¹²³I-Iomazenil SPECT Findings in a Child with Negative Myoclonus and Epilepsy

Abstract

A 9-year-old girl who suffered from intractable daily seizures from 4 years of age was studied. She had negative myoclonus (NM) in the left arm during sustained extension of the arms. Her MRI showed shrinkage in the medial surface of the right frontal region. During the NM, EEG showed spike and wave around the right central region and the surface EMG demonstrated silent periods (SP) in the left triceps brachii muscle. Jerk-locked back averaging, time-locked to the onset of the SP, showed a negative spike around the right central region preceding SP by 38msec. Although SPECT images obtained 3 hours after administration of ¹²³I-Iomazenil showed abnormal hypo-accumulation in the right basal and mesial surfaces of the frontal lobe on the visual inspection, the statistical assessment of the images, using three-dimensional stereotactic surface projection (3D-SSP), indicated significant decreased particular in the right pre-supplementary motor area (pre-SMA). Due to these clinical and laboratory findings, it was assumed that the origin of NM in the current patient might be in pre-SMA.