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[Experimental defects of the round window membrane]
1HNO-Klinik, Medizinischen Hochschule Hannover.
Abstract:
Previous and current studies of experimentally induced fistulas in the round window membrane (RWM) are reviewed. After puncture (or "micro-perforation") of the RWM leaking perilymph was not been observed and auditory evoked potentials have remained unaltered. In contrast, most publications have reported that gross incisions ("macro-perforations") of the RWM have resulted in the deterioration of auditory evoked potentials, with leaking perilymph and/or cerebrospinal fluid and/or with entrance of air bubbles into the scala tympani depending on the site of the perforation. Spontaneous healing was then observed within 4 to 8 days and was associated with normalization of the auditory evoked potentials. In a very few experimental studies pathophysiological mechanisms were simulated that may be involved clinically in patients with RWM fistulas, i.e. implosive rupture of the RWM due to an acute increase in middle ear pressure or explosive rupture of the RWM that may occur in patients trying to use forced Valsalva maneuvers to equalize decreased middle ear pressures due to blocked Eustachian tubes.
Insights
Experimentally induced round window membrane (RWM) fistulas show that micro-perforations do not affect auditory potentials, while macro-perforations cause temporary hearing deterioration and spontaneous healing. These findings inform clinical understanding of RWM fistulas.
Area of Science:
- Otolaryngology
- Auditory Neuroscience
- Experimental Surgery
Context:
- Round window membrane (RWM) fistulas are a clinical concern.
- Previous research on experimental RWM fistulas is reviewed.
- Understanding the impact of RWM perforations on auditory function is crucial.
Purpose:
- To review and synthesize findings from experimental studies on RWM fistulas.
- To analyze the effects of different types of RWM perforations on auditory evoked potentials.
- To explore simulated pathophysiological mechanisms of RWM fistulas.
Summary:
- Micro-perforations of the RWM did not alter auditory evoked potentials or cause perilymph leakage.
- Macro-perforations of the RWM led to auditory evoked potential deterioration, fluid leakage, and air bubbles, with spontaneous healing in 4-8 days.
- Simulated implosive and explosive RWM ruptures were studied to understand clinical mechanisms.
Impact:
- Provides insights into the pathophysiology of RWM fistulas.
- Informs clinical management and understanding of hearing loss associated with RWM injuries.
- Highlights the RWM's capacity for spontaneous healing after injury.
