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  • Updated 06.01.2020
  • Released 10.31.1994
  • Expires For CME 06.01.2023

Lissencephalies

Introduction

This article includes discussion of lissencephaly, Miller-Dieker lissencephaly syndrome, and lissencephaly syndrome. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.

Overview

Lissencephaly (or agyria) is a congenital disorder of cortical development wherein cerebral convolutions are absent and the surface of the brain is smooth. Patients suffer from intellectual disability, hypotonia, motor delay, and seizures. More than 25 syndromes have lissencephaly as a feature. Miller-Dieker syndrome is one of the more common of these and is characterized by facial changes, including tall forehead, thickened upper lip with inverted vermillion border, flattened midface, and a variety of extracranial anomalies. New information concerning clinical appearance and course and anatomic and genetic characteristics appears regularly in the literature and is enhanced by expanded diagnostic techniques.

Key points

• Lissencephaly (or agyria) is a congenital disorder of cortical development wherein cerebral convolutions are absent and the surface of the brain is smooth. Patients suffer from severe intellectual disability, hypotonia, motor delay, and seizures.

• More than 25 syndromes have lissencephaly as a feature. Miller-Dieker syndrome is one of the more common of these and is characterized by facial changes including tall forehead, thickened upper lip with inverted vermillion border, flattened midface, and a variety of extracranial anomalies.

• New information concerning clinical appearance and course and anatomic and genetic characteristics appears regularly in the literature and is enhanced by expanded diagnostic techniques. At present, mutations in recognized genes have been identified in over 80% of patients. This implies that additional genes are yet to be found.

Historical note and terminology

Lissencephaly (literally meaning “smooth brain”) is a neuronal migration disorder that includes both agyria and pachygyria but excludes polymicrogyria and other cortical dysplasias. It was first described in 1904 and was considered rare until CT and MRI scans came into widespread use. Most patients have mutations involving LIS1 or XLIS (DCX) genes.

A recognizable "lissencephaly syndrome," later renamed Miller-Dieker syndrome, was described in a series of papers between 1962 and 1980 (98; 34; 69). The association between Miller-Dieker syndrome and visible deletions of chromosome band 17p13.3 was first reported in 1983 (42; 133), and submicroscopic deletions of the same region were reported in 1988 (152). Children with classic lissencephaly who lack the facial changes of Miller-Dieker syndrome are classified separately as isolated lissencephaly sequence (41). The association between isolated lissencephaly sequence and smaller submicroscopic deletions in chromosome 17p13.3 was first described in 1992 (86).

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