Salt-load electrocochleography

Bradford A. Gamble, William L. Meyerhoff, Angela G. Shoup, Nathan D. Schwade

Research output: Contribution to journalArticle

3 Scopus citations

Abstract

Objective: To introduce a new protocol for diagnostic electrocochleography using a pretest oral salt load to improve test sensitivity in patients with suspected inner ear fluid imbalance. Study Design: A retrospective review of patients who reported vertigo that, by medical history, was suggestive of an inner ear fluid imbalance was preformed. The patients received a complete audiovestibular evaluation that included a baseline electrocochleogram. Despite the incapacitating nature of their vertigo, there were no symptoms or electrophysiologic abnormalities that would isolate an etiologic ear. After the baseline studies, the patients received 4 g of sodium chloride daily for 3 days before repeat electrocochleography. A control group of 13 healthy volunteers with normal baseline electrocochleography and pure tone audiometry was tested under similar conditions. Setting: This study was conducted at an ambulatory care clinic associated with a tertiary referral medical center. Intervention: Electrocochleography was performed using altemating polarity clicks presented at a rate of 9.7/sec at 95 dB nHL by an extratympanic TIPtrode electrode and recorded with a Nicolet Spirit (Nicolet Instrument Corp., Madison, WI, U.S.A.). Responses were averaged for 1000 sweeps using a 10-msec time base with bandpass filtering from 5 to 1500 Hz. A summating potential/action potential (SP/AP) ratio of 0.37 was considered the upper limit of normal. Main Outcome Measures: Enhancement in the SWAP ratio from a normal baseline value to > 0.37 after oral salt loading was indicative of a positive test. Results: None of the ears from control subjects had a positive salt load electrocochleogram, and one or both ears in 38% of the patients in the study group with normal baseline SP/AP ratios and symptoms of inner ear fluid imbalance converted to abnormal. The mean SWAP ratio of the control group for the conditions before and after salt-load was not statistically different (p = 0.48), although the difference in the mean SWAP ratio in the study group after salt loading was statistically significant (p = 1.329 x 10-5). Conclusions: A group of patients who reported vertigo with no localizing abnormalities had a statistically significant increase in the mean SP/AP ratio after ingestion of a large quantity of sodium chloride. A modest percentage had elevation of the SWAP ratio above the upper limit of normal for our audiovestibular lab. The localization of a 'salt-sensitive' ear could assist the clinician in the management of these difficult problems with longterm medical therapy or surgical treatment when alternative measures fail.

Original languageEnglish (US)
Pages (from-to)325-330
Number of pages6
JournalAmerican Journal of Otology
Volume20
Issue number3
StatePublished - May 1 1999

Keywords

  • Electrocochleography
  • Inner ear fluid imbalance
  • Meniere's disease
  • Perilymphatic fistula
  • Sodium chloride

ASJC Scopus subject areas

  • Otorhinolaryngology

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    Gamble, B. A., Meyerhoff, W. L., Shoup, A. G., & Schwade, N. D. (1999). Salt-load electrocochleography. American Journal of Otology, 20(3), 325-330.