Third Ventriculostomy and Fourth Ventricle Outlets Obstruction

Tetraventricular noncommunicating hydrocephalus: Case report and literature review

BACKGROUND

Tetraventricular hydrocephalus is a common presentation of communicating hydrocephalus. Conversely, cases with noncommunicating etiology impose a diagnostic challenge and are often neglected and underdiagnosed. Herein, we present a review of literature for clinical, diagnostic, and surgical aspects regarding noncommunicating tetrahydrocephalus caused by primary fourth ventricle outlet obstruction (FVOO), illustrating with a case from our service.

METHODS

We performed a research on PubMed database crossing the terms "FVOO," "tetraventriculomegaly," and "hydrocephalus" in English. Fifteen articles (a total of 34 cases of primary FVOO) matched our criteria and were, therefore, included in this study besides our own case.

RESULTS

Most cases presented in adulthood (47%), equally divided between male and female. Clinical presentation was unspecific, commonly including headache, nausea, and dizziness as symptoms (35.29%, 21.57%, and 9.80%, respectively), with ataxic gait (65%) and papilledema (40%) being the most frequent signs. MRI and CT were the imaging modalities of choice (11 patients each), often associated with CSF flow studies, such as cine MRI and CT ventriculogram. Endoscopic third ventriculostomy (ETV) was both the most popular and effective surgical approach (50.85% of cases, with 18.91% of recurrence) followed by ventricle-peritoneal shunt (16.95% of patients, 23.0% of recurrence).

CONCLUSION

FVOO stands for a poorly understood etiology of noncommunicating tetrahydrocephalus. With the use of ETV, these cases, once hopeless, had its morbimortality and recurrence reduced greatly. Therefore, its suspicion and differentiation from other forms of tetrahydrocephalus can improve its natural course, reinforcing the importance of its acknowledgment.

Endoscopic Third Ventriculostomy in the Fourth Ventricle Outlet Obstruction Associated with Chiari Malformation Type I and Syringomyelia: Case Report

Hydrocephalus by the fourth ventricle outlet obstruction (FVOO) associated with a Chiari malformation type I and syringomyelia is a well-known entity but a rare situation in clinical practice. Although suboccipital craniectomy with the opening of the obstruction membrane appears to be the most physiological approach, by restoring the original pathway of cerebrospinal fluid flow, the endoscopic third ventriculostomy (ETV) represents an important minimally invasive alternative. We report the case of an adult patient with tetra ventricular hydrocephalus by FVOO associated with Chiari malformation and syringomyelia. The ETV alone completely resolved all symptoms, as well as neuroimaging abnormalities on the control magnetic resonance imaging. The ETV is a minimally invasive option for the treatment of hydrocephalus in patients with obstruction at the exit of the fourth ventricle, even in cases associated with Chiari malformation and syringomyelia.

Cranial expansion and aqueductoplasty for combined isolated fourth ventricle and slit-ventricle syndrome: a surgical alternative

INTRODUCTION

An isolated fourth ventricle (IFV) is a rare entity observed in shunted patients and its treatment is still uncertain. Endoscopic aqueductoplasty has shown good results for restoring CSF flux between the third and fourth ventricles. However, it needs some grade of ventricular dilation to be performed. Some patients affected by IFV show slit-ventricle morphology in CT/MRI. Usually, the rise of opening pressure or the shunt externalization gets enough ventricular dilation. However, the lack of intracranial compliance in some patients makes these options unsuitable and high-ICP symptoms are developed without ventricular dilation.

METHODS

We present a two cases series affected by IFV with no ventricular dilation in radiological exams. ICP sensors were implanted, observing high-ICP and establishing the diagnosis of craniocerebral disproportion. A two-stage surgical plan based on a dynamic cranial expansion followed by a supratentorial endoscopic aqueductoplasty was performed. A physical and mathematical model explaining our approach was also provided.

RESULTS

Chess-table cranial expansion technique was performed in both patients. Six/seven days after the first surgery, respectively, ventricular dilation was observed in CT. Endoscopic precoronal aqueductoplasty was then performed. No postoperative complications were described. IFV symptoms improved in both patients. Eighteen and 12 months after the two-stage surgical plan, the patients remain symptom-free and void of flow is still observed between the third and the fourth ventricles in MRI.

