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Degree

Doctor of Philosophy, Case Western Reserve University, Biomedical Engineering, 1994.

Abstract

Spasticity is a motor control disorder common after stroke, and can cause the fingers to involuntarily flex and form a fist. Functional electrical stimulation can provide hand opening in hemiplegics with spastic finger flexor muscles through stimulation of the extensor digitorum communis (EDC) muscle and the ulnar nerve. The ability of electrical stimulation to extend these patient's fingers will help them to acquire objects, which will assist them in the performance of bimanual tasks. This study also sought to investigate the effects of finger extensor stimulation on the spasticity in finger flexor muscles. Electromyographic (EMG) activity was used to assess the presence of spasticity. Since EMG was recorded in muscles adjacent to stimulated muscles, it was contaminated by stimulus artifacts. An offline digital substitution procedure was developed to remove the stimulus artifacts from the flexor EMGs. Extensor stimulation did not reduce the activity in spastic finger flexor muscles, as hypothesized initially, and as might occur through a reciprocal inhibitory mechanism. In fact, flexor activity generally increased during extensor stimulation, presumably by generation of stretch reflexes. Tests conducted in able bodied subjects also found that extensor stimulation can increase the activity in finger flexor muscles; decreases in activity occurred in only a few trials of a few subjects. Although extensor stimulation did not reduce the activity in the spastic finger flexor muscles of hemiplegics, the extension force was sufficient to fully extend the fingers. Even in the presence of strong flexor spasticity, hand opening was achieved. The influence of voluntary effort on finger extension achieved by stimulation was also studied. Finger extension was generally improved when the subject was relaxed during stimulation, and did not attempt to assist extension with voluntary effort. It was also found that finger extension was greatly diminished in some subjects after they had just voluntarily flexed their fingers. This has implications for the performance of functional tasks, in which subjects could use voluntary flexion to grasp an object and then use stimulation to release the object. Closed loop control may be needed to adjust stimulation levels to achieve finger extension following voluntary flexion

Subject Headings

Engineering, Biomedical

Keywords

Spastic hemiplegia; Functional electrical stimulation

Advisor

Patrick E. Crago

Pages

181p.

Document number: case1061393914
Permalink: http://rave.ohiolink.edu/etdc/view?acc_num=case1061393914

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