Lower motor neuron involvement in ALS assessed by motor unit number index (MUNIX): Long-term changes and...

Area of Science:

• Neurology
• Neurophysiology

Background:

• Motor Unit Number Estimation (MUNE) techniques, including Motor Unit Number Index (MUNIX), are vital for quantifying motor neuron loss in amyotrophic lateral sclerosis (ALS).
• Assessing the reproducibility of MUNIX is crucial for its reliable application in tracking disease progression.

Purpose of the Study:

• To investigate the consistency and reproducibility of MUNIX measurements in ALS patients over time.
• To evaluate MUNIX's potential for monitoring disease progression in clinical settings and therapeutic trials.

Main Methods:

• MUNIX was measured bilaterally in the abductor pollicis brevis and tibialis anterior muscles of 30 ALS patients at two time points.
• Measurements were also taken in healthy controls.
• Intra-rater reproducibility was assessed using interclass correlation coefficient (ICC), correlation coefficient analysis (CCA), and coefficient of variation (CV).

Main Results:

• A significant correlation was observed between the first and second MUNIX measurements in all tested muscles (r⩾0.891, p<0.01).
• High statistical reproducibility of MUNIX was confirmed in all four measured muscles at follow-up (ICC⩾0.946, p<0.01).
• The coefficient of variation (CV) for MUNIX at follow-up ranged from 13.90% to 32.95%.

Conclusions:

• The study demonstrates good consistency and reproducibility of MUNIX measurements throughout the course of ALS.
• MUNIX is a reliable tool for tracking disease progression in ALS patients.
• The findings support the use of MUNIX in routine clinical practice and for monitoring outcomes in ALS treatment trials.