Abstracts

RATIONALE: To study the spatial extent of ictal perfusion changes during mesio-temporal lobe seizures (MTLS) with respect to ictal semiology, using SISCOM SPECT imaging.
METHODS: Twenty-one adult patients with refractory MTLS associated with hippocampal sclerosis (n=20) or amygdala gliosis (n=1) were studied using substraction ECD-SPECT coregistered to MRI (SISCOM). SPECT exams were conducted under video-EEG monitoring, and all ictal SPECT were confirmed as true ictal (ratio Captation Latency/Seizure Duration (CL/SD) [lt]1). Semi-quantitative measurements of ictal blood flow (BF) changes were made in 20 regions of interest including limbic, paralimbic, neocortical and sub-cortical areas. Patients were divided in two groups, according to the absence (group 1, n=6) or the presence (group 2, n=15) of consciousness impairment during ictal SPECT. 17 of the 19 operated patients were seizure free (mean follow up 22 months) after anterior temporal lobe resection (n=15) or disconnection (n=4). Two patients are waiting for surgery.
RESULTS: In group 1 (CL/SD ratio = 0,65 +/- 0,41), the most reliable focus of hyperperfusion was restricted to the temporal pole. Seizures consisted in epigastric aura in all 6 cases. In group 2 (CL/SD = 0,50 +/- 0,33), ipsilateral ictal hyperperfusion affected in addition the insula, and at a lower extent MTL structures, the lateral temporal cortex and the thalamus. Seizures consisted in automotor seizures and consciousness was impaired from seizure onset (n=4) or after the occurrence of an aura (n=17). Other paralimbic areas and basal ganglia were not consistently affected by BF changes.
CONCLUSIONS: In MTL seizures manifesting only with epigastric auras, the temporal pole appears as a key structure in the occurrence of symptoms. The occurrence of consciousness impairment seems to be related to the involvement of a large temporo-insulo-thalamic network, the insular part of which could constitute the main efferent output from temporal lobe structures towards subcortical areas.