Efficacy of functional electrical stimulation in rehabilitating patients with foot drop symptoms after stroke and its correlation with somatosensory evoked potentials-a crossover randomised controlled trial

Abstract

Objective: The connectivity between somatosensory evoked potentials (SEPs) and cortical plasticity remains elusive due to a lack of supporting data. This study investigates changes in pathological latencies and amplitudes of SEPs caused by an acute stroke after 2 weeks of rehabilitation with functional electrical stimulation (FES). Furthermore, changes in SEPs and the efficacy of FES against foot drop (FD) stroke symptoms were correlated using the 10-m walk test and foot-ankle strength.

Methods: A randomised controlled two-period crossover design plus a control group (group C) was designed. Group A (n = 16) was directly treated with FES, while group B (n = 16) was treated after 2 weeks. The untreated control group of 20 healthy adults underwent repeated SEP measurements for evaluation only.

Results: The repeated-measures ANOVA showed a decrease in tibial nerve (TN) P40 and N50 latencies in group A after the intervention, followed by a decline in non-paretic TN SEP in latency N50 (p < 0.05). Moreover, compared to groups B and C from baseline to 4 weeks, group A showed a decrease in paretic TN latency P40 and N50 (p < 0.05). An increase in FD strength and a reduction in step cadence in group B (p < 0.05) and a positive tendency in FD strength (p = 0.12) and step cadence (p = 0.08) in group A were observed after the treatment time. The data showed a moderate (r = 0.50-0.70) correlation between non-paretic TN latency N50 and step cadence in groups A and B after the intervention time.

Conclusion: The FES intervention modified the pathological gait in association with improved SEP afferent feedback. Registered on 25 February 2021 on ClinicalTrials.gov under identifier number: NCT04767360.

Keywords: Functional electrical stimulation; Neuroprostheses; Sensory and motor recovery; Somatosensory evoked potentials; Stroke rehabilitation.

Fig. 1

Variation of TN SEP latency: P40 and N50 of the paretic limb and N50 of the non-paretic limb. Vertical bars denote 95% confidence intervals for means. *Comparison of group A to groups B and C from baseline to 2 weeks: decrease in paretic TN P40 latency: F(2, 37) = 7.70, p = 0.001; decrease in paretic TN N50 latency: F(2, 37) = 3,1937, p = 0.05254; and decrease of non-paretic TN latency N50: F(2, 37) = 8.02, p = 0.001

Fig. 2

Variation of the motor skill parameters: FD strength and 10-m walk test results (number of steps and time). Vertical bars denote 0.95 confidence intervals for means. *Significant difference in the pre- to post-intervention increase in strength (MRC) in the paretic ankle in dorsal flexion between group B and group A, weeks 2 and 4: [F(1, 29) = 4.36, p = 0.045] and in steps [cadence] decrease between group B and group A between weeks 2 and 4: [F(1, 29) = 4.79, p = 0.036]. No effects of FES in 10-m walking test time [s] between groups A and B (p > 0.05)