We studied somatosensory evoked potentials (SSEPs) in eight Creutzfeldt-Jakob disease (CJD) patients presenting with subacute progressive dementia, generalized myoclonus, and characteristic periodic sharp wave complexes in EEG. Somatosensory evoked potentials were elicited by median nerve stimulation at the wrist. We compared SSEP findings with EEG and the clinical stage proposed by the Japanese Slow Virus Infection Research Committee (stage 1: early stage to stage 5: terminal stage). Until clinical stage 3, short-latency SSEPs showed normal findings despite the severely abnormal EEG. With the progression to clinical stages 4 and 5, however, the amplitude of N20 began to decrease and finally disappeared without prolongation of the latency of N20, whereas other short-latency components were preserved. We recorded giant SSEPs in two of three patients in stage 4, when the periodic sharp wave complex in EEG began to decrease in amplitude. The giant SSEPs decreased in amplitude with the progression of the illness. These findings suggest that the short-latency SSEP is relatively preserved until the middle phase of the disease but that it is eventually affected in the terminal phase. We conclude that our results are compatible with the CJD pathologic findings and that the amplitude of N20 reflects the extent of cortical damage in CJD patients.
Auditory evoked middlelatency responses (MLRs) to clicks were recorded in 68 normal adults (ages from 21 to 59 year-old) at 16 scalp locations, all referred to a balanced non-cephalic reference. Both Na and Pa components were clearly demonstrated in all the subjects studied through the digital high-pass filtering. Both Na and Pa components were distributed dominantly over the frontal area in all subjects. The amplitudes of Na and Pa were significantly higher with binaural stimulation than with a monaural stimulation, and the existence of binaural interaction was also suggested. Binaural effect was more prominent in Pa than in Na component. When the data recorded from F3 and F4 electrodes were compared, most of F3/F4 amplitude ratios of Na and Pa were included between 0.7 and 1.5. The F3/F4 ratio should be useful indices for the diagnosis of excessive laterality. We also demonstrated gradual phase shifts of Na and Pa between the frontal and temporooccipital area in about one-third of the records. This phenomenon strongly suggests that both Na and Pa components are derived from complex generators. evoked potentials; auditory evoked potentials; middle latency; normal adults
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