Sumit Verma1,2, Jasmine Forte1,2, Mary Ritchey3, Durga Shah3. 1. Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia. 2. Department of Neurology, Emory University School of Medicine, Atlanta, Georgia. 3. Department of Physical Therapy, Children's Healthcare of Atlanta, Atlanta, Georgia.
Abstract
BACKGROUND: Motor unit number index (MUNIX) is a validated electrophysiological biomarker in amyotrophic lateral sclerosis. MUNIX studies in spinal muscular atrophy (SMA) are limited. METHODS: Later-onset SMA children (n = 13; three SMN2 copy number) were evaluated for Hammersmith Motor Function Scale Expanded (HMFSE) and MUNIX of right abductor pollicis brevis (APB) and abductor digiti minimi (ADM) muscles. Age-matched healthy controls (n = 8) were enrolled to obtain normative APB and ADM MUNIX values. RESULTS: Mean APB and ADM MUNIX values in SMA subjects were significantly reduced (P < .001) compared with controls. HMFSE scores strongly correlated with ADM MUNIX (r 0.63). CONCLUSIONS: APB and ADM muscle MUNIX studies are feasible in SMA type 2 children. ADM MUNIX correlated with disease severity on motor function testing. MUNIX studies in later-onset SMA could be a potential biomarker of motor neuron loss.
BACKGROUND: Motor unit number index (MUNIX) is a validated electrophysiological biomarker in amyotrophic lateral sclerosis. MUNIX studies in spinal muscular atrophy (SMA) are limited. METHODS: Later-onset SMA children (n = 13; three SMN2 copy number) were evaluated for Hammersmith Motor Function Scale Expanded (HMFSE) and MUNIX of right abductor pollicis brevis (APB) and abductor digiti minimi (ADM) muscles. Age-matched healthy controls (n = 8) were enrolled to obtain normative APB and ADM MUNIX values. RESULTS: Mean APB and ADM MUNIX values in SMA subjects were significantly reduced (P < .001) compared with controls. HMFSE scores strongly correlated with ADM MUNIX (r 0.63). CONCLUSIONS: APB and ADM muscle MUNIX studies are feasible in SMA type 2 children. ADM MUNIX correlated with disease severity on motor function testing. MUNIX studies in later-onset SMA could be a potential biomarker of motor neuron loss.
Keywords:
Hammersmith motor function scale expanded; compound muscle action potential; motor unit number index; motor unit size index; spinal muscular atrophy
Authors: Laura E Habets; Bart Bartels; Fay-Lynn Asselman; Melissa T Hooijmans; Sandra van den Berg; Aart J Nederveen; W Ludo van der Pol; Jeroen A L Jeneson Journal: Brain Date: 2022-05-24 Impact factor: 15.255