# Prenatal Diagnosis and Neurodevelopmental Outcome of Children With Marked Opening of the Fourth Ventricle: Challenges and Pitfalls in MRI Diagnostic Criteria

## TL;DR

This study improves MRI criteria for prenatal diagnosis of brain malformations and identifies factors affecting child development outcomes.

## Contribution

The study introduces the tegmento-tentorial angle as a diagnostic tool and the tegmento-vermian angle as a prognostic marker.

## Key findings

- Dandy Walker malformation (DWM) and Blake's pouch cyst (BPC) can be distinguished using the tegmento-tentorial angle.
- The fetal tegmento-vermian angle correlates with neurodevelopmental outcomes.
- Prognostic factors include diagnosis type, associated malformations, and ventriculomegaly.

## Abstract

The neurodevelopmental outcome of ‘Cystic’ malformations of the posterior fossa with marked opening of the fourth ventricle, such as Dandy Walker malformation (DWM) and large Blake's pouch cyst (BPC), is a major issue. This study aimed to refine relevant MRI criteria for distinguishing DWM from BPC and identify prognostic factors.

Inclusion criteria were prenatal retrocerebellar fluid space diameter > 10 mm, marked opening of the fourth ventricle with a tegmento‐vermian angle (TVA) > 40°, and postnatal follow‐up > 2 years.

27 patients were classified as follows: 6 DWM characterized by an overall upward orientation of the tentorium, an open tegmento‐tentorial angle (TTA > 78 ) and a high TVA (median 132°); 15 BPC with a normal downward orientation of the proximal part of the tentorium (TTA < 68°) and distal upward displacement (median TVA 74°); 3 PHACE syndromes (Posterior fossa abnormalities, Haemangioma, Arterial cerebrovascular anomalies, Cardiac defects, Eye anomalies) and 3 unclassified. Four prognostic factors were identified, (i) diagnosis: DWM (two deaths, three learning disabilities and one typical development (TD)) versus BPC (five learning disabilities [4/5 with associated malformation or genetic defects] and 10 TD); (ii) associated versus isolated (36% vs. 87% TD); (iii) obstructive ventriculomegaly versus no hydraulic complications (20% vs. 91% TD); and (iv) the foetal TVA value and clinical outcome (correlation coefficient = 0.561, p = 0.006).

What is already known about this topic?◦Neurodevelopmental outcome of ‘cystic’ malformations of the posterior fossa with markedly opening of the fourth ventricle is a major issue due to their wide variability◦The relevant MRI criteria for distinguishing Dandy‐Walker malformation (DWM) from a large Blake pouch cyst (BPC) need to be refinedWhat does this study add?◦The tegmento‐tentorial angle is relevant for distinguishing DWM from large BPC◦The foetal tegmento‐vermian angle appears to be a prognostic marker to consider

What is already known about this topic?

Neurodevelopmental outcome of ‘cystic’ malformations of the posterior fossa with markedly opening of the fourth ventricle is a major issue due to their wide variability

The relevant MRI criteria for distinguishing Dandy‐Walker malformation (DWM) from a large Blake pouch cyst (BPC) need to be refined

What does this study add?

The tegmento‐tentorial angle is relevant for distinguishing DWM from large BPC

The foetal tegmento‐vermian angle appears to be a prognostic marker to consider