Hemimegalencephaly

Case contributed by Dr Alexandra Stanislavsky

Presentation

20 week morphology screen

Patient Data

Age: 20 weeks (gestation)
ultrasound

There is unilateral ventriculomegaly. No other fetal intracranial abnormality demonstrated.

There were no other ultrasound findings. Isolated asymmetric ventriculomegaly prompted referal for fetal MRI.

mri

Fetal MRI confirms unilateral right ventriculomegaly. There are also several other abnormallities involving the right hemisphere. There is dysplastic, abnormally increased sulcation and asymmetric right periventricular grey matter contiguous with the basal ganglia. The left hemisphere has a normal appearance, with the degree of sulcation normal for gestational age. 

There is mild enlargement of the right calvaria relative to the left.

Case Discussion

This case demonstrates the utility of fetal MRI in characterization and prognostication of intracranial abnormalities detected sonographically.  Routine 2nd trimester ultrasound found unilateral ventricular enlargement. However fetal neurosonography is limited in assessment of grey matter structures and sulcation.  Additional findings on the subsequent MRI included overall increased size of the right hemisphere, lateral ventricle and calvaria with suspected polymicrogyria and grey matter heterotopia.  The features are in keeping with hemimegalencephaly, which carries a poor neurological prognosis. 

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