Category Archives: Hydrocephalus

Update: Idiopathic normal pressure hydrocephalus

Idiopathic normal pressure hydrocephalus (iNPH) is a progressive neurodegenerative disease in the elderly with enlarged ventricles and normal or slightly elevated cerebrospinal fluid pressure, clinically characterized by an insidious onset and gradual progression of impairments of gait, balance, cognition, with urinary incontinence 1).


Normal Pressure Hydrocephalus first became recognized on March 10, 1964 as a distinct medical syndrome by Salomón Hakim, M.D., Ph.D.

The classic triad of magnetic apraxia, urinary incontinence, and dementia remain relevant into the 21(st) century as being the basis for symptomatic diagnosis and predicting potential benefit from ventriculoperitoneal shunting, though they have been greatly augmented by the addition of modern neuroimaging, particularly MRI.

Modern criteria recognize a wider range of diagnostic criteria, and new positive and negative prognostic indicators for treatment benefit have been discovered, though the mainstay remains initial drainage of a large volume of cerebrospinal fluid and monitoring for clinical improvement. Even with our advances in understanding both primary and secondary normal pressure hydrocephalus, diagnosis, management, and counseling remain challenging in this disorder 2).


In people over 65 years old, pooled prevalence obtained from specific population studies was 1.3%, almost 50-fold higher than that inferred from door-to-door surveys of dementia or Parkinsonism. Prevalence may be even higher in assisted-living and extended-care residents, with up to 11.6% of patients fulfilling the criteria for suspected iNPH and 2.0% of patients showing permanent improvement after cerebrospinal fluid (CSF) diversion. The only prospective population-based survey that reported iNPH incidence estimated 1.20 cases/1000 inhabitants/year, 15-fold higher than estimates obtained from studies based on hospital catchment areas. The incidence of shunt surgery for iNPH and SRiNPH obtained from incident cases of hospital catchment areas appears to be fewer than two cases and one case/100,000 inhabitants/year, respectively. Unfortunately, there is no population-based study reporting the real values for these two parameters.

iNPH appears to be extremely under-diagnosed. Properly designed and adequately powered population based studies are required to accurately characterize this disease’s epidemiology 3).

The prevalence of iNPH is high—for example, in Japan among people older than 65, the prevalence is between 0.5% and 2.9% 4)and the syndrome is both underdiagnosed and undertreated.


It is recommended that INPH be classified into probable, possible, and unlikely categories. It is hope that these criteria will be widely applied in clinical practice and will promote greater consistency in patient selection in future clinical investigations involving INPH 5).



All patients with idiopathic normal pressure hydrocephalus (INPH) who underwent shunting in Sweden in 2008-2010 were compared to age- and sex-matched population-based controls. Inclusion criteria were age 60-85 years and no dementia. The 10 most important vascular risk factor (VRFs) and cerebrovascular and peripheral vascular disease were prospectively assessed using blood samples, clinical examinations, and standardized questionnaires. Assessed VRFs were hypertension, hyperlipidemia, diabetes, obesity, psychosocial factors, smoking habits, diet, alcohol intake, cardiac disease, and physical activity.

In total, 176 patients with INPH and 368 controls participated. Multivariable logistic regression analysis indicated that hyperlipidemia (odds ratio [OR] 2.380; 95% confidence interval [CI] 1.434-3.950), diabetes (OR 2.169; 95% CI 1.195-3.938), obesity (OR 5.428; 95% CI 2.502-11.772), and psychosocial factors (OR 5.343; 95% CI 3.219-8.868) were independently associated with INPH. Hypertension, physical inactivity, and cerebrovascular and peripheral vascular disease were also overrepresented in INPH. Moderate alcohol intake and physical activity were overrepresented among the controls. The population-attributable risk percentage was 24%.

The findings confirm that patients with INPH have more VRFs and lack the protective factors present in the general population. Almost 25% of cases of INPH may be explained by VRFs. This suggests that INPH may be a subtype of vascular dementia. Targeted interventions against modifiable VRFs are likely to have beneficial effects on INPH 6).

Although the exact pathogenesis of NPH is unknown, many possible causes have been postulated, including cerebrovascular ischemia. Studies have demonstrated that periventricular blood flow and cerebrovascular autoregulation are reduced.

It is also thought that biomechanical changes, such as the combination of tissue distortion caused by ventricular dilation, CSF and interstitial fluid stasis, and impaired autoregulation may result in failure of drainage of neurotoxic compounds such as amyloid-b.

Increased CSF stroke volume through the aqueduct has also been demonstrated in the NPH population despite normal CSF pressures. The reaction of the cerebral mantle to all or some of these processes is poorly understood. It is thought that white matter tract connections serving the cortex could be disrupted in a variety of ways, including disconnection, swelling, stretching, and compression. Therefore, it is possible that some types of disruption may be more tolerable (i.e., more reversible) than others.

Only a few studies have seized the opportunity to reevaluate the theories of pathogenesis of NPH using developments in imaging techniques.

The disorders of Alzheimer disease, vascular dementia and normal pressure hydrocephalus are all causes of dementia in the elderly population. It is often the case that it is clinically very difficult to tell these diseases apart. All three forms of dementia share the same risk factors, which for the most part are vascular risk factors. Bateman proposes that there is an underlying vascular pathophysiology behind these conditions, which is related to the strength of the pulse waves induced in the craniospinal cavity by the arterial vascular tree. It is proposed the manifestation of the dementia in any one patient is dependant on the way that the pulsations interact with the brain and its venous and perivascular drainage. This interaction is predominately dependant on the compliance of the craniospinal cavity and the chronicity of the increased pulse wave stress 7).

Experimental animal model

Kaolin was injected bilaterally into the subarachnoid space overlying the cranial convexities in 20 adult rats. Magnetic resonance imaging (MRI) was obtained by using an 11.7 T scanner at 14, 60, 90, and 120 days after kaolin injection. Locomotor, gait, and cognitive evaluations were performed independently. Kaolin distribution and the associated inflammatory and fibrotic responses were histologically analyzed.

Evans index of ventriculomegaly showed significant progressive growth in ventricular size over all time points examined. The greatest enlargement occurred within the first 2 months. Evans index also correlated with the extent of kaolin distribution by MRI and by pathological examination at all time points. First gait changes occurred at 69 days, anxiety at 80, cognitive impairment at 81, and locomotor difficulties after 120 days. Only locomotor deterioration was associated with Evans index or the radiological evaluation of kaolin extension. Inflammatory/fibrotic response was histologically confirmed over the cranial convexities in all rats, and its extension was associated with ventricular size and with the rate of ventricular enlargement.

Kaolin injected into the subarachnoid space over the cerebral hemispheres of adult rats produces an inflammatory/fibrotic response leading in a slow-onset communicating hydrocephalus that is initially asymptomatic. Increased ventricular size eventually leads to gait, memory, and locomotor impairment closely resembling the course of human adult chronic hydrocephalus 8).


Disturbed cerebrospinal fluid (CSF) dynamics are part of the pathophysiology of normal pressure hydrocephalus (NPH).

A study investigated the contribution of established CSF dynamic parameters to mean pulse amplitude (AMP), a prognostic variable defined as mean amplitude of cardiac-related intracranial pressure pulsations during 10 min of lumbar infusion test, with the aim of clarifying the physiological interpretation of the variable. AMP(mean) and CSF dynamic parameters were determined from infusion tests performed on 18 patients with suspected NPH. Using a mathematical model of CSF dynamics, an expression for AMP(mean) was derived and the influence of the different parameters was assessed. There was high correlation between modelled and measured AMP(mean) (r = 0.98, p < 0.01). Outflow resistance and three parameters relating to compliance were identified from the model. Correlation analysis of patient data confirmed the effect of the parameters on AMP(mean) (Spearman’s ρ = 0.58-0.88, p < 0.05). Simulated variations of ±1 standard deviation (SD) of the parameters resulted in AMP(mean) changes of 0.6-2.9 SD, with the elastance coefficient showing the strongest influence. Parameters relating to compliance showed the largest contribution to AMP(mean), which supports the importance of the compliance aspect of CSF dynamics for the understanding of the pathophysiology of NPH 9).

