Effectiveness and safety of Tachosil® as a ventricular sealant: an observational cohort study.

PURPOSE: Surgery close to or in contact with the ventricular system is challenging due to the complications. We sought to evaluate the effectiveness and safety of TachoSil® as a ventricular sealant in preventing complications after cranial surgery with an open ventricular system (OVS). METHODS: This is a single-center and prospective cohort study We included patients who underwent elective surgery for supratentorial craniotomy and periventricular pathology between December 2020 and November 2023. We registered surgical complications arising from CSF dynamics (such as percutaneous cerebrospinal fluid (CSF) leakage, hydrocephalus, pseudomeningocele), infections, and other complications (postsurgical hematoma) adverse drug reactions (ADRs), reintervention or hospital readmission up to 90 days after surgery. RESULTS: Forty interventions were performed on 39 patients, whose median age was 56 years. Eleven patients (28.2%) had antecedents of previous surgery in the same location, 5 (12.8%) had previously received radiotherapy and chemotherapy, and 11 (28.2%) were smokers. Twenty-four patients (60%) underwent surgery for high-grade glioma, 8 (20%) for low-grade gliomas, 6 (15%) for metastasis and 2 (5%) for meningioma. Throughout the study and up to 90 days after surgery, none of the patients presented an ADR. Only 2 patients (5%) presented with a surgery complications derived from ventricular opening (one patient with a percutaneous CSF leakage and one patients with external hydrocephalus). Both patients resolved with a ventriculoperitoneal shunt. CONCLUSIONS: TachoSil® is a dural sealant that can be used safely and effectively intraparenchymally in patients whose surgery involves a ventricular opening. Only 5% of treated patients presented complications arising from CSF hydrodynamics. No patients had pseudomeningocele, infections or complications related to the use of this sealant. To confirm these positive results, randomized and comparative clinical trials assessing the efficacy of TachoSil® in patients after cranial surgery with an OVS are essential. TRIAL REGISTRATION NUMBER AND DATE OF REGISTRATION: This study was registered in the Clinical Trials.gov (NCT05717335). Date May 1st, 2022.

Anatomical Features of the Ventricular System Relevant to Endoscopic Surgery for Hydrocephalus.

In endoscopic surgery for hydrocephalus and associated intraventricular lesions, a thorough understanding of the required microsurgical anatomy is paramount. Endoscopic procedures in hydrocephalus treatment typically fall into two categories: ventriculocisternostomy and ventriculostomy for obstructive hydrocephalus. In the former, precise knowledge of intraventricular structures, such as the configuration of the ventricles and the path of internal vessels within them, is essential. In the latter, a comprehensive grasp of neural pathways, neural nuclei, and especially venous pathways beneath the ventricular wall is crucial for surgical success. Given that many cases exhibit deviations from normal anatomy, careful examination of preoperative images and a solid understanding of anatomical landmarks during surgery are indispensable. This is particularly critical in endoscopic procedures, which may lack stereoscopic vision, underscoring the importance of acquiring visual cues during the surgical intervention.

Endoscopic Cylinder Surgery for Ventricular Lesions.

Cylinder retractors have been developed to reduce the risk of brain retraction injury during surgery by dispersing retraction pressure on the brain. In recent years, various types of cylinder retractors have been developed and widely used in neurosurgery. The ventricles, being deep structures within the brain, present an effective area for cylinder retractor utilization. Endoscopy provides a bright, wide field of view in the deep surgical field, even through narrow corridors.This chapter introduces surgical techniques using an endoscope through a cylinder. Given the deep and complex shapes of the ventricles, preoperative planning is paramount. Two main surgical techniques are employed in endoscopic cylinder surgery. The wet-field technique involves the continuous irrigation of artificial cerebrospinal fluid (CSF) during the procedure, maintaining ventricle shape with natural water pressure, facilitating tumor border identification, and achieving spontaneous hemostasis. Conversely, the dry-field technique involves CSF drainage, providing a clear visual field even during hemorrhage encounters. In intraventricular surgery, both techniques are used and switched as needed.Specific approaches for lateral, third, and fourth ventricular tumors are discussed, considering their locations and surrounding anatomical structures. Detailed intraoperative findings and strategies for tumor removal and hemostasis are presented.Endoscopic cylinder surgery offers a versatile and minimally invasive option for intraventricular tumors, leading to improved surgical outcomes. Overall, this technique enhances surgical precision and patient outcomes in intraventricular tumor cases.

Practical techniques for safely removing long-term implanted ventricular catheters to minimize bleeding.

