Baseline

As shown in Table 1, 77 patients diagnosed with Bilateral Meniere’s Disease, encompassing 154 ears, were included in the study. The cohort had an average age of 50.9 years, comprising 44 males and 33 females. In terms of vestibular hydrops (VL), 27 ears were classified as Grade 0, 29 as Grade I, 85 as Grade II, and 13 as Grade III. For cochlear hydrops (CL), classifications were as follows: 13 ears at Grade 0, 66 at Grade I, 67 at Grade II, and 8 at Grade III. The overall degree of endolymphatic hydrops (EHL) was determined to be Grade I in 25 ears, Grade II in 27 ears, Grade III in 45 ears, Grade IV in 39 ears, Grade V in 16 ears, and Grade VI in 2 ears.

Table 1 This table summarizes the demographic and clinical characteristics of the study cohort

Table 1 details the distribution of male and female patients (44 males and 33 females), the average age (51 years), the classification of vestibular hydrops (VL) and cochlear hydrops (CL) into grades 0 to 3, and the overall degree of endolymphatic hydrops (EHL) categorized into grades 1 to 6. Additionally, the overall hearing level (PA) is presented with a 95% confidence interval (46.4 dB [95% CI: 43.5–49.3]).

Audiometric findings relative to hydrops severity

From Table 2, it was observed that hearing thresholds across all frequencies progressively elevated with the advancement of vestibular and cochlear hydrops in the affected ears. Specifically, in cases where the vestibular hydrops in the affected ear was graded from 0 to 3, the average PA( the mean pure tone thresholds at 0.5, 1, 2, and 4 kHz) values for affected ears were 37 dB, 40 dB, 53 dB, and 61 dB, respectively. Correspondingly, for cochlear hydrops levels from 0 to 3, the average PA values for affected ears were 38 dB, 43 dB, 52 dB, and 68 dB, respectively. Based on Fig. 3, it is evident that as the severity of hydrops increases, there is a significant decline in hearing sensitivity, highlighting the progressive impact of endolymphatic hydrops on auditory function.

Table 2 The hearing thresholds of different grades of vestibular and cochlear hydropsFig. 3

Audiometric Curves for Different Degrees of Endolymphatic Hydrops

Figure 3 displays average hearing thresholds (dB HL) across frequencies (125–8000 Hz) for varying degrees of endolymphatic hydrops. The curves represent vestibular (VL) and cochlear (CL) hydrops from degrees 0 to 3. As hydrops severity increases, there is a notable decline in hearing sensitivity. These patterns emphasize the progressive impact of endolymphatic hydrops on auditory function

Table 2 presents the hearing thresholds at different frequencies (125 Hz, 250 Hz, 500 Hz, 1 kHz, 2 kHz, 4 kHz, and 8 kHz) according to the grades of vestibular and cochlear hydrops. The low-frequency hearing level (LH), the mid-frequency hearing level (MH), the high-frequency hearing level (HH), and the overall hearing level (PA) for vestibular hydrops grades (VL = 0 to VL = 3) and cochlear hydrops grades (CL = 0 to CL = 3).

Impact of endolymphatic hydrops site on hearing loss

The analysis included 30 patients with varying numbers of endolymphatic hydropic sites in bilateral ears. Among these, 30 ears exhibited both vestibular and cochlear hydrops, 9 ears exhibited isolated vestibular hydrops, and 21 ears exhibited isolated cochlear hydrops. Hearing thresholds of bilateral ears within the same patient were compared using a paired t-test. As shown in Table 3, ears with hydrops in both the cochlea and vestibule exhibited more severe hearing loss compared to those with isolated hydrops ( cochlear or vestibular hydrops) in the same patient. It was found that ears exhibiting both vestibular and cochlear hydrops demonstrated an average low-frequency hearing threshold difference of 17 dB(95%CI 8-26 dB), a mid-frequency difference of 13 dB(95%CI 4-22 dB), a high-frequency difference of 10 dB(95%CI 1-20 dB), and a PA threshold difference of 14 dB(95%CI 5-23 dB), with all p-values less than 0.05. Additionally, the Meniere’s Disease (MD) staging of bilateral ears was compared using a paired Wilcoxon test, revealing a statistically significant difference (p < 0.05, z = 2.973), indicating more severe MD staging in ears with both vestibular and cochlear hydrops compared to ears with isolated hydrops.