Clinical Features

Elderly presenting with gait abnormality, cognitive decline, and urinary incontinence, with enlarged ventricles of the brain but normal or slightly elevated cerebrospinal fluid (CSF) pressure 10) 11).

Postural stability in NPH is predominantly affected by deficient vestibular functions, which did not improve after spinal tap test. Conditions which improved best were mainly independent from visual control and are based on proprioceptive functions 12).

The natural course of iNPH is symptom progression over time, with worsening in gait, balance and cognitive symptoms. This deterioration is only partially reversible.

Currently there is no pathological hallmark for iNPH 13).

It is frequently present with cerebral vasculopathy; significantly increased prevalence of cardiovascular disease iNPH patients, which provide evidence that cardiovascular disease is involved as an exposure in the development of iNPH 14).

Idiopathic normal pressure hydrocephalus (iNPH) may present, besides the classic triad of symptoms, extrapiramidal parkinsonian like movement disorders.



There is no accurate test for diagnosing normal pressure hydrocephalus or for screening for patients who will benefit from shunt surgery.

Shunting is possibly effective in iNPH (96% chance subjective improvement, 83% chance improvement on timed walk test at 6 months) (3 Class III). Serious adverse event risk was 11% (1 Class III). Predictors of success included elevated Ro (1 Class I, multiple Class II), impaired cerebral blood flow reactivity to acetazolamide (by SPECT) (1 Class I), and positive response to either external lumbar drainage (1 Class III) or repeated lumbar punctures. Age may not be a prognostic factor (1 Class II). Data are insufficient to judge efficacy of radionuclide cisternography or aqueductal flow measurement by MRI.

There is limited Class I evidence that impaired cerebral blood flow (CBF) reactivity to acetazolamide is a predictor of successful CSF shunting, but single photon emission computed tomography (SPECT) is not a practical screening tool for NPH.


There remains a lack of consensus about the role of individual imaging modalities in characterizing specific features of the condition and predicting the success of CSF shunting. Variability of clinical presentation and imperfect responsiveness to shunting are obstacles to the application of novel imaging techniques. Few studies have sought to interpret imaging findings in the context of theories of NPH pathogenesis 15).

Although attempts at predictive methodology, such as highvelocity aqueductal flow rate measurement on MRI, have achieved widespread acceptance in clinical practice, there is no Class I evidence (only 1 Class II study and 2 Class III studies) available to support this 16).


NPH is characterized by an ongoing periventricular neuronal dysfunction seen on MRI as periventricular hyperintensity (PVH). Clinical improvement after shunt surgery is associated with CSF changes indicating a restitution of axonal function. Other biochemical effects of shunting may include increased monoaminergic and peptidergic neurotransmission, breakdown of blood brain barrier function, and gliosis 17).

An MRI-based diagnostic scheme used in a multicenter prospective study (Study of Idiopathic Normal Pressure Hydrocephalus on Neurological Improvement [SINPHONI]) appears to suggest that features of disproportionately enlarged subarachnoid-space hydrocephalus (DESH) are meaningful in the evaluation of NPH 18).


In a retrospective cohort study, Kojoukhova et al evaluated brain CT or MRI scans of 390 patients with suspected iNPH. Based on a 24-h intraventricular pressure monitoring session, patients were classified into a non-NPH (n = 161) or probable iNPH (n = 229) group. Volumes of cerebrospinal fluid compartments (lateral ventricles, sylvian and suprasylvian subarachnoid spaces and basal cisterns) were visually assessed. Disproportionally enlarged subarachnoid spaces, flow void, white matter changes, medial temporal lobe atrophy and focally dilated sulci were evaluated. Moreover, we measured quantitative markers: Evans’ index (EI), the modified cella media index, mean width of the temporal horns and callosal angle.

iNPH was more likely in patients with severe volumetric disproportion between the suprasylvian and sylvian subarachnoid spaces than in those without disproportion (OR 7.5, CI 95 % 4.0-14.1, P < 0.0001). Mild disproportion (OR 2.6, CI 95 % 1.4-4.6, P = 0.001) and narrow temporal horns (OR per 1 mm 0.91, CI 95 % 0.84-0.98, P = 0.014) were also associated with an iNPH diagnosis. Other radiological markers had little association with the iNPH diagnosis in the final combined multivariate model. Interestingly, EI was higher in non-NPH than iNPH patients (0.40 vs. 0.38, P = 0.039). Preoperative radiological markers were not associated with shunt response.

Visually evaluated disproportion was the most useful radiological marker in iNPH diagnostics. Narrower temporal horns also supported an iNPH diagnosis, possibly since atrophy was more pronounced in the non-NPH than iNPH group 19).

The Evans index is useful as a marker of ventricular volume and thus has been proposed as a helpful biomarker in the diagnosis of normal pressure hydrocephalus (NPH)

Unfortunately it is a very rough marker of ventriculomegaly, and varies greatly depending on the location and angle of the slice.

As such Evans’ index has little role to play in day-to-day reporting.

Phase contrast magnetic resonance imaging

Psychomotor Tasks

Although gait is the primary indicator for treatment candidacy and outcome, additional monitoring tools are needed. Line Tracing Test (LTT) and Serial Dotting Test (SDT), two psychomotor tasks, have been introduced as potential outcome measures20).

Lumbar infusion test

Cerebrospinal fluid tap test

Cerebrospinal fluid tap test (CSF-TT), are often used in practice to provide further predictive value in detecting suitable patients for shunting.

Pressure recording

see Idiopathic normal pressure hydrocephalus intracranial pressure monitoring


Alzheimer disease (AD)-related pathology was assessed in cortical biopsy samples of 111 patients with idiopathic normal-pressure hydrocephalus. Alzheimer disease hallmark lesions amyloid beta (Aβ) and hyperphosphorylated tau protein (HPtau)-were observed in 47% of subjects, a percentage consistent with that for whole-brain assessment reported postmortem in unselected cohorts. Higher-immunostained area fraction of AD pathology corresponded with lower preoperative mini mental state examination scores. Concomitant Aβ and HPtau pathology, reminiscent of that observed in patients with AD, was observed in 22% of study subjects. There was a significant correlation between Aβ-immunostained area fraction in tissue and Aβ42 (42-amino-acid form of Aβ) in cerebrospinal fluid (CSF). Levels of Aβ42 were significantly lower in CSF in subjects with concomitant Aβ and HPtau pathology compared with subjects lacking pathology. Moreover, a significant correlation between HPtau-immunostained area fraction and HPtau in CSF was noted. Both HPtau and total tau were significantly higher in CSF in subjects with concomitant Aβ and HPtau pathology compared with subjects lacking pathology. The 42-amino-acid form of Aβ (Aβ42) and HPtau in CSF were the most significant predictors of the presence of AD pathology in cortical biopsies. Long-term follow-up studies are warranted to assess whether all patients with idiopathic normal-pressure hydrocephalus with AD pathology progress to AD and to determine the pathologic substrate of idiopathic normal-pressure hydrocephalus 21).

