Department of Pathology, University of Oklahoma Health Sciences Center

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Answer: Focal polymicrogyria (B)  Level of difficulty: 3 NeuroTest NeuroLearn NeuroHelp

Discussion: 

• Pathology of the Case: There are two symmetrical stretches of gyri that appear thickened and broad (Þ). On Nissl stain, there is fusion of molecular layer. The laminated architecture of normal cerebral cortex is not readily seen (Þ). These features indicate polymicrogyria.

• Polymicrogyria refers to gyri that are too numerous and too small. Sometimes the appearance is one of wide gyri with a central dimple, the so-called Morocco leather appearance, which can be mistaken for pachygyria. The abnormal cortical ribbon can be abnormally thick or thin, hypercellular or hypocellular. It can be focal or widespread. Sometimes they follow a particular arterial territory and are bilateral and symmetrical (usually the middle cerebral artery). Some of them are confined to the opercular region or depths of the insula. Polymicrogyria can occur at any part of the cerebral hemisphere but often at the edge of destructive lesions.

• Laminar architecture: It is a migration disorder and the laminar architecture is disrupted. In stead of the normal six layered architecture, there is often a single unorganized layer or four-layered cortices are often but not always seen.  Many other patterns have been described. Characteristically, fusion of the molecular layer between two abnormal gyri is seen, a feature that separate polymicrogyria from microgyria.

• Conditions associated with polymicrogyria is diversified. Some of the known associations include intrauterine ischemia and insults such as infections, rare inherited familial syndromes such as Aicardi syndrome, metabolic diseases such as Pelizaeus-Merzbacher disease and Leigh’s disease. A special situation called pachymicrogyria is seen in and peroxisomal disorders such as Zellweger’s syndrome.

Comment: KarMing-Fung@ouhsc.edu