Grey matter heterotopia: an unusual association of intractable epilepsy.

Heterotopic grey matter is an abnormality of neuronal migration that has been reported in association with refractory epilepsy. In this study we reviewed the magnetic resonance (MR) imaging records of all patients undergoing MR scanning for evaluation of intractable epilepsy and identified sixteen patients who had grey matter heterotopia. The distribution of the grey matter heterotopia was periventricular in 9 patients, laminar in 3 and was in a "band" form in 4 patients. Congenital anomalies associated with grey matter heterotopia in this study included polymicrogyria in one patient and absence of the corpus callosum in 2 patients. Grey matter heterotopia is an important MR finding in patients with intractable epilepsy.