Fourth ventricular entrapment caused by rostrocaudal herniation following shunt malfunction

The entity of the trapped fourth ventricle: A review of its history, pathophysiology, and treatment options

An isolated or trapped fourth ventricle is a relatively rare, although serious, adverse effect of hemorrhagic, infectious, or inflammatory processes that involve the central nervous system. This entity usually occurs after successful shunting of the lateral ventricles and may become clinically evident with the development of delayed clinical deterioration. This decline of the neurological status of the patient is evident after an initial period of improvement of the relevant symptoms. Surgical treatment options include cerebrospinal fluid shunting procedures, along with open surgical and endoscopic approaches. Complications related to its management are common and are related with obstruction of the fourth ventricular catheter, along with cranial nerve or brainstem dysfunction. We used the keywords: "isolated fourth ventricle," and "trapped fourth ventricle," in PubMed^® and Web of Science^®. Treatment of the trapped fourth ventricle remains a surgical challenge, although the neurosurgical treatment armamentarium has broadened. However, prompt recognition of the clinical and neurological findings that accompany any individual patient, in conjunction with the relevant imaging findings, is mandatory to organize our treatment plan on an individual basis. The current experience suggests that any individual intervention plan should be mainly based on the underlying pathological substrate of hydrocephalus. This could help us to preserve the patient's life, on an emergent basis, as well as to ensure an uneventful neurological outcome, maintaining at least the preexisting level of neurological function.

Feasibility of a Fourth Ventriculopleural Shunt for Diversion of an Isolated Fourth Ventricle: A Technical Note

Isolated fourth ventricle syndrome is an uncommon entity due to obstruction of both inlet and outflow foramina. The resulting mass effect from the progressively expanding fourth ventricle may cause symptoms from both cerebellar and brainstem compression. Although a variety of treatment modalities have been advocated for this condition, an in-depth description of placement of a fourth ventriculopleural (VPL) shunt from a single-stage prone approach has not yet been published in the literature. We describe here a case of successful placement of a fourth VPL shunt in a 22-year-old female with a history of a prior posterior fossa pilocytic astrocytoma resection who presented with symptomatic isolated fourth ventricular hydrocephalus.

Diagnosis, Classification, and Management of Fourth Ventriculomegaly in Adults: Report of 9 Cases and Literature Review

OBJECTIVE

An enlarged fourth ventricle, otherwise known as fourth ventriculomegaly (4th VM), has been reported previously in the pediatric population, yet literature on adults is scant. We report our experience with 4th VM in adults over an 11-year period and review the literature.

MATERIALS AND METHODS

This was a retrospective chart review of adult patients with the diagnosis of 4th VM admitted to the intensive care unit in a tertiary care center.

RESULTS

Nine patients were identified with 4th VM. Most presented with symptoms in the posterior fossa. Five cases were related to previous shunting and the underlying neurosurgical diseases, and average time interval to develop symptoms was 5.3 years. We divided our cases into primary, acquired, and degenerative based on the pathophysiology involved. Treatments included extended subzero cerebrospinal fluid diversion using a frontal external ventricular drain followed by low-pressure shunt revision, endoscopic third ventriculostomy, suboccipital decompression, and fourth ventricular catheter placement. Literature review identified additional published cases, and there were no reports of a formal classification scheme or treatment algorithm.

CONCLUSIONS

This case series illustrates a narrow spectrum of etiologies associated with 4th VM in adults. We propose a simple classification scheme dividing 4th VM into 3 categories: primary, acquired, and degenerative. We recommend a stepwise treatment approach starting with extended subzero cerebrospinal fluid diversion followed by shunting for symptomatic primary and acquired 4th VM. Lower success rates and greater morbidity are associated with rescue procedures such as fourth ventricle drainage catheters, endoscopic third ventriculostomies, and skull base decompression.

Isolated Fourth Ventricle: To Shunt or Stent

BACKGROUND

Of the various management options for isolated fourth ventricle (IFV), fourth ventriculoperitoneal shunts (FVPS) and aqueductal stents (AST) have been the most favored. Though effective, FVPS are often difficult to place and have higher complication rates than conventional ventricular shunts.

OBJECTIVE

To assess the efficacy of AST in IFV and compare the outcome with FVPS.

METHODS

Twenty-five patients surgically treated for IFV were analyzed. In all, a preoperative magnetic resonance imaging assessed the extent of aqueductal obstruction. Patients with an identified short-segment aqueductal stenosis were considered for AST placement; those with long-segment aqueductal obstruction underwent FVPS.

