Also known as agyria
Some 65% are associated with mutations in the LIS1 gene.
Smooth brain with no or little gyrus in the cerebral cortex
It is due to incomplete or complete failure of neuronal migration during the 12th to 24th postmentrual weeks
Microcephaly, ventriculomegaly, wide Sylvian fissures, complete or partial agenesis of the corpus callosum
2 types of Lissencephaly
A. Type 1 is associated with facial dysmorphism sometimes with deletion of 17p chromosome known as Miller Dicker syndrome
B. Type 2 is associated with hydrocephaly and dysgenesis of cerebellum - Walkar-warburg syndrome
Prenatal diagnosis of lissencephaly
Transvaginal ultrasound - imaging of the surface of the cerebral hemispheres and should facilitate in-utero diagnosis.
Prenatal diagnosis of lissencephaly probably cannot be made reliably until 26 to 28 postmenstrual weeks, when the normal gyri and sulci become well defined. Up to this time, the normal fetal brain has a smooth appearance