title: Quantitative studies of lower motor neuron degeneration in amyotrophic lateral sclerosis: evidence for exponential decay of motor unit numbers and greatest rate of loss at the site of onset.
abstract: OBJECTIVE
  To use our Bayesian method of motor unit number estimation (MUNE) to evaluate lower motor neuron degeneration in ALS.
  
  
  METHODS
  In subjects with ALS we performed serial MUNE studies. We examined the repeatability of the test and then determined whether the loss of MUs was fitted by an exponential or Weibull distribution.
  
  
  RESULTS
  The decline in motor unit (MU) numbers was well-fitted by an exponential decay curve. We calculated the half life of MUs in the abductor digiti minimi (ADM), abductor pollicis brevis (APB) and/or extensor digitorum brevis (EDB) muscles. The mean half life of the MUs of ADM muscle was greater than those of the APB or EDB muscles. The half-life of MUs was less in the ADM muscle of subjects with upper limb than in those with lower limb onset.
  
  
  CONCLUSIONS
  The rate of loss of lower motor neurons in ALS is exponential, the motor units of the APB decay more quickly than those of the ADM muscle and the rate of loss of motor units is greater at the site of onset of disease.
  
  
  CONCLUSIONS
  This shows that the Bayesian MUNE method is useful in following the course and exploring the clinical features of ALS.
authors.affiliation: Department of Neurology, Royal Brisbane & Women's Hospital, Queensland, Australia.
authors.forename: F
authors.initials: F
authors.lastname: Baumann
authors.forename: R D
authors.initials: RD
authors.lastname: Henderson
authors.forename: P
authors.initials: P
authors.lastname: Gareth Ridall
authors.forename: A N
authors.initials: AN
authors.lastname: Pettitt
authors.forename: Pamela A
authors.initials: PA
authors.lastname: McCombe
mesh_terms: D000328:Adult; D000368:Aged; D000690:Amyotrophic Lateral Sclerosis / Q000473:pathology*; D001499:Bayes Theorem; D005260:Female; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000473:pathology; D008875:Middle Aged; D008962:Models, Theoretical; D009046:Motor Neurons / Q000473:pathology*; D009410:Nerve Degeneration / Q000473:pathology*; D010543:Peroneal Nerve / Q000473:pathology; D014459:Ulnar Nerve / Q000473:pathology