Abstracts

Rationale: Ictal SPECT imaging can enhance the pre-surgical evaluation of refractory epilepsy patients, especially in patients without radiographic abnormalities, or with bilateral or extensive unilateral abnormalities. Acquisition of ictal SPECTs presents challenges for coordination of staff for injection of radiographic tracer at the ictal onset, and flexible availability of imaging equipment and in some cases sedation capabilities. Methods: We sought to evaluate the yield of these efforts by retrospective review of successful ictal SPECT studies at our institution from 2/2010 through 6/2011. Results: Forty refractory epilepsy patients with resective surgical potential admitted to our EMU underwent both ictal and inter-ictal SPECT scanning. Twenty-three of 40 patients had normal MRI scans, 6 had large unilateral lesions, 4 had bilateral lesions, 5 had small lesions of questionable clinical relevance, and 2 had failed previous resections with post-operative changes on MRI. Digital subtraction analysis showed no difference in tracer activity in 18 cases, bilateral focal abnormalities in 4, and unilateral focal abnormalities in 18. Eight of the 18 patients with focal metabolic hyperintensity by SPECT scanning have since undergone grid placement and subdural ictal EEG activity was concordant with SPECT localization in all eight cases. One child with post-encephalitic epilepsy has persistent but fewer seizures after cortical resection, two have had marked seizure reduction and 5 are seizure-free. In one patient the SPECT abnormality extended beyond the lesion border on MRI, and this area was resected as grid placement confirmed the region to be involved in seizure onset. Pathology confirmed dysplasia throughout the resected area.Conclusions: SPECT imaging contributed to surgical planning in 45% of our cases, and 100% of subdural studies showed concordance of EEG ictal onset with SPECT abnormality. Focal SPECT abnormality can therefore frequently increase the confidence of subdural grid placement in non-lesional and multi-lesional patients.