title: Evaluation of optimal electrode configurations for epidural spinal cord stimulation in cervical spinal cord injured rats.
abstract: BACKGROUND
  Epidural spinal cord stimulation is a promising technique for modulating the level of excitability and reactivation of dormant spinal neuronal circuits after spinal cord injury (SCI). We examined the ability of chronically implanted epidural stimulation electrodes within the cervical spinal cord to (1) directly elicit spinal motor evoked potentials (sMEPs) in forelimb muscles and (2) determine whether these sMEPs can serve as a biomarker of forelimb motor function after SCI.
  
  
  METHODS
  We implanted EMG electrodes in forelimb muscles and epidural stimulation electrodes at C6 and C8 in adult rats. After recovering from a dorsal funiculi crush (C4), rats were tested with different stimulation configurations and current intensities to elicit sMEPs and determined forelimb grip strength.
  
  
  RESULTS
  sMEPs were evoked in all muscles tested and their characteristics were dependent on electrode configurations and current intensities. C6(-) stimulation elicited more robust sMEPs than stimulation at C8(-). Stimulating C6 and C8 simultaneously produced better muscle recruitment and higher grip strengths than stimulation at one site.
  
  
  CONCLUSIONS
  Classical method to select the most optimal stimulation configuration is to empirically test each combination individually for every subject and relate to functional improvements. This approach is impractical, requiring extensively long experimental time to determine the more effective stimulation parameters. Our proposed method is fast and physiologically sound.
  
  
  CONCLUSIONS
  Results suggest that sMEPs from forelimb muscles can be useful biomarkers for identifying optimal parameters for epidural stimulation of the cervical spinal cord after SCI.
authors: Department of Neurosurgery, University of California, Los Angeles, CA 90095, United States.
authors: Monzurul
authors: M
authors: Alam
authors: Department of Integrative Biology and Physiology, University of California, Los Angeles, CA 90095, United States.
authors: Guillermo
authors: G
authors: Garcia-Alias
authors: Health &Technology and Neurobiology, Stony Brook University, Stony Brook, New York, United States.
authors: Prithvi K
authors: PK
authors: Shah
authors: Department of Integrative Biology and Physiology, University of California, Los Angeles, CA 90095, United States; Pavlov Institute of Physiology, St. Petersburg 199034, Russia; Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan 420006, Russia.
authors: Yury
authors: Y
authors: Gerasimenko
authors: Department of Integrative Biology and Physiology, University of California, Los Angeles, CA 90095, United States.
authors: Hui
authors: H
authors: Zhong
authors: Department of Integrative Biology and Physiology, University of California, Los Angeles, CA 90095, United States; Brain Research Institute, University of California, Los Angeles, CA 90095, United States.
authors: Roland R
authors: RR
authors: Roy
authors: Department of Integrative Biology and Physiology, University of California, Los Angeles, CA 90095, United States; Brain Research Institute, University of California, Los Angeles, CA 90095, United States; Department of Neurobiology, University of California, Los Angeles, CA 90095, United States. Electronic address: vre@ucla.edu.
authors: V Reggie
authors: VR
authors: Edgerton
mesh_terms: D000818:Animals; D015415:Biomarkers; D002574:Cervical Vertebrae / Q000473:pathology; D004195:Disease Models, Animal; D004567:Electrodes, Implanted; D004576:Electromyography; D004824:Epidural Space; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D005552:Forelimb / Q000503:physiopathology*; D018482:Muscle, Skeletal / Q000503:physiopathology*; D051381:Rats; D020318:Rats, Long-Evans; D013119:Spinal Cord Injuries / Q000628:therapy*; D062187:Spinal Cord Stimulation / Q000379:methods*
chemical_list: D015415:Biomarkers
keywords: Cervical spinal cord injury; Dorsal funiculi crush; Epidural stimulation; Motor evoked potentials