Abstracts

Single-Photon Emission Computed Tomography (SPECT) has become an important non-invasive method for localizing the seizure onset zone in epilepsy surgery candidates. Statistical Parametric Mapping (SPM) is an increasingly accepted method for analysis of functional imaging data, including SPECT. ISAS (Ictal-interictal SPECT Analysis using SPM) is an SPM-Based technique for ictal-interictal SPECT analysis (McNally et al, 2005). ISAS utilizes a group of 14 normal scan pairs to identify and assess the significance of perfusion changes between a patient[apos]s paired interictal and ictal SPECT scans. We sought to explore the utility of this technique in pediatric patients, and to confirm previously reported limitations of SPM algorithms in children under 6 years old., In 20 pediatric epilepsy surgery patients an ictal scan was compared with a corresponding interictal scan using Ictal-interictal SPECT analyzed by SPM2 (ISAS; see http://spect.yale.edu). A blinded expert (RCK) reviewed ISAS results to identify location of highest significance hyperperfusion voxel, overall localization, and overall lateralization. Unprocessed SPECT pairs were also evaluated for overall localization, and overall lateralization. True seizure localization was based on concordance of EEG, MRI, MEG, and post-resection Engel Class I or II outcome after minimum 1year follow-up., Ages of subjects ranged from 1 to 19 years old with a mean of 8 yrs 8 mo and median of 7 yrs, 7 mo, while seizure localization was temporal in 6 and extratemporal in 14 patients with age distribution TL=2,5,8, 9,14,19, exTL= 1,2,4,5,5,6,7,7,7,8,9,14,16,17. Overall ISAS correctly identified the lobe of seizure onset in 70% of patients (14/20), and correctly lateralized in 85% (17/20), while results for raw SPECT was 45% and 65% respectively. In the 8 patients under 6 years, ISAS correctly identified the lobe of seizure onset in 75% (6/8) [ages 1,2,4,5,5,6], correctly lateralized in 87.5% (7/8), while results for raw SPECT was 50% and 62.5% respectively. In 12 patients over 6, ISAS correctly identified lobe of seizure onset in 75% of patients (9/12), and correctly lateralized in 83.3% (10/12), while results for raw SPECT was 41.6% and 66.7% respectively. With ISAS the highest significance voxel of the highest significance cluster correctly identified the lobe of seizure onset in 60% (12/20) of the entire group, 62.5% (5/8) in the under 6 y/o group, and 66.7% (8/12) over 6 y/o., These results demonstrate that in pediatric patients ISAS is more sensitive for localizing both temporal and extra-temporal epilepsy than unprocessed SPECT scan pairs. No clear deterioration in sensitivity of this technique was noted in the younger patients. ISAS is a freely available technique which is useful for seizure localization in a range pediatric age groups.,