Differential diagnosis

Secondary normal pressure hydrocephalus (NPH) does indeed exist and should be differentiated from iNPH based on outcome as well as clinical, pathophysiological, and epidemiological characteristics but should not be considered as a separate entity. Evaluation of patients with NPH to identify a known cause is recommended because the response to treatment varies considerably. Although clinical presentation is often the same, a multitude of primary etiologies can lead to the development of sNPH. The most common etiologies of sNPH include SAH, traumatic brain injury, intracranial malignancies, meningitis, and stroke. Further studies are required to investigate differences in management and outcome among the diverse etiologies of sNPH 22).

In Alzheimer’s disease (AD) patients, diffuse aggregates of amyloid-β (Aβ) and neurofibrillary hyperphosphorylated tau are detected in the neocortex of the brain, while similar accumulation of Aβ is also detected in iNPH.

Apolipoprotein E (APOE4) affects the Aβ deposition in the brain of iNPH and AD patients in a similar manner 23).

APOE4 is not a risk factor for iNPH and does not predict the response to shunt. Data further support the view that the iNPH syndrome is a distinct dementing disease 24).


Shunt surgery has been established as the only durable and effective treatment for idiopathic normal pressure hydrocephalus

To maximise the benefits of shunt treatment, surgery should be performed soon after diagnosis 25).

The results of a prospective multicentre study on patients with iNPH diagnosed solely on clinical and radiological criteria support shunt surgery in patients presenting with symptoms and signs and MRI findings suggestive of iNPH 26).


Endoscopic third ventriculostomy

The only randomized trial of endoscopic third ventriculostomy (ETV) for idiopathic normal pressure hydrocephalus (iNPH) compares it to an intervention which is not a standard practice (VP shunting using a non-programmable valve). The evidence from this study is inconclusive and of very low quality. Clinicians should be aware of the limitations of the evidence. There is a need for more robust research on this topic to be able to determine the effectiveness of ETV in patients with iNPH 27).



Subdural collections, shunt malfunction, and postoperative seizures constituted the most frequent complications 28).

see Shunt overdrainage in idiopathic normal pressure hydrocephalus.

Case series


Twelve of 56 patients with NPH-like symptoms presented with morphological aqueductal stenosis (AS) (21.4 %). Patent aqueduct and non-patent aqueduct groups had similar values of mean opening lumbar pressure (8.2 vs. 8.1 mmHg), and mean opening pulse amplitude (3.1 vs. 2.9 mmHg). Mean pressure in the plateau stage (28.6 vs. 23.2 mmHg), and mean pulse amplitude in the plateau stage (12.5 vs. 10.6 mmHg) were higher in the patent aqueduct group. These differences were not statistically significant. Only Rout was significantly higher in the patent aqueduct group (13.6 vs. 10.1 mmHg/ml/min). One-third of NPH patients with AS presented Rout >12 mmHg/ml/min.

No differences in mean pressure or pulse amplitude during basal and plateau epochs of the lumbar infusion test in NPH patients were detected, regardless of aqueductal patency. However, Rout was significantly higher in patients with patent aqueduct 29).

Bir et al., retrospectively reviewed the clinical notes of 2001 patients with adult-onset hydrocephalus who presented to Louisiana State University Health Sciences Center within a 25-year span. Significant differences between the groups were analyzed by a chi-square test; p < 0.05 was considered significant.

The overall mean (± SEM) incidence of adult hydrocephalus in this population was 77 ± 30 per year, with a significant increase in incidence in the past decade (55 ± 3 [1990-2003] vs 102 ± 6 [2004-2015]; p < 0.0001). Hydrocephalus in a majority of the patients had a vascular etiology (45.5%) or was a result of a tumor (30.2%). The incidence of hydrocephalus in different age groups varied according to various pathologies. The incidence was significantly higher in males with normal-pressure hydrocephalus (p = 0.03) or head injury (p = 0.01) and higher in females with pseudotumor cerebri (p < 0.0001). In addition, the overall incidence of hydrocephalus was significantly higher in Caucasian patients (p = 0.0002) than in those of any other race.

Knowledge of the demographic variations in adult-onset hydrocephalus is helpful in achieving better risk stratification and better managing the disease in patients. For general applicability, these results should be validated in a large-scale meta-analysis based on a national population database 30).

A detailed screening process included neurological, neurosurgical and neuropsychological evaluations, followed by cerebrospinal fluid (CSF) tap test (TT) and resistance outflow (Ro) measurement. Outcome was evaluated through the Japanese NPH grading scale-revised (JNPHGSR) and the motor (third) section of the Unified Parkinson’s Disease Rating Scale (UPDRS-m). Friedman’s analysis of variance with Wilcoxon post-hoc test was used to evaluate the difference in JNPHGSR and UPDRS-m scores between pre-treatment and follow-up (12 months) in the two groups, while Kruskal-Wallis statistic and post-hoc Mann-Whitney test was used to compare the change in JNPHGSR and UPDRS-m scores between the two groups.

32/54 (59%) patients (mean age 73.2) screened in 36 months met the inclusion criteria, but only 30 were enrolled (two refused surgery), 15 in each group. Preoperative 123I-Ioflupane-cerebral SPECT (DaTSCAN) revealed striatal dopaminergic deficit in 14/30 patients (46.5%). At the final 12 months follow-up, both groups improved JNPHGSR and UPRDS-m scores. The UPDRS-m score improvement was significant in both groups, but greater in group A (p0.003); JNPHGSR score improvement was similar in the two groups.

iNPH associated with parkinsonism may be a frequent finding. In these cases, patients may benefit from VP shunt plus dopamine oral therapy 31).

From 2008 to 2013, consecutive patients diagnosed with INPH based on clinical and radiological criteria were included in a single-centre study. All patients received programmable-valve ventriculoperitoneal shunts. Outcome measures were assessed at baseline, 3, 6 and 12months post-operatively. Outcomes included gait time and scores on the Unified Parkinson’s Disease Rating Scale part III (UPDRS-III), the Addenbrooke’s Cognitive Examination Revised (ACE-R) and the Mini-Mental State Examination (MMSE). Thresholds for improvements were set a priori as ⩾20% decrease in gait time, ⩾10point decrease in UPDRS-III score, ⩾5point increase in ACE-R score and ⩾2point increase in MMSE score at last follow-up. The proportion of patients improving varied between measures, being gait time (60%), UPDRS-III (69%), MMSE (63%), and ACE-R (56%). Overall, improvement in at least one outcome measure was observed in 85% of patients and 38% improved in gait time, UPDRS-III score and cognitive scores. Only 15% of patients experienced no improvement on any measure. This study demonstrates that the majority of INPH patients can sustain improvements in multiple symptoms up to 12months after shunting 32).


A study included 29 patients with a mean age of 73.9 years; 62.1% were male and 65.5% had hypertension. Clinical improvement (complete or partial) was observed in 58% after one year and in 48% by the end of the follow-up period (mean follow-up time was 37.8 months). Older age, presence of hypertension, and surgery-related complications were more prevalent in the group responding poorly to treatment. One patient died, 20.7% experienced severe complications, and 69% were dependent (mRS ≥ 3) by the end of the follow-up period. Age at diagnosis was independently associated with poorer clinical response at one year and a higher degree of dependency by the end of follow-up.

Symptomatic benefits offered by VPS were partial and transient; treatment was associated with a high complication rate and poor functional outcomes in the long term, especially in the oldest patients 33).


Fifty-one patients were included after confirmation of the diagnosis by extensive clinical and diagnostic investigations. Surgery included ventriculoatrial or ventriculoperitoneal shunting with differential pressure valves in the majority of patients. For each of the cardinal symptoms, postoperative outcome was assessed separately with the Krauss Improvement Index, yielding a value between 0 (no benefit) and 1 (optimal benefit) for the overall outcome.

