Original article
Hand Function and Motor Cortical Output Poststroke: Are They Related?

https://doi.org/10.1016/j.apmr.2006.02.006Get rights and content

Abstract

Brouwer BJ, Schryburt-Brown K. Hand function and motor cortical output poststroke: are they related?

Objectives

To characterize hand function and cortical excitability in chronic and subacute stages of stroke recovery and to describe the relations between these measures.

Design

Observational, case-control, and cohort pre-post inpatient rehabilitation.

Setting

Motor performance laboratory.

Participants

Fourteen community-living chronic and 14 subacute inpatient stroke survivors volunteered. Fourteen similarly aged healthy subjects served as a control group.

Interventions

Not applicable.

Main Outcome Measures

Finger tapping, peg placing, and strength were measured as indicators of hand function. The amplitude and latency of motor-evoked potentials (MEPs) and the duration of the silent period in the first dorsal interosseous muscle elicited by transcranial magnetic stimulation (TMS) reflected the integrity of excitatory and inhibitory cortical circuits.

Results

Diminished hand function, small MEPs, and prolonged silent-period durations were evident in stroke compared with control subjects. Longer MEP latencies and smaller amplitudes distinguished subacute from chronic stroke. Side-to-side asymmetries were greatest in the subacute group for all TMS outcomes, although this lessened over time based on the subsample retested at discharge. Greater side-to-side MEP amplitude symmetry and lower motor threshold (lesioned side) were associated with better hand function in subacute and chronic stroke, respectively.

Conclusions

Cortical excitability is an important determinant of hand function poststroke and evolves with the time elapsed since the stroke event. The unique neural correlates of hand function evident in subacute and chronic stroke may reflect different phases of neuromuscular recovery.

Section snippets

Participants

Twenty-eight first-ever stroke survivors with unilateral hemispheric lesions resulting in impaired upper extremity and hand function participated; none had apraxia or receptive aphasia. Upper-limb impairment and function was evaluated by using 3 subscales of the Motor Assessment Scale (MAS), which collectively included 17 physical task items involving the shoulder, elbow, and hand.25 Items were scored from 0 (no muscle activity) to 4 (normal movement pattern) and summed to provide a total score

Results

All subjects tolerated the procedures well except for 1 subacute stroke survivor who reported a severe headache after TMS.

Discussion

The present study showed diminished fine-motor skill and hand function bilaterally after hemispheric stroke, which was accompanied by abnormalities in cortical excitatory and inhibitory systems. Marked interhemispheric asymmetries in MEP and silent-period characteristics distinguished subjects with subacute strokes from those with chronic strokes. Although asymmetry was also evident in chronic stroke, it was less dramatic, suggesting a shift toward normalization (symmetry) with progressive

Conclusions

TMS revealed significant abnormalities after stroke, although less severe in the chronic stage of recovery than the subacute stage. Our longitudinal data from subjects with subacute stroke confirm that abnormalities in cortical excitability lessen over time, although the rate of change is not uniform for all TMS outcomes. This may explain the emergence of unique indicators of cortical excitability identified as correlates of hand function at different stages of recovery, which may relate to the

Acknowledgments

We extend our gratitude to the Departments of Physical Medicine & Rehabilitation and Physical Therapy, St. Mary’s of the Lake Hospital, for providing space and assisting with recruitment, and we thank Margaret Henderson for assistance with data processing.

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  • Cited by (0)

    Supported by the Heart and Stroke Foundation of Ontario (grant no. NA 4839) and the Natural Sciences and Engineering Research Council (postgraduate scholarship).

    No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated.

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