The motor unit number index (MUNIX) profile of patients with adult spinal muscular atrophy

Giorgia Querin, Timothée Lenglet, Rabab Debs, Tanya Stojkovic, Anthony Behin, François Salachas, Nadine Le Forestier, Maria del Mar Amador, Lucette Lacomblez, Vincent Meininger, Gaelle Bruneteau, Pascal Laforêt, Sophie Blancho, Véronique Marchand-Pauvert, Peter Bede, Jean Yves Hogrel, Pierre François Pradat

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)


Objective: Objective of this study is the comprehensive characterisation of motor unit (MU) loss in type III and IV Spinal Muscular Atrophy (SMA) using motor unit number index (MUNIX), and evaluation of compensatory mechanisms based on MU size indices (MUSIX). Methods: Nineteen type III and IV SMA patients and 16 gender- and age-matched healthy controls were recruited. Neuromuscular performance was evaluated by muscle strength testing and functional scales. Compound motor action potential (CMAP), MUNIX and MUSIX were studied in the abductor pollicis brevis (APB), abductor digiti minimi (ADM), deltoid, tibialis anterior and trapezius muscles. A composite MUNIX score was also calculated. Results: SMA patients exhibited significantly reduced MUNIX values (p < 0.05) in all muscles, while MUSIX was increased, suggesting active re-innervation. Significant correlations were identified between MUNIX/MUSIX and muscle strength. Similarly, composite MUNIX scores correlated with disability scores. Interestingly, in SMA patients MUNIX was much lower in the ADM than in the ABP, a pattern which is distinctly different from that observed in Amyotrophic Lateral Sclerosis. Conclusions: MUNIX is a sensitive measure of MU loss in adult forms of SMA and correlates with disability. Significance: MUNIX evaluation is a promising candidate biomarker for longitudinal studies and pharmacological trials in adult SMA patients.

Original languageEnglish
Pages (from-to)2333-2340
Number of pages8
JournalClinical Neurophysiology
Issue number11
Publication statusPublished (in print/issue) - 1 Nov 2018


  • Biomarkers
  • Motor unit loss
  • SMA type III
  • SMA type IV


Dive into the research topics of 'The motor unit number index (MUNIX) profile of patients with adult spinal muscular atrophy'. Together they form a unique fingerprint.

Cite this