Mean age at surgery was 70.2 years (range, 50-87 years). Thirty patients were women, and 21 were men. Short-term (18.8 +/- 16.6 months) follow-up was available for 50 patients. The Krauss Improvement Index was 0.66 +/- 0.28. Long-term (80.9 +/- 51.6 months) follow-up was available for 34 patients. The Krauss Improvement Index was 0.64 +/-0.33. Twenty-nine patients died during the long-term follow-up at a mean age of 75.8 years (range, 55-95 years). The major causes of death were cardiovascular disorders: cardiac failure (n = 7) and cerebral ischemia (n = 12). Other causes were pneumonia (n = 2), acute respiratory distress syndrome (n = 1), pulmonary embolism (n = 1), cancer (n = 2), renal failure (n = 1), and unknown (n = 3). There was no shunt-related mortality.

Idiopathic normal pressure hydrocephalus patients may benefit from shunting over the long term when rigorous selection criteria are applied. Shunt-related mortality is negligible. The main cause of death is vascular comorbidity 34).

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26) Klinge P, Hellström P, Tans J, Wikkelsø C; European iNPH Multicentre Study Group. One-year outcome in the European multicentre study on iNPH. Acta Neurol Scand. 2012 Sep;126(3):145-53. doi: 10.1111/j.1600-0404.2012.01676.x. Epub 2012 May 10. PubMed PMID: 22571428.
27) Tudor KI, Tudor M, McCleery J, Car J. Endoscopic third ventriculostomy (ETV) for idiopathic normal pressure hydrocephalus (iNPH). Cochrane Database Syst Rev. 2015 Jul 29;7:CD010033. doi: 10.1002/14651858.CD010033.pub2. Review. PubMed PMID: 26222251.
28) Black PM. Idiopathic normal-pressure hydrocephalus. Results of shunting in 62 patients. J Neurosurg. 1980 Mar;52(3):371-7. PubMed PMID: 7359191.
29) González-Martínez EL, Santamarta D. Does aqueductal stenosis influence the lumbar infusion test in normal-pressure hydrocephalus? Acta Neurochir (Wien). 2016 Oct 11. PubMed PMID: 27730385.
30) Bir SC, Patra DP, Maiti TK, Sun H, Guthikonda B, Notarianni C, Nanda A. Epidemiology of adult-onset hydrocephalus: institutional experience with 2001 patients. Neurosurg Focus. 2016 Sep;41(3):E5. doi: 10.3171/2016.7.FOCUS16188. PubMed PMID: 27581317.
31) Broggi M, Redaelli V, Tringali G, Restelli F, Romito L, Schiavolin S, Tagliavini F, Broggi G. Normal pressure hydrocephalus and parkinsonism: preliminary data on neurosurgical and neurological treatment. World Neurosurg. 2016 Mar 9. pii: S1878-8750(16)00408-3. doi: 10.1016/j.wneu.2016.03.004. [Epub ahead of print] PubMed PMID: 26970480.
32) Shaw R, Everingham E, Mahant N, Jacobson E, Owler B. Clinical outcomes in the surgical treatment of idiopathic normal pressure hydrocephalus. J Clin Neurosci. 2016 Feb 27. pii: S0967-5868(15)00717-1. doi: 10.1016/j.jocn.2015.10.044. [Epub ahead of print] PubMed PMID: 26935749.
33) Illán-Gala I, Pérez-Lucas J, Martín-Montes A, Máñez-Miró J, Arpa J, Ruiz-Ares G. Long-term outcomes of adult chronic idiopathic hydrocephalus treated with a ventriculo-peritoneal shunt. Neurologia. 2015 Dec 31. pii: S0213-4853(15)00230-3. doi: 10.1016/j.nrl.2015.10.002. [Epub ahead of print] English, Spanish. PubMed PMID: 26749191.
34) Mirzayan MJ, Luetjens G, Borremans JJ, Regel JP, Krauss JK. Extended long-term (> 5 years) outcome of cerebrospinal fluid shunting in idiopathic normal pressure hydrocephalus. Neurosurgery. 2010 Aug;67(2):295-301. doi: 10.1227/01.NEU.0000371972.74630.EC. PubMed PMID: 20644414.

Update: Transient obstructive hydrocephalus


While obstructive hydrocephalus is a relatively common and potentially life-threatening condition, transient obstructive hydrocephalus is a rare condition in adults.


Transient obstruction of cerebrospinal fluid (CSF) flow through the ventricular system has been reported to result from systemic causes such as lead and carbon monoxide poisoning as well as CNS infections and meningitis 1).

Previous case reports have also described spontaneous resolution of obstructive hydrocephalus after intraventricular hemorrhage (IVH) in neonates and adults.

Transient acute hydrocephalus after spontaneous intracranial bleeding in adults 2).

Obstructive hydrocephalus with deterioration of consciousness from a ruptured arteriovenous malformation (AVM) requires urgent decompression, but also vigilance during the preoperative stage in case of rare spontaneous resolution 3).

The acute phase in a cerebellar infarction may become complicated with transient obstructive hydrocephalus, subsequent intracranial hypertension, and the need for surgical management. Although many patients respond well to medical treatment, clinical findings and neuroimaging methods must be considered to determine whether the hydrocephalus can be surgically treated in a timely fashion.

In fourteen patients, six required surgery for hydrocephalus management. Three of the cases had an endoscopic third ventriculostomy without complications, the rest were managed conservatively. As an average, patency was re-established in the aqueduct three months post ictus.

Management of obstructive hydrocephalus in the acute phase of a cerebellar stroke must be individualized. In cases with transient obstructive hydrocephalus, endoscopic third ventriculostomy is a good surgical treatment option that avoids the risks of a long-term ventricular shunt 4).

Case reports


Two cases of transient obstructive hydrocephalus caused by obstruction of mesencephalic duct in patients that presented with altered consciousness which resolved spontaneously in a few hours5).

A 66-year-old male was admitted with sudden onset right-sided hemiparesia. CT demonstrated a hematoma on the left basal ganglia with extension to all ventricles. The following day, the patient’s neurological status progressed to coma and developed bilateral pyramidal signs. MRI demonstrated obstructive hydrocephalus and acute diffuse infarction accompanied by elevation of the CC. On the same day there was improvement in his neurological status with significant decrease in ventricular size and complete resolution of the clot in the third ventricle. The mechanism of signal abnormalities is probably related with the neural compression of the CC against the falx. Presumably, the clot causing obstruction in the third ventricle dissolved or decayed by the help of fibrinolytic activity of CSF, which was raised after IVH and caused spontaneous improvement of hydrocephalus. Bilateral neurological symptoms suggest diffuse axonal damage and normalization of the intracranial pressure should be performed on the early onset of clinical detorioration in order to prevent axonal injury 6).


A 33-year-old man with a previously diagnosed Spetzler-Martin Grade 5 arteriovenous malformation presented with severe headache, which was found to be due to IVH. Forty hours after presentation he developed significant obstructive hydrocephalus due to the thrombus migrating to the cerebral aqueduct, and a ventriculostomy placement was planned. However, shortly thereafter his headache began to improve spontaneously. Within 4 hours after onset the headache had completely resolved, and an interval head CT scan revealed resolution of hydrocephalus.

In patients with IVH, acute obstructive hydrocephalus can develop at any time after the ictus. Though a delayed presentation of acute but transient obstructive hydrocephalus is unusual, it is important to be aware of this scenario and ensure that deterioration secondary to thrombus migration and subsequent obstructive hydrocephalus do not occur 7).

