title: Intraoperative neurophysiological monitoring of extracranial-intracranial bypass procedures.
abstract: OBJECTIVE
  Intraoperative neurophysiological monitoring (IONM) represents an established tool in neurosurgery to increase patient safety. Its application, however, is controversial. Its use has been described as helpful in avoiding neurological deterioration during intracranial aneurysm surgery. Its impact on extracranial-intracranial (EC-IC) bypass surgery involving parent artery occlusion for the treatment of complex aneurysms has not yet been studied. The authors therefore sought to evaluate the effects of IONM on patient safety, the surgeon's intraoperative strategies, and functional outcome of patients after cerebral bypass surgery. Intraoperative neurophysiological monitoring results were compared with those of intraoperative blood flow monitoring to assess bypass graft perfusion.
  
  
  METHODS
  Compound motor action potentials (CMAPs) were generated using transcranial electrical stimulation in patients undergoing EC-IC bypass surgery. Preoperative and postoperative motor function was analyzed. To assess graft function, intraoperative flowmetry and indocyanine green fluorescence angiography were performed. Special care was taken to compare the relevance of electrophysiological and blood flow monitoring in the detection of critical intraoperative ischemic episodes.
  
  
  RESULTS
  The study included 31 patients with 31 aneurysms and 1 bilateral occlusion of the internal carotid arteries, undergoing 32 EC-IC bypass surgeries in which radial artery or saphenous vein grafts were used. In 11 cases, 15 CMAP events were observed, helping the surgeon to determine the source of deterioration and to react to it: 14 were reversible and only 1 showed no recovery. In all cases, blood flow monitoring showed good perfusion of the bypass grafts. There were no false-negative results in this series. New postoperative motor deficits were transient in 1 case, permanent in 1 case, and not present in all other cases.
  
  
  CONCLUSIONS
  Intraoperative neurophysiological monitoring is a helpful tool for continuous functional monitoring of patients undergoing large-caliber vessel EC-IC bypass surgery. The authors' results suggest that continuous neurophysiological monitoring during EC-IC bypass surgery has relevant advantages over flow-oriented monitoring techniques such as intraoperative flowmetry or indocyanine green-based angiography.
authors.affiliation: Department of Neurosurgery, Charité-Universitätsmedizin Berlin, Berlin, Germany. julius.dengler@charite.de
authors.forename: Julius
authors.initials: J
authors.lastname: Dengler
authors.forename: Mario
authors.initials: M
authors.lastname: Cabraja
authors.forename: Katharina
authors.initials: K
authors.lastname: Faust
authors.forename: Thomas
authors.initials: T
authors.lastname: Picht
authors.forename: Theodoros
authors.initials: T
authors.lastname: Kombos
authors.forename: Peter
authors.initials: P
authors.lastname: Vajkoczy
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000293:Adolescent; D000328:Adult; D000368:Aged; D001794:Blood Pressure; D002545:Brain Ischemia / Q000175:diagnosis; D002533:Cerebral Angiography / Q000379:methods; D002548:Cerebral Revascularization; D002561:Cerebrovascular Disorders / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D004396:Coloring Agents; D005260:Female; D006801:Humans; D007208:Indocyanine Green; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D009044:Motor Cortex / Q000502:physiology*; D013927:Thrombosis / Q000175:diagnosis; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D055815:Young Adult
chemical_list: D004396:Coloring Agents; D007208:Indocyanine Green