ELECTROCOCHLEOGRAPHY IN RETROSIGMOID VESTIBULAR NERVE-SECTION FOR INTRACTABLE VERTIGO CAUSED BY MENIERES-DISEASE

Interest in electrocochleography has increased in recent years because of the discovery of an elevated summating potential to action potenti al amplitude ratio (SP/AP ratio) in patients with endolymphatic hydrop s caused by Meniere's disease or perilymph fistula, It was the purpose of this investigation to determine whether the intraoperative SP/AP r atio will decrease after vestibular nerve section in patients with int ractable Meniere's disease, Fourteen patients with medically intractab le classic Meniere's disease underwent retrosigmoid vestibular nerve s ection, Intraoperative transtympanic electrocochleography was performe d with alternating click stimuli presented at 95 dB HL, In all patient s the SP/AP ratio was recorded before the skin incision (''baseline'' condition) and after the dura was closed (''closing'' condition), Stat istical analysis was applied to the recorded data, In 11 (79%) patient s, the SP/AP ratio was found to be elevated above 0.30 in the baseline state, In 13 (93%) patients, the SP/AP ratio decreased more than 25% after the nerve was sectioned. These results were highly statistically significant (p < 0.001), We conclude that the SP/AP ratio does decrea se in patients with Meniere's disease after undergoing retrosigmoid ve stibular nerve section and offer a possible explanation.