title: Short-term peripheral nerve stimulation ameliorates axonal dysfunction after spinal cord injury.
abstract: There is accumulating evidence that peripheral motor axons deteriorate following spinal cord injury (SCI). Secondary axonal dysfunction can exacerbate muscle atrophy, contribute to peripheral neuropathies and neuropathic pain, and lead to further functional impairment. In an attempt to ameliorate the adverse downstream effects that developed following SCI, we investigated the effects of a short-term peripheral nerve stimulation (PNS) program on motor axonal excitability in 22 SCI patients. Axonal excitability studies were undertaken in the median and common peroneal nerves (CPN) bilaterally before and after a 6-wk unilateral PNS program. PNS was delivered percutaneously over the median nerve at the wrist and CPN around the fibular head, and the compound muscle action potential (CMAP) from the abductor pollicis brevis and tibialis anterior was recorded. Stimulus intensity was above motor threshold, and pulses (450 μs) were delivered at 100 Hz with a 2-s on/off cycle for 30 min 5 days/wk. SCI patients had consistently high thresholds with a reduced CMAP consistent with axonal loss; in some patients the peripheral nerves were completely inexcitable. Nerve excitability studies revealed profound changes in membrane potential, with a "fanned-in" appearance in threshold electrotonus, consistent with membrane depolarization, and significantly reduced superexcitability during the recovery cycle. These membrane dysfunctions were ameliorated after 6 wk of PNS, which produced a significant hyperpolarizing effect. The contralateral, nonstimulated nerves remained depolarized. Short-term PNS reversed axonal dysfunction following SCI, may provide an opportunity to prevent chronic changes in axonal and muscular function, and may improve rehabilitation outcomes.
authors: Neuroscience Research Australia, Sydney, Australia; Brain and Mind Research Institute, The University of Sydney, Sydney, Australia; Discipline of Physiotherapy, Faculty of Health Sciences, University of Sydney, Sydney, Australia michael.lee@sydney.edu.au.
authors: Michael
authors: M
authors: Lee
authors: Neuroscience Research Australia, Sydney, Australia; Brain and Mind Research Institute, The University of Sydney, Sydney, Australia;
authors: Matthew C
authors: MC
authors: Kiernan
authors: Neuroscience Research Australia, Sydney, Australia; Integrative Physiology, School of Medicine, University of Western Sydney, Sydney, Australia;
authors: Vaughan G
authors: VG
authors: Macefield
authors: Neuroscience Research Australia, Sydney, Australia; Spinal Medicine Department, Prince of Wales Hospital, Sydney, Australia; and.
authors: Bonne B
authors: BB
authors: Lee
authors: Translational Neuroscience Facility, School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, Australia;
authors: Cindy S-Y
authors: CS
authors: Lin
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001369:Axons / Q000502:physiology*; D004558:Electric Stimulation / Q000379:methods*; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008297:Male; D008875:Middle Aged; D009431:Neural Conduction / Q000502:physiology; D010525:Peripheral Nerves / Q000502:physiology*; D013119:Spinal Cord Injuries / Q000473:pathology*; D018709:Statistics, Nonparametric; D055815:Young Adult
keywords: nerve excitability; peripheral nerve stimulation; rehabilitation; spinal cord injury