title: Clinical utility and limitations of intraoperative monitoring of visual evoked potentials.
abstract: OBJECTIVE
  During surgeries that put the visual pathway at risk of injury, continuous monitoring of the visual function is desirable. However, the intraoperative monitoring of the visual evoked potential (VEP) is not yet widely used. We evaluate here the clinical utility of intraoperative VEP monitoring.
  
  
  METHODS
  We analyzed retrospectively 46 consecutive surgeries in 2011-2013. High luminance stimulating devices delivered flash stimuli on the closed eyelid during intravenous anesthesia. We monitored VEP features N75 and P100 and took patients' preoperative and postoperative visual function from patient charts. Postoperative ophthalmologic workup was performed in 25 (54%) patients and preoperatively in 28 (61%) patients.
  
  
  RESULTS
  VEP recordings were feasible in 62 of 85 eyes (73%) in 46 patients. All 23 eyes without VEP had impaired vision. During surgery, VEPs remained stable throughout surgery in 50 eyes. In 44 of these, visual function did not deteriorate and three patients (6 eyes) developed hemianopia. VEP decreased transiently in 10 eyes and visual function of all was preserved. VEPs were lost permanently in 2 eyes in two patients without new postoperative visual impairment.
  
  
  CONCLUSIONS
  Satisfactory intraoperative VEP monitoring was feasible in all patients except in those with severe visual impairment. Preservation of VEPs predicted preserved visual function. During resection of lesions in the visual cortex, VEP monitoring could not detect new major visual field defects due to injury in the posterior visual pathway. Intraoperative VEPs were sensitive enough to detect vascular damage during aneurysm clipping and mechanical manipulation of the anterior visual pathway in an early reversible stage. Intraoperative VEP monitoring influenced surgical decisions in selected patients and proved to be a useful supplement to the toolbox of intraoperative neurophysiological monitoring.
authors: Neurosurgery Department, University Hospital Zurich, Zurich, Switzerland.
authors: Yeda
authors: Y
authors: Luo
authors: Neurosurgery Department, University Hospital Zurich, Zurich, Switzerland.
authors: Luca
authors: L
authors: Regli
authors: Neurosurgery Department, University Hospital Zurich, Zurich, Switzerland.
authors: Oliver
authors: O
authors: Bozinov
authors: Neurosurgery Department, University Hospital Zurich, Zurich, Switzerland; Zurich Neuroscience Center, Eidgenössische Technische Hochschule Zurich, Zurich, Switzerland.
authors: Johannes
authors: J
authors: Sarnthein
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D005074:Evoked Potentials, Visual; D005189:False Positive Reactions; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D011184:Postoperative Period; D012189:Retrospective Studies; D013997:Time Factors; D014787:Vision Tests; D055815:Young Adult