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).
What is the syndrome associated with lissencephaly due to PAFAH1B1 (LIS1) gene mutation?
Miller-Dieker syndrome.
There is diffuse abnormality of the overlying supratentorial mantle with a reduction in the number of gyri and marked thickening of the cortex, best seen anteriorly.