Table 3 The hearing level of the ears with different endolymphatic hydrops site

Table 3 compares the low-frequency hearing level (LH), the mid-frequency hearing level (MH), the high-frequency hearing level (HH), the overall hearing level (PA), and the staging of Meniere's disease (MDS), between one ear with both vestibular and cochlear hydrops versus the other with isolated hydrops in the same patient. The differences (d), p-values (p), and 95% confidence intervals (95%CI) are provided, demonstrating statistically significant differences in the severity of hearing loss and MDS between the two groups.

Correlations between endolymphatic hydrops severity and audiological outcomesCochlear endolymphatic hydrops and hearing loss

As indicated in Table 4. A significant correlation was identified between the severity of cochlear hydrops and hearing threshold levels across all frequencies, with all p-values less than 0.05. The correlation was most pronounced with low-frequency average hearing levels (0.15–0.50 kHz) (r = 0.462, p < 0.05), and least pronounced with high-frequency average hearing levels (4-8 kHz) (r = 0.261, p < 0.05). Significant correlations were also observed with the PA (0.5-4 kHz) (r = 0.383) and Meniere’s disease staging (MDS) (r = 0.307).

Table 4 The relationship between the degree of cochlear hydrops and hearing loss

Table 4 outlines the Spearman correlation coefficients (r) and p-values (p) assessing the relationship between the degree of cochlear hydrops(CL) and hearing loss across various frequencies (125 Hz to 8 kHz), also including low-frequency (LH), mid-frequency (MH), high-frequency (HH) hearing levels, the overall hearing level (PA), and he degree of CL and Meniere’s disease staging (MDS). Significant correlations indicate a strong relationship between CL and hearing impairment across all tested frequencies and MDS.

Vestibular endolymphatic hydrops and hearing loss

As indicated in Table 5, significant correlation was noted between the severity of vestibular hydrops and hearing threshold levels across all frequencies, with all p-values less than 0.05. The strongest correlation was observed with low-frequency average hearing levels (0.15–0.50 kHz) (r = 0.468, p < 0.05), and the weakest with high-frequency average hearing levels (4-8 kHz) (r = 0.314, p < 0.05). Significant correlations were further noted with PA (0.5-4 kHz) (r = 0.464) and Meniere’s disease staging (MDS) (r = 0.436).

Table 5 The relationship between the degree of vestibular hydrops and hearing loss

Table 5 details the Spearman correlation coefficients (r) and p-values (p) evaluating the association between the degree of vestibular hydrops(VL) and hearing loss at different frequencies (125 Hz to 8 kHz), also encompassing including low-frequency (LH), mid-frequency (MH), high-frequency (HH) hearing levels, the overall hearing level (PA). And the association between the CL and Meniere’s disease staging (MDS). Significant correlations indicate strong relationships between VL and hearing impairment and MDS.

The overall endolymphatic hydrops and hearing loss

As shown in Table 6, significant correlation was established between the comprehensive degree of endolymphatic hydrops and hearing threshold levels across all frequencies, with all p-values less than 0.05. The most substantial correlation was with low-frequency average hearing levels (0.15–0.50 kHz) (r = 0.571, p < 0.05), and the least substantial with high-frequency average hearing levels (4-8 kHz) (r = 0.351, p < 0.05). Significant correlations were also seen with PA (0.5-4 kHz) (r = 0.522) and Meniere’s disease staging (MDS) (r = 0.463).

Table 6 The relationship between the degree of overall endolymphatic hydrops and hearing loss

Table 6 presents the Spearman correlation coefficients (r) and p-values (p) illustrating the correlation between the overall degree of endolymphatic hydrops (EHL) and hearing loss at various frequencies (125 Hz to 8 kHz), also including assessments of low-frequency (LH), mid-frequency (MH), high-frequency (HH) hearing levels, the overall hearing level (PA). And the association between the EHL and Meniere’s disease staging (MDS). Statistically significant correlations underscore the profound impact of EHL on hearing across and MDS.