Abstracts

Infantile spasms is a catastrophic childhood epilepsy syndrome with a distinctive presentation of refractory seizures and developmental arrest. Advances in magnetic resonance imaging (MRI) and position emission tomography (PET) have increased recognition of underlying focal abnormalities, in particular malformations of cortical development. Focal surgical resection can result in improved seizure control and i cognitive/developmental outcome. Subtraction ictal SPECT Co-registered to MRI (SISCOM) is of proven value in presurgical evaluation of localization related epilepsy and is used successfully in children. No prior studies have examined SISCOM in infantile spasms. A retrospective chart review from January 1997 to December 2004 identified patients with infantile spasms recorded on prolonged video-EEG. Ictal electrodecremental response and documented history of hypsarrhythmia were required 20 patients were identified. 6 had a SISCOM and 1 an ictal SPECT. The SPECT patients were older, had a longer epilepsy history, and had failed more anti-epileptic drugs. Etiology was evenly divided between cryptogenic/idiopathic and symptomatic disease, with symptomatic cases being slightly over represented in the SPECT patients. MRI demonstrated cortical dysplasia in 7 (4 in the SPECT group). Lateralizing semiology was noted in 1/3 of the SPECT group. 7 had other partial seizures; 2 in the SPECT group. Hypsarrhythmia was atypical in 6 and had resolved at the time of monitoring in 10, including all SPECT patients. Focal interictal discharges were more prominent in the SPECT group (57% vs 38.5%). The ictal EEG had lateralizing features in 4, 3 of whom were in the SPECT group. In the patient with only ictal SPECT, spasms could not be suppressed for sufficient time to obtain an interictal study. Half of the SISCOM studies were indeterminate. Those with localizing SISCOM were more likely to have abnormal MRI and lateralizing semiology, but not to have focal interictal or lateralizing ictal discharges. SISCOM localization was concordant with focal MRI and electrographic abnormalities when present. 2 with positive SISCOM had limited cortical resection encompassing the region of SISCOM hyperperfusion and were seizure free for 8 and 9 months. SISCOM can be successfully performed in children with refractory infantile spasms, despite brief seizure duration and generalized electrographic discharge. In patients with multilobar dysplasia, SISCOM has the potential to localize the ictal onset zone allowing tailored cortical resection. SISCOM can be technically difficult in this population. Conclusions regarding factors contributing to positive SISCOM outcome are limited in this small sample of highly selected patients. Future study regarding use of SISCOM for spasms without localizing features, as well as the value of SISCOM in relation to MRI and PET imaging is warranted. (Supported by Mayo Clinic Foundation.)