Abstracts

RATIONALE: Volume loss can occur in structures functionally connected to the hippocampus in the setting of medically refractory temporal lobe epilepsy. Detecting unilateral volume loss in subcortical structures such as the thalamus, caudate, and cerebellum, may help lateralize the epileptogenic zone in patients with partial epilepsy. METHODS: Preoperative volumetric MRI was performed on 18 adults (9men/9women) who underwent surgery for medically refractory epilepsy. These included 6 patients undergoing right temporal lobectomy (RTLE), left temporal lobectomy (LTLE), and left frontal lobe resections (LFLE), respectively. Duration of epilepsy was 22, 22, and 19 years, respectively. Sixteen had seizure free outcomes or ?75% seizure reduction postoperatively. MRI scans were acquired using three-dimensional T1 gradient echo (TE6,TR24,FA25). Hippocampi, amygdalae, thalami, cerebellar hemispheres and caudate heads were measured. RESULTS: The right-to-left hippocampal, amygdalar, thalamic cerebellar, and caudate volume rations (VR) were 0.65, 0.98, 0.94, 0.97 and 1.00 for RTLE, 1.48, 1.09, 1.01, 0.98 and 1.00 for LTLE, and 1.05, 1.06, 1.02, 0.95, and 1.00 for LFLE, respectively. Only hippocampal volumes differed statistically between the three groups, while nonsignificant differences were noted for amygdalar and thalamic VR. Cerebellar and caudate VR were more consistent among the three groups. Ipsilateral caudate atrophy was pronounced in two LFLE patients with underlying head injury, but not in the four other patients with cortical dysplasia. CONCLUSIONS: This pilot study confirmed previous findings regarding differences between hippocampal, amygdalar, and thalamic VR in patients with temporal lobe epilepsy. Larger numbers of patients and nonepileptic controls are needed to better correlate subcortical diaschisis with the location of the epileptogenic zone, etiology, and epilepsy duration.