Prenatal intracranial hypotension syndrome: new insights into the mechanisms of fenestration of septi pellucidi and ventriculomegaly in fetuses with open spinal dysraphism

Abstract

Objective

To study the prevalence of abnormalities of the septi pellucidi (SP) in a cohort of fetuses with open spinal dysraphism (OSD) and to determine whether this condition is secondary to obstructive ventriculomegaly and, therefore, part of the natural history of prenatal intracranial hypotension (PICH) syndrome.

Methods

Magnetic resonance imaging (MRI) studies from fetuses with OSD were analyzed. The SP were assessed using axial and coronal T2-weighted images of the fetal brain and classified as intact, partially absent, or completely absent. Additionally, the correlation between the presence or absence of the SP and the size of the lateral ventricles, degree of cerebellar tonsillar herniation, collapse of the fourth ventricle, and interpeduncular angle was investigated.

Results

A total of 32 fetuses with OSD were studied. Mean gestational age at the time of the fetal MRI was 25.5 ± 3.9 weeks (range, 19–35) and mean ventricular size was 16.2 ± 4.2 mm (range, 8–26). Twenty-three (71.9%) fetuses had cerebellar tonsillar herniation. The IPA was completely collapsed in 23 cases (71.9%), reduced in seven (21.9%), and unreadable in two (6.3%). Twenty (62.5%) fetuses presented with intact SP, 10 (31.3%) with partially absent SP (incomplete fenestration), and two (6.3%) with completely absent SP (complete fenestration). Fenestration of the SP correlated significantly with the degree of ventriculomegaly (Pearson’s correlation coefficient =0.459; p = .01). However, there was no correlation with the IPA, collapse of the fourth ventricle, and cerebellar tonsillar herniation.

Conclusions

More than one-third of the fetuses with OSD had fenestration of the SP. The most probable etiology is increased intraventricular pressure leading to local necrosis of the SP. As fenestration of the SP is a secondary event associated with PICH syndrome, this condition should not be considered a contraindication for intrauterine repair of the spinal defect. Instead, it should be seen as an indicator of the severity of the intraventricular pressure.

Keywords:

• Fetal brain
• fetal magnetic resonance imaging
• obstructive hydrocephaly
• prenatal diagnosis
• prenatal intracranial hypotension syndrome
• septi pellucidi
• spina bifida
• open spinal dysraphism
• ventriculomegaly

Ethics statement

Approval for this retrospective study was obtained from the Institutional Review Board at the participating centers, as well as from the Ethics Committee for the East Metropolitan Health Service, National Health Service.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data that support the findings of this study are available from the authors upon reasonable request.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

This work was supported by an unrestricted research grant from the Sociedad Profesional de Medicina Fetal ‘Fetalmed’ Ltda., Chile.