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 to modify the statistical MUNE method to exclude SMUPs ≤ 40 μV. 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 μV was compared with the exclusion of SMUP < 40 μV 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 ≤ 40 μV compared to normal controls. In conclusion, excluding SMUPs ≤ 40 lV from the statistical MUNE calculations is appropriate for SBMA subjects because their SMUP, characteristics are similar to ALS. Exclusion of the lowamplitude SMUPs reduces the calculated MUNE.
All Science Journal Classification (ASJC) codes
- Clinical Neurology
- Cellular and Molecular Neuroscience
- Physiology (medical)