W. Zev Rymer, MD, Ph.D.
Stroke is a common disease, affecting at least 500,000 people/year in the US. Many stroke survivors experience continued motor, sensory and cognitive impairments, which limits their functional capacity, and prevents their return to work or to a normal home environment. Motor impairments have especially adverse effects on functional capacity, and they include spasticity, weakness and disturbed motor coordination.
This presentation will briefly review the features of impaired neuromuscular function in hemiparetic stroke, focusing primarily on disturbances of coordination in voluntary movements of the upper extremity. The potential contributory roles for altered spatial coordinate frameworks specifying motion direction, for loss of internal models of limb mechanical behavior, and for inappropriate stretch reflex action in antagonist muscles will be addressed.
We will argue that the primary disturbance in many cases is the inability to synthesize an appropriate internal model of the limb response, preventing appropriate forward controls from being implemented. In selected instances, there appears to be restriction of limb motion, triggered by inappropriate activation of normally quiescent antagonist limb muscles.
The significance of these deficits will be addressed in the context of developing helpful physical and pharmacological interventions to promote recovery of function in stroke.