RESULTS

Of the 25, 12 were symptomatic, while 13 were asymptomatic (progressive dilation of IFV in 9, persistent dilation with distortion of the brain stem in 4). In 3 with normal ventricles, the ventricles had to be dilated by externalizing the shunt before placing the stent. Nineteen underwent AST placement, whereas in 6 FVPS was performed. Sixteen patients underwent a simultaneous cerebrospinal fluid diversion procedure and fourth ventricular decompression. At follow-up (mean: 45 mo), stent migration was observed in 2 patients. In the FVPS group, 1 had 2 shunt revisions while another developed reversible cranial nerve paresis. Though a reduction of the IFV was observed with both procedures, the extent of reduction was more with FVPS.

CONCLUSION

Both FVPS and AST are effective in managing IFV. The extent of aqueductal obstruction and degree of ventriculomegaly are often the deciding factors in choosing the management option.

Brainstem herniation into the internal acoustic canal secondary to hydrocephalus in context of spontaneous cerebrospinal fluid otorrhea: report of a novel entity

INTRODUCTION AND CLINICAL PRESENTATION

The authors report a case of a 5-year-old boy presenting with vision loss, right-sided hearing loss, and facial paralysis secondary to hydrocephalus causing brainstem herniation into the internal auditory canal (IAC) following cerebrospinal fluid (CSF) otorrhea.

MANAGEMENT AND OUTCOME

After placement of a ventriculo-peritoneal shunt (VP shunt), the vision and facial palsy improved whilst hearing loss persisted. Imaging demonstrated partial reduction of the herniated brainstem and resolution of hydrocephalus. To our knowledge, this is the first case reported of brainstem herniation into the internal auditory canal.

Anatomic Variability of the Morphometric Parameters of the Fourth Ventricle of the Brain

Objectives  The defining of the normal parameters of spacious relations and symmetry of the ventricular system of the brain depending on the gender and age is currently one of the topical research problems of clinical anatomy. The present research aims to identify the correlation between the morphometric parameters of the fourth ventricle of the brain and the shape of the skull in middle aged people. Design  This is a prospective cohort study. Setting  This study was set at the Trinity School of Medicine. Participants  A total of 118 normal computed tomography scans of the head of people aged from 21 to 86 years (mean age-48.6 years ± 17.57) were selected for the study. Main Outcome Measures  The anteroposterior, transverse diameters, and height of the fourth ventricle were measured and compared in dolichocranial, mesocranial, and brachycranial individuals. Results  The study has shown the presence of a statistically significant difference between morphometric parameters of the fourth ventricle of the brain in dolichocranial, mesocranial, and brachycranial individuals. Conclusion  The morphometric parameters of the fourth ventricle of the brain, such as height, anteroposterior, and transverse diameters, depend on the individual anatomic variability of the skull shape and gender.

The isolated fourth ventricle

Isolated enlargement of the fourth ventricle, or 'encysted' fourth ventricle is a rare late complication following shunt insertion of the lateral ventricles for hydrocephalus. Caudal and rostral obstruction of the fourth ventricle and its subsequent dilation results in compression of adjacent cerebellum and brain stem structures; treatment with further shunt insertion directly to the fourth ventricle is invariably successful. There is potential for diagnostic delay, when clinical symptoms and signs of cerebellar and brain stem compromise are unrecognised or attributed to other factors, and attention on the CT is focused on the lateral ventricular system and the already existing ventriculoperitoneal shunt, which will appear unchanged from previous scans. We report two cases with isolated fourth ventricular obstruction and review the literature to highlight the importance of recognising this condition.

Disproportionately large communicating fourth ventricle resulting from adjustable valve shunt in an infant

Disproportionately large communicating fourth ventricle (DLCFV) is usually experienced in adults with no previous experience of shunting. We present a case of an infant with an enlarged fourth ventricle similar to isolated fourth ventricle (IFV) which appeared after shunting. The patient's brain stem symptoms and the abnormal appearance of the fourth ventricle were dramatically ameliorated simply by reducing the opening pressure of the adjustable valve of the ventriculo-peritoneal shunt. The present case suggests that in the present era, with adjustable or programmable valve shunt a common procedure, DLCFV may occur, at least temporarily, even in infants and even after shunting.

[Relations of aqueduct with some structures of mesencephalon]

INTRODUCTION

Aqueductus mesencephali is the biggest part of the ventricular system and that is why it is the most common place of intraventricular obstruction of cerebrospinal fluid. This study was done in order to study topographic characteristics of aqueduct more thoroughly.