Transient obstructive hydrocephalus following traumatic brain injury 8).


Transient obstructive hydrocephalus by intraventricular fat migration after surgery of the posterior fossa 9).


A 86-year-old man with right frontal stroke developed obstructive hydrocephalus caused by blood in the cerebral aqueduct. The patient had sudden and immediate clinical improvement and a repeated head computed tomography (CT) scan showing spontaneous resolution of hydrocephalus. Spontaneous resolution of obstructive hydrocephalus is possible when the cause is minimal blood in the cerebral aqueduct without any blood in the fourth ventricle 10).


Spontaneous resolution of acute hydrocephalus without aspiration of cerebral fluid is rare. In a neonate born at full term this has only been reported once before. Abubacker et al., report on one further case that was caused by intraventricular haemorrhage (IVH). The probable mechanism is resolution of the acute haemorrhage in the region of the aqueduct, resulting in resolution of the hydrocephalus itself. The importance of considering conservative management of acute hydrocephalus in the clinically stable neonate is emphasised 11).


A 64-year-old woman presented with headache. Computerized tomography (CT) scan revealed hydrocephalus with tiny blood clots in the left foramen of Monro and in the aqueduct. Six hours after the onset, the signs and symptoms disappeared spontaneously. The second CT showed improvement of the hydrocephalus with migration of the clot into the i.v. ventricle. Aqueductal trapping and releasing of the clot formed by bleeding from the choroid plexus located in the left foramen of Monro was suspected for the origin of the transient hydrocephalus 12).


Acute transient hydrocephalus in carbon monoxide poisoning: a case report 13).


In the Sultanate of Oman acute lead encephalopathy in neonates is common. Brain oedema in acute lead encephalopathy occurs predominantly in the cerebellar vermis and may act as a midline posterior fossa mass, occluding the fourth ventricle. The resultant transient obstructive hydrocephalus may need emergency drainage of cerebro-spinal fluid. The hydrocephalus is transient as vermis oedema subsides with medical treatment. Two such cases are reported and discussed 14).


Spontaneous resolution of acute hydrocephalus. A case report 15).


One and a half years old boy was admitted with vomiting and somnolence four days after head injury. The first CT scans taken on admission showed high density areas in the prepontine and ambient cisterns and in the aqueduct. The lateral and third ventricles were dilated, while the fourth ventricle was normal. On the 2nd hospital day he was nearly asymptomatic. The second CT scans done seven days after injury no longer revealed the high density areas and the ventricular dilatation. Vomiting is one of the most important signs for intracranial mass lesions after head injury. But children often vomit even without having mass lesions, and CT scan is useful for evaluation of such cases. In our case, vomiting was probably due to aqueductal obstruction by a small clot resulting acute hydrocephalus, as revealed by CT scans. This case suggested that transient obstructive hydrocephalus must be taken into consideration as one of causes for posttraumatic vomiting 16).

1) Dubey AK, Rao KL. Pathology of post meningitic hydrocephalus. Indian J Pediatr. 1997 Nov-Dec;64(6 Suppl):30-3. Review. PubMed PMID: 11129878.
2) Hou K, Zhu X, Sun Y, Gao X, Zhao J, Zhang Y, Li G. Transient acute hydrocephalus after spontaneous intracranial bleeding in adults. World Neurosurg. 2016 Dec 31. pii: S1878-8750(16)31418-8. doi: 10.1016/j.wneu.2016.12.103. [Epub ahead of print] PubMed PMID: 28049036.
3) Inamura T, Kawamura T, Inoha S, Nakamizo A, Fukui M. Resolving obstructive hydrocephalus from AVM. J Clin Neurosci. 2001 Nov;8(6):569-70. PubMed PMID: 11683609.
4) Ramos-Zuñiga R, Jiménez-Guerra R. Rational management of transient obstructive hydrocephalus secondary to a cerebellar infarct. Minim Invasive Neurosurg. 2006 Oct;49(5):302-4. PubMed PMID: 17163345.
6) Kaymakamzade B, Eker A. Acute infarction of corpus callosum due to transient obstructive hydrocephalus. Neurol Neurochir Pol. 2016 Jul-Aug;50(4):280-3. doi: 10.1016/j.pjnns.2016.03.005. PubMed PMID: 27375144.
7) Lusis EA, Vellimana AK, Ray WZ, Chicoine MR, Jost SC. Transient Obstructive Hydrocephalus due to Intraventricular Hemorrhage: A Case Report and Review of Literature. J Clin Neurol. 2013 Jul;9(3):192-5. doi: 10.3988/jcn.2013.9.3.192. PubMed PMID: 23894243; PubMed Central PMCID: PMC3722471.
8) García Iñiguez JP, Madurga Revilla P, Palanca Arias D, Monge Galindo L, López Pisón FJ. [Transient obstructive hydrocephalus following traumatic brain injury]. An Pediatr (Barc). 2013 Jun;78(6):413-4. doi: 10.1016/j.anpedi.2012.09.022. Spanish. PubMed PMID: 23141931.
9) Zairi F, Arikat A, Allaoui M, Assaker R. Transient obstructive hydrocephalus by intraventricular fat migration after surgery of the posterior fossa. Acta Neurochir (Wien). 2012 Feb;154(2):303-4. doi: 10.1007/s00701-011-1258-0. PubMed PMID: 22207488.
10) Yaghi S, Hinduja A. Spontaneous resolution of obstructive hydrocephalus from blood in the cerebral aqueduct. Clin Pract. 2011 Apr 7;1(1):e15. doi: 10.4081/cp.2011.e15. Review. PubMed PMID: 24765269; PubMed Central PMCID: PMC3981214.
11) Abubacker M, Bosma JJ, Mallucci CL, May PL. Spontaneous resolution of acute obstructive hydrocephalus in the neonate. Childs Nerv Syst. 2001 Feb;17(3):182-4. PubMed PMID: 11305774.
12) Nomura S, Orita T, Tsurutani T, Kajiwara K, Izumihara A. Transient hydrocephalus due to movement of a clot plugging the aqueduct. Comput Med Imaging Graph. 1997 Nov-Dec;21(6):351-3. PubMed PMID: 9690009.
13) Prabhu SS, Sharma RR, Gurusinghe NT, Parekh HC. Acute transient hydrocephalus in carbon monoxide poisoning: a case report. J Neurol Neurosurg Psychiatry. 1993 May;56(5):567-8. PubMed PMID: 8505654; PubMed Central PMCID: PMC1015023.
14) Sharma RR, Chandy MJ, Lad SD. Transient hydrocephalus and acute lead encephalopathy in neonates and infants. Report of two cases. Br J Neurosurg. 1990;4(2):141-5. PubMed PMID: 2357283.
15) Braitman RE, Friedman M. Spontaneous resolution of acute hydrocephalus. A case report. Clin Pediatr (Phila). 1982 Dec;21(12):757-8. PubMed PMID: 7140131.
16) Sasaki O, Furusawa Y, Takahara Y. [Transient obstructive hydrocephalus of an infant following mild head injury (author’s transl)]. No Shinkei Geka. 1981;9(3):407-9. Japanese. PubMed PMID: 7242826.

Impact of timing of cranioplasty on hydrocephalus after decompressive hemicraniectomy in malignant middle cerebral artery infarction

There is an increasing body of evidence in the recent literature, which demonstrates that cranioplasty may also accelerate and improve neurological recovery. Although the exact pathophysiological mechanisms for this improvement remain essentially unknown, there are a rapidly growing number of neurosurgeons adopting this concept.

