A prospective 1 year follow-up study with somatosensory potentials evoked by stimulation of the posterior tibial nerve in patients with supratentorial cerebral infarction.

Somatosensory potentials evoked by stimulation of the posterior tibial nerve (tibial nerve SEPs) were studied in 40 patients with supratentorial non-haemorrhagic cerebral infarction and in 25 control subjects, SEPs were recorded twice in 39 patients and thrice in 35 patients. The first examination was carried out 4-19 days after the onset of the symptoms, the second examination 56-100 days after the stroke, and the third examination 348-393 days after the stroke. Increased side-to-side differences in the P57 and N75 peak latencies and absence of the P40 peak were the most frequent abnormal findings. The latency abnormalities were associated with involvement of the subcortical white matter of the rolandic region. The absence of the P40 peak was, in contrast, closely related to the extension of the infarcted area into the cortical gray matter of the rolandic region. When all SEP abnormalities were taken into account 55% of patients showed at least one abnormality in the tibial nerve SEP during the acute stage, 51% of patients had abnormal SEPs in the second examination and 43% of patients in the third examination. A nearly significant decrease was observed in the number of latency abnormalities, but the number of amplitude abnormalities, including absent responses, did not change during the 1 year follow-up period.