INTRODUCTION: Removing ventricular catheters, particularly those implanted for extended periods, poses significant challenges for neurosurgeons due to potential complications such as bleeding from adhesions to the ependyma or choroid plexus. OBJECTIVE: This study aimed to review various techniques for safely removing ventricular catheters, emphasizing methods that minimize the risk of hemorrhagic complications. METHODS: A comprehensive narrative review focused on techniques developed and documented in the literature for safely detaching ventricular catheters adhered to brain structures. RESULTS: Various techniques have been identified that enhance the safety of catheter removal. Notably, the use of monopolar diathermy to coagulate and release adhesions has proven effective. Innovations such as insulated suction devices and the strategic use of flexible endoscopes have also contributed to safer removal procedures, minimizing the risk of damaging surrounding cerebral tissue and preventing catastrophic hemorrhage. CONCLUSION: The removal of ventricular catheters, especially those with long-term implantation, requires precise and cautious techniques to avoid severe complications. The study underscores the importance of adopting advanced surgical techniques and the continuous evolution of safer practices in neurosurgery. These methods not only ensure patient safety but also facilitate the handling of potentially complex and life-threatening situations during catheter removal.

Neuroendoscopy-Assisted Entire-Process Visualization Technique of Ventricular Puncture for External Ventricular Drainage.

OBJECTIVE: This study aimed to investigate the feasibility, safety, and efficacy of the neuroendoscopy-assisted entire-process visualization technique (NEAEVT) of ventricular puncture for external ventricular drainage. METHODS: Eighty-eight patients with cerebral hemorrhage who underwent unilateral ventricular puncture for external ventricular drainage in our hospital from June 2021 to June 2023 were analyzed. Patients were grouped according to puncture technique: NEAEVT (30 patients), freehand (30 patients), and laser-navigation-assisted (28 patients). Operation time, drainage tube placement, and catheter-related hemorrhage incidence were compared between the groups. RESULTS: Mean operation time significantly differed between the freehand, NEAEVT, and laser-assisted groups (17.07, 18.37, and 34.04 min, respectively; P <0.0001). The position of the drainage tube was optimal or adequate in all patients of the NEAEVT group; optimal/adequate positioning was achieved in 80% of the freehand group. No catheter-related hemorrhage occurred in the NEAEVT group. Three freehand group patients and 2 laser-assisted group patients experienced catheter-related hemorrhage. CONCLUSION: The NEAEVT of ventricular puncture is accurate and achieves ventricular drainage without significantly increasing surgical trauma, operation time, or incidence of hemorrhage.

Development of an adjustable patient-specific rigid guide to improve the accuracy of external ventricular catheter placement.

OBJECTIVE: The most common method for external ventricular drain (EVD) placement is the freehand approach, which has reported inaccuracy rates of 12.3%-44.9%, especially in the case of altered ventricular anatomy. Current assistive devices require added time or equipment or do not account for shifted ventricles. To improve the accuracy of emergent EVD placement in the setting of altered ventricular anatomy, the authors designed a patient-specific EVD (PS-EVD) guide. METHODS: The PS-EVD guide has a tripod base and a series of differently angled inserts that lock in place at multiple rotational positions, allowing for numerous insertion angles. For testing, the authors designed a 3D-printed phantom skull with a gelatin brain analog containing ventricles simulating normal and altered ventricular anatomy. Low-resolution CT scans of the phantom were used to calculate the insertion angle in relation to the standard perpendicular entry. The corresponding insert at the correct rotational position within the base unit was positioned over the entry point on the phantom, and the catheter was inserted. Accuracy was evaluated with repeat CT scans. RESULTS: With normal ventricular anatomy, as well as abnormally shifted ventricles, proper use of the PS-EVD guide led to accurate catheter insertion into the ventricle in trials, as confirmed on coronal and sagittal CT images, including cases in which a perpendicular trajectory, such as with the Ghajar guide, was insufficient. CONCLUSIONS: The PS-EVD guide allows consistent and accurate EVD placement in phantom skulls with both normal and altered ventricular anatomy. Further trials comparing this device to the freehand approach are required.

The Anterior Interhemispheric Transcallosal Approach to the Ventricles: How We Do It.

