Lissencephaly Type I Classic

Etiology: abnormality of neuronal migration characterized by undermigration
Imaging: absent gyri giving a smooth brain appearance, shallow vertical Sylvian fissues giving brain an hourglass or figure of 8 appearance on axial images, thickened “cortex” – usually thinner outer layer and thicker inner layer with thin white matter layer separating the two (“cell sparse zone”), diminished cerebral white matter and often callosal hypogenesis, ventriculomegaly, occasionally cerebellar hypoplasia
DDX:
Complications:
Treatment:
Clinical: developmental delay and seizures, agyria = complete lissencephayly, pachygyria = incomplete lissencephaly, band heterotopia is milder form of classic lissencephaly

Radiology Cases of Lissencephaly Type I Classic

MRI of lissencephaly type I classic — Axial T1 (left) and axial T2 (right) MRI without contrast of the brain shows a decreased number of gyri and sulci resulting in a nearly smooth brain. There is ventriculomegaly. Overall the brain has an hourglass or figure of 8 appearance.