CONCLUSION

The two-stage approach was a suitable option for the treatment of these complex patients affected by both craniocerebral disproportion and isolated fourth ventricle.

Evidence for the involvement of caspases in establishing proper cerebrospinal fluid hydrodynamics

A large number of cells undergo apoptosis via caspase activation during and after neural tube closure (NTC) in mammals. Apoptosis is executed by either intrinsic or extrinsic apoptotic pathways, and inhibition of each pathway causes developmental defects around NTC stages, which hampers the physiological roles of apoptosis and caspases after NTC. We generated transgenic mice in which a broad spectrum of caspases could be suppressed in a spatiotemporal manner by pan-caspase inhibitor protein p35 originating from baculovirus. Mice with nervous system-specific expression of p35 (Nestin-Cre (NCre);p35V mice) exhibited postnatal lethality within 1 month after birth. They were born at the expected Mendelian ratio, but demonstrated severe postnatal growth retardation and hydrocephalus. The flow of cerebrospinal fluid (CSF) between the third and fourth ventricles was disturbed, whereas neither stenosis nor abnormality in ciliary morphology was observed in the pathway of CSF flow. Hydrocephalus and growth retardation of NCre;p35V mice were not rescued by the deletion of RIPK3, an essential factor for necroptosis which occurs in the absence of caspase-8 activation during development. The CSF of NCre;p35V mice contained a larger amount of secreted proteins than that of the controls. These findings suggest that the establishment of proper CSF dynamics requires caspase activity during brain development after NTC.

Trapped fourth ventricle-treatment options and the role of open posterior fenestration in the surgical management

BACKGROUND

Trapped fourth ventricle (TFV) is a rare and difficult to treat condition. Most patients have a past inciting event (infection, IVH, trauma) and history of prior CSF diversion. The symptoms are due to the mass effect on brainstem and cerebellum. Rarely, TFV can also be associated with syrinx formation due to a dissociated craniospinal CSF flow near the fourth ventricle outlets. We present our experience and outcomes of open posterior fenestration in 11 cases, along with an overview of the surgical management of TFV.

METHODS

Between 2011 and 2018, 11 patients of TFV were operated by the posterior approach fenestration of the fourth ventricle outlets and arachnoid dissection. The clinical and radiological findings of the patients were retrieved from the hospital database. The surgical technique is described in detail. The patients' neurological status and imaging findings in the follow-up were recorded and compared.

RESULTS

The average age of the patients was 23.55 years. The most common presenting symptoms were headache (9/11) and gait imbalance (7), with TB meningitis being the commonest etiology. Ten patients had a history of prior CSF diversion with two presenting with shunt malfunction. Mean follow-up duration was 33.33 months. The improvement in neurological status was observed in 9/11 patients, 2 remained status quo. On follow-up imaging, 8/11 (72.72%) patients had a decrease in the size of TFV while syrinx improved in 3/5 (60%).

CONCLUSION

Multiple surgical approaches have been described for TFV. Endoscopic fourth ventriculostomy with aqueductoplasty is gaining popularity in the past two decades. However, an open posterior fenestration of the midline fourth ventricle outlet (magendieplasty) along with sharp arachnoid dissection (adhesiolysis) along the cerebello-medullary cisterns and paracervical gutters is relatively simple and provides physiological fourth ventricular CSF outflow. This is especially useful in TFV with syrinx as the craniospinal CSF circulation is established.

Fourth Ventricular Outflow Obstruction in an Infant with Ileal Atresia and Laryngomalacia: Endoscopic Management

Fourth ventricle outflow obstruction (FVOO) is a rare cause of obstructive hydrocephalus. In this study, we described a case of idiopathic FVOO with ileal atresia and laryngomalacia which was managed with endoscopic third ventriculostomy (ETV) and re-endoscopy. We also described the techniques of fenestration of Liliequist membrane and partial removal of arachnoid membrane over dorsum sella (DS) to prevent closure of fenestration and recurrence of hydrocephalus. The patient was a 4-month-old infant presented with progressively increasing head size, feeding difficulty, respiratory distress, and tense fontanel. The infant had a history of laparotomy for ileal atresia. CT scan showed panventriculomegaly due to FVOO. ETV with fenestration of Liliequist membrane was done on emergency basis. After operation, the patient improved clinically and radiologically. Four weeks later, the patient returned with recurrent hydrocephalus. Endoscopic reoperation showed closure of fenestration in arachnoid membrane (Lilieqiest membrane). Endoscopic refenestration with partial excision of arachnoid on DS was done. The patient again recovered radiologically and clinically till last follow-up. In idiopathic FVOO, ETV with wide fenestration of Liliequist membrane, preferably with partial removal of arachnoid on DS, may be very useful in treating hydrocephalus (HCP) and preventing recurrent HCP even in infants.