Intraventricular tumors of the lateral and third ventricles are relatively rare, accounting for 1-2% of all primary brain tumors in most large series [1-4]. They can be uniquely challenging to approach due to their deep location, propensity to become large before they are discovered, and association with hydrocephalus [5, 6]. The surgeon's goal is to develop a route to these deep lesions that will cause the least morbidity, provide adequate working space, and achieve a complete resection. This must be performed with minimal manipulation of the neural structures encircling the ventricles, avoiding functional cortical areas, and acquiring early control of feeding vessels [7, 8].

Ventricular Access Utilizing Cutaneous Reference Points: Statistical Analysis and Proposal of a New Ventricular Entry Point.

OBJECTIVES: Perform radiologic measurements and analysis of normal brain computed tomography (CT) scans; delineate a new ventricular entry point from cutaneous landmarks, highlighting the potential surgical implications of these findings. METHODS: Six radiologic distances (AR; BR; AL; BL, C, and D) were measured in normal brain CT scans using Horos software. Statistical analysis of the measurements was performed with minitab18 software based on age, sex, and side. RESULTS: 132 brain CT scans were analyzed, yielding the following mean results: AR distance: 2.1 cm; BR distance: 7 cm; AL distance: 2.1 cm; BL distance: 7.1 cm; C distance: 12.4 cm; D distance: 7 cm; new ventricular entry point: 12.4 cm posterior to the nasion, and 2.1 cm lateral to the midline. CONCLUSIONS: The freehand technique for accessing the lateral ventricles is a common neurosurgical procedure but is often accompanied by complications. To address this, we suggest a novel entry point for ventricular access, determined by cutaneous reference points. This point is situated 12.4 cm posterior to the nasion along the midline and 2.1 cm lateral to the midline. Although our findings may play a role in presurgical planning for ventricular pathologies, future prospective studies are warranted.

Adult idiopathic bilateral occlusion of foramen of Monro: Systematic review with illustrative case.

BACKGROUND: Adult idiopathic occlusion of foramen of Monro (AIOFM) is a rare condition that results in hydrocephalus, and bilateral presentation is even rarer. Here we report a case of idiopathic bilateral stenosis of the foramen of Monro in an adult patient and performed a systematic literature review on the current treatment options and outcomes. METHODS: We performed a systematic review of SCOPUS, Science Direct, and PubMed databases in accordance with PRISMA guidelines. Data on demographics, clinical presentation, imaging findings, type of AIOFM, treatment, and outcomes were collected. RESULTS: A total of 22 cases of bilateral AIOFM were identified in the literature, including ours. The median age was 38.5 years (range: 20-53), with no sex predilection. The most common presenting symptoms were headache (n=16, 73%) and vomiting (n=10, 45%). There were 9 cases of Type 1 AIOFM (stenosis) and 13 cases of Type 2 (membrane occlusion). Majority of patients underwent surgical treatment, mostly endoscopic unilateral foraminoplasty and septostomy (59%), followed by ventriculoperitoneal shunt insertion (31%). One patient underwent medical management only to alleviate her presenting symptoms (seizures). The overall outcome was good for majority of patients at a median follow-up of 6 months. CONCLUSION: Bilateral AIOFM is a rare condition that may easily be missed, so neurosurgeons should be cognizant of this disease entity. Identification of the type of AIOFM may guide surgical decision-making. Treatment options include neuroendoscopic procedures such as septostomy and foraminoplasty, and ventriculoperitoneal shunt insertion.

Endoscopic Ventricular Lavage in Pediatric Pyogenic Cerebral Ventriculitis Associated with Shunt: Outcomes and Technical Notes.

OBJECTIVE: Pyogenic cerebral ventriculitis (PCV) is a rare infectious entity characterized by a potent inflammatory reaction of the ventricular ependyma, which in most cases leads to death. We aim to present the technical note and protocol, based on our center's 10-year experience of the use of endoscopic ventricular lavage (EVL) in pediatric patients with PCV and ventricular peritoneal shunt. METHODS: For this study, all pediatric patients (<16 years) with VP shunts and PCV who were treated with EVL between January 2012 and January 2022 were included. RESULTS: Thirty-four pediatric patients with ventriculitis were analyzed. The median age was 6 years, with 61.7% being male. Most consultations occurred on Day 2 of symptoms. Fever (38.2%) and altered consciousness (26.5%) were the most common initial symptoms. Early ventriculitis was observed in 67.7% of patients. Pathogen identification in the initial cerebrospinal fluid sample was 70.6%, while samples from ventricular peritoneal shunt yielded 23.53% and catheter culture 79.4%. Gram-positive bacteria, mainly S.epidermidis (44.1%), was the most commonly isolated agent. EVL was performed in 73.5% on the second or third day. Reinfection occurred in 23.5%, and 26.5% of patients died. Concordance analysis showed 85.3% agreement between LP and catheter tip samples. Functionality improved, with 55.88% achieving a Lansky score of 90. Early ventriculitis was associated with better Lansky scores. CONCLUSION: EVL can be a useful tool in the management of PCV in cases with VP shunts. Our study suggests a higher chance of isolating an infection-causing germ in the catheter tip culture specimen compared to the cerebrospinal fluid culture. However, future studies with a larger number of patients, or multicentric studies are required for further analysis.

