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
- lissencephaly: smooth brain surface
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 generalities and outlines the differences between the two types, which are otherwise discussed separately:
Type I (classic) lissencephaly typically presents with marked hypotonia and paucity of movement.
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.
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 appear 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 as a cobblestone complex. Band heterotopia is not evident and the cortex is thinner than in type I.
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- 6. Volpe JJ. Neurology of the newborn. W B Saunders Co. (2008) ISBN:1416039953. Read it at Google Books - Find it at Amazon