Load and grip force coordination in static bimanual manipulation tasks in multiple sclerosis

Area of Science:

• Neurology
• Rehabilitation Science
• Biomedical Engineering

Background:

• Multiple sclerosis (MS) is a demyelinating disease affecting the central nervous system.
• Hand function impairment is a common symptom in MS patients, impacting daily activities.
• Early detection of subtle sensorimotor deficits is crucial for timely intervention.

Purpose of the Study:

• To investigate specific aspects of impaired hand function in mildly affected multiple sclerosis (MS) patients.
• To differentiate between feedback and feed-forward control mechanisms in MS hand function.
• To identify early indicators of sensorimotor dysfunction in MS.

Main Methods:

• 13 mildly affected MS patients (EDSS 1.5-4) and 13 controls performed static manipulation tasks.
• Tasks involved visually controlled (feedback) tracing of load force (LF) patterns.
• Tasks also included predominantly feed-forward controlled sinusoidal LF patterns.

Main Results:

• MS patients exhibited poorer performance in feedback-controlled tasks compared to controls.
• No significant difference in performance was observed in feed-forward controlled tasks.
• MS patients showed a higher grip force (GF) to load force (LF) ratio across all tasks.

Conclusions:

• Mildly affected MS patients have sensorimotor deficits primarily in visually guided hand tasks.
• Elevated GF/LF ratio (overgripping) is an early sign in MS, preceding more severe force decoupling.
• These findings support the experimental paradigm for assessing early MS-related hand dysfunction.