[Increased variability of membrane potentials in amyotrophic lateral sclerosis]

Area of Science:

• Neuroscience
• Neuromuscular Disorders
• Electrophysiology

Context:

• Amyotrophic lateral sclerosis (ALS) involves motor neuron hyperexcitability and early large fiber involvement.
• Previous nerve excitability studies faced challenges due to disease heterogeneity and variable fiber thresholds.

Purpose:

• To investigate motor nerve excitability across different fiber populations in ALS patients.
• To compare nerve excitability characteristics between ALS patients and healthy controls.

Summary:

• Nerve excitability testing at multiple response levels revealed altered axonal membrane properties in ALS patients.
• Unlike controls, ALS patients lacked expected relationships between threshold electrotonus and fiber size, indicating increased axonal membrane potential variability.
• Some ALS patients showed threshold electrotonus changes suggestive of membrane depolarization, similar to ischemic nerves.

Impact:

• Findings suggest motor nerve excitability variability contributes to fasciculations in ALS.
• Results support prior evidence of potassium channel dysfunction and propose Na+/K+-pump failure, potentially linked to mitochondrial issues in early-stage ALS.