Membranous structures affecting the success of endoscopic third ventriculostomy in adult aqueductus sylvii stenosis

Clinical and surgical outcome of endoscopic third ventriculostomy (ETV) and ventriculoperitoneal shunt (VPS) in patients with Long-Standing Overt Ventriculomegaly in Adults (LOVA): a systematic review

OBJECTIVES

The optimal surgical procedure for long-standing overt ventriculomegaly in adults (LOVA) remains controversial.

METHODS

A systematic search of three databases was performed for studies published between January 1999 and March 2022. This systematic review included 12 studies with a total of 318 patients with LOVA surgically treated. PRISMA guidelines were followed.

RESULTS

Gait disturbance (74.8%) and headache (59.7%) were the most common clinical presentation. Overall, the rate of postoperative clinical improvement at the last follow-up was 83.6% (95% CI 78.1-86.1). A lower rate of postoperative clinical improvement or halt of progression of presenting symptoms was observed after ETV (211/257 = 82.1% 95% CI 76.2-85.1%) compared with VPS (55/61 = 90.2% 95% CI 80.3-96.1%). Overall, surgical and postoperative complications were reported in 22/297 patients (7.5% 95% CI 4.4-20%) (11 studies). A higher rate of surgical complications was observed in patients treated with VPS (19.7% 95 CI 5.9-46.7%), compared with patients treated with ETV (4.3% 95% CI 2.1-10.9%). The overall rate of second surgery due to failure of first surgical approach (ETV or VPS) was 46/275 (16.7%).

DISCUSSION

This meta-analysis confirmed the efficacy of EVT and VPS in symptomatic patients with LOVA, reporting a roughly 84% of postoperative clinical improvement or halt of progression of symptoms. A higher rate of surgical complications was observed in patients treated with VPS compared with patients treated with ETV. In addition, roughly 18% of patients treated with ETV required a further VPS. These findings should be considered when advising LOVA patients regarding the management of hydrocephalus.

Transvascular in vivo microscopy of the subarachnoid space

BACKGROUND

The micro-architectonics of the subarachnoid space (SAS) remain partially understood and largely ignored, likely the result of the inability to image these structures in vivo. We explored transvascular imaging with high-frequency optical coherence tomography (HF-OCT) to interrogate the SAS.

METHODS

In vivo HF-OCT was performed in 10 dogs in both the posterior and anterior cerebral circulations. The conduit vessels used were the basilar, anterior spinal, and middle and anterior cerebral arteries through which the perivascular SAS was imaged. The HF-OCT imaging probe was introduced via a microcatheter and images were acquired using a contrast injection (3.5 mL/s) for blood clearance. Segmentation and three-dimensional rendering of HF-OCT images were performed to study the different configurations and porosity of the subarachnoid trabeculae (SAT) as a function of location.

RESULTS

Of 13 acquisitions, three were excluded due to suboptimal image quality. Analysis of 15 locations from seven animals was performed showing six distinct configurations of arachnoid structures in the posterior circulation and middle cerebral artery, ranging from minimal presence of SAT to dense networks and membranes. Different locations showed predilection for specific arachnoid morphologies. At the basilar bifurcation, a thick, fenestrated membrane had a unique morphology. SAT average thickness was 100 µm and did not vary significantly based on location. Similarly, the porosity of the SAT averaged 91% and showed low variability.

CONCLUSION

We have demonstrated the feasibility to image the structures of the SAS with transvascular HF-OCT. Future studies are planned to further map the SAT to increase our understanding of their function and possible impact on neurovascular pathologies.

Long-Standing Overt Ventriculomegaly in Adults (LOVA): Diagnostic Aspects, CSF Dynamics with Lumbar Infusion Test and Treatment Options in a Consecutive Series with Long-Term Follow-Up

BACKGROUND

Long-standing overt ventriculomegaly in adults is a chronic form of hydrocephalus without a clear pathophysiological description and a consensus about the treatment. We present the results of endoscopic third ventriculostomy (ETV) in a consecutive series with a mean follow-up of 79 ± 23 months, highlighting how the preoperative lumbar infusion test could facilitate understanding the pathophysiology of the disease.

