Preictal versus ictal injection of radiotracer for SPECT study in partial epilepsy: SISCOM.

A 27-year-old man had complex partial seizures and a dysembryoplastic neuroepithelial tumor (DNT) in the left inferior-basal temporal region. The patient's seizures consisted of incomprehensible speech, staring, unresponsiveness, fumbling and then looking around. For the brain SPECT study, radiotracer was injected during the preictal (11s prior to seizure onset), ictal (at 25 s out of 47 s seizure duration) and interictal periods. Interictal SPECT was subtracted from preictal or ictal-injection SPECTs and then the subtracted SPECTs were overlaid on the patient's MRI (SISCOM). SISCOM with preictal-injection SPECT showed hyperperfusion at the brain lesion, whereas SISCOM with ictal-injection SPECT showed hyperperfusion at the ipsilateral amygdala-hippocampus and hypoperfusion around the tumor lesion. After the DNT and nearby temporal lobe tissues were resected with preservation of amygdala-hippocampus, the patient became seizure free without complaint of subjective postsurgical memory decline. In this patient, SISCOM with preictal injection of radiotracer localized an epileptogenic zone, whereas SISCOM with the ictal injection showed hyperperfusion at the symptomatogenic zone.