The interaction between metaplastic neuromodulation and fatigue in multiple sclerosis

Area of Science:

• Neuroscience
• Rehabilitation Medicine
• Neurology

Background:

• Neuromuscular fatigue significantly impacts quality of life in Multiple Sclerosis (MS).
• Current treatments for MS-related fatigue have limited effectiveness.
• Transcranial direct current stimulation (tDCS) shows potential for managing fatigue by modulating corticospinal excitability.

Purpose of the Study:

• To investigate the effects of cathodal tDCS (ctDCS) priming on anodal tDCS (atDCS)-induced corticospinal excitability.
• To explore tDCS-mediated modulation of neuromuscular fatigue in people with MS (pwMS).
• To assess potential metaplasticity changes in pwMS using a primed tDCS protocol.

Main Methods:

• 15 pwMS and 15 healthy controls participated.
• Participants underwent fatiguing exercise with either ctDCS or sham (stDCS) primed atDCS to the motor cortex.
• Changes in contraction force and motor evoked potential (MEP) amplitude were measured over time.

Main Results:

• Primed atDCS induced MEP elevation in healthy controls but not in pwMS, suggesting impaired metaplasticity in pwMS.
• No significant change in the magnitude of fatigue was observed with tDCS in either group.
• These findings indicate that fatigue development in MS may not be solely dependent on corticospinal excitability changes.

Conclusions:

• The study highlights differences in tDCS effects between pwMS and healthy controls.
• Impaired metaplasticity may be a factor in tDCS response in pwMS.
• Findings contribute to understanding tDCS applications and MS pathophysiology.