OBJECTIVETo evaluate the pathological status of the vestibular system associated with noise-induced inner ear impairment.

METHODSTotally 68 patients with noise-induced hearing loss (NIHL) who presented with vestibular symptoms including vertigo, dizziness, and chronic disequilibrium were screened. All patients underwent a series of conventional vestibular function tests and vestibular autorotation test and the results were retrospectively reviewed and evaluated.

RESULTSSixty-eight (14.5%) patients with NIHL were identified among 469 patients with vertigo, dizziness, or imbalance. A pure tone hearing threshold of patients with vertigo and NIHL at 4000 Hz were between 30 dB HL and 80 dB HL with an average threshold of (46.7 +/- 17.6) dB HL in left ear and (37.3 +/- 16.7) dB HL in right ear. Patients with symmetrical hearing loss at 4000 Hz accounted for 41.7% and those with asymmetrical loss accounted for 58.3%. Vestibular pathologies included benign positional paroxysmal vertigo (45.7%), unilateral decreased caloric responses (20.0%), bilateral decreased caloric responses (26.7%), abnormal vestibulo-spinal reflex function (28.6%), vestibular function response hyperactivity (3.0%), and abnormal vestibulo-ocular reflex presentation at high frequencies (97.0%).

CONCLUSIONSLoud acoustic stimulation not only damages the cochlea but also causes clear functional impairment to the vestibular end organs. Although the vestibular pathology is not correlated with the severity of the hearing loss, it correlates with the subjective symptoms of the vestibular system.