MRI and brain spect findings in patients with unilateral temporal lobe epilepsy and normal CT scan

26 patients with temporal lobe epilepsy clinically documented by several abnormal interictal surface EEGs with typical unitemporal epileptiform activity and a normal CT scan were studied. Interictal 99mTC HMPAO brain SPECT and MRI were performed in all subjects. Abnormalities were shown in 61.5% of MRI (n = 16) and 65.4% of SPECT (n = 17). Hippocampal atrophy associated to a high signal on T2-weighted MRI slices suggesting mesial temporal sclerosis was the main finding (n = 12; 75% of abnormal MRI). MRI correlated well to surface EEG in 50% (n = 13). There was also a good correlation between MRI and SPECT in 30.7% (n = 8). SPECT and EEG were in agreement in 57.7% (n = 15). MRI, SPECT and EEG were congruent in 26.9% (n = 7). These results support the usefulness of interictal brain SPECT and MRI in detecting lateralized abnormalities in temporal lobe epilepsy. On the other hand, in two cases, interictal SPECT correlated poorly with surface EEG. This functional method should not be used isolately in the detection of temporal lobe foci. MRI is more useful than CT as a neuroimaging technique in temporal lobe epilepsy. It may detect small structural lesions and mesial temporal lobe sclerosis which are not easily seen with traditional CT scanning.