To assess (1) lower extremity sensorimotor differences between multiple sclerosis (MS) subtypes, and (2) how these relate to walking performance in the MS subtypes.

Disease progression of multiple sclerosis (MS) is often monitored by ambulatory measures. However, little is known how measures of sensorimotor function relate to walking performance in relapsing-remitting (RRMS) and progressive MS (PMS).

This prospective cross-sectional study evaluated participants with RRMS (n=24, 52.8 ±10.4 y; mean±SD), and PMS (n=28, 60.3±8.5 y). Vibration perception threshold (VPT; Volts) was measured in the foot and averaged across three locations (big toe, head of 5^th metatarsal, and heel). A custom ankle manipulandum was used to assess ankle proprioception, matching the contralateral ankle at 15 degrees dorsiflexion while blindfolded. Motor function was assessed by the number of foot taps completed in 10s. Ambulation was assessed by the 25-foot walk test (25FWT) at the fastest possible speed, as instructed by the MS functional composite exam.

MS subtypes did not significantly differ in 25FWT time (p = 0.082, CI=[-6.3,0.4]). Foot VPT was lower (p<0.001, CI=[-21.4,-6.9]) and tapping was faster (p=0.001, CI=[1.9,12.4]) in RRMS compared to PMS. Ankle proprioception did not differ between MS subtypes (p=0.865, CI=[-1.4,1.7]).  Linear regression analysis showed that foot-VPT was not significantly related to 25FWT in both MS subtypes (both p’s>0.2). Increased ankle proprioception errors related to increased 25FWT in RRMS (p=0.003, r²=0.22, RMSE=3.9) but not in PMS (p=0.571, r²=0.01, RMSE=3.9). Slower foot-tapping was also related to increased 25FWT in both RRMS (p<0.001, r²=0.46, RMSE =3.1) and PMS (p=0.016, r²=0.13, RMSE = 6.5).

Foot vibration sensitivity and tapping, but not ankle proprioception, were different between MS subtypes. Foot-tapping and ankle proprioception, but not foot VPT, were related to clinical walk measures. Foot-tapping may be an easy, low-cost way to replace ambulatory measures to track the progression of the disease.