Lissencephaly
Findings:
Axial and sagittal PD/T2WI show uniformly thickened cortex
with only minimal sulcation of the frontal lobes. The sylvian fissures
are widened. Parietooccipital sulcation is absent.
Differential Diagnosis:
None exists except lissencephaly. A markedly premature
brain would not have this bizarre thickened cortex.
Discussion:
Lissencephaly is the most severe of the migrational anomalies.
Affected individuals are profoundly mentally retarded and usually have
severe seizure disorders. A global migrational abnormality is postulated,
occurring between 11-26 weeks. The cortex is abnormally thickened and sulcation
largely absent, with 2-4 instead of the normal 6 cell layers of cortex.
Colpocephaly is usually present.
Types:
I-Miller-Deiker-
assd with 17p-
II-Walker-Warburg-
assd with hydrocephalus
III-isolated
Heterotopia is the most common migrational anomaly. Others
include schizencephaly, pachygyria, and polymicrogyria, each occurring
at a different stage of fetal development.