METHODS

We retrospectively collected data regarding clinical assessment, neuroradiological findings, and preoperative lumbar infusion tests in 22 symptomatic patients.

RESULTS

In the majority of cases, patients reported imbalance and gait disorders, and 8 subjects had headaches. The preoperative lumbar infusion test demonstrated a mean opening pressure of 13.95 ± 2.88 mm Hg, with plateau values ranging from 22 to 39 mm Hg. The resistance to outflow was 11.21 ± 2.00 mm Hg/mL/min. After the procedure, all patients reported improvement or halted progression in their presenting symptoms, whereas no significant reduction was demonstrated in Evans' index. One subject underwent a second ETV procedure after more than 2 years because of the failure of the endoscopic approach.

CONCLUSIONS

A progressive exhaustion of brain compliance plays an important role in explaining the dichotomy between severe ventriculomegaly and mild clinical symptoms in patients with long-standing overt ventriculomegaly in adults. The role of the aqueductal stenosis as a diagnostic criterion might be reconsidered. The preoperative infusion test data support this observation. Preoperative assessment should include not only clinical and neuroradiological evaluation but also the study of cerebrospinal fluid dynamics. ETV should be considered the treatment of choice because of its safety and efficacy. Long-term follow-up is mandatory.

The role of the Liliequist membrane in the third ventriculostomy

Endoscopic third ventriculostomy (ETV) is a hydrocephalus treatment procedure that involves opening the Liliequist membrane (LM). However, LM anatomy has not been well-studied neuroendoscopically, because approach angles differ between descriptive and microsurgical anatomical explorations. Discrepancies in ETV efficacy, especially among children age 2 and younger, may be due to incomplete LM opening. The objective of this study was to characterize the LM anatomically from a neuroendoscopic perspective to better understand the impact of anatomical features during LM ostomy and the ETV success rate. Additionally, the ETV success score was tested to predict patient outcome after the intraoperatively difficult opening of LM. Fifty-four patients who underwent ETV were prospectively analyzed with a mean follow-up of 53.1 months (1-90 months). The ETV technical parameters of difficulty were validated by seven expert neurosurgeons. The pediatric population (44) of this study represents the majority of patients (81.4%). The overall ETV success rate was 68.5%. Anomalies on the IIIVT floor resulted in an increased rate of ETV failure. The IIIVT was anomalous, and LM was thick in 33.3% of cases. Fenestration of LM was difficult in 39% of cases, and the LM and TC were opened separately in 55.6% of cases. The endoscopic third ventriculostomy success score (ETVSS) accurately predicted the level of difficulty opening the LM (p = 0.012), and the group with easy opening presented greater durability in ETV success. Neurosurgeons should be aware of the difficulty level of the overture of LM during ETV and its impact on long-term ETV effectiveness.

Long-standing Overt Ventriculomegaly in Adults and Endoscopic Third Ventriculostomy, the Perfect Treatment for the Proper Diagnosis

OBJECTIVE

Long-standing overt ventriculomegaly in adults (LOVA) is form of hydrocephalus that develops during childhood, manifesting its symptoms during adulthood. Only a small number of LOVA case series have been published, and controversies regarding optimal management still exist. The authors collected a series of symptomatic LOVA patients treated successfully using endoscopic third ventriculostomy (ETV), aiming to strengthen what has been reported in the literature on ETV's role in both neurologic and neurocognitive outcomes.

METHODS

Between 2002 and 2020, we collected 40 case studies of patients treated using an ETV. Associated pathologies were documented in 14 cases. All patients underwent magnetic resonance scans preoperatively and postoperatively while only 29 patients were submitted during follow-up to neurocognitive assessment.

