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

INTRODUCTION

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.

PATIENTS AND

METHODS

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.

RESULTS

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).