Somatosensory evoked potentials of the posterior tibial nerve in hemiparetic patients: Relation to stance balance and walking ability

Objectives: To examine the association between stance ability and walking performance of poststroke hemiplegic patients and their posterior tibial nerve somatosensory evoked potentials (SEPs). Design and Setting: Fifteen patients, residents of a geriatric rehabilitation hospital, were evaluated twice, with a 2-week interval between sessions. In each session, clinical tests of stance balance and walking ability were performed, and bilateral SEPs to stimulation of the posterior tibial nerve were recorded. Eight healthy, age-matched control subjects underwent the same tests in a single session, but SEPs were recorded unilaterally. Correlation analysis and analysis of variance (ANOVA) were used for studying the prognostic value of the initial posterior tibial nerve SEP measurements as well as the within- and between-sessions relationships between the clinical-functional tests and the SEP data. Results: No significant correlations between the initial SEP values and functional improvement were established. Within each session, positive significant correlations existed between decreased latencies of several of the medium-latency SEP waves and the performance of stance and gait tasks. However, the between-sessions improvement in stance balance was not correlated with a decrease in latency of the SEP peaks or with an increase in their amplitudes. As to walking ability, in those patients whose gait significantly improved, a significant shortening of P37 and P54 latencies took place. Conclusions: The association between the initial and/or the 2-week changes in SEP of the posterior tibial nerve and improvement in stance and walking abilities is equivocal. In addition, the applicability of SEP measurements is limited by patients' physical status and cooperation. The clinical significance of posterior tibial nerve SEP testing in poststroke hemiparetic patients is therefore debatable.