title: Site of cochlear stimulation and its effect on electrically evoked compound action potentials using the MED-EL standard electrode array.
abstract: BACKGROUND
  The standard electrode array for the MED-EL MAESTRO cochlear implant system is 31 mm in length which allows an insertion angle of approximately 720 degrees . When fully inserted, this long electrode array is capable of stimulating the most apical region of the cochlea. No investigation has explored Electrically Evoked Compound Action Potential (ECAP) recordings in this region with a large number of subjects using a commercially available cochlear implant system. The aim of this study is to determine if certain properties of ECAP recordings vary, depending on the stimulation site in the cochlea.
  
  
  METHODS
  Recordings of auditory nerve responses were conducted in 67 subjects to demonstrate the feasibility of ECAP recordings using the Auditory Nerve Response Telemetry (ART) feature of the MED-EL MAESTRO system software. These recordings were then analyzed based on the site of cochlear stimulation defined as basal, middle and apical to determine if the amplitude, threshold and slope of the amplitude growth function and the refractory time differs depending on the region of stimulation.
  
  
  RESULTS
  Findings show significant differences in the ECAP recordings depending on the stimulation site. Comparing the apical with the basal region, on average higher amplitudes, lower thresholds and steeper slopes of the amplitude growth function have been observed. The refractory time shows an overall dependence on cochlear region; however post-hoc tests showed no significant effect between individual regions.
  
  
  CONCLUSIONS
  Obtaining ECAP recordings is also possible in the most apical region of the cochlea. However, differences can be observed depending on the region of the cochlea stimulated. Specifically, significant higher ECAP amplitude, lower thresholds and steeper amplitude growth function slopes have been observed in the apical region. These differences could be explained by the location of the stimulating electrode with respect to the neural tissue in the cochlea, a higher density, or an increased neural survival rate of neural tissue in the apex.
  
  
  BACKGROUND
  The Clinical Investigation has the Competent Authority registration number DE/CA126/AP4/3332/18/05.
authors.affiliation: Department of Otorhinolaryngology, Plastic, Aesthetic and Reconstructive Head and Neck Surgery, University of Wuerzburg, Würzburg, Germany. brill_s@klinik.uni-wuerzburg.de
authors.forename: Stefan
authors.initials: S
authors.lastname: Brill
authors.forename: Joachim
authors.initials: J
authors.lastname: Müller
authors.forename: Rudolf
authors.initials: R
authors.lastname: Hagen
authors.forename: Alexander
authors.initials: A
authors.lastname: Möltner
authors.forename: Steffi-Johanna
authors.initials: SJ
authors.lastname: Brockmeier
authors.forename: Thomas
authors.initials: T
authors.lastname: Stark
authors.forename: Silke
authors.initials: S
authors.lastname: Helbig
authors.forename: Jan
authors.initials: J
authors.lastname: Maurer
authors.forename: Thomas
authors.initials: T
authors.lastname: Zahnert
authors.forename: Clemens
authors.initials: C
authors.lastname: Zierhofer
authors.forename: Peter
authors.initials: P
authors.lastname: Nopp
authors.forename: Ilona
authors.initials: I
authors.lastname: Anderson
authors.forename: Stefan
authors.initials: S
authors.lastname: Strahl
mesh_terms: D000200:Action Potentials; D000328:Adult; D000368:Aged; D003051:Cochlea / Q000502:physiology*; D003054:Cochlear Implants; D003056:Cochlear Nerve / Q000503:physiopathology*; D004558:Electric Stimulation; D004567:Electrodes, Implanted; D004867:Equipment Design; D005072:Evoked Potentials, Auditory; D005260:Female; D006319:Hearing Loss, Sensorineural / Q000503:physiopathology* / Q000628:therapy; D006801:Humans; D008297:Male; D008875:Middle Aged; D009928:Organ Specificity; D011930:Reaction Time; D055815:Young Adult