Communicating hydrocephalus is an almost universal finding in patients after hemicraniectomy. Delayed time to cranioplasty is linked with the development of persistent hydrocephalus, necessitating permanent CSF diversion in some patients.

Waziri et al., propose that early cranioplasty, when possible, may restore normal intracranial pressuredynamics and prevent the need for permanent CSF diversion in patients after hemicraniectomy 1).


One modifiable factor that may alter the risk of cranioplasty is the timing of cranioplasty after craniectomy. Case series suggest that early cranioplasty is associated with higher rates of infection while delaying cranioplasty may be associated with higher rates of bone resorption.

When considering ideal timing for cranioplasty, predominant issues include residual brain edema, brain retraction into the cranial vault, risk of infection, and development of delayed post-traumatic hydrocephalus.

Waiting to perform cranioplasty is important to prevent the development of devitalized autograft or allograft infections.

It is generally accepted to wait 3 to 6 months before reconstructive surgery. If there is an infected area, this waiting period can be as long as one year.

Cranioplasty is performed after craniectomy when intracranial pressure is under control for functional and aesthetic restorations and for protection, but it may also lead to some neurological improvement after the bone flap placement 2) 3) 4).

Timing of cranioplasty after decompressive craniectomy for trauma

The optimal timing of cranioplasty after decompressive craniectomy for trauma is unknown.

After decompressive craniectomy for trauma, early (<12 weeks) cranioplasty does not alter the incidence of complication rates. In patients <18 years of age, early (<12 weeks) cranioplasty increases the risk of bone resorption. Delaying cranioplasty (≥12 weeks) results in longer operative times and may increase costs 5).

Timing of cranioplasty after decompressive craniectomy for malignant middle cerebral artery infarction

Patients with malignant middle cerebral artery infarction frequently develop hydrocephalus after decompressive hemicraniectomy. Hydrocephalus itself and known shunt related complications after ventriculoperitoneal shunt implantation may negatively impact patients outcome.

A later time point of cranioplasty might lead to a lower incidence of required shunting procedures in general 6).

1) Waziri A, Fusco D, Mayer SA, McKhann GM 2nd, Connolly ES Jr. Postoperative hydrocephalus in patients undergoing decompressive hemicraniectomy for ischemic or hemorrhagic stroke. Neurosurgery. 2007 Sep;61(3):489-93; discussion 493-4. PubMed PMID: 17881960.
2) Honeybul S, Janzen C, Kruger K, Ho KM. The impact of cranioplasty on neurological function. Br J Neurosurg. 2013;27:636–641. doi: 10.3109/02688697.2013.817532.
3) Jelcic N, De Pellegrin S, Cecchin D, Della Puppa A, Cagnin A. Cognitive improvement after cranioplasty: a possible volume transmission-related effect. Acta Neurochir (Wien) 2013;155:1597–1599. doi: 10.1007/s00701-012-1519-6.
4) Di Stefano C, Sturiale C, Trentini P, Bonora R, Rossi D, Cervigni G, et al. Unexpected neuropsychological improvement after cranioplasty: a case series study. Br J Neurosurg. 2012;26:827–831. doi: 10.3109/02688697.2012.692838.
5) Piedra MP, Nemecek AN, Ragel BT. Timing of cranioplasty after decompressive craniectomy for trauma. Surg Neurol Int. 2014 Feb 25;5:25. doi: 10.4103/2152-7806.127762. PubMed PMID: 24778913; PubMed Central PMCID: PMC3994696.
6) Finger T, Prinz V, Schreck E, Pinczolits A, Bayerl S, Liman T, Woitzik J, Vajkoczy P. Impact of timing of cranioplasty on hydrocephalus after decompressive hemicraniectomy in malignant middle cerebral artery infarction. Clin Neurol Neurosurg. 2016 Dec 9;153:27-34. doi: 10.1016/j.clineuro.2016.12.001. [Epub ahead of print] PubMed PMID: 28012353.

Neurosurgical Focus: September 2016

Hydrocephalus: the role of cerebral aquaporin-4 channels and computational modeling considerations of cerebrospinal fluid

Introduction: Adult hydrocephalus

Timing of surgical treatment for idiopathic normal pressure hydrocephalus: association between treatment delay and reduced short-term benefit

Endoscopic third ventriculostomy for treatment of adult hydrocephalus: long-term follow-up of 163 patients

Low-dose acetylsalicylic acid and bleeding risks with ventriculoperitoneal shunt placement

Epidemiology of adult-onset hydrocephalus: institutional experience with 2001 patients

Revisiting secondary normal pressure hydrocephalus: does it exist? A review

Laparoscopy versus mini-laparotomy peritoneal catheter insertion of ventriculoperitoneal shunts: a systematic review and meta-analysis

Hydrocephalus: the role of cerebral aquaporin-4 channels and computational modeling considerations of cerebrospinal fluid

Cerebral venous overdrainage: an under-recognized complication of cerebrospinal fluid diversion

Imaging normal pressure hydrocephalus: theories, techniques, and challenges

The role of diffusion tensor imaging and fractional anisotropy in the evaluation of patients with idiopathic normal pressure hydrocephalus: a literature review

Update: Fourth ventricle hydrocephalus

Synonyms: Entrapped fourth ventricle; Isolated fourth ventricle.

Udayakumaran and Panikar reiterate that a Fourth ventricle hydrocephalus or trapped fourth ventricle (TFV) is a functional concept with imaging being at most only corroboratory 1).

In adults, Ferrer and de Notaris call this condition the functional trapped fourth ventricle because in none of there cases they have found physical obstruction of CSF flow 2).


Fourth ventricle hydrocephalus, or a “trapped” fourth ventricle is a rare and uncommon entity which has been observed as a complication after intraventricular hemorrhage, infection/ meningitis or as a result of chronic shunt overdrainage after hydrocephalic shunting 3) 4) 5) 6).

A postinfectious occlusion of fourth ventricle outflow (foramen of Luschka and Magendie) and aqueduct of sylvius is the second most common cause for the development of trapped fourth ventricle 7).

This condition is caused by blockage of both the outlets (Foramen of Luschka, Foramen of Magendie) and the inlet of the fourth ventricle at the level of the aqueduct of Sylvius 8).

Progressive dilation of the fourth ventricle is due to continuing CSF production by the choroid plexus of the fourth ventricle within a closed space.

An increased cerebrospinal fluid (CSF) pressure within the fourth ventricle can lead secondary to the enlargement of the central canal in terms of communicating secondary syringomyelia. The exact pathophysiological mechanism of developing syringomyelia generally is not well established and remains yet controversial although several theories have been postulated 9).

In a follow-up study of 164 hydrocephalic children without tumors treated with ventriculoperitoneal shunts, 46 (28.0%) developed slit ventricle syndrome, 5 (3.0%) developed isolated fourth ventricles, and 4 (2.4%) developed isolated unilateral hydrocephalus. All of the patients with isolated unilateral hydrocephalus and 3 with isolated fourth ventricles had associated slit ventricles, 2 of whom had enlarged ventricles as double-compartment hydrocephalus. Reopening of the foramen of Monro or the aqueduct was achieved in one of the former and two of the latter cases with re-expansion of the slit ventricles. It is suggested that in some cases, the slit ventricle could be a causative factor in post-shunt isolated ventricle 10).

Clinical features

Such an entrapment may lead to clinical symptoms secondary to distortion of the brainstem and lower CNs. The clinical findings are mostly non localizing, even when there are obvious bulbar signs.


Imaging may corroborate clinical findings but may not be diagnostic by itself.

