Ictal and interictal technetium-99m-bicisate brain SPECT in children with refractory epilepsy

Identification of epileptogenic foci in patients with refractory epilepsy remains a significant diagnostic challenge. Magnetic resonance imaging studies frequently fail to reveal an anatomic origin for the seizures, and scalp electroencephalography is often limited to identification of the involved hemisphere. Functional imaging modalities such as PET and SPECT are more promising tools for this application because they reflect the functional pathology associated with the seizure. These changes are more pronounced ictally, but until recently, no radiopharmaceutical was available that could be used routinely for ictal SPECT. The present study was therefore undertaken to determine whether 99mTc-bicisate could be used in ictal SPECT in pediatric patients with refractory epilepsy, to compare the patterns of ictal and interictal blood flow in these patients and to compare the localization information provided by ictal SPECT with that available from other techniques.

Technetium-99m-bicisate/SPECT was compared prospectively with scalp EEG for its ability to identify a possible seizure focus in pediatric patients with refractory epilepsy. Ictal and interictal SPECT studies were performed in 10 patients (3-19 yr old, mean age 10.9 +/- 4.3 yr; 7 female, 3 male) in whom MRI scans revealed no lesions that might be responsible for the seizures.

Ictal SPECT was performed in all patients, and all ictal studies revealed focal perfusion abnormalities. By comparison, four of the interictal SPECT studies showed regional hypoperfusion that corresponded to the regions of hyperperfusion in the ictal studies, and three showed regional hyperperfusion corresponding to the hyperperfused regions in the ictal studies. Three interictal studies revealed no abnormal perfusion. Scalp EEG provided localization information in five patients.

These initial results suggest that ictal SPECT with 99mTc-bicisate is a more promising tool for the identification of epileptogenic foci than interictal SPECT or scalp EEG in patients without focal abnormalities on MRI.