Lissencephaly Type I Classic

• Etiology:
  — Abnormality of neuronal migration characterized by undermigration
  — Agyria = complete lissencephayly, pachygyria = incomplete lissencephaly, band heterotopia is milder form of classic lissencephaly
• Imaging MRI:
  — Absent gyri giving brain a smooth unsulcated 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

Radiology Cases of Lissencephaly Type I Classic