MAYO CLINIC SISCOM PROTOCOL
Subtraction periictal single-photon emission computed tomography (SPECT) coregistered to magnetic resonance imaging (MRI) (SISCOM) is performed in selected patients being considered for surgical treatment (1–9). The current protocol at the Mayo Clinic in Rochester, Minnesota, requires an MRI head seizure protocol and routine EEG before admission to the epilepsy-monitoring unit (1–3). Review of the outpatient evaluation and the initial video-EEG findings will be used to determine the potential candidates for a SISCOM study. The periictal neuroimaging studies are performed from 7 a.m. to 11 p.m. on 7 days of the week. The radioligand technetium-99m ethyl cysteinate diethylester (99mTc-ECD) is injected as soon after seizure onset as possible (1–4,6). The interictal injection and scan are performed 24 h or later after the ictal imaging study. Patients are treated with antiepileptic drug medication (including benzodiazepine therapy if necessary) to suppress seizure activity during the period between the two injections. Individuals undergo continuous EEG monitoring at the time of the ictal and interictal SPECT injections (9). If appropriate, the patients receive sedation at the of the neuroimaging studies. A nurse accompanies the patient to nuclear medicine. The patients ultimately are discussed at a surgical epilepsy conference, at which time the comprehensive presurgical evaluation is reviewed. Selected candidates may proceed with prolonged intracranial EEG recordings or epilepsy surgery, or both. Neuropsychometry, visual perimetry, and cerebral arteriography with a sodium amobarbital study are performed before surgical treatment.