Low-Frequency Air-Bone Gaps Indicator for Endolymphatic Hydrops

by Amy E. Hamaker •

Is there a relationship between endolymphatic hydrops (EH) and hearing level, focusing on the degree of vestibular EH and low-frequency air-bone gaps (LFABGs), and if so, what are their pathogenic mechanisms?

Bottom line
The appearance of LFABGs suggests deterioration of endolymphatic hydrops, particularly in ears with Ménière’s disease, and could be a useful indicator for evaluating and treating patients with endolymphatic hydrops.

Background: Meniere’s disease (MD) is a disorder of the inner ear that causes vertigo attacks, fluctuating hearing loss, tinnitus, and aural fullness. EH, in which excessive endolymph accumulates in the inner ear, typically resulting in sensorineural hearing loss, is a characteristic pathological finding in MD. Occasionally, audiograms of MD patients show unexplained conductive components, or air-bone gaps (ABGs), predominantly at low frequencies, even though no middle ear pathology can be demonstrated.

Study design: Retrospective study of 1,548 ears from 775 patients who underwent magnetic resonance imaging examination in a university hospital between January 2012 and December 2015 to investigate possible endolymphatic hydrops.

Setting: Nagoya University Graduate School of Medicine, Nagoya, Japan.

Synopsis: After exclusion criteria, 41 ears showed significant cochlear and vestibular EH adjacent to the stapes footplate, and 79 ears showed significant nonadjacent cochlear and vestibular EH. Most of the ears having EH adjacent to the stapes footplate showed significant cochlear and vestibular EH. Average hearing thresholds in air- and bone-conduction testing at all frequencies, and the average ABG at 250 Hz, were significantly higher in the adjacent EH group than in the nonadjacent group. Clinical diagnosis and symptoms for 41 adjacent ears: MD = 27; delayed endolymphatic hydrops (DEH) = two; fluctuating hearing loss = six; acute sensorineural hearing loss (SNHL) = two; and other types with otological and symptoms (chronical hearing loss, vertigo, and ear fullness) = four. Clinical diagnosis for 79 nonadjacent ears: MD = 35; DEH = one; fluctuating hearing loss = five; acute SNHL = nine; and others with otological and symptoms (including chronical hearing loss, vertigo, floating sensation, ear fullness, tinnitus, and hyperacusia) = 29. Limitations included a lack of computed tomography examinations for all ears, and a lack of multiple MRI evaluations in ears showing fluctuating LFABGs.

Citation: Sugimoto S, Yoshida T, Teranishi M, Okazaki Y, Naganawa S, Sone M. The relationship between endolymphatic hydrops in the vestibule and low-frequency air-bone gaps; Laryngoscope. November 5, 2017. doi: 10.1002/lary.26898.