The diagnostic and treatment dilemma is to differentiate between a “true” symptomatic TFV and other conditions associated with a large fourth ventricle. This dilemma is especially significant when one is attempting to identify those patients who may benefit from surgery, as opposed to those patients with a well-compensated process that simply have a similar clinical and a radiological picture of a large fourth ventricle.

Differential diagnosis

Posterior fossa cysts are usually divided into Dandy Walker malformations, posterior fossa arachnoid cysts, and isolated and/or trapped fourth ventricles.


Treatment of the TFV remains a formidable challenge. However, prompt recognition and intervention may aid in the preservation of life and neurological function 11).

Treatment extends from placement of fourth ventriculoperitoneal shunt, endoscopic aqueductoplasty and interventriculostomy to open fenestration via suboccipital craniotomy 12) 13).

Prone position is better compared to the sitting position. Apart from the risk of air embolism and post operative pneumocephalus in the sitting position, the air may get trapped in the ventricle and interfere in intraoperative visualization 14).

Unfortunately, these techniques showed a high rate of dysfunction and complications.

Standard management of loculated fourth ventricle hydrocephalus consists of fourth ventricle shunt placement via a suboccipital approach. An alternative approach is stereotactic-guided transtentorial fourth ventricle shunt placement via the nondominant superior parietal lobule.


The development of neuroendoscopy has dramatically changed the outcome of these patients and the literature review suggest that endoscopic trans-fourth ventricle aqueductoplasty and stent placement is a minimally invasive, safe, and effective technique for the treatment of TFV and should be strongly recommended, especially in patients with supratentorial slit ventricles 15).

Aqueduct stent placement is technically feasible and can be useful in selected patients either with endoscopy or open surgery 16).

Essentially, the main cause of a TFV, namely, the aqueductal obstruction, is addressed using an endoscopic technique, and hence it is the most rational of all surgeries for this condition. The aqueduct can be dilated and kept open using a stent either through a transfrontal (trans-third ventricle) route or through a trans-fourth ventricular route. The latter is a shorter route, but is less commonly used probably due to the lack of familiarity with the endoscopic anatomy of the region of the fourth ventricle.

With either route, the surgeon has to decide whether a simple dilatation of the aqueduct will suffice or to leave a stent in place. The advantage of a stent is that the patency of the aqueduct is ensured in the postoperative period unless the stent migrates. The major disadvantage is that of infection due to the presence of a foreign body. Gallo et al., placed a stent whenever the dilated aqueduct was narrower than the width of the stent. Although theoretically it is possible to produce additional neurological deficits by introducing a wider stent through a narrower aqueduct, in the authors’ series, the complications (two patients with ophthalmoparesis) were equally distributed between those who had a stent placed and those who underwent aqueductoplasty alone. Hence, it appears that fear of additional deficits should not deter a surgeon from using a stent 17).

Longatti et al., suggest a very simple method of steering the tip of standard ventricular catheters by using materials commonly available in all operating rooms. The main advantage of this method is that it permits less invasive transaqueductal drainage of trapped fourth ventricles, especially in cases of narrow third ventricle, because the scope and catheter are introduced in sequence and not in a double-barreled fashion. Two illustrative cases are reported 18).

Stereotactic parietal transtentorial approach

Stereotactic parietal transtentorial shunt placement may be considered for patients with loculated fourth ventricle hydrocephalus, especially when shunt placement via the standard suboccipital approach fails. It is therefore reasonable to offer this procedure either as a first option for the treatment of fourth ventricle hydrocephalus or when the need for fourth ventricle shunt revision arises 19).

In 10 patients, Turner et al., used an alternative technique involving stereotactic and endoscopic methods to place a catheter in symptomatic posterior fossa cysts across the tentorium. Discussion of these cases is included, along with a review of various approaches to shunt placement in this region and recommendations regarding the proposed technique.

No patient suffered intracranial hemorrhage related to the procedure and catheter implantation. All 3 patients who underwent placement of a new transtentorial cystoperitoneal shunt and a new ventriculoperitoneal shunt did not suffer any postoperative complication; a decrease in the size of their posterior fossa cysts was evident on CT scans obtained during the 1st postoperative day. Follow-up CT scans demonstrated either stable findings or further interval decrease in the size of their cysts. In 1 patient, the postoperative head CT demonstrated that the transtentorial catheter terminated posterior to the right parietal occipital region without entering the retrocerebellar cyst. This patient underwent a repeat operation for proximal shunt revision, resulting in an acceptable catheter implantation. The patient in Case 8 suffered from a shunt infection and subsequently underwent hardware removal and aqueductoplasty with stent placement. The patient in Case 9 demonstrated a slight increase in fourth ventricle size and was returned to the operating room. Exploration revealed a kink in the tubing connecting the distal limb of the Y connector to the valve. The Y connector was replaced with a T connector, and 1 week later, CT scans exhibited interval decompression of the ventricles. This patient later presented with cranial wound breakdown and an exposed shunt. His shunt hardware was removed and he was treated with antibiotics. He later underwent reimplantation of a lateral ventricular and transtentorial shunt and suffered no other complications during a 3-year follow-up period 20).


Frassanito et al., report an exceptional case of Descending transtentorial herniation (DTH) complicating the implant of a CSF shunting device in the trapped fourth ventricle of a 17-year-old boy in whom a second CSF shunting device had been implanted for neonatal posthemorrhagic and postinfectious hydrocephalus. The insidious clinical and radiological presentation of DTH, mimicking a malfunction of the supratentorial shunt, is documented. Ultimately, the treatment consisted of removal of the infratentorial shunt and endoscopic acqueductoplasty with stenting. The absence of supratentorial mass lesion and other described etiologies of DTH prompted the authors to speculate on the hydrodynamic pathogenesis of DTH in the present case 21).

Cranial nerve palsy is rarely seen after shunt placement in an isolated fourth ventricle. In the few reports of this complication, neuropathies are thought to be caused by catheter injury to the brainstem nuclei either during the initial cannulations or after shrinkage of the fourth ventricle. The authors treated a child who suffered from delayed, progressive palsies of the sixth, seventh, 10th, and 12th cranial nerves several weeks after undergoing ventriculoperitoneal shunt placement in the fourth ventricle. Magnetic resonance imaging revealed the catheter tip to be placed well away from the ventricular floor but the brainstem had severely shifted backward, suggesting that the pathogenesis of the neuropathies was traction on the affected cranial nerves. The authors postulated that the siphoning effect of the shunt caused rapid collapse of the fourth ventricle and while the cerebellar hemispheres were tented back by adhesions to the dura, the brainstem became the only mobile component in response to the suction forces. Neurological recovery occurred after surgical opening of the closed fourth ventricle and lysis of the basal cistern adhesions, which restored moderate ventricular volume and released the brainstem to its normal position 22).

Case series


Pomeraniec et al retrospectively reviewed 8 consecutive cases involving pediatric patients with TFV following VP shunting for IVH due to prematurity between 2003 and 2012. The patients ranged in gestational age from 23.0 to 32.0 weeks, with an average age at first shunting procedure of 6.1 weeks (range 3.1-12.7 weeks). Three patients were managed with surgery. Patients received long-term radiographic (mean 7.1 years; range 3.4-12.2 years) and clinical (mean 7.8 years; range 4.6-12.2 years) follow-up.

The frequency of TFV following VP shunting for neonatal posthemorrhagic hydrocephalus was found to be 15.4%. Three (37.5%) patients presented with symptoms of posterior fossa compression and were treated surgically. All of these patients showed signs of radiographic improvement with stable or improved clinical examinations during postoperative follow-up. Of the 5 patients treated conservatively, 80% experienced stable ventricular size and 1 patient experienced a slight increase (3 mm) on imaging. All of the nonsurgical patients showed stable to improved clinical examinations over the follow-up period.

