Periventricular Nodular Heterotopia, Cerebellar Hypodysgenesis, and Mesial Temporal Malformation Detected on Fetal MRI: An Underrecognized Association.

Periventricular nodular heterotopia (PNH) is a neuronal migrational anomaly frequently associated with filamin-A (FLNA) gene variants. However, in the absence of a pathogenic FLNA gene or in the context of other genetic mutations, PNH may demonstrate a distinct pattern of distribution, often accompanied by a variety of brain abnormalities. PNH associated with cerebellar hypodysgenesis (CHD) and malformation of cortical development (MCD) involving the mesial temporal lobes, without detectable FLNA variants, is a known but under-reported association. PNH in this context demonstrates a phenotypically distinct distribution (ie, along the infrasylvian lateral ventricles). In this review, we report the prenatal MRI finding of this unusual association and provide key insights into this abnormality.