What are the two types of lissencephaly and what is the fundamental difference between them?
Unimaginatively called type I and type II. The former (this case) represents undermigration of neurons and is on a spectrum with pachygyria and subcortical band heterotopia. The latter is due to overmigration of neurons through the glia terminale.
How do individuals with type I lissencephaly usually present?
Hypotonia, poor feeding and infantile epilepsy (West syndrome).
There is diffuse abnormality of the overlying supratentorial mantle with reduction in number gyri and marked thickening of the cortex, best seen anteriorly.