Ictal single photon emission computed tomography in epileptic auras.

OBJECTIVES: Little is known about whether ictal single photon emission computed tomography (SPECT) during an isolated aura can localize the epileptogenic zone (EZ). This study seeks to evaluate the yield of ictal SPECT injection in isolated epileptic auras. METHODS: We identified 20 patients with focal epilepsy studied during 26 isolated auras by ictal interictal subtraction SPECT coregistered to magnetic resonance imaging (SISCOM). Studies were rated by two readers who blindly scored the images for presence or absence of an area of dominant hyperperfusion and the lateralization and localization of ictal hyperperfusion; kappa statistics were calculated. Results are correlated with the localization or lateralization of the EZ, time of injection, and electroencephalography (EEG) findings during aura. RESULTS: Fourteen (53%) of 26 injections in 13 patients were rated by both readers as having an area of dominant hyperperfusion with poor interobserver agreement (k = 0.128). Nine of 26 injections in eight patients were correctly lateralized to the side of the EZ (κ = 0.46), but only one of 21 injections in one patient was correctly localized (κ = 0.146). No difference was found when comparing temporal and extratemporal cases. Studies obtained in auras with ictal EEG change were no more likely to be correctly localized than in ones without (p = 0.19). The timing of injection was not a predictor of success. SIGNIFICANCE: Ictal SPECT injection during an isolated aura has a low yield of correct localization of the EZ and cannot be relied on alone during presurgical evaluation. A repeat injection during a seizure with clinical signs and ictal EEG accompaniment is recommended.