RESULT

At a mean follow-up of 6 years, 36 patients (90%) reported either an improvement or a stabilization of their presenting symptoms. Headache improved subjectively in 11 patients (27.5%), balance and gait disturbances improved in all patients, urinary incontinence improved in 24 patients (60%), memory disturbances subjectively improved in 21 patients (52.5%), and visual deficits improved in 5 patients (12.5%). Four patients (10%) had symptom progression, which occurred 6 to 24 months after surgery with radiologic evidence of ETV failure.

CONCLUSIONS

LOVA is a form of hydrocephalus that must be correctly identified. A correct magnetic resonance study and comprehensive neuropsychologic assessment are crucial to identify it in order to define proper management. From our analysis, ETV represents the gold standard treatment granting rewarding results that are maintained in a long-term follow-up.

Natural History of Endoscopic Third Ventriculostomy in Adults: Serial Evaluation with High-Resolution CISS

BACKGROUND AND PURPOSE

Endoscopic third ventriculostomy is a well-accepted treatment choice for hydrocephalus and is used most frequently with a known impediment to CSF flow between the third ventricle and basal cisterns. However, there are scarce data on the imaging evolution of the defect in the floor of the third ventricle and how this affects patency rates and clinical outcomes. The purpose of this study was to assess whether, and how, the endoscopic third ventriculostomy defect changes in size with time.

MATERIALS AND METHODS

All high-resolution endoscopic third ventriculostomy protocol MRIs performed between 2009 through 2014 were retrospectively identified. Two fellowship-trained neuroradiologists, blinded to clinical information, independently reviewed all retrospective cases.

RESULTS

A total of 98 imaging studies were included from 34 patients. The average change in the area throughout the studied period was 0.02 mm²/day (7.5 mm²/year), with a higher increase in size noted in the first 3 postsurgical months, with a gradual decrease in the degree of defect-size change. Use of the NICO Myriad device was correlated with the area of the endoscopic third ventriculostomy defect on the last follow-up, demonstrating a larger final defect size in patients in whom the surgical technique included debridement of the endoscopic third ventriculostomy defect walls with the NICO Myriad device (28.21 versus 11.25 mm, P < .05).

CONCLUSIONS

High-resolution MR imaging with sagittal CISS images is useful in the postoperative evaluation of endoscopic third ventriculostomies. Such findings may prove useful in determining the optimal duration of follow-up with MR imaging of patients who have undergone endoscopic third ventriculostomy.

Reduced subarachnoid fluid diffusion in enlarged subarachnoid spaces of infancy

Background and purpose Enlargement of the subarachnoid spaces in infancy (ESSI) is a common cause of macrocephaly without proven explanation. We have observed subarachnoid diffusion to be decreased in these patients. We aim to quantify the diffusivity of ventricular and subarachnoid cerebrospinal fluid in ESSI patients, to determine if diffusion characteristics deviate from normocephalic infants, and to propose a unique mechanism for ESSI. Materials and methods 227 consecutive brain magnetic resonance exams from different macrocephalic children were retrospectively reviewed after institutional review board waiver. Patients with noncommunicating hydrocephalus, substantial ventriculomegaly, atrophy, structural bone and/parenchymal abnormalities, abnormal brain signal, hemorrhages, meningitis, and normal imaging were excluded. A total of 53 exams from macrocephalic patients and 21 normocephalic subjects were analyzed. Mean quantitative apparent diffusion coefficient (ADC) values were obtained from the ventricular frontal horn and frontal subarachnoid spaces. The subarachnoid:ventricular ADC ratios were compared using a Mann-Whitney U-test. Results The mean age was 13 +/-8 months (macrocephalic cohort) and 13 +/- 6 months (normocephalic cohort). The subarachnoid fluid mean ADC was 2.50+/-0.26 × 10^-3 mm²/s in the macrocephalic group and 2.84+/-0.29 × 10^-3 mm²/s in the normocephalic group. The ventricular fluid mean ADC was 2.97+/-0.37 × 10^-3 mm²/s and 2.74 +/-0.32 × 10^-6 mm²/s, respectively. The mean quantitative ADC ratios in the macrocephalic group were 0.85, significantly smaller than the normocephalic group (1) ( z = -6.3; p = 0). Conclusion Subarachnoid space fluid diffusivity is reduced in patients with enlarged subarachnoid spaces of infancy. We propose insufficient frontotemporal capillary protein resorption to be the initiating factor in ESSI, leading to unbalanced osmotic/hydrostatic pressures, and secondary congestion.

