Abstracts

To assess the additional value of subtraction ictal SPECT co-registrated to MRI (SISCOM) for localisation of the epileptogenic zone in epilepsy surgery., We retrospectively analyzed 49 consecutive epilepsy patients who had undergone invasive monitoring between January 2000 and Mars 2006 and had presurgical examination with high resolution 1.5T MRI or higher field strength. Attempts for ictal SPECT as part of the pre-surgical work-up was made for 29 patients, two patients had no seizures during ictal SPECT preparedness, SISCOM analysis showed areas with significant hyperperfusions in 26 patients.
By SISCOM analysis interictal and ictal images were normalized, subtracted and coregistered with MRI. The standard deviation of the ictal hyperperfusion was measured in each hemisphere and the hemisphere with the least standard deviation was used as reference. Hyperperfusions exceeding 3.5 SD were considered significant.
Two independent epileptologists evaluated if SISCOM results (A) altered the hypothesis and extended the strategy for electrode placement at invasive recording, or (B) did not alter the strategy. We defined that SISCOM had an impact on seizure outcome if the seizure onset zone was seen in electrodes overlying a brain region with a significant hyperperfusion. Engel class I-II was considered favorable outcome at one-year postoperative follow-up. SISCOM was considered a prerequisite for favorable outcome when concordant with invasive ictal onset in extended electrodes., Twenty-six patients were offered surgery; 20 had localizing data from SISCOM and [gt] 1 y follow-up whereof 40 % had favorable outcome.
A. SISCOM findings were complementary to other localizing non-invasive findings and altered and extended the strategy for electrode placement at invasive recording in 15 patients. SISCOM was a prerequisite for seizure outcome in all 6 patients with favorable outcome. Nine patients had poor results from surgery; SISCOM was concordant with invasive EEG in 6 patients, and discordant with invasive EEG with no impact on outcome in 3 patients.
B. SISCOM findings did not change the hypothesis for electrode placement at invasive recording in 5 patients, but SISCOM was confirmatory with other localizing data in the 2 patients with favorable outcome. Three patients had poor results from surgery; SISCOM was concordant with invasive EEG in 1 patient, and discordant with invasive EEG and with no impact on results in 2 patients.
When SISCOM was concordant with invasive EEG the predictive value for favorable outcome was 53%., SISCOM is valuable for the identification of the epileptogenic zone in patients with drug resistant epilepsy scheduled for invasive video-EEG. In all patients with favorable seizure outcome at one year follow-up SISCOM analysis was either a prerequisite for the favorable result or concordant with other localizing data.,