The effect of noise on ears with a hole in the vestibule RONEN PEREZ1, CAHTIA ADELMAN2, JEAN YVES SICHEL1, SHARON FREEMAN3 & HAIM SOHMER3 Acta Oto-Laryngologica, 2010; 130: 659-664 1Department of Otolaryngology and Head and Neck Surgery, Shaare Zedek Medical Center, 2Speech & Hearing Center, Hadassah University Hospital and 3Department of Physiology, Hebrew University-Hadassah Medical School, Jerusalem, Israel
Conclusion: A hole in the vestibule of the inner ear leads to
augmentation of the hearing loss following noise exposure. Further
research is needed to ascertain the mechanism. Objectives: The
possible effects of a hole in the wall of the inner ear at the vestibule
on noise-induced hearing loss were assessed. Methods: The study
was conducted on a total of 14 sand rats. Of these 14 animals, 10 underwent
baseline auditory nerve and brainstem evoked response (ABR) threshold
measurements in each ear separately (insert earphone), opening of middle
ear bulla in both ears and drilling of a hole in the vestibule of one
inner ear. The other ear was sham-operated. Following immediate re-assessment
of ABR threshold, the 10 animals were exposed to 113 dB SPL broadband
noise during 4 nights, and 3 days later ABR measurements were repeated.
Four additional animals with a hole in one vestibule, not exposed to noise,
served as controls. Results: Following noise exposure, ABR thresholds
were elevated by 28.5 ± 9.1 dB in the ears with the hole,
and by 15.5 ± 7.2 dB in the opposite ear without the hole
(significant difference, p < 0.003). In the four control ears,
ABR threshold was not elevated a week after drilling the hole. (Bold text
emphasis by Martin Braun) Comment: A hole in the vestibule necessarily functions as a pressure outlet during
sound exposure via the middle ear. The anatomical reason for this is that
the scala vestibuli of the cochlea, where sound pressure enters from the
middle ear, has a common perilymphatic fluid chamber with the vestibule.
An evident effect of an experimental pressure outlet in the vestibule
is that fluid shift that can move the basilar membrane (BM) in the cochlea
is reduced. |