title: Alterations in multidimensional motor unit number index of hand muscles after incomplete cervical spinal cord injury.
abstract: The objective of this study was to apply a novel multidimensional motor unit number index (MD-MUNIX) technique to examine hand muscles in patients with incomplete cervical spinal cord injury (SCI). The MD-MUNIX was estimated from the compound muscle action potential (CMAP) and different levels of surface interference pattern electromyogram (EMG) at multiple directions of voluntary isometric muscle contraction. The MD-MUNIX was applied in the first dorsal interosseous (FDI), thenar and hypothenar muscles of SCI (n = 12) and healthy control (n = 12) subjects. The results showed that the SCI subjects had significantly smaller CMAP and MD-MUNIX in all the three examined muscles, compared to those derived from the healthy control subjects. The multidimensional motor unit size index (MD-MUSIX) demonstrated significantly larger values for the FDI and hypothenar muscles in SCI subjects than those from healthy control subjects, whereas the MD-MUSIX enlargement was marginally significant for the thenar muscles. The findings from the MD-MUNIX analyses provide an evidence of motor unit loss in hand muscles of cervical SCI patients, contributing to hand function deterioration.
authors.affiliation: Department of Rehabilitation Medicine, The First Affiliated Hospital, Sun Yat-Sen University Guangzhou, China ; Department of Physical Medicine and Rehabilitation, University of Texas Health Science Center at Houston, and TIRR Memorial Hermann Research Center Houston, TX, USA.
authors.forename: Le
authors.initials: L
authors.lastname: Li
authors.affiliation: Department of Physical Medicine and Rehabilitation, University of Texas Health Science Center at Houston, and TIRR Memorial Hermann Research Center Houston, TX, USA.
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Li
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago Chicago, IL, USA.
authors.forename: Jie
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Physical Medicine and Rehabilitation, University of Texas Health Science Center at Houston, and TIRR Memorial Hermann Research Center Houston, TX, USA ; Biomedical Engineering Program, University of Science and Technology of China Hefei, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Zhou
keywords: CMAP; EMG; MD-MUNIX; MD-MUSIX; SCI; hand muscles