were summarized for comparison. Mass reduction of cyst contents in most cases was usually associated with prompt and marked improvement of the symptoms suggesting neuroapraxia caused by compression of the tumor content and/or mild ischemia. Among them, two cases showed strangulation of the affected nerves by the tumor capsule whose preoperative dysfunction did not improve after surgery in spite of meticulous microsurgical removal of the lesion. Involved facial and abducent nerves in these two cases showed distortion of nerve axis and nerve atrophy distal to the strangulation site.

Hasegawa et al. report the first direct evidence of etiology of cranial nerve dysfunction caused by cerebellopontine angle epidermoid tumors. Young age and rapidly progressive neurological deficit might be the characteristics for strangulation of the affected nerves by the cyst capsule. Even though the number of cases might be limited, immediate decompression and release of the strangulating band might be urged in such patients to prevent irreversible deficits 9).

17 patients, including 7 with tumor limited to the cerebellopontine angle, 7 with cerebellopontine angle tumor penetrating supratentorially, and 3 with cerebellopontine angle tumor extending along skull base to contralateral cerebellopontine angle. All patients were followed-up for the mean duration of 126 months.

On admission cranial nerve symptoms predominated. Total tumor removal was achieved in 5 patients, and incomplete removal (with small tumor remnants left on vessels, nerves, or brainstem) in 12 patients. Postoperatively, preoperative deficits worsened in 2 and new postoperative deficits occurred in 10 patients. The extent of tumor expansion had no effect on postoperative morbidity and risk of recurrence. During long-term follow-up, improvement or resolution of preoperative deficits was seen in 11 of 17 patients, and new postoperative deficits in 8 of 10 patients. Symptomatic recurrences after an average of more than 9 years were noted in 5 patients, 3 of whom were reoperated. Recurrences occurred in some younger patients and always in area of primary tumor. No effect of extent of tumor removal on risk of recurrence was found.

The extent of tumor removal had no effect on the risk of recurrence, and thus it may be acceptable to leave tumor capsule fragments adhering closely to nerves, vessels, or brainstem. During long-term follow-up, resolution or improvement of present preoperatively and new postoperative neurological deficits may be expected in most patients 10).


In a case series, pathophysiology of cranial nerve dysfunction in CPA epidermoid cysts was evaluated with special attention to a new mechanism of capsule strangulation caused by stratified tumor capsule. Twenty-two cases since 2005 were reviewed. Clinical status of the patients before the surgery and post-operative functional outcome were recorded. Available data from the English literature were summarized for comparison. Mass reduction of cyst contents in most cases was usually associated with prompt and marked improvement of the symptoms suggesting neurapraxia caused by compression of the tumor content and/or mild ischemia. Among them, two cases showed strangulation of the affected nerves by the tumor capsule whose preoperative dysfunction did not improve after surgery in spite of meticulous microsurgical removal of the lesion. Involved facial and abducent nerves in these two cases showed distortion of nerve axis and nerve atrophy distal to the strangulation site. Hasegawa et al. report the first direct evidence of etiology of cranial nerve dysfunction caused by cerebellopontine angle epidermoid tumors. Young age and rapidly progressive neurological deficit might be the characteristics for strangulation of the affected nerves by the cyst capsule. Even though the number of cases might be limited, immediate decompression and release of the strangulating band might be urged in such patients to prevent irreversible deficits 11)

Hu et al. performed a retrospective analysis of clinical data of 13 male and 17 female patients (mean age: 42.4 ± 11.4 years) who presented with a CPA epidermoid cyst and underwent whole course neuroendoscopy. Complications and tumor recurrence were assessed at follow-up. Results Clinical manifestations included an initial symptom of headache (n = 21), gait instability (n = 6), intracranial hypertension (n = 13), posterior cranial nerve symptoms (n = 6), ataxia (n = 5), and hydrocephalus (n = 1). All patients tolerated tumor resection with subsequent symptomatic improvement, and the results of the postoperative magnetic resonance imaging scan did not show any remnants of tumor. Mean duration of surgery was 2.61 ± 0.47 hours, mean loss of blood was 96.8 ± 35.4 mL, and the mean duration of hospitalization was 7.5 ± 2.25 days. Postoperative complications (8 of 30 [26.7%]) included fever (n = 5), communicating hydrocephalus (n = 1), facial nerve paralysis (n = 1), and abducens nerve palsy (n = 1). Tumor recurrence was observed in two patients (6.7%). No deaths or intracranial hemorrhage was reported.

The characteristics of epidermoid cysts make them amenable to whole course neuroendoscopic resection. Use of physiologic/pathologic interspaces and neuroendoscopic angulations decreases traction on the brain, improves complete resection rates, and decreases postoperative complications 12).


Between 1996 and 2004, 10 patients with typical symptoms of trigeminal neuralgia were found to have cerebellopontine angle epidermoids and treated surgically.

Total resection was done in 6 patients (60%). Surgical removal of tumor and microvascular decompression of the trigeminal nerve were performed simultaneously in one case. One patient died due to postoperative aseptic meningitis. The others showed total relief from pain. During follow-up, no patients experienced recurrence of their trigeminal neuralgia (TN).

The clinical features of TN from CPA epidermoids are characterized by symptom onset at a younger age compared to TN from vascular causes. In addition to removal of the tumor, the possibility of vascular compression at the root entry zone of the trigeminal nerve should be kept in mind. If it exists, a microvascular decompression (MVD) should be performed. Recurrence of tumor is rare in both total and subtotal removal cases, but long-term follow-up is required 13).


Thirty cases of cerebellopontine angle epidermoid cysts treated over a period of 20 years are reviewed with regard to their clinical features, the pathophysiology of their symptoms and their management. The predominating symptoms were related to the 7th and 8th cranial nerves and headaches. The signs and symptoms were present for an average period of 4 months. It was not always possible to determine if the signs and symptoms were due to local involvement by the epidermoid, increased intracranial pressure, or both. Diagnostic procedures evolved from angiography and ventriculography to non-invasive computed tomography and MRI. The posterior cranial fossa approach was used in 27 cases. Total excision of the epidermoid was the aim and was carried out in five (18%) patients but concern regarding the preservation of nearby important neurovascular structures forced partial removal in 22 patients. To minimise reformation, the residual epidermoid was carefully coagulated with the aid of the operating microscope and bipolar cautery without damaging surrounding neurovascular structures 14).

Case reports


Malignant transformation of a residual cerebellopontine angle epidermoid cyst 15).


Guan et al. the case of a 13-year-old female with a newly diagnosed cerebellopontine angle EC who presented with worsening headaches, photophobia, and emesis. Magnetic resonance imaging demonstrated significant pericystic brainstem edema and mass effect with effacement of the fourth ventricle. Refractory symptoms prompted repeat imaging, revealing cyst enlargement and dense rim enhancement. Resection of the EC resolved both her symptoms and the brainstem edema. This case documents the radiographic evolution of EC rupture and subsequent clinical course 16).

A case of an unusual epidermoid cyst of the cerebellopontine angle extending into the upper cervical canal that appeared hyper-dense on computed tomography scanning, hyper-intense on T1-weighted magnetic resonance (MR) images, and hypo-intense on T2-weighted MR images 17).


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Hasegawa M, Nouri M, Nagahisa S, Yoshida K, Adachi K, Inamasu J, Hirose Y, Fujisawa H. Cerebellopontine angle epidermoid cysts: clinical presentations and surgical outcome. Neurosurg Rev. 2015 Nov 14. [Epub ahead of print] PubMed PMID: 26566990.

Berger M, Wilson C. Epidermoid cysts of the posterior fossa. J Neurosurg. 1985;62:214–219.
5) , 6) , 7) , 14)

deSouza CE, deSouza R, da Costa S, Sperling N, Yoon TH, Abdelhamid MM, Sharma RR, Goel A. Cerebellopontine angle epidermoid cysts: a report on 30 cases. J Neurol Neurosurg Psychiatry. 1989 Aug;52(8):986-90. PubMed PMID: 2795068; PubMed Central PMCID: PMC1031839.
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Hu Z, Guan F, Kang T, Huang H, Dai B, Zhu G, Mao B, Kang Z. Whole Course Neuroendoscopic Resection of Cerebellopontine Angle Epidermoid Cysts. J Neurol Surg A Cent Eur Neurosurg. 2015 Aug 24. [Epub ahead of print] PubMed PMID: 26302403.

Hasegawa M, Nouri M, Nagahisa S, Yoshida K, Adachi K, Inamasu J, Hirose Y, Fujisawa H. Cerebellopontine angle epidermoid cysts: clinical presentations and surgical outcome. Neurosurg Rev. 2016 Apr;39(2):259-66; discussion 266-7. doi: 10.1007/s10143-015-0684-5. PubMed PMID: 26566990.

Czernicki T, Kunert P, Nowak A, Wojciechowski J, Marchel A. Epidermoid cysts of the cerebellopontine angle: Clinical features and treatment outcomes. Neurol Neurochir Pol. 2016;50(2):75-82. doi: 10.1016/j.pjnns.2015.11.008. PubMed PMID: 26969562.

Son DW, Choi CH, Cha SH. Epidermoid tumors in the cerebellopontine angle presenting with trigeminal neuralgia. J Korean Neurosurg Soc. 2010 Apr;47(4):271-7. doi: 10.3340/jkns.2010.47.4.271. PubMed PMID: 20461167; PubMed Central PMCID: PMC2864819.

Pikis S, Margolin E. Malignant transformation of a residual cerebellopontine angle epidermoid cyst. J Clin Neurosci. 2016 Nov;33:59-62. doi: 10.1016/j.jocn.2016.04.008. Review. PubMed PMID: 27519146.

Guan Z, Hollon T, Bentley JN, Garton HJ. Ruptured pediatric cerebellopontine angle epidermoid cyst: a case report detailing radiographic evolution and clinical course. J Neurosurg Pediatr. 2015 Aug 21:1-5. [Epub ahead of print] PubMed PMID: 26295366.

