Standard and modified statistical MUNE evaluations in spinal-bulbar muscular atrophy.
Motor unit number estimation (MUNE), a technique used in amyotrophic lateral sclerosis (ALS) clinical trials to quantitatively assess motor neuron loss, should also be valuable in assessing progression in spinal bulbar muscular atrophy (SBMA), an x-linked neuronopathy. In ALS, instability of single motor units (SMUP) prompted Shefner et al.6(6) to modify the statistical MUNE method to exclude SMUPs < or = 40 microV. It is unknown if there is similar SMUP instability in the more chronic degenerative disease of SBMA. In this study the standard parameter of excluding SMUP < 10 microV was compared with the exclusion of SMUP < 40 microV in the calculation of the statistical MUNE. The mean statistical MUNE, using the standard method and the Shefner et al. method, was 60 +/- 21 to 47 +/- 23, respectively. Similar to ALS, SBMA showed an increased proportion (17%) of individual SMUPs < or = 40 microV compared to normal controls. In conclusion, excluding SMUPs < or = 40 microV from the statistical MUNE calculations is appropriate for SBMA subjects because their SMUP, characteristics are similar to ALS. Exclusion of the low-amplitude SMUPs reduces the calculated MUNE.
Lehky
Tanya J
TJ
EMG Section, NINDS, NIH, Building 10/Room 7-5680, 10 Center Drive, Bethesda, Maryland 20892-1404, USA. lehkyt@ninds.nih.gov
Chen
Cheun Ju
CJ
di Prospero
Nicholas A
NA
Rhodes
Lindsay E
LE
Fischbeck
Kenneth
K
Floeter
Mary Kay
MK
D000200:Action Potentials / Q000502:physiology; D000328:Adult; D000368:Aged; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D018485:Muscle Fibers, Skeletal / Q000473:pathology / Q000502:physiology; D009134:Muscular Atrophy, Spinal / Q000473:pathology / Q000503:physiopathology*; D011999:Recruitment, Neurophysiological / Q000502:physiology*