Value of HM-PAO SPECT in selective temporal lobe surgery for epilepsy

The purpose of this study was to assess the value of interictal ^99mTc-hexamethyl-propylenamine oxime (HM-PAO) single-photon emission computed tomography (SPECT) in the preoperative evaluation of epileptic patients with medically refractory seizures of temporal lobe (TL) origin. For this study, we selected 31 patients, who were preoperatively evaluated according to the Zürich presurgical protocol. All patients underwent selective amygdalohippocampectomy. Their surgery was based on ictal and interictal EEG recordings, using scalp and foramen ovale electrodes simultaneously. Postoperatively, 27 patients (87%) were seizure-free or had more than a 90% seizure reduction. All patients had preoperative interictal SPECT and magnetic resonance imaging (MRI) performed. Postoperative SPECT was performed in 18 patients. Preoperative MRI showed structural lesions in 20 cases, and 23 patients had abnormal histopathological findings. Preoperative SPECT determined correctly the primary epileptogenic area in 15 cases (48%), showing a zone of hypoperfusion restricted either to the TL (n = 9; 29%) or exceeding the TL structures (n = 6; 19%). In two patients (6%), the SPECT findings were located contralateral to the affected TL, and in one (3%) there was reduced regional cerebral blood flow in the ipsilateral basal ganglia. Thirteen patients (42%) had normal SPECT. No significant correlations were found among preoperative SPECT findings, MRI and histopathological results, and the postoperative clinical outcome. Based on the results of this study, we regard HM-PAO SPECT to be a useful confirmatory diagnostic tool in presurgical evaluation of epileptic patients. Given the present technological level, it cannot, however, replace the semi-invasive EEG methods.