Lim J, Cho K. Epidermoid cyst with unusual magnetic resonance characteristics and spinal extension. World J Surg Oncol. 2015 Aug 7;13:240. doi: 10.1186/s12957-015-0651-1. PubMed PMID: 26245481; PubMed Central PMCID: PMC4527251.

Update: Molsidomine

Molsidomine is an orally active, long acting vasodilator. Molsidomine is metabolized in the liver to the active metabolite linsidomine. Linsidomine is an unstable compound that releases nitric oxide (NO) upon decay as the actual vasodilating compound.

Belongs to the drug class of sydnones . SIN-1A metabolite of Molsidomine has pharmacologically active group of NO, which by increasing levels of cGMP, decreases levels of intracellular calcium ions in smooth muscle cells. This effect leads to relaxation of smooth muscle vasculature, inhibits platelets aggregation and has indirect antiproliferative effect. In clinical observations no effect of tolerance to the drug was observed. Experimental data show additional mechanism of action of the drug: SIN-1C metabolites protects the reoxygenated cardiomyocyte from post-reperfusion damage. Indications for use of Molsidomine are: ischaemic heart disease, chronic heart failure and pulmonary hypertension. Effects of Molsidomine use in acute myocardial infarction and unstable angina were compared in clinical trials to effects of nitroglycerin use. Both drugs were found equally potent, but authors underline the fact of better Molsidomine tolerability comparing NTG, but longer serum half-time of Molsidomin effects that control of the treatment is worse. In clinical trials it was suggested that intravenous use of Molsidomine metabolite SIN-1 during PTCA procedures is more effective than use of isosorbide dinitrate in the same procedures. In other clinical trials molsidomin was found to produce beneficial effects in patients with heart failure due to ischaemic cardiomyopathy, dilatative cardiomyopathy, in essential hypertension, pulmonary artery hypertension in COPD patients and in congestive heart failure 1).

Ehlers et al. examined the effects of treatment with molsidomine with regard to decreasing the incidence of spasm-related delayed cerebral infarctions and improving clinical outcome in patients with SAH.

Seventy-four patients with spontaneous aneurysmal subarachnoid hemorrhage (SAH) were included in this post hoc analysis. Twenty-nine patients with SAH and proven cerebral vasospasm (CVS) received molsidomine in addition to oral or intravenous nimodipine. Control groups consisted of 25 SAH patients with proven vasospasm and 20 SAH patients without. These patients received nimodipine therapy alone. Cranial computed tomography (CCT) before and after treatment was analyzed for CVS-related infarcts. A Modified National Institutes of Health Stroke Scale (mNIHSS) and the modified Rankin Scale (mRS) were used to assess outcomes at a 3-month clinical follow-up.

Four of the 29 (13.8%) patients receiving molsidomine plus nimodipine and 22 of the 45 (48%) patients receiving nimodipine therapy alone developed vasospasm-associated brain infarcts (p < 0.01). Follow-up revealed a median mNIHSS score of 3.0 and a median mRS score of 2.5 in the molsidomine group compared with scores of 11.5 and 5.0, respectively, in the nimodipine group with CVS (p < 0.001). One patient in the molsidomine treatment group died, and 12 patients in the standard care group died (p < 0.01).

In this post hoc analysis, patients with CVS who were treated with intravenous molsidomine had a significant improvement in clinical outcome and less cerebral infarction. Molsidomine offers a promising therapeutic option in patients with severe SAH and CVS and should be assessed in a prospective study 2).

Durak et al., investigated the protective and therapeutic effects of molsidomine (MOL) in a rat model of whole brain radiotherapy (RT). Forty female rats were divided into five groups of eight: group 1, control; group 2, 15 Gy single dose RT (RT); group 3, 4 mg/kg MOL treated for 5 days (MOL); group 4, 4 mg/kg MOL for 5 days, 10 days after RT treatment (RT + MOL); group 5, 4 mg/kg MOL treatment for 5 days before RT treatment and for 5 days after RT treatment (MOL + RT). All rats were sacrificed on day 16. Neurodegenerative changes in the brain and tissue levels of oxidants and antioxidants were evaluated. The oxidative parameters were increased and antioxidant status was decreased in group RT compared to groups MOL + RT and RT + MOL. Histopathological examination showed that treatment with MOL after RT application and treatment with MOL before RT treatment decreased neuronal degeneration. No difference in neuronal appearance was found between groups RT + MOL and MOL + RT. MOL treatment protected the nervous system of rats and may be a treatment option for preventing RT induced neural injury 3)

1) Kmieć M, Ochmański W. [Molsidomine: importance in treatment of circulation disorders]. Przegl Lek. 1998;55(10):532-6. Review. Polish. PubMed PMID: 10224868.
2) Ehlert A, Schmidt C, Wölfer J, Manthei G, Jacobs AH, Brüning R, Heindel W, Ringelstein EB, Stummer W, Pluta RM, Hesselmann V. Molsidomine for the prevention of vasospasm-related delayed ischemic neurological deficits and delayed brain infarction and the improvement of clinical outcome after subarachnoid hemorrhage: a single-center clinical observational study. J Neurosurg. 2016 Jan;124(1):51-8. doi: 10.3171/2014.12.JNS13846. Epub 2015 Jul 10. PubMed PMID: 26162034.
3) Durak MA, Parlakpinar H, Polat A, Vardi N, Ekici K, Ucar M, Ozhan O, Yildiz A, Pasahan R. Protective and therapeutic effects of molsidomine on radiation induced neural injury in rats. Biotech Histochem. 2017 Feb 6:1-10. doi: 10.1080/10520295.2016.1271454. [Epub ahead of print] PubMed PMID: 28166419.

Update: Intracanalicular vestibular schwannoma

The current practitioner is more often managing intracanalicular vestibular schwannomas than in the past, as improved imaging and heightened awareness leads to earlier diagnosis of these tumors.

Case courtesy of Dr Ian Bickle, <a href=“”></a>. From the case <a href=“”>rID: 48853</a>

Differential diagnosis

Intracanalicular meningioma

Pantopaque (iophendylate) is an oily contrast medium historically used during spine imaging. Due to its persistence in the subarachnoid space and the potential to lead to severe arachnoiditis, it is no longer used today. Deep et al., present a 40-year-old male with new-onset headaches, imbalance, and vertigo. Brain magnetic resonance imaging revealed a 2-mm T1 -hyperintense intracanalicular lesion. Numerous hyperdense foci were scattered throughout the subarachnoid space on computed tomography. Further history revealed the patient received Pantopaque 30 years prior, after sustaining spinal trauma. Remnant Pantopaque contrast is an important differential when evaluating a patient with a suspected intracranial tumor in order to avoid unwarranted surgical intervention 1).

A 46-year-old man with venous compression of the vestibulocochlear nerve inside the internal auditory canal (IAC). The patient presented with a 2-year history of recurrent attacks of disabling vertigo and intermittent high-frequency tinnitus on the right side. Magnetic resonance images showed a small, contrast-enhancing lesion in the fundus of the right IAC, which was suspicious for vestibular schwannoma. During surgical exploration, a large venous loop was found extending into the IAC and compressing the vestibulocochlear nerve. The vessel was mobilized and rerouted out of the IAC. The presumed vestibular schwannoma at the cochlear fossa was left in situ. The patient’s symptoms resolved immediately after surgery. Hearing was unchanged postoperatively. On follow-up, there has been no growth of the contrast-enhancing lesion in the IAC for 3 years so far.Disabling vertigo can also be caused by venous microvascular compression of the vestibulocochlear nerve inside the IAC and may be treated successfully by microvascular decompression. A sensitive, conservative approach to lesions in the fundus may be justified in the presence of an additional, more prominent pathology that causes compression of the vestibulocochlear nerve 2).


The role of observation, microsurgery, and radiation treatment in the management of intracanalicular tumors continues to evolve.

Watchful waiting is an important management option for patients with minimal symptoms. The literature on the natural history of small vestibular schwannomas continues to expand, with particular emphasis on the expected hearing outcomes.

Microsurgical techniques also focus on hearing preservation. Presence of fundal fluid and good or normal hearing preoperatively are positive predictors of hearing preservation after surgery. Long-term follow-up after radiation therapy for vestibular schwannomas continues to demonstrate excellent tumor control rates, although hearing preservation rates are modest.

Multiple factors, including status of hearing, presence of vestibular symptoms, patient age, medical comorbidities, institutional outcomes, and patient preferences, help determine the management strategy for patients with an intracanalicular vestibular schwannoma 3).

Complete surgical removal of intracanalicular vestibular schwannomas with nerve VII and VIII sparing and without worsening patient’s status is challenging. Also the choice of an optimal surgical technique, which is usually limited to selection between retrosigmoid transmeatal (RT) and middle fossa (MF) approach, can be a challenge. Although many previous studies documented superiority of RT to MF approach and vice versa, still no consensus has been reached regarding an optimal approach to intracanalicular vestibular schwannomas. In a technical note, Turek et al., present RT approach with an endoscopic assistance and highlight its advantages over MF approach in surgical management of pure intracanalicular vestibular schwannomas.

RT approach with an endoscopic assistance is presented as an optimal surgical treatment for intracanalicular vestibular schwannomas, and its advantages are compared to those offered by MF approach.

Under an endoscopic guidance, they found a residual tumor in the fundus of the inner acoustic canal and performed its gross total resection.

RT approach is an excellent technique suitable for safe radical surgical treatment of T1 vestibular schwannomas; this technique is associated with lower morbidity risk than MF approach 4).

A longitudinal study of a series of consecutive patients operated on with the 2 techniques by the same surgeon was conducted. Selection criteria included tumor confined to the internal auditory canal (IAC) with a length ranging from 4 to 12 mm and hearing class A or B. Patients were alternately assigned to 1 of the 2 groups regardless of auditory class and distance of the tumor from the IAC fundus. Thirty-five subjects were operated on with the RS-TM technique and 35 via the MF route.

