Spatial Analysis of Multichannel Surface EMG in Hemiplegic Stroke

Area of Science:

• Neuroscience
• Biomedical Engineering
• Rehabilitation Science

Background:

• Motor impairments following stroke can significantly affect upper extremity function.
• Understanding changes in muscle activation patterns is crucial for effective rehabilitation strategies.

Purpose of the Study:

• To investigate spatial activation patterns of upper extremity muscles in individuals with and without stroke.
• To determine if motor impairments post-stroke are associated with alterations in muscle activity maps and spatial distribution.

Main Methods:

• Utilized a 128-channel surface electromyogram (EMG) grid to record biceps brachii muscle activity during isometric contractions.
• Processed EMG data to generate 2-D root mean square (RMS) maps of muscle activity.
• Analyzed spatial patterns, size, location, and textural properties of muscle activity maps, correlating with Fugl-Meyer and modified Ashworth scores.

Main Results:

• Muscle activity maps were consistent within subjects across contraction levels but significantly different between stroke-affected and non-affected arms.
• Chronic stroke altered the size and location of active regions, potentially due to changes in muscle structure (atrophy, fat infiltration, fibrosis).
• Increased pixel-to-pixel variability in EMG activity maps was observed in stroke-affected muscles, linked to functional impairment and spasticity.

Conclusions:

• Spatial muscle activation patterns are significantly altered in the chronic stroke-affected upper extremity.
• These alterations in muscle architecture and morphology correlate with the degree of motor impairment and spasticity.
• Findings highlight potential targets for therapeutic interventions aimed at restoring muscle function post-stroke.