Altered Modulation of Locomotor Cutaneous Reflexes in Ambulatory Individuals With Chronic Spinal Cord Injury

Abstract

<h3>Research Objectives</h3> The purpose of this study was to examine lower limb cutaneous (CUT) reflexes during walking in people with chronic incomplete spinal cord injury (SCI). In neurologically intact individuals, CUT reflexes to non-noxious stimulus are phase-dependently modulated during walking with nerve specificity, so as to avoid stumbling and falling [1]. Currently, CUT reflexes in ambulatory individuals with SCI are not well understood. <h3>Design</h3> CUT reflexes were elicited by stimulating the sural (SR), superficial peroneal (SP), or tibial nerve (TN) near the ankle of the clinically more spastic leg. For each nerve stimulation, a 5 × 1-ms pulse train (200 Hz) at ≈1.7 x radiating threshold was delivered pseudo-randomly across the entire step cycle while the participant walked on a treadmill at his/her comfortable speed. Electromyography (EMG) was recorded from the soleus and tibialis anterior (TA) bilaterally, and medial and lateral gastrocnemius, vastus lateralis, and biceps femoris in the stimulated leg. <h3>Setting</h3> University. <h3>Participants</h3> Eight individuals with chronic incomplete SCI volunteered to participate in this study. <h3>Interventions</h3> Not applicable. <h3>Main Outcome Measures</h3> Medium (80-120 ms post-stimulus) latency CUT reflexes were quantified in 8 equal bins of the step cycle. <h3>Results</h3> CUT reflexes are phase-dependently modulated in ambulatory individuals with SCI, with less nerve specificity than that in people without injuries [2]. Nerve specificity was clear for the ipsilateral TA, which showed strong excitation in the early swing phase following TN (56% max non-stimulated EMG) but suppression following SR (-4%) and SP (-13%). Contralateral TA was suppressed during late swing uniformly following TN (-15%), SR (-14%), and SP (-18%). <h3>Conclusions</h3> The presence and patterns of CUT reflex modulation could be useful measures of neuroplasticity in people with SCI. <h3>Author(s) Disclosures</h3> No conflicts.