No significant differences in auditory and facial nerve function results between the 2 techniques were observed. The RS-TM approach, however, showed better facial nerve results at discharge. VS size, IAC enlargement, and, particularly, the distance from the IAC fundus were found to influence the postoperative results more than the type of approach itself.

The MF approach has been described as being the better technique for VS surgery in terms of auditory results. However, this claim lacks statistical substantiation because no prospective studies are to be found in the literature. The present longitudinal investigation shows that the MF approach does not afford any particular advantages over the RS-TM route in terms of auditory results in intracanalicular VS, with the exception of tumors reaching the IAC fundus 5).

Case series


A retrospective study was done in 14 patients who underwent MFA for vestibular schwannoma in Asan Medical Center.

The median age at diagnosis was 46.3 years. At initial presentation, 57% of the patients had vertigo, 43% hearing disturbance, and 64% tinnitus. The mean tumor size was 9.7 mm. The tumors were completely resected in 86% of the patients. Hearing was post-operatively preserved in 12 patients and two patients lost their hearing following surgery. Facial nerve function post-operatively remained unchanged in 12 patients (86%) 6).

A retrospective analysis of 19 patients with intracanalicular VS and disabling vestibular dysfunction as the main or only symptom (Group A). All of the patients reported having had disabling vertigo attacks. Subjective evaluation of the impairment of patients was performed before surgery, 3 weeks after surgery, 3 months after surgery, and 1 year after surgery, using the Dizziness Handicap Inventory (DHI). The main outcome measures were improvement in quality of life as measured using the DHI, and general and functional outcomes, in particular facial function and hearing. Patient age, preoperative tumor size, preoperative DHI score, and preservation of the nontumorous vestibular nerve were tested using a multivariate regression analysis to determine factors affecting the postoperative DHI score. The Mann-Whitney U-test was used to compare the postoperative DHI score at 3 weeks, 3 months, and 1 year after surgery with a control group of 19 randomly selected patients with intracanalicular VSs, who presented without vestibular symptoms (Group B). The occurrence of early postoperative discrete vertigo attacks was also compared between groups. RESULTS The preoperative DHI score was ≥ 54 in all patients. All patients reported having had disabling rotational vertigo before surgery. The only significant factor to affect the DHI outcome 3 weeks and 3 months after surgery was the preoperative DHI score. The DHI outcome after 1 year was not affected by the preoperative DHI score. Compared with the control group, the DHI score at 3 weeks and 3 months after surgery was significantly worse. There was no significant difference between the groups after 1 year. Vertigo was improved in all patients and completely resolved after 1 year in 17 patients.

Disabling vestibular dysfunction that affects quality of life should be considered an indication for surgery, even in otherwise asymptomatic patients with intracanalicular VS. Surgical removal of the tumor is safe and very effective in regard to symptom relief. All patients had excellent facial nerve function within 1 year after surgery, with a very good chance of hearing preservation 7).

156 patients diagnosed with an intracanalicular VS managed conservatively.

After a follow-up of 9.5 years, tumor growth had occurred in 37% and growth into the cerebellopontine angle had occurred in 23% of patients. Conservative treatment failed in 15%. The pure tone average had increased from 51- to 72-dB hearing level, and the speech discrimination score (SDS) had decreased from 60% to 34%. The number of patients with good hearing (SDS > 70%) was reduced from 52% to 22%, and the number of patients with American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) class A hearing was reduced from 19% to 3%. Hearing was preserved better in patients with 100% SDS at diagnosis than in patients with even a small loss of SDS. Serviceable hearing was preserved in 34% according to AAO-HNS (class A-B) and in 58% according to the word recognition score (class I-II). Rate of hearing loss was higher in patients with growing tumors.

Tumor growth occurred in only a minority of patients diagnosed with an intracanalicular VS during 10 years of observation. The risk of hearing loss is small in patients with normal discrimination at diagnosis. Serviceable hearing is preserved spontaneously in 34% according to AAO-HNS and in 58% according to the word recognition score 8).


31 patients who were followed up for more than 1 year among patients diagnosed as having VS limited to the internal auditory canal. The median follow-up period was 31 months (range, 12-84 mo). We analyzed the patients’ clinical features, clinical courses, and audiologic changes.

The most frequent initial presenting symptom in patients with ICVS was hearing loss, and one-half of the patients (8 of 16) had a history of sudden hearing loss. Seven patients (22.5%) showed tumor growth during the follow-up period. When we considered the initial tumor size in ICVS, the patients larger in size than the median showed a significantly higher rate of tumor growth. In terms of the initial hearing levels of ICVS according to the Consensus Meeting Guidelines, five patients were classified as Class A (normal hearing) and six patients were classified as Class B. Only one patient among patients with useful hearing (Classes A and B) showed tumor growth. The follow-up hearing levels of all Class A patients were preserved; however, all Class B patients deteriorated to Class C.

Patients with ICVS showed favorable results with conservative management. Among them, patients with small tumors and normal hearing showed a good prognosis 9).


47 patients with a unilateral intracanalicular vestibular schwannoma. Evaluation of growth was monitored by repeat MRI scanning. Repeated pure-tone and speech audiometry results were evaluated for subgroups of patients showing growth or no growth and by subsite location of tumor in the internal auditory canal.

Patients had a mean follow-up of 3.6 years. Over the entire population, the pure-tone average thresholds at 0.5, 1, 2, and 3 kHz and the word recognition scores both significantly deteriorated from 38 to 51 dB HL, and from 66% to 55%, respectively. Overall, 74% of subjects with good hearing, according to the 50/50 rule, maintained hearing above this rule. There were no significant differences in hearing loss by subsite in the internal auditory canal (porus, fundus, central) or by growth status (stable, growing, shrinking). Only 6 patients showed a large hearing change. This happened early during follow-up, with relatively stable hearing after this.

Hearing will deteriorate in some intracanalicular vestibular schwannomas, regardless of tumor growth. Hearing deterioration, if on a large scale, most likely occurs early in follow-up. The present results using conservative management in these tumors appear similar to those reported for stereotactic radiotherapy or microsurgery 10).


Forty-seven patients (22 men and 25 women) harboring an intracanalicular vestibular schwannoma were followed prospectively. Mean age at the time of inclusion was 54.4 (20-71) years. The mean follow-up period was 43.8 months (+/-40 months) ranging from 9 to 222 months. Failure was defined as significant tumor growth and/or hearing deterioration that required a microsurgical or radiosurgical treatment. Failure was observed in 35 cases while a conservative treatment is still ongoing in 12 patients. Ten patients kept an unchanged tumor size (21.3%), while 36 patients experienced a tumor growth (76.6%), and 1 patient experienced a mild decreased tumor size (2.1%). Among the 40 patients who where available for hearing level study, 24 patients (60%) did not change their Gardner and Robertson hearing class. Fifteen patients (37.5%) experienced a >10-dB hearing loss and 2 of them became deaf. One patient (2.5%) improved her hearing level from 56.3 to 43.8 dB over a 39.5-month follow-up period. These data suggest that the wait and see policy exposes the patient to degradation of hearing and tumor growth. Both events may occur in an independent way in the middle-term period. This information has to be given to the patient, and a careful sequential follow-up may be adopted when the wait and see strategy is chosen 11).

Between 1987 and 2003, 96 patients (65 men and 31 women) underwent gamma knife stereotactic radiosurgery (SRS) for intracanalicular tumors. The median patient age was 54 years (range, 22-80 years). Hearing was graded using the Gardner-Robertson (GR) and the American Academy of Otolaryngology-Head and Neck Surgery classifications. Dose planning was performed on intraoperative stereotactic images using multiple 4-mm isocenters. The median tumor volume was 0.112 mm3 (range, 0.05-0.447 mm3), and the median margin dose was 13 Gy (range, 10-18 Gy).

The mean and median audiologic follow-up periods were 42 months and 28 months (range, 12-144 months), respectively. Serviceable hearing was preserved in 31 of 40 (77.5%) patients with initial American Academy of Otolaryngology-Head and Neck Surgery Class A hearing. Serviceable hearing was preserved in 40 of 79 (64.5%) patients with GR Grade I or II pre-SRS hearing. Ninety-two patients had GR Grade I, II, or III hearing before SRS, and GR Grade I, II, or III hearing was maintained in 78 patients (85%). Hearing grades improved in 7 patients. Facial and trigeminal nerve function was preserved in all patients. The tumor control rate (freedom from additional intervention) was 99.0% (95 of 96) at a median follow-up of 28 months (range, 12-144 months). One patient underwent tumor resection 18 months after radiosurgery.

SRS is a minimally invasive first-line management option for patients with intracanalicular tumors and provides high rates of hearing preservation with minimal morbidity 12).


40 patients with 40 unilateral VS in the period 1973 to 1996 (mean 3.6 years). Twenty-seven tumours (67.5%) revealed growth and 13 tumours (32%) had no measurable growth. Four growth patterns were observed: (i) 15 tumours (37.5%) exhibited constant growth; (ii) 13 tumours (32.5%) had no measurable growth; (iii) 8 tumours (20%) revealed growth subsequent to a no-growth period; and (iv) 4 tumours (10%) manifested different growth patterns during the observation period. The mean diameter growth per year was 3.2 mm. The findings of the present study, especially those achieved in groups B (the non-growing tumours) and C (tumour growth subsequent to a silent period), question the reliability of the results achieved by radiosurgery, as no tumour growth may occur with no intervention13).

Case reports


A unique case of unilateral widening of the internal auditory canal (IAC) with no significant contact with an ipsilateral intracanalicular vestibular schwannoma (VS), raising the issue of the cause(s) of this IAC widening.

The medical record and radiologic data were reviewed of a patient presenting an enlarged unilateral IAC, which led to the diagnosis of an intracanalicular VS that could not account for the dilation.

The patient had a unilateral dilation of the IAC that did not match the ipsilateral VS he had. As a result, this case motivated discussion of whether such dilation of the IAC was congenitally asymmetrical or the result of the mechanisms involved in the widening of the IAC.

