[1] Microlissencephaly is a malformation of cortical development (MCD) that occurs due to failure of neuronal migration between the third and fifth month of gestation as well as stem cell population abnormalities.

[citation needed] This phenotype consists of polyhydramnios (probably due to poor fetal swallowing), severe congenital microcephaly, weak respiratory effort, and survival for only a few hours or days.

[14] Microlissencephaly with intermediate cortex and abrupt anteroposterior gradient[citation needed] Microlissencephaly with mildly to moderately thick (6–8 mm) cortex, callosal agenesis[citation needed] Microlissencephalic patients suffer from spasticity, seizures, severe developmental delay and intellectual disabilities with survival varying from days to years.

[8][15][16] Microlissencephaly may arise as a part of Baraitser-Winter syndrome which comprises also ptosis, coloboma, hearing loss and learning disability.

[21][16][22] Human NDE1 mutations and mouse Nde1 loss lead to cortical lamination deficits, which, together with reduced neuronal production cause microlissencephaly.

Homozygous frameshift mutations in NDE1 gene was found to cause microlissencephaly with up to 90% reduction in brain mass and seizures starting early in life.

It is hypothesized that the KATNB1-associated microlissencephaly is the result of a combined effect of reduced neural progenitor populations and impaired interaction between the Katanin P80 subunit (encoded by KATNB1) and LIS1 (a.k.a.

[28] A loss-of-function mutation in the Doublesex- and Mab-3–Related Transcription factor A2 (DMRTA2, also known as DMRT5) gene has been reported in a case of microlissencephaly, implicating DMRTA2 as a critical regulator of cortical neural progenitor cell dynamics.

[16] Both microlissencephaly and microcephaly with simplified gyral pattern result from either decreased stem cell proliferation or increased apoptosis in the germinal zone of the cerebral cortex.

Microlissencephaly is characterized by a smooth cortical surface (absent sulci and gyri) with a thickened cortex (> 3 mm) and is usually associated with other congenital anomalies.

A PhD thesis has estimated the prevalence of microlissencepahly in southeastern Hungary between July 1992 and June 2006 to be a case every 91,000 live births (0.11:10,000).