Spontaneous third ventriculostomy in patients undergoing fetal surgery for myelomeningocele correction

Advanced cerebrospinal fluid flow MRI findings of aqueductal stenosis caused by web

BACKGROUND

The aqueductal web (AW) is one of the causes of aqueductus stenosis (AS). Recent advances in Magnetic resonance (MR) imaging have enabled us to better reveal the cerebrospinal fluid (CSF) flow dynamics and aqueductal anatomy.

PURPOSE

The aim of this study is to evaluate the CSF flow dynamics of patients with AW with phase contrast Magnetic resonance imaging (MRI) and compare them with the imaging findings.

MATERIALS AND METHODS

We evaluated 23 patients under 65-year-old age. On constructive interference in steady-state (T2 CISS) images, the width of prepontine cistern (PPC) and the width of Sylvian aqueduct (SA) were measured. Localization and number of webs were evaluated. The existence of flow at the aqueduct and the presence of spontaneous third ventriculostomy (STV) were evaluated on sagittal Sampling Perfection with Application optimized Contrast (SPACE) sequences.

RESULTS

Of the 23 patients included in the study, 11 were male and 12 were female. The mean age was 34.02 (0.5-64). A total of 31 AWs were detected in 23 patients. Six of 23 patients (26.1%) had STV and 17 of those not. Four of 23 patients (17.4%) had aqueductal flow on SPACE sequences. The PPC distance was significantly wider in patients with STV (median: 6.7-4.5, interquartile range (IQR): 1.35, p = 0.004). In the cases where artifact secondary to flow is observed in SPACE sequences in aqueduct, the Evan index (EI) was significantly lower (median: 0.2955-0.3900, IQR: 0.03-0.14, p < 0.001).

CONCLUSION

In patients with a low EI, there may be flow in the SA even if there is a web. In patients with a wide PPC distance, it is necessary to consider the presence of STV and evaluate the presence of flow with the SPACE sequences.

Spontaneous Third Ventriculostomy in Cases of Aqueductal Stenosis: A Retrospective Case Series

BACKGROUND

Spontaneous third ventriculostomy (STV) is a rare occurrence in cases of obstructive hydrocephalus where the walls of the third ventricle rupture, communicating the ventricular system, and the subarachnoid space leading to arrest of active hydrocephalus. We aim to review our series of STVs while reviewing previous reports.

METHODS

A retrospective review of cases undergoing cine phase-contrast magnetic resonance imaging (PC-MRI) from 2015 to 2022 of any age with imaging evidence of arrested obstructive hydrocephalus was performed. Patients in which aqueductal stenosis was radiologically evident and the presence of third ventriculostomy through which cerebrospinal fluid flow was detectable were included. Patients who previously underwent endoscopic third ventriculostomy were excluded. Data on patient demographics, presentation, and imaging details of STV and aqueductal stenosis were collected. We searched the PubMed database using the following keyword combination: ((("spontaneous ventriculostomy") OR ("spontaneous third ventriculostomy")) OR ("spontaneous ventriculocisternostomy")) including English reports of STV published between 2010 and 2022.

RESULTS

Fourteen cases were included (7 adults, 7 pediatrics), all with history of hydrocephalus. STV occurred in the floor of the third ventricle in 57.1% of the cases, at the lamina terminalis in 35.7%, and at both sites in 1 case. Eleven publications reporting 38 cases of STV were identified from 2009 to date. Minimum follow-up period was 10 months and maximum follow-up is 77 months.

CONCLUSIONS

In cases of chronic obstructive hydrocephalus, neurosurgeons should be minded with the possibility of the presence of an STV on cine phase-contrast magnetic resonance imaging leading to arrested hydrocephalus. The delayed flow at the aqueduct of Sylvius might not be the only determinant of the necessity of cerebrospinal fluid diversion and the presence of an STV should be factored into the neurosurgeon's decision considering the patient's clinical picture.

Chiari III malformation with defect in Liliequist membrane on MR imaging

The Liliequist membrane is a radiologically neglected structure, with routine evaluation only carried out in pre-operative and post-operative cases of third ventriculostomy. We report two cases of Chiari III malformation in two unrelated females with similar findings on magnetic resonance imaging study including occipital and low cervical encephalocele, hydrocephalus, and segmentation anomalies in cervical spine. Along with these findings, we report a flow void on T2-weighted images observed in both cases across the site of Liliequist membrane between interpeduncular and chiasmatic cistern. Our findings of CSF flow across the Liliequist membrane may represent spontaneous third ventriculostomy or another congenital defect in the myriad of anomalies seen in cases of Chiari III malformation.