A prospective one-year follow-up study with somatosensory potentials evoked by stimulation of the median nerve in patients with cerebral infarct.

Somatosensory potentials evoked by stimulation of the median nerve (median nerve SEPs) were studied in a prospective and sequential series of 40 patients with first supratentorial and nonhaemorrhagic cerebral infarct. In 35 patients the SEPs were recorded three times during the first year after the stroke. The location of the infarcted zone was reflected in the number of detected abnormalities: most patients with infarct changes extending to the gray matter of the Rolandic cortex showed abnormalities in the median nerve SEPs, and all patients with involvement of both precentral and postcentral cortical gray matter had abnormal median nerve SEPs. In the entire patient group when both latency and amplitude abnormalities were included about half (48%) of the patients had abnormal median nerve SEPs a week after the stroke, 39% 2-3 months after the stroke and 29% about one year after the stroke. These changes were not significant. When separately surveying the changes in the numbers of latency and amplitude abnormalities the difference between the first and the third examinations was nearly significant only in the number of latency abnormalities. Furthermore, in the absolute latency and amplitude values, no significant changes could be seen within the first two-three months after the infarct; within the whole one-year follow-up period a nearly significant change was noted between the second and the third examination in only one parameter (P22 peak latency). Thus, the abnormalities in the median nerve SEPs, especially the amplitude abnormalities, were relatively permanent during the one-year period after cerebral infarct.