[MR imaging of large heterotopic gray matter]

One and a half year-old boy was admitted to our hospital with a history of intractable myoclonic epilepsy. Seizures were fairly controlled on carbamazepine, phenobarbital, diphenylhydantoin and clonazepam, but still occurred several times per month. Neurological examination showed mild psychomotor retardation. The CT and MR imaging studies showed both large heterotopic gray matter and supracerebellar arachnoid cyst. No enhancement was noted after the administration of contrast medium. No calcification was present. In the MR image, a large nodule in the right hemisphere showed almost the same signal intensity as the cortical gray matter. The right lateral ventricle was absent for a portion of the anterior horn. The sulci on the right parietal lobe were almost absent, suggesting the region of agyria.