Introduction
Stroke is a leading cause of long-term adult motor disability. While current rehabilitation strategies carry promise, gains in function are modest where approximately 60-80% of survivors continue to experience motor impairments of the upper-limb well into the chronic phase of recovery. One reason for the modest recovery of upper-limb function is the diminishing time available for rehabilitation, where therapists are required to administer best practice in a limited number of sessions. Therefore, current research emphasizes the need for maximizing and accelerating outcomes of rehabilitation within constraints of time permitted for outpatient clinical therapy.
One strategy to maximize rehabilitative outcomes emphasizes the importance of engaging the paretic upper-limb in intensive movements/activities, defined operationally here as ‘unilateral therapies.’ Examples include constraint-induced movement therapy (CIMT) that requires patients to use the paretic upper-limb in tasks of daily living while restraining use of the non-paretic upper-limb, or electrical stimulation that targets weaker muscles to elicit more movement of the paretic upper-limb. Unilateral therapies are emphasized because they are derived from a popular, standard neurophysiologic model of stroke recovery commonly referred to as the ‘interhemispheric competition model’ (figure 1). According to this model, paresis originates from loss of output to the paretic upper-limb, but it persists due to inter-hemispheric imbalances.
The contralesional hemisphere excessively inhibits the ipsilesional hemisphere that is too weak to counter. As patients rely on using the non-paretic upper-limb to compensate for failures in using the paretic upper-limb, inter-hemispheric ‘competition’ intensifies. Output from the ipsilesional hemisphere weakens further, while excitability and inhibition imposed from the contralesional hemisphere continues to rise.
To maximize output to the paretic upper-limb, the model recommends emphasizing use of the paretic upper-limb in unilateral therapies and disregarding or de-incentivizing use of the non-paretic upper-limb. …
TBI Rehabilitation 