Findings of Intravenous Gadolinium Inner Ear Magnetic Resonance Imaging in Patients With Acute Low-Tone Sensorineural Hearing Loss

Abstract

Objectives: Acute low-tone sensorineural hearing loss (ALHL) is thought to have a different etiology from that of idiopathic sudden sensorineural hearing loss. We hypothesized that endolymphatic hydrops (EH) in the inner ear organ contributes to ALHL, even in patients without vertigo. This study investigated the presence of EH in ALHL and compared the clinical characteristics of patients with or without EH.

Methods: We retrospectively reviewed 38 patients diagnosed with ALHL without vertigo from January 2017 to March 2022. EH was measured in all patients using inner ear magnetic resonance imaging (MRI). In addition, we selected patients who showed only mid- or high-frequency hearing loss and had available MRI data as a control group and compared the ALHL and control groups.

Results: After treatment, the pure-tone average at low frequencies significantly improved compared to the initial hearing (P<0.001). Hearing recovery was observed in 63.1% of patients; however, the recovery rate did not differ based on the treatment method. During the follow-up period, six patients (15.8%) progressed to Meniere's disease, and 18 (47.4%) experienced recurrence. In the ALHL group, the cochlear hydrops ratio on the affected side (0.34±0.09) was significantly higher than on the contralateral side (0.29±0.12) (P=0.005), and most patients showed hydrops in the apex area of the cochlea. Compared with the control group (0.25±0.15), the ALHL group showed a significantly higher cochlear hydrops ratio (P=0.043). The correlation analysis showed a tendency for hearing thresholds at low frequencies to increase as the hydrops ratio increased, albeit without statistical significance.

Conclusion: The cochlear hydrops ratio, especially in the apex area on the affected side, was significantly higher in patients with ALHL, suggesting that EH in the cochlea contributes to the pathogenesis of ALHL.

Keywords: Endolymphatic Hydrops; Low Frequency Hearing Loss; Magnetic Resonance Imaging; Sensorineural Hearing Loss.

Fig. 1.

Hearing changes at low frequencies after treatment. The hearing thresholds at frequencies significantly improved from 46.1±11.9 dB before treatment to 31.2±17.1 dB after treatment (P<0.001).

Fig. 2.

Endolymphatic hydrops (EH) ratio in acute low-tone sensorineural hearing loss patients. Results showing the proportions of (A) cochlear hydrops and (B) vestibular hydrops on the affected side and the contralateral side. (C) Measurements of cochlear hydrops in apical and midbase turns on the affected side. Values are presented as mean±standard deviation.

Fig. 3.

Setting a region of interest (ROI) by dividing the cochlear area. (A) In a magnetic resonance cisternography (MRC) image, the apical turn and mid-base turn of the cochlea were identified, and an ROI was set by drawing along their contours. (B) The previously determined ROI from the MRC image was then copied and pasted into the HYDROPS-Mi2 image. The endolymphatic hydrops ratio was calculated by dividing the number of pixels with negative signal intensity (black area) within the ROI by the total number of pixels in the total ROI.

Fig. 4.

Cochlear hydrops ratio compared between the acute lowtone sensorineural hearing loss (ALHL) group and control groups. Values are presented as mean±standard deviation. MD, Meniere’s disease; MF, mid-frequency; HF, high-frequency.

Fig. 5.

(A) Correlation between the overall cochlear hydrops ratio and hearing threshold at low frequencies. (B) Correlation between the hydrops ratio in the apex and hearing threshold at low frequencies. The correlation analysis showed a tendency for hearing thresholds at low frequencies to increase as the hydrops ratio increased, albeit without statistical significance (P=0.140, P=0.308, respectively).