Trapped fourth ventricle: a rare complication in children after supratentorial CSF shunting

PURPOSE

Trapped fourth ventricle (TFV) is a well-identified problem in hydrocephalic children. Patients with post-hemorrhagic hydrocephalus (PHH) are mostly affected. We tried to find out predisposing factors and describe clinical findings to early diagnose TFV and manage it.

METHODS

We reviewed our database from 1991 to 2018 and included all patients with TFV who required surgery. We analyzed prematurity, cause of hydrocephalus, type of valve implanted, revision surgeries, modality of treatment of TFV, and their clinical examination and MRI imaging.

RESULTS

We found 21 patients. Most of patients suffered from PHH (16/21), tumor (2/21), post-meningitis hydrocephalus (2/21), and congenital hydrocephalus (1/21). Seventeen patients were preterm. Seven patients suffered from a chronic overdrainage with slit ventricles in MRI. Thirteen patients showed symptoms denoting brain stem dysfunction; in 3 patients, TFV was asymptomatic and in 5 patients, we did not have available information regarding presenting symptoms due to missing documentation. An extra fourth ventricular catheter was the treatment of choice in 18/21 patients. One patient was treated by cranio-cervical decompression. Endoscopic aqueductoplasty with stenting was done in last 2 cases.

CONCLUSION

Diagnosis of clinically symptomatic TFV and its treatment is a challenge in our practice of pediatric neurosurgery. PHH and prematurity are risk factors for the development of such complication. Both fourth ventricular shunting and endoscopic aqueductoplasty with stenting are effective in managing TFV. Microsurgical fourth ventriculostomy is not recommended due to its high failure rate. Early detection and intervention may help in avoiding fatal complication and improving the neurological function.

Fourth Ventricle Outlet Obstruction and Diverticular Enlargement of Luschka Foramina in a Child with Down Syndrome

INTRODUCTION

Hydrocephalus is not usually part of Down syndrome (DS). Fourth ventricle outlet obstruction is a rare cause of obstructive hydrocephalus, difficult to diagnose, because tetraventricular dilatation may suggest a communicant/nonobstructive hydrocephalus.

CASE PRESENTATION

We describe the case of a 6-year-old boy with obstructive tetraventricular hydrocephalus, caused by Luschka and Magen-die foramina obstruction and diverticular enlargement of Luschka foramina (the so-called fourth ventricle outlet obstruction) associated with DS. He was treated with endoscopic third ventriculostomy (ETV) without complications, and a follow-up MRI revealed reduction of the ventricles, disappearance of the diverticula, and patency of the ventriculostomy.

CONCLUSION

Diverticular enlargement of Luschka foramina is an important radiological finding for obstructive tetraventricular hydrocephalus. ETV is a viable option in tetraventricular obstructive hydrocephalus in DS.

Neuroendoscopic Aspiration of Blood Clots in the Cerebral Aqueduct and Third Ventricle During Posterior Fossa Surgery in the Prone Position

BACKGROUND

During surgery in the posterior fossa in the prone position, blood can sometimes fill the surgical field, due both to the less efficient venous drainage compared to the sitting position and the horizontally positioned surgical field itself. In some cases, blood clots can wedge into the cerebral aqueduct and the third ventricle, and potentially cause acute hydrocephalus during the postoperative course.

OBJECTIVE

To illustrate a technique that can be used in these cases: the use of a flexible scope introduced through the opened roof of the fourth ventricle with a freehand technique allows the navigation of the fourth ventricle, the cerebral aqueduct, and the third ventricle in order to explore the cerebrospinal fluid pathways and eventually aspirate blood clots and surgical debris.

METHODS

We report on one patient affected by an ependymoma of the fourth ventricle, for whom we used a flexible neuroendoscope to explore and clear blood clots from the cerebral aqueduct and the third ventricle after the resection of the tumor in the prone position. Blood is aspirated with a syringe using the working channel of the scope as a sucker.

