title: Does electrode impedance affect the recording of ocular vestibular-evoked myogenic potentials?
abstract: BACKGROUND
  In evoked potential testing, it is common practice to abrade the skin surface as a means of reducing and balancing electrode impedance. The effects of skin preparation and electrode impedance on ocular vestibular-evoked myogenic potential (oVEMP) prevalence and amplitudes are not known.
  
  
  OBJECTIVE
  We sought to determine whether comparable oVEMP waveforms could be recorded without excessive skin preparation.
  
  
  METHODS
  This was a prospective study with a repeated-measures (within-subjects) design.
  
  
  METHODS
  The study group comprised 20 healthy participants (12 females and 8 males) ages 21-57 yr.
  
  
  METHODS
  oVEMP reflexes were recorded in response to air-conducted and bone-conducted (AC and BC) stimuli in three conditions. In the first condition (no skin preparation), electrodes were simply placed over the skin surface. For the second condition (moderate skin preparation), oVEMP testing was repeated after the skin had been prepared with 70% isopropyl alcohol swabs. oVEMPs recorded in these two conditions were then compared with those recorded using a third conventional protocol whereby the skin was abraded with skin preparation gel until electrode impedances were low and balanced. For BC stimuli, reflex amplitudes and latencies were compared using a repeated-measures general linear model. For AC stimuli, rates of reflex detection were analyzed using a generalized estimating equation. Nonparametric Friedman tests were used to compare AC oVEMP amplitudes across the three conditions.
  
  
  RESULTS
  There was no significant effect of electrode impedance on reflex amplitudes, latencies, or rates of detection (p > 0.05). The results indicated significant stimulus-related artifact (≥3 μV) in 25 of 40 recordings under the high-impedance condition in response to BC stimulation. The stimulus artifact was detectable in 12 of 40 recordings after moderate skin preparation and in 5 recordings after skin abrasion.
  
  
  CONCLUSIONS
  Comparable rates of reflex detection and oVEMP amplitudes were recorded in the three conditions, implying that rigorous rubbing of the facial skin is largely unnecessary in clinical oVEMP testing. However, for oVEMPs recorded in response to a single-polarity stimulus, reducing and balancing electrode impedances with either isopropyl alcohol wipes or skin abrasion may help reduce unwanted stimulus artifact.
authors.affiliation: Equal contribution; Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Central Clinical School, University of Sydney, Sydney, Australia.
authors.forename: Rachael L
authors.initials: RL
authors.lastname: Taylor
authors.affiliation: Equal contribution; Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Central Clinical School, University of Sydney, Sydney, Australia; Department of Neuroscience and Locomotion, Division of Otorhinolaryngology, Faculty of Health Sciences, Linköping University, Linköping Sweden.
authors.forename: Mikael
authors.initials: M
authors.lastname: Schulin
authors.affiliation: Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Central Clinical School, University of Sydney, Sydney, Australia.
authors.forename: Samanthi
authors.initials: S
authors.lastname: Goonetilleke
authors.affiliation: Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Central Clinical School, University of Sydney, Sydney, Australia.
authors.forename: Miriam S
authors.initials: MS
authors.lastname: Welgampola
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods*; D000328:Adult; D017097:Electric Impedance; D004566:Electrodes; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D058585:Vestibular Evoked Myogenic Potentials / Q000502:physiology*; D014722:Vestibule, Labyrinth / Q000502:physiology*; D055815:Young Adult