Cerebrospinal Fluid Diversion from the Cisterna Magna in Patients with Idiopathic Intracranial Hypertension and Slit Ventricles: Long-Term Effectiveness, Revision Rates, and Clinical Outcomes.

OBJECTIVE: Idiopathic intracranial hypertension (IIH) is a cerebrospinal fluid (CSF) disorder defect that is frequently treated with CSF shunts. Shunts utilizing the cisterna magna as a proximal reservoir have been described in literature; however, long-term outcomes are unknown. The present study aims to describe the long-term effectiveness, revision rates, and clinical outcomes of this shunt in 14 patients with IIH and slit ventricles. METHODS: A single-center retrospective review of 14 IIH patients treated by cisterna magna shunts was performed. Shunt histories, including revision rate and time until first shunt failure for ventricular, lumbar, and cisterna magna shunts were recorded. "Revision rate" was calculated as the total number of shunt revisions over years of total shunt placement. The average follow-up time was 12.08 years. RESULTS: The mean age at first cisterna magna shunt placement was 18.1 years (6.6-43.3 years) and all patients had radiological evidence of slit ventricles. Cisterna magna shunts improved or resolved clinical symptoms for all 14 patients and had a lower rate of revisions (0.42 revision/year) compared to ventricular (0.72 revision/year) and lumbar (1.30 revision/year) shunts. Of the 11 patients still requiring CSF diversion at the end of the study, eight had functioning shunts that utilized the cisterna magna. CONCLUSIONS: The cisterna magna shunt may be a suitable option for patients with IIH and slit ventricles. Further study is needed to understand the clinical utility of this shunt for the population in which it is indicated.

Prediction of short- and long-term outcomes using pre-operative ventricular size in infants with post-hemorrhagic ventricular dilation.

PURPOSE: Post-hemorrhagic ventricular dilation (PHVD) leads to developmental delays in premature infants, yet the optimal timing of neurosurgical interventions is unknown. Neuroimaging modalities have emerged to delineate injury and follow the progression of PHVD. Fronto-temporal horn ratio (FTHR) is used as a marker of ventricular dilation and can be a standardized tool to direct the timing of neurosurgical intervention. Our study determined a pre-operative FTHR measurement threshold to predict short- and long-term outcomes. METHODS: This is a retrospective cohort study of premature infants with severe intraventricular hemorrhage (IVH) who developed PHVD requiring neurosurgical intervention and were treated in a level IV NICU between 2012 and 2019. Receiver operating characteristic (ROC) curve and area under the curve (AUC) analyses were performed to evaluate the accuracy of pre-operative FTHR for predicting developmental delay. In-hospital outcomes and developmental assessments were analyzed. RESULTS: We reviewed 121 charts of infants with IVH and identified 43 infants with PHVD who required neurosurgical intervention. We found FTHR measurements were an excellent predictor of cognitive and motor delay with an AUC of 0.89 and 0.88, respectively. An average pre-operative FTHR of ≥ 0.67 was also associated with worse lung and feeding outcomes. There was excellent inter-observer reliability of individual components of FTHR measurements. CONCLUSIONS: Early intervention for PHVD is ideal but not always practical. Identification of ventricular size thresholds associated with better outcomes is needed to direct timing of neurosurgical intervention.

Mother-Daughter Ventricular Endoscopy: A Technical Note and 2-Dimensional Video.

