Abstracts

RATIONALE: Cerebral blood flow (CBF) changes measured by SPECT difference imaging provides a powerful non-invasive technique for imaging both cortical and subcortical activity during seizures. However, interpretation of these CBF changes has been difficult because: 1. during the course of seizures CBF first increases, then decreases, 2. seizures propagate, 3. SPECT injection timing with epilepsy patients is unpredictable, and 4. seizure types may vary widely from one patient to the next. Ictal SPECT investigations would be greatly facilitated by studying a group of patients with homogeneous seizure type and predictable timing. METHODS: We performed SPECT injections at specific times in relation to seizures elicited by either bilateral or right unilateral electroconvulsive therapy (ECT) used for treating depression. Interictal injections were performed under the same anesthesia used in ECT. RESULTS: Both right unilateral and bilateral ECT produced generalized tonic-clonic seizures. Nevertheless, with injections done 30-60 seconds after the ECT stimulus, focal changes ranging from 30-70% were seen on SPECT difference imaging. Thus, in bilateral ECT there were bilateral CBF increases in the fronto-temporal areas, while in right unilateral ECT there were unilateral increases in the right fronto-temporal region. CONCLUSIONS: SPECT difference imaging performed during both unilateral and bilateral ECT revealed CBF increases in the presumed regions of seizure onset. Thus, ECT may serve as a model system for studying partial seizures with secondary generalization. By investigating the timecourse of SPECT changes during ECT-induced seizures it may be possible to better interpret SPECT scans from spontaneous seizures in patients with epilepsy. In addition, the relative sparing of left temporal structures seen here in right unilateral ECT could explain why right unilateral ECT causes less severe memory deficits than bilateral ECT. Supported by the Dana Foundation, NIH NS02060, and a Pfizer fellowship.