Motor cortex abnormalities in amyotrophic lateral sclerosis with transcranial direct-current stimulation

Area of Science:

• Neuroscience
• Neurology
• Electrophysiology

Background:

• Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease affecting upper and lower motor neurons.
• Identifying reliable neurophysiological markers for upper motor neuron (UMN) involvement is crucial for ALS diagnosis and management.
• Transcranial direct-current stimulation (tDCS) is a non-invasive brain stimulation technique that can modulate cortical excitability.

Purpose of the Study:

• To identify a neurophysiological marker for upper motor neuron involvement in sporadic amyotrophic lateral sclerosis (ALS).
• To evaluate the after-effects of transcranial direct-current stimulation (tDCS) on motor cortex excitability in ALS patients and healthy controls.

Main Methods:

• Eight patients with sporadic ALS and eight healthy controls underwent transcranial direct-current stimulation (tDCS).
• Motor cortex excitability was assessed by measuring corticospinal excitability changes following anodal and cathodal tDCS.

Main Results:

• Healthy controls exhibited significant, polarity-specific changes in corticospinal excitability (+/-45%) after tDCS (anodal: facilitation, cathodal: inhibition).
• ALS patients demonstrated no significant changes in corticospinal excitability following either anodal or cathodal tDCS.

Conclusions:

• The absence of tDCS after-effects in ALS patients suggests potential alterations in the motoneuronal membrane or disordered glutamate neurotransmission.
• These findings may indicate a novel and reliable electrophysiological marker for upper motor neuron involvement in ALS.
• Further research is warranted to validate these results and explore their clinical implications.