Absence of Motor-Evoked Potentials Does Not Predict Poor Recovery in Patients With Severe-Moderate Stroke: An Exploratory Analysis.

OBJECTIVE: To better understand the role of the presence or absence of motor-evoked potentials (MEPs) in predicting functional outcomes following a severe-moderate stroke. DESIGN: Retrospective exploratory analysis. We compared the effects of the stimulation condition (active or sham), MEP status (+ or -), and a combination of stimulation condition and MEP status on outcome. Within-group and between-group changes were assessed with longitudinal repeated measures analysis of variance and longitudinal repeated measures analysis of covariance, respectively. The proportions of participants who achieved minimal clinically important differences (MCIDs) for the main outcome measures were calculated. SETTING: University research laboratory within a rehabilitation hospital. PARTICIPANTS: A total of 129 subjects with severe-moderate stroke-related motor impairments who participated in previous studies combining neuromodulation and motor training. INTERVENTIONS: Neuromodulation (active or sham) and motor training. MAIN OUTCOME MEASURES: Fugl-Meyer Assessment (FMA) and Action Research Arm Test (ARAT). RESULTS: When participants were grouped by stimulation condition or MEP status, all groups improved from baseline to immediate postintervention and follow-up evaluations (all P<.05). Analysis by stimulation condition and MEP status found that the MEP-/active group improved by 4.2 points on FMA (P<.0001) and 1.8 on ARAT (P=.003) post intervention. The MEP+/active group improved by 5.7 points on FMA (P<.0001) and 3.9 points on ARAT (P<.0001) post intervention. There were no between-group differences (P>.05). Regarding MCIDs, in the MEP-/active group, 14.5% of individuals reached MCID on FMA and 8.3% on ARAT post intervention. In the MEP+/active group, 33.3% of individuals reached MCID on FMA and 27.3% on ARAT post intervention. CONCLUSION: As expected, the MEP+ group had the greatest improvement in motor function. However, it was shown that individuals without MEPs can also achieve meaningful changes, as reflected by MCID, when neuromodulation is paired with motor training. To our knowledge, this is the first study to differentiate the effects of neuromodulation by MEP status.

Time configuration of combined neuromodulation and motor training after stroke: A proof-of-concept study.

BACKGROUND: Intensive motor training is a therapeutic intervention that supports recovery of movement function after stroke by capitalizing on the brain's capacity for neuroplastic change. Peripheral nerve stimulation and transcranial direct current stimulation are neuromodulation techniques that can upregulate neuroplasticity and, in turn, enhance outcomes of motor training after stroke. Few studies have investigated possible adjuvant effects between peripheral nerve stimulation, transcranial direct current stimulation, and intensive motor training. OBJECTIVE: This proof-of-concept study investigated whether timing variations in neuromodulation paired with robot-assisted motor training effect differential outcomes for subjects with chronic, moderate-to-severe upper extremity impairment after stroke. METHODS: Ten subjects in the chronic phase (>12 months after stroke) of recovery completed the study. Subjects received 10 daily sessions of transcranial direct current stimulation either at the start (n = 4) or at the end (n = 6) of peripheral nerve stimulation preceding intensive motor training. Pre-post changes in motor function (Fugl-Meyer Assessment; Stroke Impact Scale) and neuroplasticity (transcranial magnetic stimulation) were assessed by condition. RESULTS: Significant improvement in Stroke Impact Scale (p = 0.02) and no change in Fugl-Meyer Assessment were associated with the start condition. No changes in Stroke Impact Scale and Fugl-Meyer Assessment were associated with the end condition. Only 1 subject in the start group had measurable neuroplastic responses and demonstrated an increase in ipsilesional cortical map volume. Only 1 subject in the end group had measurable neuroplastic responses and demonstrated a decrease in ipsilesional cortical map volume. Opposite shifts in ipsilesional cortical centers of gravity occurred relative to condition. CONCLUSION: In cases of moderate-to-severe impairment after stroke, transcranial direct current stimulation at the start, rather than the end, of peripheral nerve stimulation prior to motor training may effect better functional outcomes. Future research with a larger sample size is needed to validate the findings of this proof-of-concept study.

Closed-loop afferent electrical stimulation for recovery of hand function in individuals with motor incomplete spinal injury: early clinical results.

Afferent electrical stimulation is known to augment the effect of rehabilitative therapy through use-dependent cortical plasticity. Experiments pairing transcranial magnetic stimulation (TMS) with peripheral nerve stimulation (PNS) have shown a timing-dependent effect on motor evoked potential (MEP) amplitude suggesting that PNS applied in closed-loop (CL) mode could augment this effect through positive reinforcement. We present early results from a clinical trial in which an EEG brain-machine interface (BMI) was used to apply PNS to two subjects in response to motor intent detected from sensorimotor cortex in a cue-driven hand grip task. Both subjects had stable incomplete cervical spinal cord injury (SCI) with impaired upper limb function commensurate with the injury level. Twelve sessions of CL-PNS applied over a 4-6 week period yielded results suggesting improved hand grip strength and increased task-related modulation of the EEG in one hand of both subjects, and increased TMS-measured motor map area in one. These observations suggest that rehabilitation using such interactive therapies could benefit affected individuals.