Emilien Delmont1, François Wang2, Jean-Pascal Lefaucheur3, Angela Puma4, Céline Breniere5, Guillemette Beaudonnet6, Pascal Cintas7, Romain Collin2, Etienne Fortanier8, Aude-Marie Grapperon8, Laurent Jomir5, Hafida Kribich8, Ludivine Kouton8, Thierry Kuntzer9, Timothee Lenglet10, Armelle Magot11, Tarik Nordine3, François Ochsner9, Gaëlle Bolloy11, Yann Pereon11, Emmanuelle Salort-Campana8, Céline Tard12, Alex Vicino9, Annie Verschueren8, Shahram Attarian8. 1. Referral Centre for Neuromuscular Diseases and ALS, La Timone Hospital, Marseille, France; Aix-Marseille University, Timone Neuroscience Institute, UMR CNRS 7289, 13005 Marseille, France. Electronic address: emilien.delmont@ap-hm.fr. 2. Department of Neurophysiology, CHU Sart Tilman B35, 4000 Liège, Belgium. 3. EA 4391, Excitabilité Nerveuse et Thérapeutique, Université Paris-Est-Créteil, Créteil, France; Unité de Neurophysiologie Clinique, Hôpital Henri Mondor, Assistance Publique - Hôpitaux de Paris, Créteil, France. 4. Université Côte d'Azur, Peripheral Nervous System and Muscle Department, CHU Nice, France. 5. Department of Neurology, Hospices Civiles de Lyon, France. 6. Unité de Neurophysiologie Clinique et Epileptologie, CHU Bicêtre, Le Kremlin Bicêtre, France. 7. Department of Neurology, Toulouse, France. 8. Referral Centre for Neuromuscular Diseases and ALS, La Timone Hospital, Marseille, France. 9. Nerve Muscle Unit, Department of Clinical Neurosciences, Lausanne University Hospital, Lausanne, Switzerland. 10. Department of Clinical Neurophysiology, APHP, Pitié-Salpêtrière Hospital, Paris, France. 11. Laboratoire d'explorations fonctionnelles, Referral Centre for Neuromuscular Disease Atlantique-Occitanie-Caraïbes, Hôtel-Dieu, 44093 Nantes, France. 12. U1172 Lille Neuroscience et Cognition, CHU de Lille, Centre de référence des maladies neuromusculaires Nord Est Ile de France, Department of Neurology, Lille, France.
Abstract
OBJECTIVE: Motor unit number index (MUNIX) is proposed to monitor neuromuscular disorders. Our objective is to determine the intra-individual variability over time of the MUNIX. METHODS: In 11 different hospital centres, MUNIX was assessed twice, at least 3 months apart (range 90-360 days), in tibialis anterior (TA), abductor pollicis brevis (APB), abductor digiti minimi (ADM) and deltoid muscles in 118 healthy subjects. MUNIX sum score 2, 3 and 4 were respectively the sum of the MUNIX of the TA and ADM, of the TA, APB and ADM and of the TA, APB, ADM and deltoid muscles. RESULTS: The repeatability of the MUNIX was better for sum scores than for single muscle recordings. The variability of the MUNIX was independent of sex, age, interval between measurements and was lower for experienced than non-experienced operators. The 95th percentile of the coefficient of variability of the MUNIX sum score 2, 3 and 4 were respectively 22%, 18% and 15% for experienced operators. CONCLUSIONS: The MUNIX technique must be performed by experienced operators on several muscles to reduce its variability and improve its reliability. SIGNIFICANCE: A variation of the MUNIX sum score ≥20% can be interpreted as a significant change of muscle innervation.
OBJECTIVE: Motor unit number index (MUNIX) is proposed to monitor neuromuscular disorders. Our objective is to determine the intra-individual variability over time of the MUNIX. METHODS: In 11 different hospital centres, MUNIX was assessed twice, at least 3 months apart (range 90-360 days), in tibialis anterior (TA), abductor pollicis brevis (APB), abductor digiti minimi (ADM) and deltoid muscles in 118 healthy subjects. MUNIX sum score 2, 3 and 4 were respectively the sum of the MUNIX of the TA and ADM, of the TA, APB and ADM and of the TA, APB, ADM and deltoid muscles. RESULTS: The repeatability of the MUNIX was better for sum scores than for single muscle recordings. The variability of the MUNIX was independent of sex, age, interval between measurements and was lower for experienced than non-experienced operators. The 95th percentile of the coefficient of variability of the MUNIX sum score 2, 3 and 4 were respectively 22%, 18% and 15% for experienced operators. CONCLUSIONS: The MUNIX technique must be performed by experienced operators on several muscles to reduce its variability and improve its reliability. SIGNIFICANCE: A variation of the MUNIX sum score ≥20% can be interpreted as a significant change of muscle innervation.