INTERICTAL BRAIN SPET IN FRONTAL EPILEPSY - CORRELATIONS WITH STEREO-ELECTROENCEPHALOGRAPHY

Single photon emission tomography (SPET) imaging holds promise for loc alization of the site of extratemporal seizures, but limited data curr ently exist; in particular, correlations with stereo-electroencephalog raphy (S-EEG) have not been made. Ten patients aged 14-44 years (mean 25 years) with a proven frontal or central epilepsy by S-EEG and post- surgical follow-up were studied retrospectively: 7 patients had fronta l cortectomy and one patient had a callosotomy for bifrontal epilepsy. All patients underwent clinical, inter-ictal and ictal video-EEG, com puted tomography scan and/or magnetic resonance imaging, SPET and S-EE G examinations. SPET was performed inter-ictally, while on usual epile ptic medications, using Tc-99(m)-HMPAO (n=4) or I-123-IMp (n=6) as the perfusion tracer. The SPET images were evaluated independently by two observers, blind to any data other than the diagnosis of frontal or c entral epilepsy. Localization of inter-ictal SPET hypoperfusion was co mpared with the epileptogenic (EZ), irritative (IZ) and lesional (LZ) zones, as defined by S-EEG. Six patients showed structural frontal abn ormalities. One patient had normal SPET and one had a contralateral hy poperfusion. Therefore, concordance of sides was found in 8 of 10 pati ents (including one with bilateral SPET and S-EEG abnormalities). The hypoperfusion was equal to or larger than the EZ + IZ + LZ in 6 patien ts (5 had a frontal lesion). SPET hypoperfusion was smaller than the E Z in one patient, and different from the EZ, IZ and LZ in two patients . Although this was a retrospective study, it provides qualitative dat a regarding the significance of inter-ictal SPET abnormalities in fron tal or central epilepsy. The inter-ictal SPET hypoperfusion did not pr ovide a precise definition of the epileptogenic focus; it was often la rger than the EZ, including the IZ and LZ. This result indicates frequ ent widespread dysfunction in the brain of patients with frontal lobe epilepsy.