RESULTS

A large blood clot that was lying on the roof of the third ventricle was aspirated, setting the ventricle completely free. Other clots were aspirated from the right foramen of Monro and from the optic recess.

CONCLUSION

We describe this novel technique, which represents a safe and efficient way to clear the surgical field at the end of posterior fossa surgery in the prone position. The unusual endoscopic visual perspective and instrument maneuvers are easily handled with proper neuroendoscopic training.

Disproportionately large communicating fourth ventricle: two case reports

Background

Management of the disproportionately large communicating fourth ventricle is still problematic.

Case presentation

Two cases of disproportionately large communicating fourth ventricle were treated successfully. One was a case of a 51-year-old Han Chinese woman with a complaint of headache and dizziness of 1 year’s duration. Magnetic resonance imaging (MRI) demonstrated hydrocephalus with a disproportionately large fourth ventricle. She underwent a ventriculo-peritoneal shunt of the right lateral ventricle. Her symptoms were relieved totally. Five years later, magnetic resonance imaging showed she had a normal ventricular system. The other case was a 24-year-old Han Chinese man with a 2-month history of headache and dizziness accompanied by progressive loss of bilateral vision. Magnetic resonance imaging revealed hydrocephalus with a disproportionately large fourth ventricle, crowded posterior cranial fossa, and syringomyelia extending from C1 to C5. He underwent suboccipital and C1 decompression and duraplasty. Shortly after the surgery, his symptoms were relieved completely, the syringomyelia completely disappeared, and the fourth ventricle became significantly smaller.

Conclusions

The management of the disproportionately large communicating fourth ventricle should be individualized. If it coexists with crowded posterior cranial fossa or syringomyelia, posterior fossa decompression could be an option for initial management. If there is no sign of crowded posterior cranial fossa or syringomyelia, shunt of the lateral ventricles might be the first choice.

Surgical Techniques and Long-Term Outcomes of Flexible Neuroendoscopic Aqueductoplasty and Stenting in Infants with Obstructive Hydrocephalus: A Single-Center Study

OBJECTIVE

To technically review and explore long-term follow-up results of aqueductoplasty and stenting under flexible neuroendoscopy in infantile obstructive hydrocephalus.

METHODS

The clinical data, surgical techniques, and long-term effects in 14 infants with obstructive hydrocephalus treated by flexible neuroendoscopic aqueductoplasty and stenting between 2008 and 2010 were analyzed retrospectively.

RESULTS

The 14 infants had a mean age of 5.71 ± 3.10 months (range, 2-11 months) and a mean duration of follow-up of 62.64 ± 34.52 months (range, 9-121 months). Subdural effusion was observed in 4 infants (28.6%) after surgery. There were no deaths or serious complications related to intracranial stent placement. Three infants (21.4%) failed, 2 due to proximal aqueduct occlusion from a short stent length and 1 due to intraluminal ependymal adhesion obstruction. One case was abandoned when a second surgical adjustment stent was unsuccessful, and the other 2 cases went to shunt surgery.

CONCLUSIONS

Aqueductoplasty with stenting is a feasible and safe surgical procedure for treating infants with midbrain aqueduct stenosis or occlusion. However, the optimal stent material and definitive outcomes after this procedure require additional long-term follow-up studies in large numbers of infants.

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.

Transtentorial Distortion Syndrome: Consistent Complication Following Lateral and Fourth Ventricular Shunting in Adults

BACKGROUND

Complex hydrocephalus affecting lateral and fourth ventricles separately is occasionally managed with cerebrospinal fluid diversion via supratentorial and infratentorial ventricular catheters. The optimal configuration to reduce complications is currently unknown in adults. We describe a consistently similar clinical presentation of patients with complex hydrocephalus and a fourth ventricle separately drained by infratentorial shunt insertion.

METHODS

This was a retrospective single-center case series. Medical notes were reviewed for clinical presentation, brain imaging, and neurophysiologic tests results. All patients underwent intracranial pressure monitoring (ICPM). Outcomes were determined by ventricular appearance on brain imaging computed tomography and symptomatic improvements postoperatively.

