Nerve Stimulation Enhances Task-Oriented Training in Chronic, Severe Motor Deficit After Stroke

Stroke is a major cause of death and disability. Inter ventions to limit tissue damage during the acute phase of stroke have resulted in some success. However, there is a need for further research on interventions to maximize recovery of function after acute stages of stroke, particularly with regard to upper extremity (UE) movement function in cases of severe hemiparesis (almost no active movement). These interventions may capitalize on neuroplastic change, which has been associated with functional recovery in cases of neurological impairment. Neuroplastic change and recovery of motor function after cortical lesions can be significantly influenced by sensory input. During performance of motor tasks, repetitive activation of sensory input enhances motor cortical plasticity, establishing a mechanism for the role of sensory input in motor skill acquisition. A sensory-based intervention called peripheral nerve stimulation (PNS) has been shown to increase motor cortical excitability and enhance outcomes of motor training after stroke. In a study of 22 subjects <6 months after stroke, PNS paired with 1 week of intensive task–oriented UE training was associated with more significant improvement in movement function than the effects of training alone as measured by the Wolf Motor Function Test (WMFT). A separate study by Sawaki et al investigated the effects of PNS on voluntary movement of paretic thumb in 7 subjects at least 6 months post stroke. Significantly more neuroplastic change was associated with active PNS compared with sham conditions. Background and Purpose—A sensory-based intervention called peripheral nerve stimulation can enhance outcomes of motor training for stroke survivors with mild-to-moderate hemiparesis. Further research is needed to establish whether this paired intervention can have benefit in cases of severe impairment (almost no active movement). Methods—Subjects with chronic, severe poststroke hemiparesis (n=36) were randomized to receive 10 daily sessions of either active or sham stimulation (2 hours) immediately preceding intensive task-oriented training (4 hours). Upper extremity movement function was assessed using Fugl–Meyer Assessment (primary outcome measure), Wolf Motor Function Test, and Action Research Arm Test at baseline, immediately post intervention and at 1-month follow-up. Results—Statistically significant difference between groups favored the active stimulation group on Fugl–Meyer at postintervention (95% confidence interval [CI], 1.1–6.9; P=0.008) and 1-month follow-up (95% CI, 0.6–8.3; P=0.025), Wolf Motor Function Test at postintervention (95% CI, −0.21 to −0.02; P=0.020), and Action Research Arm Test at postintervention (95% CI, 0.8–7.3; P=0.015) and 1-month follow-up (95% CI, 0.6–8.4; P=0.025). Only the active stimulation condition was associated with (1) statistically significant within-group benefit on all outcomes at 1-month follow-up and (2) improvement exceeding minimal detectable change, as well as minimal clinically significant difference, on ≥1 outcomes at ≥1 time points after intervention. Conclusions—After stroke, active peripheral nerve stimulation paired with intensive task–oriented training can effect significant improvement in severely impaired upper extremity movement function. Further confirmatory studies that consider a larger group, as well as longer follow-up, are needed. Clinical Trial Registration—URL: http://www.clinicaltrials.gov. Unique identifier: NCT02633215. (Stroke. 2016;47:1879-1884. DOI: 10.1161/STROKEAHA.116.012671.)