Single photon emission computed tomography (SPECT) using N-isopropyl-p-[123I]-iodoamphetamine in epilepsy

In order to delineate a seizure focus and to clarify the cerebral blood flow in epilepsy, single photon emission computed tomography (SPECT) using N-isopropyl-p-[123I]-iodoamphetamine (123I-IMP) was performed on 38 patients (14 symptomatic and 24 idiopathic epilepsy including one patient who was studied on both ictal and interictal phase), and the findings of 123I-IMP SPECT were compared with those of X-ray computed tomography (X-CT) and electroencephalogram (EEG). Abnormality of accumulation of 123I-IMP was observed in 13 out of the 14 symptomatic, 16 out of the 23 interictal idiopathic and all of the 2 ictal idiopathic epileptic patients. On the other hand, in idiopathic epilepsy the detectability (2/24) of focal abnormality in the brain by X-CT was found to be lower than that of 123I-IMP SPECT. In 6 out of the 10 interictal idiopathic epileptic patients, showing normal EEG, the abnormality of accumulation of the radionuclide was observed on 123I-IMP SPECT. Among these 6 idiopathic epileptic patients, however, the pattern of the accumulation of the radionuclide was variable; some patients showed the increased accumulation in the seizure focus, others did the decreased perfusion. Furthermore, some cases showed the decreased perfusion in the different areas from the lesions of epileptic discharge on EEG. Although the mechanism of accumulation of 123I-IMP in the seizure foci is not completely clear, 123I-IMP SPECT was thought to be useful in the detection of focal abnormality in brain in epilepsy. (author)