Although asymmetry of IAC is a current notion, this case demonstrates a contrario that increased pressure exerted on the walls of the IAC cannot be the only mechanism in such widening 14).


The first reported case of hemifacial spasm responsive to gamma knife radiosurgery in a patient with an intracanalicular vestibular schwannoma. Both the resolution of the spasm as well as tumor growth control were achieved with a single session of gamma knife radiosurgery. We report a 49-year-old male patient with a 6-month history of right-sided hearing loss and hemifacial spasm. MR examination revealed an intracanalicular vestibular schwannoma. The patient was treated with radiosurgery and received 13 Gy to the 50 % isodose line. Tumor growth control was achieved and no change in the tumor volume was present at the last follow-up at 22 months. The hemifacial spasm completely resolved after one year. Surgical removal of the presumably causative mass lesion has been reported to be the sole treatment in secondary hemifacial spasm. This case report indicates that it may be responsive to gamma knife radiosurgery. Whether or not this might be a treatment option in selected refractory cases of hemifacial spasm remains to be defined 15).


A 68-year-old man with complete deafness of the left ear since childhood, who developed sudden, profound sensorineural hearing loss in the right ear. Magnetic resonance imaging revealed a small right-sided intracanalicular tumor. Treatment with high-dose corticosteroids produced only minimal improvement in hearing. Subsequent emergency decompression and resection of a VS resulted in rapid improvement and restoration of hearing, with facial nerve preservation. Although most neurotologic lesions in patients with hearing in only one ear are managed nonsurgically, resection of small tumors in the setting of sudden hearing loss should be considered in selected cases. This finding indicates that a therapeutic window may exist during which sudden hearing loss caused by intracanalicular tumors is reversible 16).


An unusual case in which they recognized an additional branch arising from the jugular bulb. Three-dimensional computed tomography (3-D CT) revealed this anomaly beforehand, enabling us to avert excessive bleeding upon resection of the tumour. The abnormal vein was thought to be a remnant of the petrosquamosal sinus in the embryonic stage 17).

1) Deep NL, Patel AC, Hoxworth JM, Barrs DM. Pantopaque contrast mimicking intracanalicular vestibular schwannoma. Laryngoscope. 2016 Oct 11. doi: 10.1002/lary.26340. [Epub ahead of print] PubMed PMID: 27726152.
2) Wuertenberger CJ, Rosahl SK. Vertigo and tinnitus caused by vascular compression of the vestibulocochlear nerve, not intracanalicular vestibular schwannoma: review and case presentation. Skull Base. 2009 Nov;19(6):417-24. doi: 10.1055/s-0029-1220209. PubMed PMID: 20436843; PubMed Central PMCID: PMC2793889.
3) Quesnel AM, McKenna MJ. Current strategies in management of intracanalicular vestibular schwannoma. Curr Opin Otolaryngol Head Neck Surg. 2011 Oct;19(5):335-40. doi: 10.1097/MOO.0b013e32834a3fa7. Review. PubMed PMID: 22552696.
4) Turek G, Cotúa C, Zamora RE, Tatagiba M. Endoscopic assistance in retrosigmoid transmeatal approach to intracanalicular vestibular schwannomas – An alternative for middle fossa approach. Technical note. Neurol Neurochir Pol. 2017 Jan 19. pii: S0028-3843(16)30222-5. doi: 10.1016/j.pjnns.2016.12.005. [Epub ahead of print] PubMed PMID: 28162791.
5) Colletti V, Fiorino F. Is the middle fossa approach the treatment of choice for intracanalicular vestibular schwannoma? Otolaryngol Head Neck Surg. 2005 Mar;132(3):459-66. PubMed PMID: 15746862.
6) Kang WS, Kim SA, Yang CJ, Nam SH, Chung JW. Surgical outcomes of middle fossa approach in intracanalicular vestibular schwannoma. Acta Otolaryngol. 2016 Nov 25:1-4. [Epub ahead of print] PubMed PMID: 27885877.
7) Samii M, Metwali H, Gerganov V. Efficacy of microsurgical tumor removal for treatment of patients with intracanalicular vestibular schwannoma presenting with disabling vestibular symptoms. J Neurosurg. 2016 Jun 17:1-6. [Epub ahead of print] PubMed PMID: 27315031.
8) Kirchmann M, Karnov K, Hansen S, Dethloff T, Stangerup SE, Caye-Thomasen P. Ten-Year Follow-up on Tumor Growth and Hearing in Patients Observed With an Intracanalicular Vestibular Schwannoma. Neurosurgery. 2016 Aug 26. [Epub ahead of print] PubMed PMID: 27571523.
9) Lee JD, Park MK, Kim JS, Cho YS. The factors associated with tumor stability observed with conservative management of intracanalicular vestibular schwannoma. Otol Neurotol. 2014 Jun;35(5):918-21. doi: 10.1097/MAO.0000000000000338. PubMed PMID: 24686291.
10) Pennings RJ, Morris DP, Clarke L, Allen S, Walling S, Bance ML. Natural history of hearing deterioration in intracanalicular vestibular schwannoma. Neurosurgery. 2011 Jan;68(1):68-77. doi: 10.1227/NEU.0b013e3181fc60cb. PubMed PMID: 21099722.
11) Roche PH, Soumare O, Thomassin JM, Régis J. The wait and see strategy for intracanalicular vestibular schwannomas. Prog Neurol Surg. 2008;21:83-8. doi: 10.1159/000156710. PubMed PMID: 18810203.
12) Niranjan A, Mathieu D, Flickinger JC, Kondziolka D, Lunsford LD. Hearing preservation after intracanalicular vestibular schwannoma radiosurgery. Neurosurgery. 2008 Dec;63(6):1054-62; discussion 1062-3. doi: 10.1227/01.NEU.0000335783.70079.85. PubMed PMID: 19057318.
13) Thomsen J, Charabi S, Tos M, Mantoni M, Charabi B. Intracanalicular vestibular schwannoma–therapeutic options. Acta Otolaryngol Suppl. 2000;543:38-40. PubMed PMID: 10908971.
14) Kania RE, Herman P, Guichard JP, Tran Ba Huy P. [Dilation of the internal auditory canal and intracanalicular vestibular schwannoma: what are the mechanisms involved?]. Ann Otolaryngol Chir Cervicofac. 2008 Nov;125(5):256-60. doi: 10.1016/j.aorl.2008.07.006. French. PubMed PMID: 18786666.
15) Peker S, Ozduman K, Kiliç T, Pamir MN. Relief of hemifacial spasm after radiosurgery for intracanalicular vestibular schwannoma. Minim Invasive Neurosurg. 2004 Aug;47(4):235-7. PubMed PMID: 15346321.
16) Meiteles LZ, Liu JK, Couldwell WT. Hearing restoration after resection of an intracanalicular vestibular schwannoma: a role for emergency surgery? Case report and review of the literature. J Neurosurg. 2002 Apr;96(4):796-800. PubMed PMID: 11990824.
17) Tsutsumi T, Tsunoda A, Shimamoto K, Komatsuzaki A. Aberrant jugular bulb vein obstructing approach to intracanalicular vestibular schwannoma. J Laryngol Otol. 1998 Aug;112(8):772-4. PubMed PMID: 9850321.

Spinal schwannoma


Incidence: 0,3-0,4/100.000/yr.

Schwannomas have an incidence of 3% of all spinal tumors.

Most occur sporadically and are solitary, but they may also be associated with Neurofibromatosis type 2, but can occur with Neurofibromatosis type 1.

Spinal schwannoma constitutes approximately 25% of the intradural spinal tumors 1) 2) 3) 4) 5) 6) 7). 8) 9) 10) 11) 12).


In a paraspinal location, they are the commonest cause of intradural extramedullary tumors but may also be extradural or extramedullary 13).

Most are entirely intradural, but 8-32 % may be completely extradural 14) 15). 1-19 % are a combination, 6-23 % are dumbbell spinal schwannomas, and 1 % are intramedullary schwannomas.

The most common location of spinal schwannomas are the lumbar spine (48%) 16).

Schwannomas are frequently located in the extramedullary region, and may present as dumbbell shaped in 10-15% of cases. They may also be located at the intramedullary region. Ten percent of the tumors were in the extradural location, and 1% in the intradural intramedullary regional location.

Up to 2.7% of schwannomas are located in the retroperitoneal region 17).

Most arise from the dorsal root of spinal nerve (sensory) rootlets (75%). Paraspinal schwannomas involve the dorsal nerve roots, affecting people in the fourth and fifth decades of life 18).



Antoni A and Antoni B tissue.

Clinical features

Patients typically present with local pain. Early symptoms are often radicular.

Neurological deficits develop late.

Tumor may cause radiculopathy, myelopathy, radiculomyelopathy or cauda equina syndrome.


The final diagnosis should be established by clinical findings and imaging methods and MRI is the best method for diagnosis and differential diagnosis.

The size and specific margins of the mass demonstrate the localization and invasion to the contiguous structures. The changes such as foramen enlargement and erosion in the pedicles detected in the direct graphs may be seen as masses with sharp margins and involve the peripheral contrast in the CT scans.

Paraspinal schwannomas are frequently asymptomatic and diagnosed incidentally on imaging of the spine 19).


Surgical resection is the treatment of choice 20) 21).

They need a tailored treatment, which in most cases works through one surgical approach. Usually it is possible to perform a complete resection with a good postoperative prognosis 22).

Unlike neurofibromas, schwannomas do not arise from the nerve fibers and so the tumor is easily separated from nerve fibers without neurologic compromise. In the rare case that this is impossible, the remnant tumor may be followed up radiographically if it is histologically benign. Malignant schwannomas are treated with adjuvant radiation therapy.

In the series of Asazuma et al., a posterior approach was used in 35 patients; 7 others underwent a combined anterior and posterior approach. A posterior approach was used for all type IIa and IIIa tumors, and for some type IIIb (upper cervical), IV, and VI tumors; a combined posterior and anterior approach was used for type IIb and the remainder of type IV and VI. Reconstruction was performed using spinal instrumentation in 4 patients (9.5%). Resection was subtotal in 6 patients (14.3%) and total in 36 (85.7%). 23).


