title: An examination of motor unit number index in adults with cerebral palsy.
abstract: Spinal motor neuron loss may be a factor contributing to weakness in central disorders. The aim of this study was to assess whether motor unit numbers are reduced in the hand musculature of adults with cerebral palsy (CP) using the motor unit number index (MUNIX) technique. In this prospective, case-control study, 10 adults with CP were matched with healthy controls. MUNIX was computed using area and power of voluntary surface hypothenar electromyographic (EMG) signals and the compound muscle action potential (CMAP) recorded with ulnar nerve stimulation. The motor unit size index (MUSIX) was calculated based on maximum CMAP amplitude and MUNIX value. Gross Motor Function Classification Scale (GMFCS) and Manual Abilities Classification Scale (MACS) levels were rated for CP subjects. MUNIX was significantly lower for CP participants (Mean 167.8 vs. 214.4, p=.022). MUNIX values did not correlate with GMFCS or MACS. MUSIX values were higher, though not significantly, for CP subjects (p=.11). MUSIX increased with increasing MACS levels (r(2)=.4017, p=.049). Thus, motor unit numbers in ulnar hand muscles may be decreased with CP. MUSIX values are associated with greater hand impairment. Therefore, peripheral motor unit loss as a component of the weakness found with CP deserves further evaluation.
authors.affiliation: Department of Physical Medicine and Rehabilitation and the Department of Neurology, Northwestern University Feinberg Medical School and the Rehabilitation Institute of Chicago. Electronic address: cmarciniak@ric.org.
authors.forename: Christina
authors.initials: C
authors.lastname: Marciniak
authors.affiliation: Department of Physical Medicine and Rehabilitation, University of Texas Health Science Center, and TIRR Memorial Hermann Research Center, Houston, TX 77030, USA.
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Physical Medicine and Rehabilitation, University of Texas Health Science Center, and TIRR Memorial Hermann Research Center, Houston, TX 77030, USA; Biomedical Engineering Program, University of Science and Technology of China, Hefei, 230027, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Zhou
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D002547:Cerebral Palsy / Q000175:diagnosis* / Q000503:physiopathology*; D004576:Electromyography / Q000379:methods; D005260:Female; D006225:Hand / Q000294:innervation / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009046:Motor Neurons / Q000473:pathology* / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation / Q000503:physiopathology; D011446:Prospective Studies; D011999:Recruitment, Neurophysiological / Q000502:physiology; D055815:Young Adult
keywords: Cerebral palsy; Electromyography; Motor unit; Muscular weakness