RESULTS

Five adult patients referred to the hydrocephalus service had separate infratentorial and supratentorial shunt systems. A common clinical presentation was observed, including lower motor neuron facial palsy (confirmed with electrophysiology), ophthalmoplegia, dysarthria, impaired gait headache, and nausea. We refer to this as transtentorial distortion syndrome. Twenty-four-hour ICPM demonstrated clear low pressures. All patients underwent shunt revision connecting the transtentorial shunts via a Y-connector and the addition of a distal valve. All subjects had improved ventricular appearance on computed tomography scans post revision, and normalization of ICPM was observed. In the follow-up period of 6 months, no patient required further shunt revision.

CONCLUSION

To prevent transtentorial distortion syndrome, supratentorial and infratentorial shunt constructs in adults with encysted fourth ventricles should be similar to the shunt systems widely known in the pediatric population with Dandy-Walker syndrome (i.e., joint output to a single valve distal to the connection of the 2 proximal drainage catheters).

Fourth Ventricle Outlet Obstruction with Expanding Space on the Surface of Cerebellum

BACKGROUND

Hydrocephalus is classified as noncommunicating and communicating based on whether all ventricular and subarachnoid spaces are communicating. Although the diagnosis between the two different states is crucial, it is difficult in certain conditions. In particular, communicating hydrocephalus and noncommunicating hydrocephalus owing to fourth ventricle outlet obstruction are highly misdiagnosed. We describe a case of fourth ventricle outlet obstruction of unknown origin that was initially misdiagnosed as communicating hydrocephalus.

CASE DESCRIPTION

A 66-year-old woman with gait disturbance and incontinence caused by hydrocephalus underwent ventriculoperitoneal shunt surgery. After 9 months, her fourth ventricle became enlarged and could not be controlled by lowering the shunt pressure. Magnetic resonance imaging (MRI) demonstrated obstruction at the foramen of Magendie, foramina of Luschka, and the cerebral aqueduct. Endoscopic surgery for aqueduct plasty with third ventriculostomy was planned. Because the aqueduct was observed to open spontaneously, only the standard third ventriculostomy was performed. When MRI findings were reviewed retrospectively, an unnatural space was observed between the lower cranial nerves and cerebellar hemisphere that grew along with the fourth ventricular enlargement. This space was determined by MRI cisternography to be the cystic membrane ballooning out from the foramen of Luschka. The primary hydrocephalus likely resulted from fourth ventricle outlet obstruction.

CONCLUSIONS

Enlargement of the whole ventricular system with an expanded space between the lower cranial nerves and cerebellar hemisphere can be caused by fourth ventricle outlet obstruction. In such cases, preoperative evaluation of anatomic architecture and cerebrospinal fluid obstruction using MRI cisternography is essential and leads to a successful endoscopic strategy.

Predictors of Outcome Following Cerebral Aqueductoplasty: An Individual Participant Data Meta-analysis

BACKGROUND

The evidence supporting the efficacy and safety of cerebral aqueductoplasty (CA) is limited to small surgical series.

OBJECTIVE

To perform an individual participant data meta-analysis to determine the efficacy and safety of CA and to determine the effect of patient's age, etiology, surgical approach, and use of stent on success.

METHODS

Electronic databases (MEDLINE, EMBASE, and CINAHL) were searched with no language or date restrictions to identify cohort studies of consecutive participants undergoing CA (without concomitant endoscopic third ventriculostomy or cerebrospinal fluid [CSF] shunt) that reported outcome. Outcome was defined as the time elapsed from the index operation until a second procedure was performed for CSF diversion.

RESULTS

Of 146 citations, 14 articles reporting on 137 participants were eligible. One hundred three participants (75%) did not require a second CSF diversion procedure. The mean duration until repeat CSF diversion procedure was 121.6 months (95% confidence interval [CI], 102.2-141.0). In multivariate analysis, older age at surgery (hazard ratio [HR], 0.43; 95% CI, 0.21-0.88; P = .020), congenital etiology (HR, 0.18; 95% CI, 0.04-0.85; P = .030), and use of stent (HR, 0.30; 95% CI, 0.13-0.70; P = .006) were independent predictors of good outcome. Morbidity, mainly ophthalmoparesis and hemorrhage, was experienced in 22% of participants.

CONCLUSION

Small retrospective cohort studies are inherently prone to biases, some of which are overcome through the use of individual participant data. The best available evidence suggests that CA is an effective procedure with a moderate morbidity profile. Older age at surgery, congenital etiology, and use of stent predict a good outcome with respect to delaying the requirement for a second CSF diversion procedure.