Assessment of Liliequist membrane by 3D-SPACE technique at 3 T

INTRODUCTION

Liliequist membrane (LM) is the most important anatomic structure for the success of endoscopic third ventriculostomy (ETV). Identification of this membrane is difficult with conventional MRI techniques. The purpose of this retrospective study is to determine the impact of three-dimensional sampling perfection with application-optimized contrasts using different flip-angle evolutions (3D-SPACE) sequence with variant flip-angle mode (VFAM) in the assessment of LM at 3-T MRI devices.

METHODS

3D-SPACE with VFAM images were obtained in 445 patients. LM visibility and integrity were scored as 0 (good), 1 (moderate), and 2 (poor) on these images for each parts (sellar, diencephalic, and mesencephalic) and overall of the membrane.

RESULTS

According to the LM overall integrity scores, 11 % (48 cases) of the patients had perforated membrane. According to subsegmental integrity scores, sellar part was completely intact in 63 % of patients, diencephalic segment was completely intact in 60 % of the patients, and mesencephalic segment was completely intact in 95 % of the patients. Visibility scores of the third ventricle inferior wall were significantly higher in the patients with intact LM (p = 0.001). There was not any statistically significant relationship between LM pattern and overall integrity (p = 0.352). LM attachment sites could be detected easier in the patients who had better visibility of third ventricle inferior wall or intact LM (p < 0.001 for both).

CONCLUSION

3D-SPACE technique is a useful alternative for the evaluation of morphology, integrity, individual variations, topographic relationships, and visibility of LM since it has some advantages including lower SAR values, fewer artifacts, and high-resolution images.

Visualization of Liliequist's membrane prior to endoscopic third ventriculostomy

PURPOSE

Endoscopic third ventriculostomy (ETV) is an effective treatment in patients with obstructive hydrocephalus caused by aqueductal stenosis. Operative failure may occur if an unnoticed membrane below the floor of the third ventricle is present, such as Liliequist's membrane (LM). To analyze how often LM can be visualized by high-resolution heavily T2-weighted 3D-MRI prior to ETV, and to find out potential reasons for diagnostic failure.

MATERIALS AND METHODS

Preoperative 3D-MR images of 37 consecutive patients (19 female, median 42 years) were retrospectively analyzed. Visualization of three LM segments (sellar, diencephalic, mesencephalic), dimensions of the space below the third ventricle, and extent of hydrocephalus were measured. Image quality was scored (score 1[poor] to 3[excellent]). Preoperative imaging findings were compared with intraoperative findings.

RESULTS

Patients were subdivided into group 1 (no segment of LM identified, n = 18), and group 2 (at least one segment of LM was identified, n = 19). The sellar segment of LM was most often positively identified (10 out of 19 cases). The mean distance between the pons and the sella/clivus was significantly shorter in group 1 than in group 2 (3.7 vs. 6.2 mm; p < 0.01). Other variables, such as the distance between tip of the pons and the mamillary bodies as well as the image quality, were not significantly different between both groups. Intraoperatively, LM was present in 78 % of group 2 patients, and in 28 % of group 1 patients, respectively (p < 0.03).

CONCLUSIONS

LM can be detected in about half of patients prior to ETV. Reduced PSD influences visualization of LM.

