CORRELATION BETWEEN INTERICTAL REGIONAL CEREBRAL BLOOD-FLOW AND DEPTH-RECORDED INTERICTAL SPIKING IN TEMPORAL-LOBE EPILEPSY

Purpose: Single photon emission computed tomography (SPECT) is used as an adjunctive method in preoperative localization of epileptic foci. In temporal lobe epilepsy (TLE), interictal hypoperfusion is observed in 60-70% of cases. Correlation with ictal EEG changes is observed in similar to 50-60% of cases. Relationships with interictal EEG have bee n studied less. We compared interictal SPECT data obtained in 20 patie nts with their interictal intracerebral electrical activity recorded b y depth electrodes to evaluate a potential relationship.Methods: We st udied 20 sequential patients whose clinical, surface, and depth EEG da ta indicated seizure originating in the temporal lobe and who had inte rictal [Tc-99m]hexamethylpropylene amine oxime (HMPAO)-SPECT stereo-EE G (SEEG). Intracerebral electrodes were placed according to the patien ts profile, The interictal extent of epileptiform activity allowed del ineation of the irritative zone. Interictal spike frequency was also a nalyzed semiquantitatively. Visual and numerical SPECT analysis was pe rformed blind to SEEG data. Results: Interictal hypoperfusion was obse rved in 16 patients, involving the epileptogenic temporal lobe in 14. Except for 1 patient who manifested lateral temporal hypoperfusion cor responding to a mass lesion, two distinctive patterns of hypoperfusion were noted: (a) mesial hypoperfusion (5 patients), and (b) global tem poral hypoperfusion (8 patients). In 8 patients, hypoperfusion had als o extended into the adjacent cortex, Temporal mesial hypoperfusion was associated with spiking limited to the mesial structures, whereas glo bal temporal hypoperfusion or hypoperfusion extending beyond the tempo ral lobe was associated with a similar topographic pattern of spikes, Conclusions: Comparison between SPECT and SEEG data collected in the i nterictal phase indicated that the extent of the hypoperfused area cor related topographically with that of the underlying irritative zone.