Identifying Changes After Stroke  

Following stroke, there is usually hemiparesis, the partial paralysis of one side of the body. Often, this muscle weakness is a major barrier to recovery and restoration of everyday functioning after stroke and one possible cause is atrophy of muscles in the impaired arm and/or hand. Muscle atrophy refers to a decrease in the size of skeletal muscle. Since the ability to exert force is related to muscle mass, it is intuitive that muscle weakness is at least in part a result of atrophy. The primary objective of this project is to assess muscle atrophy in stroke survivors using a combination of ultrasonography and MR Imaging. The peak cross-sectional area of the extrinsic and intrinsic muscles controlling the movement of the index finger will be recorded and analyzed.  
The MR images are imported into commercial software for viewing/analysis whereby coronal sections will be examined to determine maximum cross-sectional area of each slice and the peak area, which is computed from outlines. The captured ultrasound images will be used to estimate muscle thickness (assuming uniform atrophy).  The percent differences in muscle parameters between impaired (contraloateral) and ipsilateral arms for stroke survivors as well as between dominant/non-dominant arms of healthy individuals will be utilized to determine the extent of the muscle atrophy.

There is evidence for coupling of proximal and distal segments of the human upper limb, both by biomechanical and neurological means. This coupling may be of particular importance in the context of motor impairment of the upper limb after stroke. First, it is possible that distal motor activity post-stroke can be influenced by proximal sensory input. Second, the neural coupling of upper limb muscles may be altered after stroke, thereby resulting in the emergence of abnormal patterns of muscle activity. The research that I am conducting at the Coleman Neuromuscular Hand Rehabilitation Laboratory with Dr. Derek Kamper and Dr. Brian Schmit addresses these two issues. Specifically, we are investigating a) the effect of static arm posture and proximal surface electrical stimulation on two measures of motor impairment of the hand, namely spasticity of the finger flexors and voluntary finger contraction, and b) the activities of muscles throughout the upper limb during the assessment of these two measures. Finger flexor spasticity is assessed by the stretch reflex response to imposed extension at the metacarpophalangeal (MCP) joints of the four fingers, and voluntary finger contraction is assessed by maximum isometric flexion and extension efforts at the same joints. We postulate that modifying the sensory feedback from proximal upper limb joints will significantly change reflex activity and voluntary motor activity of the fingers post-stroke. Further, we anticipate abnormal reflex coupling of muscle activities between finger flexors and proximal upper limb muscles in stroke subjects, in particular muscles that do not cross the MCP joints. The results from the present study are expected to impact rehabilitation of the upper limb of stroke survivors. Specifically, manipulation of proximal sensory input could play an important role in therapeutic interventions aimed at hand rehabilitation.