1) Provide an overview of the more common variations of PMG encountered in the clinical setting. 2) Where applicable, detail additional intra and extracranial features in order to assist the Clinical Radiologist in determining the likely aetiology.

Polymicrogyria (PMG) is one of several heterogenous disorders of cortical malformation and is characterised by multiple small and prominent convolutions separated by shallow sulci with an irregular appearance of the cortical surface and cortical white matter.1 It is the end point of different aetiological processes which can occur at different stages of fetal cortical development.2 PMG can be focal or diffuse, unilateral or bilateral and can occur in isolation or in association with other brain malformations or as part of several congenital syndromes. In addition,...

PMG and Macrocephaly: mTORopathy Where PMG is identifed in the setting of macrocephaly, further features suggestive of an mTORopathy shoulde be sought, specifically Megalencephaly Polymicrogyria Polydactyly Hydrocepalus (MPPH) syndrome and Megalencephaly Capillary Malformation (MCAP) syndrome.6,7 Other abnormalities associated with the PIK3-AKT-mTOR pathway include segmental body overgrowth patterns including CLOVES syndrome, fibroadipose hyperplasia and Fibroadipose Vascular Anomalies (FAVA). PMG and Microcephaly: CMV infection In the presence of microcephaly, PMG is most commonly associated with antenatal CMV infection and less commonly with antenatal Toxoplasmosis, Zika virus or...

Polymicrogyria is a common heterogenous disorder of cortical malformation which is encountered frequently in tertiary paediatric institutions. In unison with the increasing availability of MRI, developments in understanding the molecular basis of PMG and cytogenetic advances; we seek to provide a pictorial summary of established PMG features and a summary of the salient extracranial features to assist the Clinical Radiologist in determining the underlying aetiology and thereby increasing diagnostic accuracy.

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