BACKGROUND AND IMPORTANCE: While navigating the ventricles with a rigid endoscope provides excellent visualization and the ability to use endoscopic instruments for complex surgery, these endoscopes are often too large to navigate tight areas. We present a surgical video showing the technique of mother-daughter endoscopy, which consists of the introduction of a flexible 1-mm fiberoptic endoscope through the channel of a large rigid endoscope to allow visualization across small spaces or channels, in this case, the cerebral aqueduct. This combination of superior visualization and handling of rigid endoscopes and flexibility and small size of fiberoptic endoscopes enhances safety and broadens possibilities in ventricular surgery. CLINICAL PRESENTATION: A 64-year-old woman with prior endoscopic aqueductoplasty for triventricular hydrocephalus and a failed endoscopic third ventriculostomy presented with focal restenosis of the aqueduct. A repeat endoscopic aqueductoplasty with stent placement were performed. Mother-daughter endoscopy was used to explore the occluded aqueduct for improved safety before fenestration and to ensure proper stent placement after fenestration. CONCLUSION: Mother-daughter endoscopy can add safety to complex or high-risk endoscopic procedures, particularly those with tight spaces that the large mother endoscope cannot visualize.

The prepontine block and its relevance for the development and treatment of hydrocephalus.

OBJECTIVE: Pulsatile CSF flow patterns include flow through the ventricles to the subarachnoid space and cisterns and from the infra- to the supratentorial subarachnoid space. In this study, we demonstrate how an obstruction at the level of the prepontine space may lead to obstructive hydrocephalus with specific radiological characteristics, as well as the implications for treatment options. METHODS: We retrospectively collected data of patients who underwent surgery between February 2010 and December 2022 for hydrocephalus secondary to a suspected prepontine block. One additional patient diagnosed with prepontine block who did not undergo surgery was also included. We excluded patients with a background of previous unrelated neurosurgical procedures or CNS infections. RESULTS: Six children and two adults were included. Three presented with hydrocephalus on imaging, without any other underlying pathology. Five had a suprasellar arachnoid cyst, with its lower border abating the pons and occluding the spinal subarachnoid space (SAS). All cases had an open aqueduct on T2 sagittal sequences, as well as an infracerebellar or retrocerebellar CSF collection. In most cases, a horizontal web was identified in the prepontine region. Seven cases were treated with an endoscopic fenestration. One patient subsequently underwent a shunt surgery. All the operated children reached normal developmental milestones after surgery. CONCLUSIONS: This paper describes a rather small series of cases where clear obstruction was observed at the level of the prepontine subarachnoid space. We believe this anatomical subtlety adds to a better understanding of CSF pathways and the role of ETV in treating hydrocephalus, focusing on a small subgroup of patients without a clear obstruction.

Septostomy and Monroplasty in Isolated Lateral Ventricle After Removal of a Third Ventricle Colloid Cyst: 2-Dimensional Operative Video.

Isolated unilateral hydrocephalus (IUH) is a condition caused by unilateral obstruction of the foramen of Monro.1 Etiopathogenic causes include tumors, congenital lesions, infective ventriculitis, intraventricular haemorrhage, and iatrogenic causes such as the presence of contralateral shunts.2,3 Neuroendoscopic management is considered the "gold-standard" treatment in IUH.4 Even if endoscopic septostomy and foraminoplasty in IUH are well-known procedures,5,6 IUH after an interhemispheric transcallosal transchoroidal approach for removal of a III ventricle colloid cyst is a complication barely described in literature. Video 1 describes this rare complication and the neuroendoscopic treatment adopted, including the operative room setup, patient's positioning, instrumentation needed, and a series of intraoperative tips for the performance of septostomy and Monroplasty via a single, precoronal burr hole. The scalp entry point and endoscope trajectory, homolateral to the dilated ventricle, were planned on the neuronavigation system. The avascular septal zone away from the septal veins and body of the fornix was reached, and the ostomy was performed. At the end of the procedure, Monroplasty was performed, too. The procedure was effective in solving the hydrocephalus and patient's clinical picture. No surgical complications occurred. Imaging demonstrated an evident and progressive reduction of enlarged lateral ventricle. In authors' opinion, the single burr-hole approach, ipsilateral to the enlarged ventricle, provides an optimal identification the intraventricular anatomy and allows Monroplasty to be performed, if deemed feasible during surgery. The patient consented to the procedure. The participants and any identifiable individuals consented to publication of their images.

Fetal surgery for open neural tube defect with severe ventriculomegaly.