Investigating cerebral oedema using poroelasticity

Cerebral oedema can be classified as the tangible swelling produced by expansion of the interstitial fluid volume. Hydrocephalus can be succinctly described as the abnormal accumulation of cerebrospinal fluid (CSF) within the brain which ultimately leads to oedema within specific sites of parenchymal tissue. Using hydrocephalus as a test bed, one is able to account for the necessary mechanisms involved in the interaction between oedema formation and cerebral fluid production, transport and drainage. The current state of knowledge about integrative cerebral dynamics and transport phenomena indicates that poroelastic theory may provide a suitable framework to better understand various diseases. In this work, Multiple-Network Poroelastic Theory (MPET) is used to develop a novel spatio-temporal model of fluid regulation and tissue displacement within the various scales of the cerebral environment. The model is applied through two formats, a one-dimensional finite difference - Computational Fluid Dynamics (CFD) coupling framework, as well as a two-dimensional Finite Element Method (FEM) formulation. These are used to investigate the role of endoscopic fourth ventriculostomy in alleviating oedema formation due to fourth ventricle outlet obstruction (1D coupled model) in addition to observing the capability of the FEM template in capturing important characteristics allied to oedema formation, like for instance in the periventricular region (2D model).

Idiopathic fourth ventricle outlet obstruction successfully treated by endoscopic third ventriculostomy: a case report

Introduction

Fourth ventricle outlet obstruction (FVOO) is a rare cause of obstructive hydrocephalus. We describe a case of idiopathic FVOO that was successfully treated with endoscopic third ventriculostomy (ETV).

Case report

A 3-year old boy without any remarkable medical history presented with a headache and vomiting. Computed tomography (CT) images, which had incidentally been taken 2 years previously due to a minor head injury, showed no abnormality. Magnetic resonance imaging on admission showed tetra-ventricular hydrocephalus associated with the dilatation of the fourth ventricle outlets, without any obstructive lesions. However, CT ventriculography, involving contrast medium injection through a ventricular catheter, suggested mechanical obstruction of the cerebrospinal fluid (CSF) at the fourth ventricle outlets. Thus, the patient was diagnosed with FVOO and ETV was performed; the hydrocephalus was subsequently resolved. Although hydrocephalus recurred 1 year postoperatively, re-ETV for the highly stenosed fenestration successfully resolved this condition.

Conclusions

ETV should be considered for FVOO treatment, particularly in idiopathic cases without CSF malabsorption.

Exploring the efficacy of endoscopic ventriculostomy for hydrocephalus treatment via a multicompartmental poroelastic model of CSF transport: a computational perspective

This study proposes the implementation of a Multiple-Network Poroelastic Theory (MPET) model coupled with finite-volume computational fluid dynamics for the purpose of studying, in detail, the effects of obstructing CSF transport within an anatomically accurate cerebral environment. The MPET representation allows the investigation of fluid transport between CSF, brain parenchyma and cerebral blood, in an integral and comprehensive manner. A key novelty in the model is the amalgamation of anatomically accurate choroid plexuses with their feeding arteries and a simple relationship relaxing the constraint of a unique permeability for the CSF compartment. This was done in order to account for the Aquaporin-4-mediated swelling characteristics. The aim of this varying permeability compartment was to bring to light a feedback mechanism that could counteract the effects of ventricular dilation and subsequent elevations of CSF pressure through the efflux of excess CSF into the blood system. This model is used to demonstrate the impact of aqueductal stenosis and fourth ventricle outlet obstruction (FVOO). The implications of treating such a clinical condition with the aid of endoscopic third (ETV) and endoscopic fourth (EFV) ventriculostomy are considered. We observed peak CSF velocities in the aqueduct of the order of 15.6 cm/s in the healthy case, 45.4 cm/s and 72.8 cm/s for the mild and severe cases respectively. The application of ETV reduced the aqueductal velocity to levels around 16-17 cm/s. Ventricular displacement, CSF pressure, wall shear stress (WSS) and pressure difference between lateral and fourth ventricles (ΔP) increased with applied stenosis, and subsequently dropped to nominal levels with the application of ETV. The greatest reversal of the effects of atresia come by opting for ETV rather than the more complicated procedure of EFV.