The frequency of TFV among premature IVH patients is relatively high. Most patients with TFV are asymptomatic at presentation and can be managed without surgery. Symptomatic patients may be treated surgically for decompression of the fourth ventricle 23).


Of 1044 aneurysms treated, 3 patients were identified who required fourth ventricular shunting, for the treatment of the isolated ventricle. All 3 patients underwent microsurgical clip obliteration of their aneurysms and had subsequent frontal approach ventriculoperitoneal cerebrospinal fluid diversion. These patients had no evidence of infection of the cerebrospinal fluid as measured by serial cultures. Subsequently, all 3 patients presented in a delayed fashion with symptoms attributable to a dilated fourth ventricle and syringomyelia or syringobulbia. Either exploration or percutaneous tapping confirmed the function of the supratentorial shunt. These patients then underwent fourth ventriculoperitoneal cerebrospinal fluid diversion by the use of a low-pressure shunt system. The symptoms attributable to the isolated fourth ventricle resolved rapidly in all 3 patients after shunting. This clinical improvement correlated with the fourth ventricular size.

Isolated fourth ventricle, in an adult, is a rare phenomenon associated with intracranial posterior circulation aneurysm rupture treated with microsurgical clip obliteration. Fourth ventriculoperitoneal cerebrospinal fluid diversion is effective at resolving the symptoms attributed to the trapped ventricle and associated syrinx 24).


Between February 1998 and February 2007, 12 children were treated for TFV in Dana Children’s Hospital by posterior fossa craniotomy/craniectomy and opening of the TFV into the spinal subarachnoid space. The authors performed a retrospective analysis of relevant data, including pre- and postoperative clinical characteristics, surgical management, and outcome.

Thirteen fenestrations of trapped fourth ventricles (FTFVs) were performed in 12 patients. In 6 patients with prominent arachnoid thickening, a stent was left from the opened fourth ventricle into the spinal subarachnoid space. One patient underwent a second FTFV 21 months after the initial procedure. No perioperative complications were encountered. All 12 patients (100%) showed clinical improvement after FTFV. Radiological improvement was seen in only 9 (75%) of the 12 cases. The follow-up period ranged from 2 to 9.5 years (mean 6.11 ± 2.3 years) after FTFV 25).


Between January 1986 and December 1995, Eder et al., treated 292 children younger than 16 years for hydrocephalus: 7 (2.4%) developed an isolated IV ventricle, and 5 of these were symptomatic with posterior fossa signs. These 5 patients required posterior fossa shunting, after which their neurological status improved. However, 1 week and 6 weeks after surgery, respectively, 2 patients developed new cranial nerve deficits related to a slit-like IV ventricle with secondary irritation of the brain stem by the IV ventricular catheter. Shortening the catheter and replacing the valve eliminated the cranial nerve palsies, implying that these complications were not caused by direct injury of the brain stem during placement of the shunt. Alternative surgical techniques and the use of different (flow-regulating) valves may avoid such complications 26).


Isolated fourth ventricles were diagnosed by computed tomography (CT) in 16 children in a 3 year period. They all had shunting of the lateral ventricles for hydrocephalus, and all needed subsequent shunt revisions. Seven patients without signs of raised intracranial pressure clinically had new posterior fossa signs at different intervals after lateral ventricular shunting. The clinical findings in the other nine patients were much less specific and in some cases the isolated fourth ventricle was an incidental finding. CT is essential for the diagnosis. The isolated fourth ventricle needs to be differentiated from posterior fossa cysts and cystic tumors. Shunting of the fourth ventricle improved the clinical condition in six of 14 children 27).


Signs of cerebellar dysfunction combined with signs suggestive of shunt malfunction developed in three children with obstructive hydrocephalus. Shunt function was normal. In all cases, the cerebellar signs persisted and computerized tomography scans revealed enlargement of the fourth ventricle. Shunting of the fourth ventricle returned the patients to normal function 28).

Case reports


Trapped Fourth Ventricle With Vasogenic Edema 29).


A 28-year-old female who had previously undergone treatment of intracerebral hemorrhage and meningitis developed a hydrocephalus with TFV. After 3 years she developed disturbance of walking and coordination. Cranial-CT revealed an enlargement of the shunted fourth ventricle as a result of shunt dysfunction. Furthermore a cervical syringomyelia developed. The patient underwent a revision of a failed fourth ventriculo-peritoneal shunt. Postoperatively, syringomyelia resolved within 6 months and the associated neurological deficits improved significantly. An insufficiency of cerebrospinal fluid draining among patients with TFV can be associated with communicating syringomyelia. An early detection and treatment seems important on resolving syringomyelia and avoiding permanent neurological deficits. Ventriculo-peritoneal shunt in trapped fourth ventricles can resolve a secondary syringomyelia 30).


A 4-year-old girl with a ventriculoperitoneal shunt presented with complaints of ataxia and altered consciousness. These symptoms were subacute at onset and progressive in nature.

Radiological evaluation revealed a trapped fourth ventricle with brainstem compression, associated with abnormal diffuse diencephalic signal changes compatible with edema. The entrapment was managed by foramen magnum decompression, resulting in complete symptom resolution and improvement in the abnormal magnetic resonance findings.

While trapped fourth ventricle is a well-described entity, we could not find a similar reported case where such an acute clinical syndrome was associated with such a distinct radiological picture 31).

A 20-year-old man with complex hydrocephalus and trapped fourth ventricle underwent a suboccipital placement of a VP shunt. Postprocedure patient developed double vision. Magnetic resonance imaging showed that the catheter was penetrating the dorsal brainstem at the level of the pontomedullary junction. Patient was referred to our Neuroendoscopic Clinic. Physical exam demonstrated pure right VI cranial nerve palsy. Patient underwent flexible endoscopic exploration of the ventricular system. Some of the endoscopic findings were severe aqueductal stenosis and brainstem injury from the catheter. Aqueductoplasty, transaqueductal approach into the fourth ventricle, and endoscopic repositioning of the catheter were some of the procedures performed. Patient recovered full neurological function. The combination of endoscopic exploration and shunt is a good alternative for patients with complex hydrocephalus. A transaqueductal approach to the fourth ventricle with flexible scope is an alternative for fourth ventricle pathology 32).


Cranial nerve palsy is rarely seen after shunt placement in an isolated fourth ventricle. In the few reports of this complication, neuropathies are thought to be caused by catheter injury to the brainstem nuclei either during the initial cannulations or after shrinkage of the fourth ventricle. The authors treated a child who suffered from delayed, progressive palsies of the sixth, seventh, 10th, and 12th cranial nerves several weeks after undergoing ventriculoperitoneal shunt placement in the fourth ventricle. Magnetic resonance imaging revealed the catheter tip to be placed well away from the ventricular floor but the brainstem had severely shifted backward, suggesting that the pathogenesis of the neuropathies was traction on the affected cranial nerves. The authors postulated that the siphoning effect of the shunt caused rapid collapse of the fourth ventricle and while the cerebellar hemispheres were tented back by adhesions to the dura, the brainstem became the only mobile component in response to the suction forces. Neurological recovery occurred after surgical opening of the closed fourth ventricle and lysis of the basal cistern adhesions, which restored moderate ventricular volume and released the brainstem to its normal position 33).


The first reported case was a patient with cysticercosis meningitis and communicating hydrocephalus in whom signs of a posterior fossa mass developed a few months after shunting of the lateral ventricles . Air studies and posterior fossa exploration demonstrated an encysted fourth ventricle due to occlusion of its outlets as well as of the aqueduct 34).

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