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

Elizabeth S Powell; Philip M Westgate; Larry B Goldstein; Lumy Sawaki

doi:10.1016/j.arrct.2019.100023

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

Arch Rehabil Res Clin Transl. 2019 Sep 12;1(3-4):100023. doi: 10.1016/j.arrct.2019.100023. eCollection 2019 Dec.

Authors

Elizabeth S Powell¹, Philip M Westgate², Larry B Goldstein³, Lumy Sawaki¹

Affiliations

¹ Department of Physical Medicine and Rehabilitation, University of Kentucky, Lexington, Kentucky.
² Department of Biostatistics, College of Public Health, University of Kentucky, Lexington, Kentucky.
³ Department of Neurology, University of Kentucky, Lexington, Kentucky.

Abstract

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.

Keywords: ARAT, Action Research Arm Test; BMI, brain-machine interface; FMA, Fugl-Meyer Assessment; MCID, minimal clinically important difference; MEP, motor-evoked potential; MSO, maximum stimulator output; PNS, peripheral nerve stimulation; Rehabilitation; TMS, transcranial magnetic stimulation; Transcranial direct current stimulation; Transcranial magnetic stimulation; tDCS, transcranial direct current stimulation.