Localised neuronal migration disorder and intractable epilepsy: a prenatal vascular aetiology.

Localised neuronal heterotopias are an increasingly recognised cause of intractable focal epilepsies. The aetiology of these circumscribed disorders of neuronal migration is often unknown although in some instances proximity to areas of prenatal infarction suggests that severe ischaemia was responsible. A patient is described with intractable complex partial seizures associated with heterotopic grey matter and cerebral hypoplasia confined to the territory of the left posterior cerebral artery; the left hippocampus was spared. Angiography showed a normal left anterior choroidal artery but a hypoplastic left posterior cerebral artery, implicating prenatal ischaemia without frank infarction as the aetiology of the malformation.