Liliequist membrane: radiological evaluation, clinical and therapeutic implications

In a simplistic and succinct way, Liliequist membrane may be understood as a projection formed by an arachnoid membrane extending from the dorsum sellae to the mammillary bodies. In spite of being well known to neurosurgeons, many radiologists neither know this anatomical structure nor give importance to its study. The imaging evaluation of this membrane is feasible and may be interesting for a better preoperative planning; postoperative evaluation of third ventriculostomies; and understanding of suprasellar arachnoid cysts and perimesencephalic hemorrhage. The present article illustrates the anatomy of the membrane, with emphasis on imaging findings, besides describing its possible clinical and surgical implications.

Endoscopic third ventriculostomy

Endoscopic third ventriculostomy (ETV) is considered as a treatment of choice for obstructive hydrocephalus. It is indicated in hydrocephalus secondary to congenital aqueductal stenosis, posterior third ventricle tumor, cerebellar infarct, Dandy-Walker malformation, vein of Galen aneurism, syringomyelia with or without Chiari malformation type I, intraventricular hematoma, post infective, normal pressure hydrocephalus, myelomeningocele, multiloculated hydrocephalus, encephalocele, posterior fossa tumor and craniosynostosis. It is also indicated in block shunt or slit ventricle syndrome. Proper Pre-operative imaging for detailed assessment of the posterior communicating arteries distance from mid line, presence or absence of Liliequist membrane or other membranes, located in the prepontine cistern is useful. Measurement of lumbar elastance and resistance can predict patency of cranial subarachnoid space and complex hydrocephalus, which decides an ultimate outcome. Water jet dissection is an effective technique of ETV in thick floor. Ultrasonic contact probe can be useful in selected patients. Intra-operative ventriculo-stomography could help in confirming the adequacy of endoscopic procedure, thereby facilitating the need for shunt. Intraoperative observations of the patent aqueduct and prepontine cistern scarring are predictors of the risk of ETV failure. Such patients may be considered for shunt surgery. Magnetic resonance ventriculography and cine phase contrast magnetic resonance imaging are effective in assessing subarachnoid space and stoma patency after ETV. Proper case selection, post-operative care including monitoring of ICP and need for external ventricular drain, repeated lumbar puncture and CSF drainage, Ommaya reservoir in selected patients could help to increase success rate and reduce complications. Most of the complications develop in an early post-operative, but fatal complications can develop late which indicate an importance of long term follow up.

Radiologic evaluation of pediatric hydrocephalus

INTRODUCTION

The aim of this review is to present the contemporary role of radiology in evaluating pediatric hydrocephalus. Although conventional brain imaging with ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI) reveal the degree of ventricular enlargement and often the etiology of the hydrocephalus, the diagnosis and management of hydrocephalus present common problems in pediatric populations.

DISCUSSION

US, usually sufficient to assess and monitor ventricular size, is used most commonly in preterm infants who have germinal matrix hemorrhages and not able to tolerate transport to the radiology department. Although CT can demonstrate gross dilatation of ventricles, in most cases, it will be necessary to more closely define the nature of the obstruction, either functionally or anatomically. MRI is the best imaging modality to provide such functional and anatomic information. However, since identification of obstructive pathologic processes at any level through the cerebrospinal fluid (CSF) pathway in patients with hydrocephalus is of significant importance because it can change the treatment options, avoiding shunt insertion, a more sophisticated MRI approach is needed instead of obtaining a routine cranial MRI. Furthermore, the outcome after neuroendoscopic procedures is clearly related to patient selection under guidance of neuroimaging.

CONCLUSION

Therefore, the article focuses mainly on the effective usage of various MRI sequences in both diagnosis and follow-up of pediatric hydrocephalus, such as 3D CISS, cine PC, TSE, and GRE T2* sequences, to be able to investigate all possible obstructive pathology through the CSF pathway and to assess the efficiency of treatment in a standardized way.