Clinical Observation on Acute Low-Frequency Hearing Loss Without Vertigo

Abstract

Even though it is currently not possible to prove a pathological diagnosis for inner ear disease, acute low-frequency hearing loss (ALFHL) without vertigo could be caused by inner ear hydrops because progression into the clinical spectrum of endolymphatic hydrops (EH) frequently occur among patients with the initial clinical presentation. Therefore, audiological measures representative of inner ear hydrops, such as the cochlear hydrops analysis masking procedure (CHAMP) test, may be used to predict the prognosis of ALFHL without vertigo. To test this hypothesis, we prospectively investigated patients with ALFHL unaccompanied by vertigo and examined whether the CHAMP test generated more useful information for prediction of progression into clinical spectrum of EH compared with other neurotologic parameters. A prospective clinical study of 28 patients who initially presented with ALFHL without vertigo was conducted. Detailed neurotologic findings from pure-tone audiometry, electrocochleography, CHAMP, spontaneous nystagmus, head-shaking nystagmus, vibration-induced nystagmus, the bithermal caloric test, and the rotatory chair test were recorded at the time of initial presentation. A regular audiological and clinical examination was conducted until either the last follow-up at our clinic or on the day on which secondary audiovestibular symptoms occurred. The rates of progression to Ménière's disease (MD) or clinical presentation compatible with isolated cochlear hydrops during the study period were calculated by the log-rank test and relative risk. A receiver operating characteristics curve was plotted to determine the prognostic value of CHAMP. Of 28 patients, 15 (53%) showed improvement in hearing on pure-tone audiometry. Seven patients (25%) showed hearing fluctuation and nine (32%) developed a vertigo attack during the observation period. Of these, three patients experienced both vertigo and a hearing fluctuation. Abnormal results of electrocochleography and neurotologic tests reflecting vestibular ocular reflex on yaw plane were common at the time of diagnosis of ALFHL in many patients, but these parameters were not associated with an increased risk of progression of clinical spectrum of EH. In contrast, patients with an abnormal complex amplitude ratio (CAR) on CHAMP had a 2.6-fold increased risk of progression to a clinical spectrum of EH (either hearing fluctuation or MD). The hazard ratio of developing MD for patients with normal CAR as compared with those with an abnormal CAR was 0.137 (95% confidence interval 0.03-0.57; p < 0.001), which indicates an 84.3% reduced risk of developing MD in those with normal CAR. A CAR value of 0.975 or less indicated the possibility of developing either a hearing fluctuation or vertiginous episode with a sensitivity of 82% and a specificity of 73% by receiver operating characteristics curve analysis. The results of the study suggest that CHAMP measurement may be useful for determining the prognosis of patients with ALFHL without vertigo. A CAR value of 0.975 or less indicates the possibility of developing fluctuating hearing loss or vertigo in patients with ALFHL unaccompanied by vertigo.