title: Cortical motor neuron excitability during cutaneous silent period.
abstract: OBJECTIVE
  To investigate cortical motor neuron excitability during cutaneous silent period (CSP), motor evoked potentials (MEPs) from abductor pollicis brevis following transcranial magnetic stimulation (TCM) were recorded with and without a conditioning of ipsilateral painful digital nerve electric stimulation.
  
  
  METHODS
  MEPs following TCM were recorded with and without a conditioning stimulation at an interstimulus interval (ISI) from 0 ms to 100ms in 6 controls and four patients who had reduced pain sensation in unilateral upper limbs associated with cervical syringomyelia. In addition MEPs and evoked spinal cord potentials (ESCPs) from cervical epidural space following TCM with and without a conditioning stimulation were recorded in four patients with thoracic myelopathy.
  
  
  RESULTS
  MEP amplitude was clearly attenuated by a conditioning stimulation at an ISI from 40 ms to 80 ms in controls (statistically significant at 60 ms). In patients with cervical syringomyelia, MEP amplitude was attenuated by a conditioning stimulation in asymptomatic hands similarly in controls but that was unchanged by a conditioning stimulation in the symptomatic hand with reduced pain sensation. In patients with thoracic myelopathy MEP amplitude was attenuated by conditioning stimulation similarly in controls, but ESCP amplitude was unchanged.
  
  
  CONCLUSIONS
  We demonstrated that noxious cutaneous nerve stimulation suppressed spinal motor neurons but cortical motor neuron excitability was unchanged during CSP. In clinical practice, measurement of MEP suppression after noxious cutaneous nerve stimulation may provide useful information in patients with damaged pain related nerve fibers.
authors.affiliation: Department of Orthopedic Surgery, Yamaguchi University Hospital, Ube City, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Kaneko
authors.forename: S
authors.initials: S
authors.lastname: Kawai
authors.forename: T
authors.initials: T
authors.lastname: Taguchi
authors.forename: Y
authors.initials: Y
authors.lastname: Fuchigami
authors.forename: H
authors.initials: H
authors.lastname: Yonemura
authors.forename: H
authors.initials: H
authors.lastname: Fujimoto
mesh_terms: D000328:Adult; D003213:Conditioning, Psychological / Q000502:physiology; D004558:Electric Stimulation; D019054:Evoked Potentials, Motor; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D006801:Humans; D008280:Magnetics; D008297:Male; D009046:Motor Neurons / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology; D010146:Pain / Q000175:diagnosis / Q000503:physiopathology; D010525:Peripheral Nerves / Q000502:physiology; D012867:Skin / Q000294:innervation; D013595:Syringomyelia / Q000175:diagnosis* / Q000503:physiopathology*