Purpose: The aim of this study was to investigate a relationship between sensory dysfunction examined with somatosensory-evoked potentials of the posterior tibial nerve (tSSEP) and walking speed in patients with clinically isolated syndrome.
Methods: In 120 patients (mean age 32.2 +/- 8.7 years, 84 females), Expanded Disability Status Scale (EDSS), timed 25-foot walk test (T25FW), brain and spinal cord MRI, and tSSEP were performed. P40 latencies and N22a-P40 interlatencies were analyzed, and the z-score for each latency was calculated and combined into total tSSEP z-score.
Results: T25FW significantly correlated with total tSSEP z-score (rs = 0.211; P = 0.021). When looking at each component of the tSSEP separately, T25FW significantly correlated with z-scores of P40 wave latencies (rs = 0.223; P = 0.014) and N22a-P40 interlatencies (rs = 0.241; P = 0.008) of the left side. There were no significant correlations with N22a wave latencies. Patients who presented with transverse myelitis (N = 41) and patients who had spinal cord lesions on MRI (N = 53) had significantly higher total tSSEP z-score compared with other patients (0.07 vs. -0.28, P = 0.019 and -0.02 vs. -0.38 P = 0.023; respectively). Somatosensory-evoked potentials of the posterior tibial nerve z-score corrected for age, sex, cervical spinal cord MRI lesions, and total number of supratentorial T2 lesions was a statistically significant predictor for T25FW (B = 0.267, P = 0.023).
Conclusions: Spinal somatosensory dysfunction is one of the factors associated with reduction in walking speed in early patients with multiple sclerosis. Somatosensory-evoked potentials of the posterior tibial nerve may potentially be useful in identifying patients at higher risk for the development of walking impairment in the future.
(C) 2017 by the American Clinical Neurophysiology Society