title: The N20 in post-anoxic coma: are you listening?
abstract: OBJECTIVE
  Persistent absence of the median nerve N20 response in patients suffering from postanoxic coma after a cardiac arrest is invariably associated with a poor outcome. Preservation of the N20 response, however, does not indicate a good recovery. We wish to improve our understanding on this issue.
  
  
  METHODS
  We discuss the limited specificity of the presence of the N20 response regarding a favourable outcome and the selective neuronal damage that may be responsible for this clinical scenario. We also present EEG and SSEP data from post-anoxic patients.
  
  
  RESULTS
  We show data from a patient suffering from a severe post-anoxic encephalopathy, with a nearly flat EEG recording, but preserved N20 responses obtained after median nerve stimulation and propose a simple model for these observations.
  
  
  CONCLUSIONS
  Somatosensory neurons have both "receiving" and "sending" properties, where the latter mainly reflects cortical synaptic function. After hypoxic insults, these two modes may be selectively damaged. Preservation of the N20 reflects an intact "receiving mode", while the EEG mainly reflects the "sending mode".
  
  
  CONCLUSIONS
  Insight into the physiological processes underlying the generation of the SSEP and the EEG is relevant in clinical decision making and may guide novel monitoring strategies.
authors.affiliation: Department of Clinical Neurophysiology, Medisch Spectrum Twente and Clinical Neurophysiology at MIRA-Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, The Netherlands. m.j.a.m.vanputten@tnw.utwente.nl
authors.forename: Michel J A M
authors.initials: MJ
authors.lastname: van Putten
mesh_terms: D055592:Biophysical Phenomena / Q000502:physiology; D003128:Coma / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology*; D004558:Electric Stimulation; D004569:Electroencephalography / Q000379:methods*; D005073:Evoked Potentials, Somatosensory / Q000502:physiology; D006323:Heart Arrest / Q000150:complications*; D006801:Humans; D002534:Hypoxia, Brain / Q000503:physiopathology; D008475:Median Nerve / Q000502:physiology*; D008991:Monitoring, Physiologic / Q000295:instrumentation / Q000379:methods; D009474:Neurons / Q000502:physiology*; D011379:Prognosis; D012189:Retrospective Studies; D013003:Somatosensory Cortex / Q000502:physiology*