MATERIALS AND METHODS

Transversal sections of mesencephalon were made in three levels. The first section was made caudally immediately from the posterior commissure. The second section was made in the middle part of the superior colliculi, and the third section was made in the rostral parts of the caudal sections of the superior colliculi. Distances of the aqueduct from structures of mesencephalon, obtained on the second section, are: 1. The distance of the aqueduct from the superior colliculi - 6.96 mm; 2. The distance of the aqueduct from the red nucleus - 6.02 mm; 3. The distance of the aqueduct from the substantia nigra - 12.29 mm; 4. The distance of the aqueduct from the interpeduncular fossa - 10.22 mm.

CONCLUSION

Knowledge of the anatomy of the aqueductus mesencephali is very important because of interpretation of patogenesis of hidrocefalus as well as of other syndromes that occure in some pathological processes in the system of ventricles.

Shunts vs endoscopic third ventriculostomy in infants: are there different types and/or rates of complications? A review

INTRODUCTION

The decision-making process when we compare endoscopic third ventriculostomy (ETV) with shunts as surgical options for the treatment of hydrocephalus in infants is conditioned by the incidence of specific and shared complications of the two surgical procedures.

REVIEW

Our literature review shows that the advantages of ETV in terms of complications are almost all related to two factors: (a) the avoidance of a foreign body implantation and (b) the establishment of a 'physiological' cerebrospinal fluid (CSF) circulation. Both these kinds of achievements are particularly important in infants because of the relative high rate of some intraoperative (i.e. abdominal) and late (secondary craniosynostosis, slit-ventricle syndrome) shunt complications in this specific subset of patients. On the other side, the main factor which is claimed against ETV is the relatively high risk of immediate mortality and neurological complications. Clinical manifestations of neurological structure damage seem to be more frequent in infants, probably due to the more relevant effect of parenchymal and vascular damage in this age group; however, both the immediate mortality and neurological damage risk of ETV procedures should be weighted against the long-term mortality and the late neurological damage which is not infrequently described as a consequence of shunt malfunction and proximal shunt revision procedures. Infections are possible in both ETV and extrathecal CSF procedures, especially in infants. However, the incidence of infective complications is significantly lower in case of ETV (1-5% vs 1-20%). Moreover, different from shunting procedures, infections in children with third ventriculostomy have a more benign course, being generally controlled by antibiotic treatment alone.

Etiological differences between the isolated lateral ventricle and the isolated fourth ventricle

OBJECTIVE

To determine if an etiological difference exists between isolation of the lateral ventricle and isolation of the fourth ventricle after ventricular shunting.

METHODS

Cases of symptomatic isolation of the lateral and fourth ventricles were reviewed retrospectively. The ages at presentation of ventricular isolation, the time course to development of isolation, the number of shunt surgeries leading up to symptomatic isolation, the types of shunt valves utilized, and the background of infection were analyzed.

RESULTS

Twenty-six patients had lateral ventricle isolation and 11 patients had fourth ventricle isolation. Infection, hemorrhage, Chiari malformation/myelomeningocele, and aqueductal stenosis were factors contributing to hydrocephalus requiring treatment in these patients. Compared to 26.9% of patients with lateral ventricle isolation, 90.9% of patients with fourth ventricle isolation had a previous history of infection.

CONCLUSIONS

Prior meningitis and ventriculitis frequently contributed to fourth ventricle isolation. Lateral ventricle isolation seems to arise from functional obstruction of the foramen of Monro related to prior shunting.

Management strategies for treatment of the trapped fourth ventricle

BACKGROUND

An isolated or trapped fourth ventricle (TFV) is an occasional, serious sequela of hemorrhagic, infectious, or inflammatory conditions of the central nervous system. The TFV usually occurs after successful shunting of the lateral ventricles. It may be heralded by delayed clinical deterioration after an initial period of symptomatic improvement. The typical clinical findings suggest an expanding posterior fossa mass lesion. Surgical treatments include CSF diversionary procedures as well as open and endoscopic approaches. Complications related to the treatment of the TFV are common and relate to catheter obstruction and cranial nerve or brainstem dysfunction.

METHODS

The author reviews the clinical features, pathophysiology, and available treatment options for the TFV, with special reference to complication avoidance and advances in ventriculoscopy and frameless stereotaxy.

CONCLUSIONS

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