Recurrence is rare after total excision (except in neurofibromatosis).

The risk for motor deficit is higher for schwannomas than for neurofibromas, for cervical vs. lumbar tumors, and for cervical tumors wiyh extradural extension.

Case series


The subjects were 48 patients (22 males and 26 females) with spinal schwannoma who were classified into three subgroups: iso/homo, high/rim, and hetero/hetero, based on T2WI/contrast T1WI. A retrospective analysis of tumor size and MIB-1 index was performed in the context of these MRI findings. Intraoperative findings and pre- and postoperative motor performance were also examined.

The average tumor size was 32.4 mm (range 10-130 mm) and the average MIB-1 index was 3.8% (range 1-12). In the three subgroups, there were no significant differences in sex, age, duration of disease, tumor lesion, and dumbbell type. In the hetero/hetero group, the tumor size was significantly greater and the MIB-1 index was significantly higher (both P < 0.05), than the other two groups. The tumor adherence rate was significantly higher for hetero tumors (P < 0.05) and preoperative paralysis was more common in cases with tumor adhesion. The rate of paralysis improvement at 1 month was significantly lower for hetero tumors, but all cases had improved at 6 months.

Contrast T1WI MRI was useful for prediction of the proliferative activity and growth of spinal schwannomas, which are associated with increased tumor size and adhesion. A heterogeneous pattern on contrast T1WI indicated an increase in size and adhesion of the tumor. This pattern reflected the preoperative motor status and postoperative motor recovery 24).

Thirty-two patients with giant spinal schwannomas underwent surgery between September 1998 and May 2013. Tumor size ranged from 2.5 cm to 14.6 cm with a median size of 5.8 cm. There were 9 females (28.1%) and 23 males (71.9%), and the median age was 47 years (range 23-83 years). The median follow-up duration was 36.0 months (range 12.2-132.4 months). Three patients (9.4%) experienced recurrence and required further treatment. All recurrences developed following subtotal resection (STR) of cellular or melanotic schwannoma. There were 3 melanotic (9.4%) and 6 cellular (18.8%) schwannomas included in this study. Among these histological variants, a 33.3% recurrence rate was noted. In 1 case of melanotic schwannoma, malignant transformation occurred. No recurrence occurred following gross-total resection (GTR) or when a fibrous capsule remained due to its adherence to functional nerve roots.

Resection is the treatment of choice for symptomatic or growing giant schwannomas, frequently requiring anterior or combined approaches, with the goals of symptom relief and prevention of recurrence. In this series, tumors that underwent GTR, or where only capsule remained, did not recur. Only melanotic and cellular schwannomas that underwent STR recurred 25).


Consecutive 49 patients with intradural extramedullary (IDEM) schwannoma were surgically resected: 31 patients via MIS approach (MIS group), 6 patients via muscle-splitting using tubular retractor, and 25 patients via unilateral hemilaminectomy preserving the contralateral paraspinal muscle. Eighteen patients underwent total laminectomy (TL group). Medical record including perioperative data and radiologic data were reviewed.

On initial magnetic resonance image, mean maximal sagittal diameter of tumor was 23.9 mm and 26.9 mm, and mean maximal axial diameter was 16.1 mm and 22.8 mm in MIS and TL group, respectively (p=0.452 and p=0.011, respectively). The foraminal extension of tumor was identified in 8 in MIS and 9 in TL group (p=0.081). The tumor location involved was mostly observed in 20 lumbar spines in MIS group and 17 cervicothoracic spines in TL group (p=0.001). Intraoperatively, all tumors in MIS group could be totally resected with reduced operative time and blood loss. During the follow-up period of 38.2 months and 51.2 months in the MIS and TL group, the clinical improvement was not different between the surgical approaches (p=0.332).

Safe and complete resection of IDEM schwannoma was obtained through MIS approach. Regardless of sagittal extension of tumor, axial diameter within 16 mm-sized schwannoma located at the lumbar spine could be an effective indication for MIS approach even for foraminal extension 26).


Conti et al., present a series of 179 spinal neurinomas consecutively observed at the Department of Neurosurgery at the University of Florence for a period of 30 years (between 1967 and 1997). We decided to limit the retrospective study to obtain at least 5 years of follow-up. Therefore, 20 additional neurinomas treated between 1997 and 2002 were excluded.

All the cases are evaluated under statistical, clinical, neuroradiological, and surgically technical profiles based on data from clinical records and from periodic check-ups after surgery. In particular, the results are analyzed on the basis of an accurate pre- and postsurgical evaluation using Karnofsky’s scale and Kleklamp-Samii’s scoring system.

We treated 179 spinal neurinomas in 152 (93 male and 59 female) patients. The mean age was 44.3. In 33 cases the neurinoma was sited in the cervical tract, in 59 cases in the dorsal tract, and in 87 cases in the lumbo-sacral tract. Eleven patients harbored Recklinghausen’s neurofibromatosis (7 NF1 and 4 NF2 of which 1 was intramedullary). In 123 cases the neurinoma was intradural, in 11 cases it was extradural, in 2 intra/extradural, in 9 it had a dumbbell form, and in 2 cases it was intramedullary; the remaining cases had neurofibromatosis. The most common presurgical symptom was segmental pain. Total removal of the lesion was possible in the first operation for 174 neurinomas. We encountered 3 cases of malignant neurinoma of which 1 was in NF2. The result of surgery was recovery in 108 cases; 2 patients with NF2 died, and local recurrence occurred even after total exeresis (excision) and radiotherapy in the cases of malignant neurinoma.

Schwannomas represent the most frequent tumor lesions of the spine with prevalence for the cervical-inferior tract and the dorso-lumbar passage. Intramedullary neurinomas are rarely observed. The total surgical removal of neurinomas is often an attainable goal, and clinical improvement is the common outcome with exception to malignant forms and NF2 neurofibromatosis. We describe a series of 179 treated schwannomas 27).


Are spinal schwannomas as benign as we think? To what extent do patients recover? Are patients prone to develop late complications such as cystic myelopathy or symptomatic spinal deformity? Is their life expectancy compromised? In an effort to answer these questions, the authors analyzed the long-term outcome for 187 patients from one neurosurgical department with surgically treated spinal schwannoma. Median follow-up period was 12.9 years (2454 patient years). One-fifth of the patients considered themselves free of symptoms at follow-up examination. The most common late complaint was local pain (46%), followed by radiating pain (43%), paraparesis (31%), radicular deficit (28%), sensory deficit due to a spinal cord lesion (27%), and difficulty voiding (19%). Late complications occurred in 21% of the patient population, including cystic myelopathy (2%), spinal arachnoiditis (6%), spinal deformity (6%), and troublesome pain (7%). Life expectancy of the patients corresponded to that of the general population 28).

1) Engelhard HH, Villano JL, Porter KR, et al. Clinical presentation, histology, and treatment in 430 patients with primary tumors of the spinal cord, spinal meninges, or cauda equina. J Neurosurg Spine. 2010;13:67–77.
2) Safavi-Abbasi S, Senoglu M, Theodore N, et al. Microsurgical management of spinal schwannomas: evaluation of 128 cases. J Neurosurg Spine. 2008;9:40–47.
3) Holland K, Kaye AH. Spinal tumors in neurofibromatosis-2: management considerations – a review. J Clin Neurosci. 2009;16:169–177.
4) Klekamp J, Samii M. Surgery of spinal nerve sheath tumors with special reference to neurofibromatosis. Neurosurgery. 1998;42:279–289.
5) Celli P, Trillò G, Ferrante L. Spinal extradural schwannoma. J Neurosurg Spine. 2005;2:447–456.
6) Jankowski R, Szmeja J, Nowak S, Sokół B, Blok T. Giant schwannoma of the lumbar spine: a case report. Neurol Neurochir Pol. 2010;44:91–95.
7) , 15) , 16) Conti P, Pansini G, Mouchaty H, Capuano C, Conti R. Spinal neurinomas: retrospective analysis and long-term outcome of 179 consecutively operated cases and review of the literature. Surg Neurol 2004; 61: 34-43.
8) , 14) , 28) Seppälä MT, Haltia MJ, Sankila RJ, Jääskeläinen JE, Heiskanen O. Long-term outcome after removal of spinal schwannoma: a clinicopathological study of 187 cases. J Neurosurg. 1995 Oct;83(4):621-6. PubMed PMID: 7674010.
9) De Verdelhan O, Haegelen C, Carsin-Nicol B, et al. MR imaging features of spinal schwannomas and meningiomas. J Neuroradiol. 2005;32:42–49.
10) Ahn DK, Park HS, Choi DJ, Kim KS, Kim TW, Park SY. The surgical treatment for spinal intradural extramedullary tumors. Clin Orthop Surg. 2009;1:165–172.
11) Sim JE, Noh SJ, Song YJ, Kim HD. Removal of intradural-extramedullary spinal cord tumors with unilateral limited laminectomy. J Korean Neurosurg Soc. 2008;43:232–236.
12) McCormick PC, Post KD, Stein BM. Intradural extramedullary tumors in adults. Neurosurg Clin N Am. 1990;1:591–608.
13) , 20) Wein S, Gaillard F. Intradural spinal tumours and their mimics: A review of radiographic features. Postgrad Med J. 2013;89(1054):457–69.
17) Cury J, Coelho RF, Srougi M. Retroperitoneal schwannoma: Case series and literature review. Clin São Paulo Braz. 2007;62(3):359–62.
18) , 19) , 21) Chamberlain MC, Tredway TL. Adult primary intradural spinal cord tumors: A review. Curr Neurol Neurosci Rep. 2011;11(3):320–8.
22) Krätzig T, Dreimann M, Klingenhöfer M, Floeth FW, Krajewski K, Eicker SO. Treatment of large thoracic and lumbar paraspinal schwannoma. Acta Neurochir (Wien). 2015 Jan 11. [Epub ahead of print] PubMed PMID: 25577451.
23) Asazuma T, Toyama Y, Maruiwa H, Fujimura Y, Hirabayashi K. Surgical strategy for cervical dumbbell tumors based on a three-dimensional classification. Spine (Phila Pa 1976). 2004 Jan 1;29(1):E10-4. PubMed PMID: 14699292.
24) Kobayashi K, Imagama S, Ando K, Hida T, Ito K, Tsushima M, Ishikawa Y, Matsumoto A, Morozumi M, Tanaka S, Ishiguro N. Contrast MRI Findings for Spinal Schwannoma as Predictors of Tumor Proliferation and Motor Status. Spine (Phila Pa 1976). 2017 Feb;42(3):E150-E155. doi: 10.1097/BRS.0000000000001732. PubMed PMID: 27306258.
25) Sowash M, Barzilai O, Kahn S, McLaughlin L, Boland P, Bilsky MH, Laufer I. Clinical outcomes following resection of giant spinal schwannomas: a case series of 32 patients. J Neurosurg Spine. 2017 Jan 13:1-7. doi: 10.3171/2016.9.SPINE16778. [Epub ahead of print] PubMed PMID: 28084933.
26) Lee SE, Jahng TA, Kim HJ. Different Surgical Approaches for the Spinal Schwannoma: A Single Surgeon’s Experience with 49 Consecutive Cases. World Neurosurg. 2015 Aug 29. pii: S1878-8750(15)01043-8. doi: 10.1016/j.wneu.2015.08.027. [Epub ahead of print] PubMed PMID: 26325210.
27) Conti P, Pansini G, Mouchaty H, Capuano C, Conti R. Spinal neurinomas: retrospective analysis and long-term outcome of 179 consecutively operated cases and review of the literature. Surg Neurol. 2004 Jan;61(1):34-43; discussion 44. Review. PubMed PMID: 14706374.

