Animal model of cochlear third window in the scala vestibuli or scala tympani

Joseph Attias, Michal Preis, Rafi Shemesh, Tuvia Hadar, Ben I. Nageris

Research output: Contribution to journalArticlepeer-review

Abstract

Hypothesis: The auditory impact of a cochlear third window differs by its location in the scala vestibuli or scala tympani. Background: Pathologic third window has been investigated primarily in the vestibular apparatus of animals and humans. Dehiscence of the superior semicircular canal is the clinical model. Methods: Fat sand rats (n = 11) have a unique inner-ear anatomy that allows easy surgical access. A window was drilled in the bony labyrinth over the scala vestibuli in 1 group (12 ears) and over the scala tympani in another (7 ears) while preserving the membranous labyrinth. Auditory brain stem responses to high- and low-frequency stimuli delivered by air and bone conduction were recorded before and after the procedure. Results: Scala vestibuli group: preoperative air-conduction thresholds to clicks and tone-bursts averaged 8.3 and 9.6 dB, respectively, and bone-conduction thresholds, 4.6 and 3.3 dB, respectively; after fenestration, air-conduction thresholds averaged 40.4 and 41.8 dB, respectively, and bone-conduction thresholds, -1 and 5.6 dB, respectively. Scala tympani group: preoperative air-conduction thresholds to clicks and tone-bursts averaged 8.6 dB each, and bone-conduction thresholds, 7.9 dB and 7.1 dB, respectively; after fenestration, air-conduction thresholds averaged 11.4 and 9.3 dB, respectively, and bone-conduction thresholds, 9.3 and 4.2 dB, respectively. The changes in air- (p = 0.0001) and bone-conduction (p = 0.04) thresholds were statistically significant only in the scala vestibuli group. Conclusion: The presence of a cochlear third window over the scala vestibuli, but not over the scala tympani, causes a significant increase in air-conduction auditory thresholds. These results agree with the theoretic model and clinical findings and contribute to our understanding of vestibular dehiscence.

Original languageEnglish
Pages (from-to)985-990
Number of pages6
JournalOtology and Neurotology
Volume31
Issue number6
DOIs
StatePublished - Aug 2010

Keywords

  • Air and bone auditory brainstem response
  • Fenestration
  • Hearing
  • Vestibular symptoms

ASJC Scopus subject areas

  • Clinical Neurology
  • Sensory Systems
  • Otorhinolaryngology

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