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Neurorehabil Neural Repair. 2019 Jul;33(7):568-580. doi: 10.1177/1545968319850138. Epub 2019 Jun 6.

Differential Poststroke Motor Recovery in an Arm Versus Hand Muscle in the Absence of Motor Evoked Potentials.

Author information

1
1 New York University School of Medicine, New York, NY, USA.
2
2 Columbia University, New York, NY, USA.
3
3 Johns Hopkins University, Baltimore, MD, USA.
4
4 University Hospital of Zurich, Zurich, Switzerland.
5
5 cereneo Center for Neurology and Rehabilitation, Vitznau, Switzerland.

Abstract

Background. After stroke, recovery of movement in proximal and distal upper extremity (UE) muscles appears to follow different time courses, suggesting differences in their neural substrates. Objective. We sought to determine if presence or absence of motor evoked potentials (MEPs) differentially influences recovery of volitional contraction and strength in an arm muscle versus an intrinsic hand muscle. We also related MEP status to recovery of proximal and distal interjoint coordination and movement fractionation, as measured by the Fugl-Meyer Assessment (FMA). Methods. In 45 subjects in the year following ischemic stroke, we tracked the relationship between corticospinal tract (CST) integrity and behavioral recovery in the biceps (BIC) and first dorsal interosseous (FDI) muscle. We used transcranial magnetic stimulation to probe CST integrity, indicated by MEPs, in BIC and FDI. We used electromyography, dynamometry, and UE FMA subscores to assess muscle-specific contraction, strength, and inter-joint coordination, respectively. Results. Presence of MEPs resulted in higher likelihood of muscle contraction, greater strength, and higher FMA scores. Without MEPs, BICs could more often volitionally contract, were less weak, and had steeper strength recovery curves than FDIs; in contrast, FMA recovery curves plateaued below normal levels for both the arm and hand. Conclusions. There are shared and separate substrates for paretic UE recovery. CST integrity is necessary for interjoint coordination in both segments and for overall recovery. In its absence, alternative pathways may assist recovery of volitional contraction and strength, particularly in BIC. These findings suggest that more targeted approaches might be needed to optimize UE recovery.

KEYWORDS:

motor cortex; motor evoked potential; neurorehabilitation; stroke recovery; transcranial magnetic stimulation

PMID:
31170880
DOI:
10.1177/1545968319850138

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