Update: Parinaud’s Syndrome

Parinaud’s syndrome (Paralysie des mouvements associe´s des yeux named for Henri Parinaud (1844–1905). 1) is a supranuclear paralysis of vertical gaze 2) resulting from damage to the mesencephalon 3).




Parinaud’s Syndrome results from injury, which compresses the the quadrigeminal plate at the rostral interstitial nucleus of medial longitudinal fasciculus (riMLF), specifically, compression or ischemic damage of the mesencephalic tectum, including the superior colliculus adjacent oculomotor (origin of cranial nerve III) and Edinger-Westphal nuclei, causing dysfunction to the motor function of the eye.

Pineal region tumors.

A dilated suprapineal recess can compress the mesencephalic tectum, due to hydrocephalus.

Stroke or brainstem hemorrhage in the upper part.

Guillain Barré syndrome

Myasthenia gravis



Gradual benign loss of upgaze in senescence.

Sylvian aqueduct syndrome

Aberrant regeneration of the third nerve

Limited upgaze in elderly patients

Progressive supranuclear palsy

Niemann-pick disease

Whipple’s disease.

Classically, it has been associated with three major groups:

Pineal region tumor: Pinealoma (intracranial germinomas) are the most common lesion producing this syndrome).

Women in their 20s-30s with multiple sclerosis.

A 26 year old Pakistani lady with first presentation of a demyelinating event, presenting as Parinaud’s syndrome. A video demonstrates a convergence-retraction nystagmus on upgaze and failure of accommodation, and her brain imaging confirms a corresponding pre-tectal contrast enhancing T2 hyperintense lesion suggestive of demyelination 4).

Older patients following stroke of the upper brainstem However, any other compression, ischemia or damage to this region can produce these phenomena: obstructive hydrocephalus, midbrain hemorrhage, cerebral arteriovenous malformation, trauma and brainstem toxoplasmosis infection. Neoplasms and giant aneurysms of the posterior fossa have also been associated with the midbrain syndrome.

Vertical supranuclear ophthalmoplegia has also been associated with metabolic disorders, such as Niemann-Pick disease, Wilson’s disease, kernicterus, and barbiturate overdose.

Isolated Oculomotor Nerve Nucleus Infarct 5).

Unilateral vascular ischemic lesion 6).

A case of longstanding, undiagnosed spontaneous intracranial hypotension (SIH) with an acute presentation of Parinaud’s syndrome, in whom serial imaging demonstrated development of a midbrain mass. The patient was ultimately diagnosed with tumefactive venous infarction secondary to SIH. However, this patient underwent a brainstem biopsy, which in retrospect may have been avoidable. This case demonstrates the imaging features of tumefactive venous infarction in SIH and highlights the risk of misinterpretation as a neoplasm with potentially catastrophic consequences 7).

Migraine 8).

Miller Fisher syndrome 9).

Clinical features

Parinaud’s syndrome, includes multiple clinical signs, with the most prominent being paralysis of upward gaze.

Parinaud’s Syndrome is a cluster of abnormalities of eye movement and pupil dysfunction, characterized by:

Paralysis of upgaze: Downward gaze is usually preserved. This vertical palsy is supranuclear, so doll’s head maneuver should elevate the eyes, but eventually all upward gaze mechanisms fail.

Pseudo-Argyll Robertson pupils: Accommodative paresis ensues, and pupils become mid-dilated and show light-near dissociation.

Convergence-Retraction nystagmus: Attempts at upward gaze often produce this phenomenon. On fast up-gaze, the eyes pull in and the globes retract. The easiest way to bring out this reaction is to ask the patient to follow down-going stripes on an optokinetic drum.

Eyelid retraction (Collier’s sign) Conjugate down gaze in the primary position: “setting-sun sign”. Neurosurgeons will often see this sign most commonly in patients with failed ventriculoperitoneal shunts. It is also commonly associated with bilateral papilledema. It has less commonly been associated with spasm of accommodation on attempted upward gaze, pseudoabducens palsy (also known as thalamic esotropia) or slower movements of the abducting eye than the adducting eye during horizontal saccades, see-saw nystagmus and associated ocular motility deficits including skew deviation, oculomotor nerve palsy, trochlear nerve palsy and internuclear ophthalmoplegia.


MRI is very helpful in determining the cause and thus guiding appropriate treatment.

Case reports

A 3-year-old boy presented with headache, disturbance of consciousness, and Parinaud’s syndrome. Magnetic resonance (MR) imaging revealed a pineal mass lesion, and total resection of the tumor was achieved. The histological diagnosis was mature teratoma. He did not receive further treatment, and did well without recurrence for 20 years. However, he suffered headache 21 years after resection, and MR imaging revealed a homogeneously enhanced pineal mass with low minimum apparent diffusion coefficient value and proton MR spectroscopy showed a huge lipid peak. The levels of tumor markers were not elevated. Cerebrospinal fluid (CSF) cytology found atypical cells with large nuclei and irregularly shaped nucleoli. To elucidate the relationship between the primary and recurrent tumors, we reviewed the histological specimens and CSF cytology at the initial treatment and found a subset of incompletely differentiated components resembling fetal tissues in the histological specimen and atypical large cells in the CSF. Based on these radiological and histological findings, Mano et al., presume that the recurrent disease was disseminated germinoma after the resection of disseminated IMT. He received chemotherapy and craniospinal radiation therapy, and the enhanced lesion and atypical cells in the CSF disappeared. This case demonstrates that disseminated IMT can be controlled for the long term without adjuvant therapy, but may recur as germinoma. Tumor dormancy may account for this unusual course 10).

1) Parinaud H. Paralysie des movements associe´s des yeux. Archives de Neurologie 1883;5:145–72.
2) Pierrot-Deseilligny C, Chain F, Gray M, et al. Parinaud’s syndrome. Brain 1982;105:667–96.
3) Pearce JM. Parinaud’s syndrome. J Neurol Neurosurg Psychiatry. 2005 Jan;76(1):99. PubMed PMID: 15608003; PubMed Central PMCID: PMC1739319.
4) Gnanapavan S, Sillery E, Acheson JF, Toosy AT. Parinaud’s syndrome – A rare presentation of clinically isolated syndrome. Mult Scler Relat Disord. 2014 May;3(3):398-401. doi: 10.1016/j.msard.2013.09.003. PubMed PMID: 25876480.
5) Kumar Y, Hooda K, Sapire J. A Case Report of Isolated Oculomotor Nerve Nucleus Infarct: A Rare Cause of Parinaud’s Syndrome. Conn Med. 2016 Mar;80(3):167-8. PubMed PMID: 27169301.
6) Serino J, Martins J, Páris L, Duarte A, Ribeiro I. Parinaud’s syndrome due to an unilateral vascular ischemic lesion. Int Ophthalmol. 2015 Apr;35(2):275-9. doi: 10.1007/s10792-015-0045-y. PubMed PMID: 25649259.
7) Bray TJ, Chandrashekar H, Rees J, Burke A, Merve A, Thust S. Venous infarction mimicking a neoplasm in spontaneous intracranial hypotension: an unusual cause of Parinaud’s syndrome. J Surg Case Rep. 2016 Mar 17;2016(3). pii: rjw037. doi: 10.1093/jscr/rjw037. PubMed PMID: 26987945; PubMed Central PMCID: PMC4794942.
8) Jumma OK, Hamdalla HM. Parinaud’s syndrome due to migraine. Can J Neurol Sci. 2013 Jan;40(1):125. PubMed PMID: 23427358.
9) Mallia M, Chircop C, Aquilina J. An unusual case of Parinaud’s syndrome. BMJ Case Rep. 2012 Nov 21;2012. pii: bcr2012006722. doi: 10.1136/bcr-2012-006722. PubMed PMID: 23175005; PubMed Central PMCID: PMC4544412.
10) Mano Y, Kanamori M, Kumabe T, Saito R, Watanabe M, Sonoda Y, Tominaga T. Extremely Late Recurrence 21 Years after Total Removal of Immature Teratoma: A Case Report and Literature Review. Neurol Med Chir (Tokyo). 2017 Jan 15;57(1):51-56. doi: 10.2176/ PubMed PMID: 27928096; PubMed Central PMCID: PMC5243165.

