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Lissencephaly - pachygyria spectrum

The lissencephaly-pachygyria spectrum is useful in describing the spectrum of diseases that cause relative smoothness of the brain surface and includes agyria (no gyri), pachygyria (broad gyri) and lissencephaly (smooth brain surface).  It is a basket term for a number of congenital cortical malformations characterised by absent or minimal sulcation

Lissencephaly - pachygyria can be further divided into types I (classic) and type II, which differ in clinical presentation, underlying genetic abnormalities, and both microscopic and macroscopic (including imaging) appearances 2,6. They themselves represent a heterogeneous group of disorders. This article highlights a few few generalities and outlines the differences between the two types, which are otherwise discussed separately:

Clinical presentation

Type I (classic) lissencephaly typically presents with marked hypotonia and paucity of movement, whereas type II lissencephaly is associated with muscular dystrophy-like syndromes and includes Walker-Warburg syndromeFukuyama syndrome, and muscle-eye-brain (MEB) disease 2,6.

Radiographic features

Although lissencephaly can be identified on all cross-sectional modalities (antenatal and neonatal ultrasound, CT and MRI), MRI is the modality of choice to fully characterise the abnormalities. 

MRI 

Type I and type II lissencephaly demonstrate vaguely similar appearances (thus the common term lissencephaly) but different macroscopic and imaging appearances are visible. 

Type I (classic) lissencephaly can apear as the classic hour glass or figure-8 appearance or with a few poorly formed gyri (pachygyria) and a smooth outer surface. It is usually associated with band heterotopia

Type II lissencephaly on the other hand has a microlobulated surface referred to cobblestone complex. There is not band heterotopia and the cortex is thinner than type I. 

See also

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