Fasciculation potentials and earliest changes in motor unit physiology in ALS

Area of Science:

• Neurology
• Neurophysiology

Background:

• Limited understanding of early motor unit (MU) physiology changes in amyotrophic lateral sclerosis (ALS).
• Need to understand the temporal development of neurophysiological features in ALS.

Purpose of the Study:

• Investigate earliest abnormalities in MU physiology in ALS.
• Track changes in MU physiology over time in ALS patients.

Main Methods:

• Observational, cross-sectional, and longitudinal study design.
• Evaluated tibialis anterior (TA) muscle in 73 ALS patients, 10 with benign fasciculation, and 37 controls.
• Assessed fasciculation potentials (FPs), fibrillation/sharp-waves (fibs-sw), MU potentials (MUPs), and jitter.

Main Results:

• FPs detected in ALS patients with normal MUPs, preceding MUP instability and later neurophysiological changes.
• FP complexity varied with disease stage and severity, being simpler in early ALS and benign fasciculations.
• Longitudinal studies confirmed FPs as an early marker, followed by MUP instability and then widespread fibs-sw.

Conclusions:

• Fasciculation potentials (FPs) are a very early marker of ALS, indicating increased axonal excitability.
• FP morphology analysis is crucial for differential diagnosis of ALS.
• Benign fasciculations represent a distinct phenomenon from early ALS changes.