Update: Microvascular decompression for trigeminal neuralgia

Microvascular decompression (MVD) via lateral suboccipital approach is the standard surgical intervention for trigeminal neuralgia (TN).


It has proven to be the most successful and durable surgical approach for trigeminal neuralgia (TN).

However, not all patients with TN manifest unequivocal neurovascular compression (NVC). Furthermore, over time patients with an initially successful MVD manifest a relentless rate of TN recurrence.

It does not achieve 100 % cure rate. Re-exploration of the posterior fossa may carry increased risk over first-time MVD and is not always successful, so other treatments are needed.

Case series


Clinical characteristics, intraoperative findings, and postoperative curative effects were analyzed in 72 patients with trigeminal neuralgia who were treated by microvascular decompression. The patients were divided into arterial and venous compression groups based on intraoperative findings. Surgical curative effects included immediate relief, delayed relief, obvious reduction, and invalid result. Among the 40 patients in the arterial compression group, 32 had immediate pain relief of pain (80.0%), 5 cases had delayed relief (12.5%), and 3 cases had an obvious reduction (7.5%). In the venous compression group, 12 patients had immediate relief of pain (37.5%), 13 cases had delayed relief (40.6%), and 7 cases had an obvious reduction (21.9%). During 2-year follow-up period, 6 patients in the arterial compression group experienced recurrence of trigeminal neuralgia, but there were no recurrences in the venous compression group. Simple artery compression was followed by early relief of trigeminal neuralgia more often than simple venous compression. However, the trigeminal neuralgia recurrence rate was higher in the artery compression group than in the venous compression group 1).


Indocyanine green videoangiography was performed in 17 TN patients undergoing microvascular decompression.

von Eckardstein et al., focused on whether ICG angiography is helpful in determining the site of conflict, particularly when not directly visible via the microscope, and whether fluorescence is strong enough to shine through the nerve obliterating the direct view of the compressing vessel.

In four patients, the site of conflict was immediately apparent after opening the cerebellopontine cistern, and ICG angiography did not provide the neurosurgeon with additional information. In another two patients, imaging quality and fluorescence were too poor. Of the remaining 11 patients with a hidden site of nerve-vessel conflict, ICG angiography was found to be helpful in anticipating the site of compression and the course of the artery in 7 patients, particularly in regard to the so-called shining-through effect through fiber bundles of the thinned nerve. Of all the patients, 88% reported at least improvement or cessation of their symptoms, including all of the patients with a shine-through effect.

ICG angiography could be a helpful adjunct in decompressing the trigeminal nerve and can guide the surgeon to the nerve-vessel conflict. Intensity of the fluorescence is powerful enough to shine through thinned and splayed trigeminal nerve fiber bundles 2).

A retrospective review of patient records from 1998 to 2015 identified a total of 942 patients with TN and 500 patients who underwent MVD. After excluding several cases, 306 patients underwent MVD as their first surgical intervention and 175 patients underwent subsequent MVD. Demographics and clinicopathological data and outcomes were obtained for analysis.

In patients who underwent subsequent MVD, surgical intervention was performed at an older age (55.22 vs 49.98 years old, p < 0.0001) and the duration of symptoms was greater (7.22 vs 4.45 years, p < 0.0001) than for patients in whom MVD was their first surgical intervention. Patients who underwent initial MVD had improved pain relief and no improvement in pain rates compared with those who had subsequent MVD (95.8% and 4.2% vs 90.3% and 9.7%, respectively, p = 0.0041). Patients who underwent initial MVD had significantly lower rates of facial numbness in the pre- and postoperative periods compared with patients who underwent subsequent MVD (p < 0.0001). The number of complications in both groups was similar (p = 0.4572).

The results demonstrate that patients who underwent other procedures prior to MVD had less pain relief and a higher incidence of facial numbness despite rates of complications similar to patients who underwent MVD as their first surgical intervention 3).


A retrospective analysis of clinical data was performed in 99 patients who underwent MVD from May 2012 to June 2015. The outcome data from 27 MVD operations for 27 patients aged 70-80 years (mean 74.6 years) were compared with 72 MVD operations with 72 patients aged 25-69 years (mean 55.7 years). Preoperative comorbidities were recorded and postoperative worsening comorbidities and non-neurological complications were evaluated at discharge. Efficacy of the surgery and neurological complications were evaluated in July 2015.

No decrease in activity of daily living was found in any patient. Complete pain relief without medication was achieved in 77.8% and partial pain relief in 14.8% in the elderly group, and 83.3% and 9.7%, respectively, in the non-elderly group (p=0.750). Permanent neurological complication was not observed in the elderly group, whereas Vth nerve and VIIIth nerve complications were observed in the non-elderly group. Rates of preoperative multiple comorbidities and of cardiovascular comorbidity were significantly higher in the elderly group (p<0.01). Worsening comorbidity and new pathology at discharge were mainly hypertension in both groups, but glaucoma attack and asthma attack were observed in the elderly group. All pathologies were successfully managed.

MVD for elderly patients with TN can be achieved safely with careful perioperative management. Information of comorbidity should be shared with all staff involved in the treatment, who should work as a team to avoid worsening comorbidity. The possibility of unpredictable events in the elderly patients should always be considered 4).

Since 2004, there were a total of 51 patients with TIC and 12 with HS with available MRI scans. All patients underwent preoperative MRI to rule out non-surgical etiologies for facial pain and facial spasm, and confirm vascular compression. Follow-up after surgery was 13±22 months for the patients with TIC and 33±27 months for the patients with HS.

There were 45 responders to MVD in the TIC cohort (88%), with a Visual analog scale (VAS) of 1±3. All patients with HS responded to MVD between 25 and 100%, with a mean of 75±22%. Wound complications occurred in 10% of patients with MVD for TIC, and 1 patient reported hearing loss after MVD for HS, documented by audiogram. The congruence rate between the preoperative MRI and operative findings of vascular compression was 84% in TIC and 75% in HS.

MVD is an effective and safe modality of treatment for TIC and HS. In addition to ruling out structural lesions, MRI can offer additional information by highlighting vascular loops associated with compressions. On conventional scans as obtained here, the resolution of MRI was congruent with operative findings in 84% in TIC and 75% in HS. This review emphasizes that the decision to undertake MVD in TIC or HS should be based on clinical diagnosis and not visualization of a compressing vessel by MRI. Conversely, the presence of a compressing vessel by MRI demands perseverance by the surgeon until the nerve is decompressed 5).

The trigeminal nerve was sectioned into 5 zones. Zone 1, 2, 3, 4 was located at the rostral, caudal, ventral, and dorsal part of the nerve root entry zone (REZ) respectively, and zone 5 was located at the distal of the nerve root. This study contained 86 patients with trigeminal neuralgia underwent microvascular decompression. Every zone was exposed through preoperative imaging. During the operation, offending vessels were explored from zone 1 to zone 5, and different decompression techniques were used for different types of vessels.

Through zone exploration, the sensitivity of preoperative imaging was 96.5% and specificity was 100%. Location of the neurovascular conflict was in the zone 1 in 53.5% of the patients, zone 2 in 32.6%, zone 3 in 45.3%, zone 4 in 29.1%, and zone 5 in 34.9%. In total, 2 zones were both involved in 59.3%, and 3 zones were involved in 18.6%. All offending arteries were moved away and interposed with Teflon sponge. Offending veins of 11 patients were too small to interpose, and coagulated and cut was adopted. The other offending veins were interposed with wet gelatin and Teflon sponge, respectively 6).


Lee et al. performed a retrospective review of cases of TN Type 1 (TN1) or Type 2 (TN2) involving patients 18 years or older who underwent evaluation (and surgery when indicated) at Oregon Health & Science University between July 2006 and February 2013. Surgical and imaging findings were correlated.

The review identified a total of 257 patients with TN (219 with TN1 and 38 with TN2) who underwent high-resolution MRI and MR angiography with 3D reconstruction of combined images using OsiriX. Imaging data revealed that the occurrence of TN1 and TN2 without NVC was 28.8% and 18.4%, respectively. A subgroup of 184 patients underwent surgical exploration. Imaging findings were highly correlated with surgical findings, with a sensitivity of 96% for TN1 and TN2 and a specificity of 90% for TN1 and 66% for TN2. Conclusions Magnetic resonance imaging detects NVC with a high degree of sensitivity. However, despite a diagnosis of TN1 or TN2, a significant number of patients have no NVC. Trigeminal neuralgia clearly occurs and recurs in the absence of NVC 7).


A study comprises 42 cases of trigeminal neuralgia that underwent operation with endoscopic-assisted microvascular decompression between October 1992 and October 1998. This study was performed in the Ear, Nose, and Throat Department, Nord Hospital, in Marseille, France. The decompression was performed by means of a minimally invasive retrosigmoid approach without a cerebellar retractor. The cerebellopontine angle was then explored by a 30-degree endoscope that gives a panoramic view of this space, with clear visualization of the trigeminal nerve from the pons to Meckel’s cave, allowing for the identification of the precise location of the site of the conflict. Microvascular decompression was performed under the microscope by separating the offending vessel from the trigeminal nerve; separation was maintained by the insertion of a piece of Teflon.

The site of conflict was detected at the root entry zone of the nerve in 35 patients (83.3%) and at Meckel’s cave in 7 patients (16.7%). In 32 cases (76.2%), the type of contact between the vessel and the nerve was of the simple type (1 vessel coming in contact with the nerve in a single point); in 6 cases (14.3%), it was a multiple type (2 vessels touching the nerve in the same point); and in 4 cases (9.5%), it was a nutcracker type (2 vessels compressing the nerve between them). After at least 1-year follow-up and a single operation (cases that required a second operation for revision were considered failures), a successful result was obtained in 31 cases (73.8%), and an improvement was obtained in 4 cases (9.5%). The operation was a failure or early recurrence occurred in 7 cases (16.7%). Postoperative complications were rare. A cerebrospinal fluid leak occurred in only 1 case (2.4%) and was subsequently treated with lumbar puncture and a compressive bandage.

