Inter-ictal brain SPET in frontal epilepsy: correlations with stereo-electroencephalography

Single photon emission tomography (SPET) imaging holds promise for localization of the site of extratemporal seizures, but limited data currently exist; in particular, correlations with stereo-electroencephalography (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 frontal cortectomy and one patient had a callosotomy for bifrontal epilepsy. All patients underwent clinical, inter-ictal and ictal video-EEG, computed tomography scan and/or magnetic resonance imaging, SPET and S-EEG examinations. SPET was performed inter-ictally, while on usual epileptic medications, using 99Tcm-HMPAO (n = 4) or 123I-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 frontral or central epilepsy. Localization of inter-ictal SPET hypoperfusion was compared with the epileptogenic (EZ), irritative (IZ) and lesional (LZ) zones, as defined by S-EEG. Six patients showed structural frontal abnormalities. One patient had normal SPET and one had a contralateral hypoperfusion. Therefore, concordance of sides was found in 8 of 10 patients (including one with bilateral SPET and S-EEG abnormalities). The hypoperfusion was equal to or larger than the EZ + IZ + LZ in 6 patients (5 had a frontal lesion). SPET hypoperfusion was smaller than the EZ in one patient, and different from the EZ, IZ and LZ in two patients. Although this was a retrospective study, it provides qualitative data regarding the significance of inter-ictal SPET abnormalities in frontal or central epilepsy.(ABSTRACT TRUNCATED AT 250 WORDS)