3.2 Basic features of the included researches
Table 1 shows the clinical features of the included researches. Of the 4290 participants, 1720 were categorized into the SSHL with vertigo group, 2507 were categorized into the SSHL without vertigo group, and the follow-up time to the beginningof deafness were between 1-11.4 months. In 23 studies, Siegel’s criteria was applied to assess the degree of hearing improvement, and hearing improvement >15 db was judged to be effective. Fourteen studies[4,8,11-17,19] and fourteen studies[4,8,11-17,19,20,22,26,28] used steroid-based systemic medication; seven studies[3,7,21,23-26] used a combination of medication and intratympanic steroid injections; four studies[6,24,26,27] used medication in combination with HBOT; and two studies used intratympanic steroid injections alone. Among them, Hideaki Suzuki[24] divided the study population into two groups: one receiving a combination of medication with intradermal injection of steroid hormones and one receiving a combination of medication with HBOT. Seiji Hosokawa[26] divided the study population into three groups: those receiving medication alone, those receiving a combination of medication with intradermal injection of steroid hormones, and those receiving a combination of medication with HBOT.
The included researches’ quality and risk of bias were assessed by the Newcastle–Ottawa scale, and the total score of the 23 studies[3,4,6-8,11-28] ranged from 7–8 (Table 2).
All the studies depicted the incidences of better hearing outcomes in a dichotomous pattern (groups without and with vertigo). The meta-analysis of the data was conducted (Figure. 2A), and it presented a high degree of heterogeneity, with I2=68.3%. For the analysis, a random effects model was applied, and the meta-analysis showed that the hearing recovery rate for SSHL without vertigo was 53.76%, and the hearing recovery rate for SSHL with vertigo was 40.8%. A pronounced difference (P = 0.000), OR = 2.13 (95% CI, 1.63-2.79; I2 = 68.3%) was found. In addition, the patients were classified into three subgroups according to treatment regimens (Figure 2B). A total of 12 studies[4,8,11-17,22,26,28]were conducted, and 1552 patients were included in the subgroup receiving medication alone. In this subgroup, there were 544 patients with vertigo and 1008 patients free from vertigo. The rate of hearing recovery was 56.75% for SSHL free from vertigo and 35.48% for SSHL suffering from vertigo (P = 0.018; OR = 2.65; 95% CI, 1.84-3.83; I2 = 50.8%). A total of 4 studies[6,24,26,27] with 847 people were contained in the subgroup analysis of patients with medical treatment combined with hyperbaric chamber therapy. In this subgroup, there were 375 patients with vertigo and 472 patients free from vertigo. The rate of hearing recoverywas 65.25% for SSHL with vertigo and 62.13% for SSHL with vertigo (P = 0.018; OR = 1.76; 95% CI, 0.75-4.15; I2 = 84.9%). In a total of seven[3,7,21,23-26] studies, 1372 patients were enrolled in the pharmacologic therapy combined with intracameral steroid injection therapy subgroup, which included 663 patients with vertigo and 709 patients free from vertigo. The rate of hearing recoverywas 47.53% for SSHL without vertigo and 35.74% for SSHL with vertigo; these two groups were significantly different (P = 0.008), OR = 1.62 (95% CI, 1.02-2.58; I2 = 65.6%).
The existence of publication bias was evident in our data from 23 studies,and according to the omission regulation, sensitivity analyses were further conducted to assess and correct for publication bias, with the following results (Figure 3).
DISCUSSION
This paper included 23 research papers and 4290 patients, including 1720 patients with SSHL with vertigo and 2507 patients with SSHL free from vertigo. The rate of hearing recovery was 53.76% in the group with SSHl without vertigo and 40.8% in the group with SSHL with vertigo. According to the statistical analysis, vertigo was obviously connected with worse hearing recovery (OR = 2.13; 95% CI, 1.63-2.79; I2 = 68.3%). These findings were consistent with those of Yu[9] et al.
