Needle placement with transtympanic electrocochleography

Electrocochleography (ECoG) is an objective, electrophysiologic test useful in the clinical diagnosis of endolymphatic hydrops, or Meniere's disease. The purpose of this study was to determine if the position of the needle, using transtympanic methodology, gives a variable SP/AP (summating potential/action potential) response. SP/AP ratios were obtained during routine tympanoplasty procedures. After the tympanic membrane remnant was removed using a lateral graft technique, precise needle placement was obtained at the medial and lateral round window niches, as well as on the promontory. SP/AP ratios were obtained in these three needle positions. There was no significant difference in the SP/AP ratio responses despite the location of needle placement. The use of transtympanic electrocochleography can give very good wave form morphology and consistent results. Therefore, if elevated SP/AP ratios do occur, they are thought to be due to a pathologic process of the ear and not needle placement.