Interictal Te-99m-HMPAO SPECT in temporal lobe epilepsy: Relation to clinical variables

Purpose: Factors affecting blood flow observed by interictal single-photon emission computed tomography (SPECT) images in temporal lobe epilepsy (TLE) have not been systematically studied or consistently demonstrated. We eval uated interictal SPECT results with respect to many clinical variables in a large population of TLE patients, all of whom underwent temporal lobectomy . Methods: Interictal Tc-99m-HMPAO SPECT scans from 61 TLE patients were obta ined before an anterior temporal lobectomy. SPECT was analyzed using a regi on of interest analysis (ROI) in the cerebellum, anterior temporal lobe, la teral temporal lobe, mesial temporal lobe, whole temporal lobe, and inferio r frontal lobe. Asymmetry indices (AIs) were calculated. Correlative analys is of AIs and clinical variables was performed. Results: The AIs from TLE patients differed significantly from those of con trols in the anterior temporal (p < 0.01), lateral temporal (p < 0.001), an d whole temporal (p < 0.01) regions. No consistent overall correlation betw een the AIs and clinical variables existed. In right TLE (RTLE) only, Als i n the lateral and whole temporal lobe were positively correlated with age o f onset (r = 0.470, p < 0.05; r = 0.548, p < 0.01, respectively). Similarly , in RTLE only, duration of epilepsy was negatively correlated with the ant erior (r = -0.395, p < 0.05) and mesial (r = -0.45, p < 0.05) temporal lobe AI. No correlations were found between clinical variables and AIs in left TLE (LTLE) patients. Conclusions: Significant correlation of age at onset and duration of epilep sy with AIs in RTLE but not LTLE suggests physiologic processes may be dete rmined in part by laterality of TLE. Clinical applications are problematic.