Motor Unit Number Index (MUNIX) detects motor neuron loss in pre-symptomatic muscles in Amyotrophic Lateral Sclerosis. Issue 3 (March 2017)

• Record Type: Journal Article
• Authors: Neuwirth, Christoph; Barkhaus, Paul E.; Burkhardt, Christian; Castro, José; Czell, David; de Carvalho, Mamede; Nandedkar, Sanjeev; Stålberg, Erik; Weber, Markus
• Is Part Of: Clinical neurophysiology. Volume 128:Issue 3(2017:Mar.)
• Page Start: 495
• Page End: 500
• Publication Date: 2017-03
• Subjects: ADM abductor digiti minimi muscle -- AH abductor hallucis muscle -- ALS Amyotrophic Lateral Sclerosis -- ALSFRS-R revised amyotrophic lateral sclerosis functional rating scale -- APB abductor pollicis brevis muscle -- BB biceps brachii muscle -- CI Confidence Intervals -- CMAP compound muscle action potential -- EDB extensor digitorum brevis muscle -- FDI first dorsal interosseus muscle -- LMN lower motor neuron -- MMT manual muscle testing -- MUNE motor unit number estimation -- MUNIX motor unit number index -- SD standard deviation -- TA tibialis anterior muscle -- UMN upper motor neuron; MUNIX -- Pre-symptomatic ALS -- Biomarker -- Multicentre -- ALSFRS-R; Neurophysiology -- Periodicals; Electroencephalography -- Periodicals; Electromyography -- Periodicals; Neurology -- Periodicals; 612.8
• DOI: 10.1016/j.clinph.2016.11.026
• Languages: English
• ISSNs: 1388-2457

Abstract

Highlights: In pre-symptomatic muscles MUNIX can detect motor unit loss. MUNIX is more sensitive to change compared to CMAP and ALSFRS-R. This makes MUNIX a biomarker candidate for disease progression. Abstract: Objective: Motor Unit Number Index (MUNIX) is a quantitative neurophysiological measure that provides an index of the number of lower motor neurons supplying a muscle. It reflects the loss of motor neurons in patients with Amyotrophic Lateral Sclerosis (ALS). However, it is unclear whether MUNIX also detects motor unit loss in strong, non-wasted muscles. Methods: Three centres measured MUNIX in 49 ALS patients every three months in six different muscles (abductor pollicis brevis, abductor digiti minimi, biceps brachii, tibialis anterior, extensor digitorum brevis, abductor hallucis) on the less affected side. The decline of MUNIX in initially non-wasted, clinically strong muscles (manual muscle testing, MMT grade 5) was analysed before and after onset of weakness. Results: In 49 subjects, 151 clinically strong muscles developed weakness and were included for analysis. The average monthly relative loss of MUNIX was 5.0% before and 5.6% after onset of weakness. This rate of change was significantly higher compared to ALS functional rating scale (ALSFRS-R) and compound muscle action potential (CMAP) change over 12 months prior to the onset of muscle weakness ( p = 0.024). Conclusion: MUNIX is an electrophysiological marker that detects lower motor neuron loss in ALS, before clinical weakness becomes apparent by manual muscle testing. Significance: This makes MUNIX a good biomarker candidate for disease progression and possibly pharmacodynamics responds.