Superior canal dehiscence effect on hearing thresholds: animal model

Area of Science:

• Otolaryngology
• Neuroscience
• Auditory Physiology

Background:

• Superior semicircular dehiscence syndrome (SSDS) is characterized by vestibular symptoms and an audiometric air-bone gap.
• This condition is thought to result from a pathological bony "third window" in the superior semicircular canal.
• Understanding the auditory changes in SSDS is crucial for diagnosis and management.

Purpose of the Study:

• To evaluate changes in air- and bone-conduction thresholds in an animal model.
• To investigate the effects of bony fenestration of the superior semicircular canal on auditory function.
• To compare the auditory changes in the animal model to those observed in human SSDS.

Main Methods:

• A surgical model was created in 5 fat sand rats by drilling a hole in the superior semicircular canal.
• Auditory brainstem responses (ABRs) were measured using air and bone conduction before and after fenestration.
• Stimuli included clicks and 1-kHz tone bursts to assess low- and high-frequency hearing.

Main Results:

• A significant air-bone gap was observed after fenestration, primarily due to deteriorated air-conduction thresholds.
• Bone-conduction thresholds remained largely unchanged.
• ABR patterns showed increased latency, similar to middle ear dysfunction, without altered interpeak latencies.

Conclusions:

• Bony fenestration of the superior semicircular canal in a rodent model effectively replicates the auditory loss pattern seen in SSDS.
• The study supports the hypothesis that a dehiscent membrane in the superior semicircular canal is responsible for the auditory changes in SSDS.