August 20, 2015: Lissencephaly

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Brought to you by the Residents & Fellows Section of Neurology.

August 20, 2015


Lissencephaly is a cortical developmental malformation occurring secondary to abnormal neuronal migration. Cortical developmental malformations are the result of one of three causes: migration, organization or cell proliferation. In classic lissencephaly, type I, there are reduced numbers of layers in the cortex – this often results in only four layers of cortex compared to the typical six layers. The cortex does appear thick. Overall, there are a reduced number of cortical gyrations and sometimes no gyri, leading to a smooth brain. Miller-Dieker syndrome is commonly associated with lissencephaly type I, with associated microcephaly, facial dysmorphic features, developmental delay, hypotonia, and seizures. Miller-Dieker syndrome leads to abnormalities in the LIS1 gene on chromosome 17, which interferes with neuronal migration secondary to alterations in microtubule formation. Cobblestone lissencephaly, or type II, is characterized by reduced number of gyri that appear like cobblestones, with no recognizable layers in the cortex.


  1. Spalice A, Parisi P, Nicita F, Pizzardi G, Del Balzo F, Iannetti P. Neuronal migration disorders: clinical, neuroradiologic and genetic aspects. Acta Paediatr. 2009; 98: 421-433.

Submitted by James Addington, M.D. Resident Physician, Department of Neurology, University of Virginia.

Disclosures: Dr. Addington is a member of the Residents & Fellows Section of Neurology

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