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The effect of mannitol upon cochlear dysfunction induced by transient local anoxia
1Department of Otolaryngology, Institute of Clinical Medicine, University of Tsukuba, Tennodai, Japan.
Hearing Research
|January 1, 1999
Summary
Local cochlear anoxia exceeding 10 minutes causes irreversible dysfunction. Mannitol administration improved recovery after 15-30 minutes of anoxia, but not after 60 minutes, suggesting a partially protective effect.
Area of Science:
- Oto-neurology
- Vascular Physiology
- Auditory Neuroscience
Background:
- Cochlear anoxia can lead to hearing loss.
- Understanding the duration-dependent effects of cochlear ischemia is crucial for developing treatments.
Purpose of the Study:
- To investigate the impact of transient local cochlear anoxia on cochlear function.
- To evaluate the efficacy of mannitol in mitigating anoxia-induced cochlear dysfunction.
Main Methods:
- Transient local anoxia was induced in 106 guinea pigs by occluding the labyrinthine artery.
- Cochlear blood flow was monitored using a laser-Doppler flowmeter.
- Compound action potential (CAP) and endocochlear potential (EP) were measured before and after anoxia durations of 5 to 60 minutes.
- Mannitol was administered intravenously to assess its neuroprotective effects.
Main Results:
- Anoxia lasting less than 10 minutes did not cause post-anoxic dysfunction.
- Anoxia durations of 10 minutes or longer resulted in irreversible cochlear dysfunction.
- CAP threshold recovery worsened with prolonged anoxia, with near-complete abolition after 60 minutes.
- Mannitol significantly improved CAP threshold recovery for anoxia durations of 15-30 minutes, but not 60 minutes.
Conclusions:
- Local cochlear anoxia of 10 minutes or longer induces significant and irreversible cochlear dysfunction.
- Mannitol offers partial neuroprotection against cochlear anoxia, particularly for moderate durations.
- The findings highlight the critical time window for intervention in cochlear ischemia.