Abstracts

RATIONALE: Positive and negative subtraction SISCOM images have the ability to demonstrate the regional cerebral blood flow (CBF) changes in partial epilepsy. During the interpretation of subtracted SPECT, we frequently find widespread areas of CBF changes beyond the epileptogenic focus. Only a few reports pinpoint the presence of such changes. Most of them documented the changes of CBF in the frontal lobe during complex partial seizures of temporal lobe in origin. Regional blood flow changes in other areas have not been systematically studied. We assess the pattern of widespread CBF changes, using both positive and negative subtraction SISCOM, in TLE patients.
METHODS: We retrospectively reviewed the video recordings, ictal-interictal SPECT scans, and brain MR images of 20 intractable TLE patients. The positive (ictal minus interictal), and negative (interictal minus ictal) subtraction SPECT coregistered with MRI were obtained using ANALYZE AVW 3.1. The positive subtraction SISCOM images (segmented to show voxels of 2 SD from the mean subtraction) demonstrating hyperperfusion areas, and the negative subtraction SISCOM images (segmented to show voxels of 1 SD from the mean subtraction) demonstrating hypoperfusion areas were reviewed simultaneously. The presence of ictal hyper or hypoperfusion in frontal, temporal, occipital, cerebellar, and basal ganglia were determined in reference to epileptogenic areas, which were determined by standard methods of seizure localization.
RESULTS: The mean age was 32.7 years (range, 12 to 48 years). The mean seizure duration was 78.3 seconds (range, 23 to 144 seconds). The mean latency of radioisotope injection after seizure onset was 34.6 seconds (range, 12 to 86 seconds). All radioisotope injections were performed during the clinical seizure. Fifteen patients (75%) showed ictal hyperperfusion in the temporal lobe of seizure origin, three patients (15%) had bitemporal hyperperfusion but more prominence on one side, one patient demonstrated temporal hyperperfusion on the contralateral side of seizure onset, and one patient showed no temporal hyperperfusion. Frontal hyperperfusion was found in nine patients (45%), basal ganglia hyperperfusion in five patients (25%), and cerebellar hyperperfusion in six patients (30%). For the negative subtraction SISCOM images, there were two patients who demonstrated temporal hypoperfusion (one on the contralateral side of epileptogenic focus). Seventeen patients (85%) had frontal hypoperfusion (ipsilateral in six, contralateral in seven, and bilateral in four). No basal ganglia hypoperfusion was observed. Cerebellar hypoperfusion was found in 11 patients (55%) (ipsilateral in five, contralateral in five, and bilateral in one). Occipital hypoperfusion was shown in seventeen patients (85%) (ipsilateral in nine and contralateral in eight patients).
CONCLUSIONS: During temporal lobe epileptic seizures, there are diffuse changes of CBF beyond the epileptogenic focus. Although there is no specific pattern, the frontal and occipital hypoperfusion are the common findings. Our data support the importance of modifications in the synaptic network and interconnection between the temporal and extratemporal regions, and also provide further insight of the complex pathophysiology underlying TLE.