Polymicrogyria-MRI

18 days old  full term normal delivery  non consanguineous  origin baby with  seizures suggests neuronal proliferation anomalies possibly polymicrogyria (PMG type 1) with hypoplastic callosum (no microcephaly ) and unremarkable cerebellum.

 Teaching Points by Dr MGK Murthy, Dr GA Prasad and Mr Maniyam.

Disorders of neuronal development can be of 3 types

 (a) proliferation (2-4 months) starts from ventricular  and subventricular zones . Microlissencephaly from too few neurons,  hemimegalencephaly from too many , and Focal cortical dysplasia(FCD) from abnormal neurons.  These extend from ventricles to piamater

 (b) migration (3-5 months) guided by radial glial cells , classic lissencephaly,  from arrest of neuronal migration; cobblestone lissencephaly,  from over migration of the neurons; and heterotopia, result of ectopic neuronal migration.  These are limited to white matter

(c) organisation (22 weeks to 2 years) differentiate in to pyramidal cells, stellate cells, which organize into horizontal laminar aggregates and vertical columns. Usually results from prenatal ischemia or  infection and are limited to cortex Polymicrogyria (PMG)  from injury of the superficial part of the brain, & schizencephaly  due to insult of the whole thickness of the brain.