OBJECTIVE: Prenatal open neural tube defect (ONTD) repair is performed to decrease the risk of needing treatment for hydrocephalus after birth and to preserve motor function. Some centers may not consider patients to be candidates for surgery if severe ventriculomegaly is present and there is no expected benefit in risk for hydrocephalus treatment. This study sought to compare the postnatal outcome of fetuses with ONTD and severe ventriculomegaly (ventricular width ≥ 15 mm) that underwent prenatal repair with the outcome of fetuses with severe ventriculomegaly that underwent postnatal repair and fetuses without severe ventriculomegaly (< 15 mm) that underwent prenatal repair. METHODS: This was a retrospective study of fetuses with ONTD that underwent prenatal or postnatal repair between 2012 and 2021 at a single institution. The cohort was divided into two groups based on preoperative fetal ventricular size: those with severe ventriculomegaly (ventricular width ≥ 15 mm) and those without severe ventriculomegaly (< 15 mm). Fetal ventricular size was measured by magnetic resonance imaging before surgery using the standardized approach and the mean size of the left and right ventricles was used for analysis. Motor function of the lower extremities was assessed at the time of referral by ultrasound and if flexion-extension movements of the ankle were seen it was considered as preserved S1 motor function. Postnatal outcomes, including motor function of the lower extremities at birth and the need for a diversion procedure for hydrocephalus treatment during the first year after birth, were collected and compared between groups. Multivariate regression analysis was used to adjust for potential confounders. RESULTS: In this study, 154 patients were included: 145 underwent fetal surgery (101 fetoscopic and 44 open hysterotomy) and nine with severe ventriculomegaly underwent postnatal repair. Among the 145 patients who underwent fetal surgery, 22 presented with severe ventriculomegaly. Fetuses with severe ventriculomegaly at referral that underwent prenatal repair were significantly more likely to need hydrocephalus treatment by 12 months after birth than those without severe ventriculomegaly (61.9% vs 28.9%, P < 0.01). However, motor function assessment at birth was similar between both prenatal repair groups (odds ratio, 0.92 (95% CI, 0.33-2.59), P = 0.88), adjusted for the anatomical level of the lesion. The prenatal repair group with severe ventriculomegaly had better preserved motor function at birth compared to the postnatal repair group with severe ventriculomegaly (median level, S1 vs L3, P < 0.01; proportion with S1 motor function, 68.2% vs 11.1%, P < 0.01). Fetuses with severe ventriculomegaly that underwent prenatal repair had an 18.9 (95% CI, 1.2-290.1)-times higher chance of having intact motor function at birth, adjusted for ethnicity, presence of club foot at referral and gestational age at delivery, compared with the postnatal repair group. There was no significant difference in the need for hydrocephalus treatment in the first year after birth between prenatal and postnatal repair groups with severe ventriculomegaly (61.9% vs 87.5%, P = 0.18). CONCLUSIONS: Although fetuses with ONTD and severe ventriculomegaly do not seem to benefit from fetal surgery in terms of postnatal hydrocephalus treatment, there is an increased chance of preserved motor function at birth. Results from this study highlight the benefit of prenatal ONTD repair for cases with severe ventriculomegaly at referral to preserve motor function. © 2024 International Society of Ultrasound in Obstetrics and Gynecology.

Expanding Ventricular Diverticulum Overlying the Cerebral Hemisphere through an Open-Lip Schizencephalic Cleft: A Report of Two Pediatric Cases.

INTRODUCTION: Open-lip-type schizencephaly is characterized by trans-cerebral clefts filled with cerebrospinal fluid (CSF) between the subarachnoid space at the hemisphere surface and the lateral ventricles. Disorders related to CSF retention, including hydrocephalus and arachnoid cysts, have reportedly been associated with open-lip schizencephaly and have induced intracranial hypertension in some cases. However, detailed neuroimaging and surgical treatment findings have rarely been described. CASE PRESENTATION: We report 2 cases of open-lip schizencephaly with an expanding CSF-filled cavity overlying the ipsilateral cerebral hemisphere that manifested as signs of intracranial hypertension. Detailed three-dimensional heavily T2-weighted imaging revealed thin borders between the CSF-filled cavity and the subarachnoid space, but no separating structures between the cavity and the lateral ventricle, suggesting that the cavity was directly connected to the lateral ventricle through the schizencephalic cleft but not to the subarachnoid space. Neuroendoscopic observation in case 1 confirmed this finding. Endoscopic fenestration of the cavity to the prepontine cistern was ineffective in case 1. Shunting between the lateral ventricle (case 1) or CSF-filled cavity (case 2) and the peritoneal cavity slightly decreased the size of the CSF-filled cavity. DISCUSSION: We speculate that the thin borders along the margin of the CSF-filled cavity are membranes that previously covered the schizencephalic cleft and are now pushed peripherally. In addition, we believe that the cavity is a ventricular diverticulum protruding through the cleft and that shunting operation is effective against such expanding cavity. Detailed magnetic resonance imaging can be useful for evaluating patients with schizencephaly associated with CSF retention disorders.