title: The motor neuron response to SMN1 deficiency in spinal muscular atrophy.
abstract: BACKGROUND
  The purpose of this study was to measure and analyze motor unit number estimation (MUNE) values longitudinally in spinal muscular atrophy (SMA).
  
  
  METHODS
  Sixty-two children with SMA types 2 and 3 were observed prospectively for up to 42 months. Longitudinal electrophysiological data were collected, including compound motor action potential (CMAP), single motor unit action potential (SMUP), and MUNE.
  
  
  RESULTS
  Significant motor neuron loss and compensatory collateral reinnervation were noted at baseline. Over time, there was a significant mean increase in MUNE (4.92 units/year, P = 0.009), a mean decrease in SMUP amplitude (-6.32 μV/year, P = 0.10), and stable CMAP amplitude.
  
  
  CONCLUSIONS
  The unexpected longitudinal results differ from findings in amyotrophic lateral sclerosis studies, perhaps indicating that compensatory processes in SMA involve new motor unit development. A better understanding of the mechanisms of motor unit decline and compensation in SMA is important for assessing novel therapeutic strategies and for providing key insights into disease pathophysiology.
authors.affiliation: Department of Neurology, Boston Children's Hospital and Harvard Medical School, 300 Longwood Avenue, Boston, Massachusetts, 02115, USA.
authors.forename: Peter B
authors.initials: PB
authors.lastname: Kang
authors.forename: Clifton L
authors.initials: CL
authors.lastname: Gooch
authors.forename: Michael P
authors.initials: MP
authors.lastname: McDermott
authors.forename: Basil T
authors.initials: BT
authors.lastname: Darras
authors.forename: Richard S
authors.initials: RS
authors.lastname: Finkel
authors.forename: Michele L
authors.initials: ML
authors.lastname: Yang
authors.forename: Douglas M
authors.initials: DM
authors.lastname: Sproule
authors.forename: Wendy K
authors.initials: WK
authors.lastname: Chung
authors.forename: Petra
authors.initials: P
authors.lastname: Kaufmann
authors.forename: Darryl C
authors.initials: DC
authors.lastname: de Vivo
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000222:Adaptation, Physiological / Q000502:physiology*; D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D018450:Disease Progression; D004576:Electromyography; D005091:Exons; D005260:Female; D017353:Gene Deletion; D006720:Homozygote; D006801:Humans; D007223:Infant; D016014:Linear Models; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009046:Motor Neurons / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000503:physiopathology*; D011446:Prospective Studies; D014897:Spinal Muscular Atrophies of Childhood / Q000235:genetics* / Q000503:physiopathology; D055533:Survival of Motor Neuron 1 Protein / Q000235:genetics*; D055815:Young Adult
chemical_list: C526471:SMN1 protein, human; D055533:Survival of Motor Neuron 1 Protein
keywords: compound motor action potential; electrophysiology; motor neuron disease; motor unit number estimation; spinal muscular atrophy
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