Magnetic resonance imaging of intractable complex partial seizures: pathologic and electroencephalographic correlation

Prior studies indicate variable usefulness of magnetic resonance imaging (MRI) in the evaluation of patients with complex partial seizures (CPS), but sensitivities as low as 12% have been reported. We analyzed the MRI examinations of 20 patients with medically refractory CPS who later underwent resection of the seizure focus proven by electroencephalography (EEG). MRI studies were correlated with surgical pathology in all patients. Eleven of the 20 CPS patients had mesial temporal sclerosis (MTS). Seven of the 11 (64%) exhibited an MRI abnormality at the site of the EEG-demonstrated histopathologic focus. MRI abnormalities included temporal lobe hypoplasia or atrophy (four patients), and increased signal intensity on long repetition time (TR) sequences (three patients). Four patients had no MRI abnormalities corresponding to the histopathologic focus. Nine of the 20 CPS patients had other abnormalities responsible for the seizures, including astrocytoma, cryptic vascular malformation, hamartoma, polymicrogyria, tuberous sclerosis (forme fruste), arachnoid cyst, and congenital hemiatrophy. No patient had normal MRI studies. Our single most useful MRI sequence was the coronal long TR/dual echo sequence, using cardiac gating and first-order gradient moment nulling to diminish flow-related artifacts that could hinder evaluation of medial temporal lobe structures.