The effect of distal afferent input on the spasticity and motor control of the post stroke upper extremity
Spasticity is one of many components of the upper motor syndrome and is a common consequence of a stroke. It is characterized by an increased velocity-dependent resistance to passive stretch (Lance 1980). Spasticity has been used synonymously with enhanced or hyperactive stretch reflexes. This enhancement in the stretch reflex is thought to occur largely through a loss of descending inhibitory input that occurs post stroke. The effect of spasticity on motor control has been debated, but spasticity has been implicated in errors in motor control, joint contracture, and interference in activities of daily living (ADLs). As a result of these problems, spasticity is often clinically treated using a variety of techniques. To accurately determine the necessity and efficacy of one of these treatments, an accurate and reliable measure of spasticity must be available.
Similarly, volitional movement of the upper extremity post stroke is also problematic. Strength, or the ability to generate torque in a desired direction, is often impaired post stroke. Movement in "synergy patterns", as has been characterized by Brunnstrom and others (Brunnstrom 1970), is a typical form of discoordination seen post stroke. For example, abduction of the shoulder is often associated with flexion of the elbow. This impairs upper extremity movement as well as ADLs. Accurate assessment of these "synergy patterns" has been difficult as well. The Fugl-Meyer Scale addresses movement patterns loosely, along with other functional activities. However, the Fugl-Meyer scale does not appear to have adequate sensitivity to assess changes in movement patterns that may be a result of a given intervention. Thus, a sensitive, reliable measure of synergy patterns would be useful as well.
Two common interventions for the impairments listed above have been electrical stimulation and injection of Botulinum Toxin A (Botox) into the spastic muscles. It has been anecdotally noted that when these interventions are applied at the distal upper extremity, the more proximal joints benefit as well. This study will use novel biomechanical tools to assess the effects of electrical stimulation and Botox applied at the distal arm on the spasticity and motor control of the proximal muscles of the arm. It is hoped that the results of this study will be used clinically to enhance the quality of life of stroke survivors.