Linear nevus sebaceous syndrome: megalencephaly and heterotopic gray matter.

A 3-month-old white male with linear nevus sebaceous syndrome (LNSS), facial deformities, brain malformations, and cortical blindness is presented. Facial deformities included left ear hypertrophy and a left-sided hamartomatous neck mass. Magnetic resonance imaging suggested that a central nervous system (CNS) abnormality, involving gray and white matter, should be linked with LNSS. Magnetic resonance imaging was more useful than computed tomography in demonstrating the full spectrum of CNS anomalies, including unilateral lissencephaly, a paucity of white matter, excessive and heterotopic gray matter, apparent left schizencephaly, and unilateral left colpocephaly (dilation of atrium and posterior horn of lateral ventricle). Postmortem examination revealed left hemisphere megalencephaly with a dilated posterior horn of the lateral ventricle. The impressive gray matter heterotopias likely were the source of the patient's seizures and perhaps the ultimate cause of death. Megalencephaly and other deviations of neuronal migration should be considered as a dramatic component of LNSS.