Contralateral hemimicrencephaly in neonatal hemimegalencephaly.

Identification of abnormalities in the contralateral hemisphere in patients with hemimegalencephaly is critical in their management. In this report, we present a 5-day-old neonate with hemimegalencephaly who demonstrated an enlarged ipsilateral cerebral hemisphere and diffuse volume loss in the contralateral hemisphere on conventional MR imaging sequences. The ipsilateral frontal white matter demonstrated relatively increased NAA, fractional anistropy, and cerebral blood volume values compared to published normative data. In addition, the white matter of the contralateral hemisphere demonstrated elevated lactate and increased mean diffusivity compared to published normative data, supporting the abnormal conventional MR findings. Advanced MR neuroimaging techniques may help further confirm and characterize abnormalities in the smaller contralateral hemisphere in neonatal hemimegalencephaly.