Findings:
Coronal T1 and axial T2WI show a thick subcortical mantle
of intermediate signal that is isointense to gray matter on both sequences.
Colpocephaly is present.
Differential Diagnosis:
A severe migrational anomaly is almost certain. The distinction
between lissencephaly and band heterotopia is made by the relatively preserved
sulcation seen with heterotopia in this case. The images shown simulate
markedly thickened cortex, but there is a thin subcortical rim of white
matter. Migrational anomalies can coexist.
Discussion:
Gray matter heterotopia is a migrational anomaly of variable
severity which occurs between 2-5 months of gestation. It is the most common
migrational anomaly. Heterotopia may be divided into nodular and band types,
the nodular type being much more common than band heterotopia. Other migrational
anomalies include lissencephaly, pachygyria, schizencephaly, and polymicrogyria.