N-isopropyl I-123 p-iodoamphetamine brain scans with single photon emission computed tomography: mental sweating and EEG abnormality.

We studied a patient with hyperhidrosis and electroencephalographic (EEG) abnormality using N-isopropyl I-123 p-iodoamphetamine (I-123 IMP) with single photon emission computed tomography (SPECT). EEG abnormality was found predominantly in the frontal area, and sharp wave bursts were induced by hyperventilation. Ictal and nonictal scans were obtained with simultaneous EEG recordings. Ictal scans revealed increased uptake of IMP in the frontal cortex, reflecting hyperperfusion to the frontal area. The ratio of IMP uptake of the frontal to the parietal cortex (F/P ratio) was calculated both in the ictal and nonictal phase. In the ictal phase, the F/P ratio was 1.23, compared with 0.91 in the nonictal phase. The data indicated altered regional cerebral blood flow with EEG abnormality and hyperventilation load. Although the relationship between sweating and cortical function is not fully understood, our study indicates that excessive mental sweating is related to frontal cortical dysfunction. I-123 IMP-SPECT seems valuable for topographical demonstration of epileptogenic lesions and understanding the pathophysiological process of mental sweating.