title: Neural Substrates of Motor Recovery in Severely Impaired Stroke Patients With Hand Paralysis.
abstract: In well-recovered stroke patients with preserved hand movement, motor dysfunction relates to interhemispheric and intracortical inhibition in affected hand muscles. In less fully recovered patients unable to move their hand, the neural substrates of recovered arm movements, crucial for performance of daily living tasks, are not well understood. Here, we evaluated interhemispheric and intracortical inhibition in paretic arm muscles of patients with no recovery of hand movement (n = 16, upper extremity Fugl-Meyer Assessment = 27.0 ± 8.6). We recorded silent periods (contralateral and ipsilateral) induced by transcranial magnetic stimulation during voluntary isometric contraction of the paretic biceps and triceps brachii muscles (correlates of intracortical and interhemispheric inhibition, respectively) and investigated links between the silent periods and motor recovery, an issue that has not been previously explored. We report that interhemispheric inhibition, stronger in the paretic triceps than biceps brachii muscles, significantly correlated with the magnitude of residual impairment (lower Fugl-Meyer scores). In contrast, intracortical inhibition in the paretic biceps brachii, but not in the triceps, correlated positively with motor recovery (Fugl-Meyer scores) and negatively with spasticity (lower Modified Ashworth scores). Our results suggest that interhemispheric inhibition and intracortical inhibition of paretic upper arm muscles relate to motor recovery in different ways. While interhemispheric inhibition may contribute to poorer recovery, muscle-specific intracortical inhibition may relate to successful motor recovery and lesser spasticity.
authors.affiliation: Georgetown University Medical Center, Washington, DC, USA MedStar National Rehabilitation Hospital, Washington, DC, USA Mh672@georgetown.edu.
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Harris-Love
authors.affiliation: MedStar National Rehabilitation Hospital, Washington, DC, USA.
authors.forename: Evan
authors.initials: E
authors.lastname: Chan
authors.affiliation: Georgetown University Medical Center, Washington, DC, USA MedStar National Rehabilitation Hospital, Washington, DC, USA District of Columbia VA Medical Center, Washington, DC, USA.
authors.forename: Alexander W
authors.initials: AW
authors.lastname: Dromerick
authors.affiliation: Human Cortical Physiology and Neurorehabilitation Section, NINDS, NIH, Bethesda, MD, USA.
authors.forename: Leonardo G
authors.initials: LG
authors.lastname: Cohen
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001132:Arm / Q000503:physiopathology*; D019054:Evoked Potentials, Motor; D005260:Female; D006225:Hand / Q000503:physiopathology*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D009128:Muscle Spasticity / Q000503:physiopathology; D018482:Muscle, Skeletal / Q000503:physiopathology*; D009433:Neural Inhibition / Q000502:physiology*; D010243:Paralysis / Q000503:physiopathology*; D020127:Recovery of Function / Q000502:physiology*; D012720:Severity of Illness Index; D020521:Stroke / Q000503:physiopathology*; D050781:Transcranial Magnetic Stimulation
keywords: arm; cerebrovascular accident; interhemispheric inhibition; rehabilitation; stroke; transcranial magnetic stimulation; upper extremity paresis