Nonparetic arm force does not overinhibit the paretic arm in chronic poststroke hemiparesis.
OBJECTIVE
To determine whether nonparetic arm force overinhibits the paretic arm in patients with chronic unilateral poststroke hemiparesis.


METHODS
Case-control neurophysiological and behavioral study of patients with chronic stroke.


METHODS
Research institution.


METHODS
Eighty-six referred patients were screened to enroll 9 participants (N=9) with a >6 month history of 1 unilateral ischemic infarct that resulted in arm hemiparesis with residual ability to produce 1Nm of wrist flexion torque and without contraindication to transcranial magnetic stimulation. Eight age- and handedness-matched healthy volunteers without neurologic diagnosis were studied for comparison.


METHODS
Not applicable.


METHODS
Change in interhemispheric inhibition targeting the ipsilesional primary motor cortex (M1) during nonparetic arm force. We hypothesized that interhemispheric inhibition would increase more in healthy controls than in patients with hemiparesis.


RESULTS
Healthy age-matched controls had significantly greater increases in inhibition from their active to resting M1 than patients with stroke from their active contralesional to resting ipsilesional M1 in the same scenario (20%±7% vs -1%±4%, F1,12=6.61, P=.025). Patients with greater increases in contralesional to ipsilesional inhibition were better performers on the 9-hole peg test of paretic arm function.


CONCLUSIONS
Our findings reveal that producing force with the nonparetic arm does not necessarily overinhibit the paretic arm. Though our study is limited in generalizability by the small sample size, we found that greater active contralesional to resting ipsilesional M1 inhibition was related with better recovery in this subset of patients with chronic poststroke.
Human Cortical Physiology and Stroke Neurorehabilitation Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD. Electronic address: mdimyan@umm.edu.
Michael A
MA
Dimyan
Human Cortical Physiology and Stroke Neurorehabilitation Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD.
Monica A
MA
Perez
Clinical Neurosciences Program, Division of Intramural Research, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD.
Sungyoung
S
Auh
Human Cortical Physiology and Stroke Neurorehabilitation Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD.
Erick
E
Tarula
Human Cortical Physiology and Stroke Neurorehabilitation Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD.
Matthew
M
Wilson
Human Cortical Physiology and Stroke Neurorehabilitation Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD.
Leonardo G
LG
Cohen
D000368:Aged; D000369:Aged, 80 and over; D001132:Arm / Q000503:physiopathology*; D002908:Chronic Disease; D005081:Exercise Therapy / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology; D009048:Motor Skills / Q000502:physiology*; D010291:Paresis / Q000209:etiology / Q000503:physiopathology / Q000534:rehabilitation*; D020127:Recovery of Function; D012189:Retrospective Studies; D020521:Stroke / Q000150:complications* / Q000503:physiopathology; D000071939:Stroke Rehabilitation; D013647:Task Performance and Analysis; D016896:Treatment Outcome
Neurophysiology; Paresis; Rehabilitation; Stroke