The minimally invasive retrosigmoid endoscopic-assisted microvascular decompression is an acceptable treatment of primary trigeminal neuralgia. Endoscopy provides a unique way to explore the cerebellopontine angle and to identify the exact location of the neurovascular conflict 8).

1) Shi L, Gu X, Sun G, Guo J, Lin X, Zhang S, Qian C. After microvascular decompression to treat trigeminal neuralgia, both immediate pain relief and recurrence rates are higher in patients with arterial compression than with venous compression. Oncotarget. 2017 Jan 20. doi: 10.18632/oncotarget.14765. [Epub ahead of print] PubMed PMID: 28122347.
2) von Eckardstein KL, Mielke D, Akhavan-Sigari R, Rohde V. Enlightening the Cerebellopontine Angle: Intraoperative Indocyanine Green Angiography in Microvascular Decompression for Trigeminal Neuralgia. J Neurol Surg A Cent Eur Neurosurg. 2016 Sep 23. PubMed PMID: 27704490.
3) Theodros D, Rory Goodwin C, Bender MT, Zhou X, Garzon-Muvdi T, De la Garza-Ramos R, Abu-Bonsrah N, Mathios D, Blitz AM, Olivi A, Carson B, Bettegowda C, Lim M. Efficacy of primary microvascular decompression versus subsequent microvascular decompression for trigeminal neuralgia. J Neurosurg. 2016 Jul 15:1-7. [Epub ahead of print] PubMed PMID: 27419826.
4) Amagasaki K, Watanabe S, Naemura K, Shono N, Nakaguchi H. Safety of microvascular decompression for elderly patients with trigeminal neuralgia. Clin Neurol Neurosurg. 2015 Dec 31;141:77-81. doi: 10.1016/j.clineuro.2015.12.019. [Epub ahead of print] PubMed PMID: 26765772.
5) Hitchon PW, Zanaty M, Moritani T, Uc E, Pieper CL, He W, Noeller J. Microvascular decompression and MRI findings in trigeminal neuralgia and hemifacial spasm. A single center experience. Clin Neurol Neurosurg. 2015 Oct 22;139:216-220. doi: 10.1016/j.clineuro.2015.10.012. [Epub ahead of print] PubMed PMID: 26519891.
6) Feng BH, Zheng XS, Liu M, Wang XQ, Wang XH, Ying TT, Li ST. Microvascular Decompression for Trigeminal Neuralgia: Zone Exploration and Decompression Techniques. J Craniofac Surg. 2015 Oct 21. [Epub ahead of print] PubMed PMID: 26501973.
7) Lee A, McCartney S, Burbidge C, Raslan AM, Burchiel KJ. Trigeminal neuralgia occurs and recurs in the absence of neurovascular compression. J Neurosurg. 2014 May;120(5):1048-54. doi: 10.3171/2014.1.JNS131410. Epub 2014 Feb 7. PubMed PMID: 24506241.
8) El-Garem HF, Badr-El-Dine M, Talaat AM, Magnan J. Endoscopy as a tool in minimally invasive trigeminal neuralgia surgery. Otol Neurotol. 2002 Mar;23(2):132-5. PubMed PMID: 11875338.

Virtual reality in neurosurgery

Virtual reality (VR), sometimes referred to as immersive multimedia, is a computer-simulated environment that can simulate physical presence in places in the real world or imagined worlds. Virtual reality can recreate sensory experiences, including virtual taste, sight, smell, sound, touch, etc.

Chan et al., highlights a selection of recent developments in research areas related to virtual reality simulation, including anatomic modeling, computer graphics and visualization, haptics, and physics simulation, and discusses their implication for the simulation of neurosurgery 1).

Medicine and surgery are turning towards simulation to improve on limited patient interaction during residency training. Many simulators today utilize virtual reality with augmented haptic feedback with little to no physical elements.

To optimize the learning exercise, it is essential that both visual and haptic simulators are presented to best present a real-world experience. Many systems attempt to achieve this goal through a total virtual interface.

Bova et al., approach has been to create a mixed-reality system consisting of a physical and a virtual component. A physical model of the head or spine is created with a 3-dimensional printer using deidentified patient data. The model is linked to a virtual radiographic system or an image guidance platform. A variety of surgical challenges can be presented in which the trainee must use the same anatomic and radiographic references required during actual surgical procedures.

Using the aforementioned techniques, they have created a ventriculostomy simulators, percutaneous radiofrequency trigeminal rhizotomy, and spinal instrumentation.

The system has provided the residents an opportunity to understand and appreciate the complex 3-dimensional anatomy of the 3 neurosurgical procedures simulated. The systems have also provided an opportunity to break procedures down into critical segments, allowing the user to concentrate on specific areas of deficiency 2).

Shakur et al., developed a real-time augmented reality simulator for percutaneous trigeminal rhizotomy using the ImmersiveTouch platform. Ninety-two neurosurgery residents tested the simulator at American Association of Neurological Surgeons Top Gun 2014. Postgraduate year (PGY), number of fluoroscopy shots, the distance from the ideal entry point, and the distance from the ideal target were recorded by the system during each simulation session. Final performance score was calculated considering the number of fluoroscopy shots and distances from entry and target points (a lower score is better). The impact of PGY level on residents’ performance was analyzed.

Seventy-one residents provided their PGY-level and simulator performance data; 38% were senior residents and 62% were junior residents. The mean distance from the entry point (9.4 mm vs 12.6 mm, P = .01), the distance from the target (12.0 mm vs 15.2 mm, P = .16), and final score (31.1 vs 37.7, P = .02) were lower in senior than in junior residents. The mean number of fluoroscopy shots (9.8 vs 10.0, P = .88) was similar in these 2 groups. Linear regression analysis showed that increasing PGY level is significantly associated with a decreased distance from the ideal entry point (P = .001), a shorter distance from target (P = .05), a better final score (P = .007), but not number of fluoroscopy shots (P = .52).

Because technical performance of percutaneous rhizotomy increases with training, they proposed that the skills in performing the procedure in there virtual reality model would also increase with PGY level, if this simulator models the actual procedure. The results confirm this hypothesis and demonstrate construct validity 3).

Alaraj et al., developed a real-time sensory haptic feedback virtual reality aneurysm clipping simulator using the ImmersiveTouch platform. A prototype middle cerebral artery aneurysm simulation was created from a computed tomographic angiogram. Aneurysm and vessel volume deformation and haptic feedback are provided in a 3-dimensional immersive virtual reality environment. Intraoperative aneurysm rupture was also simulated. Seventeen neurosurgery residents from 3 residency programs tested the simulator and provided feedback on its usefulness and resemblance to real aneurysm clipping surgery.

Residents thought that the simulation would be useful in preparing for real-life surgery. About two-thirds of the residents thought that the 3-dimensional immersive anatomic details provided a close resemblance to real operative anatomy and accurate guidance for deciding surgical approaches. They thought the simulation was useful for preoperative surgical rehearsal and neurosurgical training. A third of the residents thought that the technology in its current form provided realistic haptic feedback for aneurysm surgery.

Neurosurgical residents thought that the novel immersive VR simulator is helpful in their training, especially because they do not get a chance to perform aneurysm clippings until late in their residency programs 4).

Lemole et al., use the ImmersiveTouch (ImmersiveTouch, Inc., Chicago, IL) virtual reality platform, developed at the University of Illinois at Chicago, to simulate the task of ventriculostomy catheter placement as a proof-of-concept. Computed tomographic data are used to create a virtual anatomic volume.

Haptic feedback offers simulated resistance and relaxation with passage of a virtual three-dimensional ventriculostomy catheter through the brain parenchyma into the ventricle. A dynamic three-dimensional graphical interface renders changing visual perspective as the user’s head moves. The simulation platform was found to have realistic visual, tactile, and handling characteristics, as assessed by neurosurgical faculty, residents, and medical students.

They developed a realistic, haptics-based virtual reality simulator for neurosurgical education. The first module recreates a critical component of the ventriculostomy placement task. This approach to task simulation can be assembled in a modular manner to reproduce entire neurosurgical procedures 5).

1) Chan S, Conti F, Salisbury K, Blevins NH. Virtual reality simulation in neurosurgery: technologies and evolution. Neurosurgery. 2013 Jan;72 Suppl 1:154-64. doi: 10.1227/NEU.0b013e3182750d26. PubMed PMID: 23254804.
2) Bova FJ, Rajon DA, Friedman WA, Murad GJ, Hoh DJ, Jacob RP, Lampotang S, Lizdas DE, Lombard G, Lister JR. Mixed-reality simulation for neurosurgical procedures. Neurosurgery. 2013 Oct;73 Suppl 1:138-45. doi: 10.1227/NEU.0000000000000113. PubMed PMID: 24051877.
3) Shakur SF, Luciano CJ, Kania P, Roitberg BZ, Banerjee PP, Slavin KV, Sorenson J, Charbel FT, Alaraj A. Usefulness of a Virtual Reality Percutaneous Trigeminal Rhizotomy Simulator in Neurosurgical Training. Neurosurgery. 2015 Sep;11 Suppl 3:420-5; discussion 425. doi: 10.1227/NEU.0000000000000853. PubMed PMID: 26103444.
4) Alaraj A, Luciano CJ, Bailey DP, Elsenousi A, Roitberg BZ, Bernardo A, Banerjee PP, Charbel FT. Virtual reality cerebral aneurysm clipping simulation with real-time haptic feedback. Neurosurgery. 2015 Mar;11 Suppl 2:52-8. doi: 10.1227/NEU.0000000000000583. PubMed PMID: 25599200; PubMed Central PMCID: PMC4340784.
5) Lemole GM Jr, Banerjee PP, Luciano C, Neckrysh S, Charbel FT. Virtual reality in neurosurgical education: part-task ventriculostomy simulation with dynamic visual and haptic feedback. Neurosurgery. 2007 Jul;61(1):142-8; discussion 148-9. Review. PubMed PMID: 17621029.