Sensory nerve stimulation causes an immediate improvement in motor function of persons with multiple sclerosis: A pilot study.

Abstract

BACKGROUND\nMultiple sclerosis (MS) symptoms reported in the first year of the disease include sensory impairment, fatigue, reduced mobility, and declines in hand function. The progressive reduction in motor function experienced by persons living with MS is invariably preceded by changes in sensory processing, which are strongly associated with the declines in both walking performance and manual dexterity.\n\n\nAIMS\nTo assess the influence of concurrent sensory stimulation using augmented transcutaneous electrical nerve stimulation (aTENS) applied to leg and hand muscles on clinical tests of motor function in individuals whose mobility was compromised by MS.\n\n\nMETHODS\nThirteen persons with MS (52\u202f±\u202f8 years; 6 women) and 12 age- and sex-matched healthy adults (52\u202f±\u202f9 years) met the inclusion criteria. Participants visited the lab on two occasions with one week between visits. Each visit involved the participant performing four tests of motor function and completing two health-related questionnaires (PDDS and MSWS-12). The tests assessed walking performance (6-min test and 25-ft test), dynamic balance (chair-rise tes, and manual dexterity (grooved pegboard test). aTENS was applied through pads attached to the limbs over the tibialis anterior and rectus femoris muscles of the affected leg, and over the median nerve and the thenar eminence of the dominant hand. The pads were attached during both visits, but the current was only applied during the second visit. The stimulation comprised continuous asymmetrical biphasic pulses (0.2\u202fms) at a rate of 50\u202fHz and an intensity that elicited slight muscle contractions.\n\n\nRESULTS\nAt baseline and during both treatment sessions, the performance on all four tests of motor function was worse for the MS group than the Control group. The MS group experienced significant improvements in all outcomes during the aTENS session with medium-to-large effect sizes. PDDS ratings improved (from 2.8\u202f±\u202f1.3 to 2.0\u202f±\u202f1.5; effect size d\u202f=\u202f-0.70) and the MSWS-12 scores declined (from 36\u202f±\u202f11 to 28\u202f±\u202f12; effect size d\u202f=\u202f-1.52). The concurrent application of aTENS enabled the MS group to walk further during the 6-min test (from 397\u202f±\u202f174\u202fm to 415\u202f±\u202f172\u202fm; effect size d\u202f=\u202f0.81), to complete the 25-ft test in less time (6.7\u202f±\u202f3.0\u202fs to 6.3\u202f±\u202f2.9\u202fs; effect size d\u202f=\u202f-0.76), to increase the counts in the chair-rise test (from 11.2\u202f±\u202f3.8 to 13.6\u202f±\u202f4.8; effect size d\u202f=\u202f1.52), and to perform the grooved pegboard test more quickly (from 110\u202f±\u202f43\u202fs to 99\u202f±\u202f37\u202fs; effect size d\u202f=\u202f-0.98). The only significant effect for the Control group was a significant increase in the 6-min walk distance (from 725\u202f±\u202f79 to 740\u202f±\u202f82\u202fm; effect size d\u202f=\u202f0.87).\n\n\nCONCLUSIONS\nStimulation of sensory fibers with aTENS evoked clinically significant improvements in four tests of motor function and the self-reported level of walking limitations in persons who were moderately disabled by MS. Moreover, the improvements in function elicited by the concurrent application of aTENS were immediate.