In the subgroup with medication alone, the rate of hearing recovery was 56.75% in the SSHL without vertigo group and 35.48% in the SSHL with vertigo group. An obvious difference (P = 0.018), OR = 2.65 (95% CI, 1.84-3.83; I2 = 50.8%) was found. In the subgroup treated with medication combined with hyperbaric chamber therapy, the rate of hearing recovery was 65.25% in the group with SSHL without vertigo and 62.13% in the group with SSHLwith vertigo; these values were significantly different (P = 0.018), OR = 1.76 (95% CI, 0.75-4.15; I2 = 84.9%). In the subgroup treated with medication combined with intracameral steroid injection, the rate of hearing recoverywas 47.53% in the group with SSHL without vertigo and 35.74% in the group with SSHL with vertigo; these values were significantly different (P = 0.008, OR = 1.62; 95% CI, 1.02-2.58; I2 = 65.6%). In both subgroups of patients treated with combination therapy, we found a significant reduction in the prognostic association between vertigo and sudden sensorineural hearing loss, which may suggest improved efficacy of combination therapy. In the subgroup treated with pharmacological treatment combined with intracameral steroid injection, the rate of hearing recovery was significantly lower in people suffering from SSHL than in patients in the other subgroups. We reviewed the seven papers included in this subgroup and found that, in these seven papers, the level of initial hearing loss in the target population was predominantly severe to profound degree of hearing loss and that the degree of initial hearing impairment in the population was greater than that in the other subgroups, which might explain the lower rate of improvement in this subgroup than in the other subgroups.
Sudden sensorineural hearing loss has always been a controversial medical phenomenon and has subsequently become a research hotspot attracting numerous people. Moreover, there is extensive heterogeneity in terms of initial hearing loss, accompanying symptoms, and hearing recovery in patients in clinical practice, which further exacerbates the difficulty of related research. Clinicians have observed that patients with severe hearing loss often have vertigo, which has been empirically recognized as a negative factor in hearing recovery. Many researchers have studied this issue. Anestis D.[12] reviewed the hearing changes and long-term prognosis of 80 patients over a 15-year period in a retrospective analysis. The study showed that treatment was ineffective in 80.6% of people suffering from SSHL accompanied by vertigo; however, the ineffectiveness was only 56.1% in people suffering from SSHL not accompanied by vertigo. Y-J TSA et al.[29] concluded vertigo was a negative prognostic indicator for SSHL in a follow-up research of 128 people suffering from SSHL for an average of up to 11.4 months. Ryosuke Kitoh[30] et al. conducted a multicenter, large-sample epidemiological survey that investigated the clinical features of 3,419 people suffering from SSHL and statistically analyzed the correlation between the degree of severity of hearing loss and patient prognosis. Vertigo symptoms were found to be significantly associated with poor prognosis. Similarly, Jae Ho Chung et al.[4] concluded that vertigo is a negative predictor of hearing recovery in people suffering from SSHL and that the labyrinth damage degree may be correlated with the severity of cochlear impairment, with the likelihood of hearing recovery decreasing with increasing labyrinth involvement. However, several scholars have shown the opposite results. S HOSOKAWA et al.[6] studied 334 patients suffering from SSHL and reported that the rate of hearing improvement was 62.4% in people suffering from vertigo and 72.8% in people free from vertigo; moreover, no statistically obvious difference in the difference between the two recovery rates (p=0.062) was found. Suphi Bulğurcu et al.[31] studied 154 patients with a mean follow-up of up to 7.4 months and found that patients with vertigo had a lower but not statistically significant treatment success rate. According to multivariate analysis, Adriana Perez Ferreira Neto[28] et al. reported that the level of statistical significance between vertigo and a poor prognosis for hearing restoration was marginal (p=0.088). These studies suggest that whether vertigo serves as a poor prognostic element for SSHL remains controversial.
Yu et al. (2018) published a meta-analysis discussing whether vertigo is a poor prognostic element for SSHL. This meta-analysis included 10 articles with 4814 patients. They found that vertigo was obviously connected with poorer hearing improvement (OR = 2.22; 95% CI, 1.54-3.20; I2 = 74%) [9]. With the continuous updating of relevant researches, the meta-analysis was conducted again, updating the previous articles and screening the included literature to improve the stability of the conclusions. In the end, we obtained the same conclusion as Yu et al.: vertigo is a negative prognostic factor for SSHL.
Limitations of the article
At the beginning of this study, we attempted to analyze patient subgroups for the presence of tinnitus, degree of hearing loss, frequency band of hearing loss, frequency band of hearing loss, and level of hearing benefit. We attempted to use subgroup analysis to quantify the specificity of the SSHL population and in order to clarify the appropriateness of the treatment regimen for a specific population. However, we had to abandon these subgroups because of the paucity of literature that could extract the relevant metrics.
Moreover, there is no standardization of treatment protocols among studies on sudden sensorineural hearing loss. The means of intervention, drug dosage, hormone type, duration of intervention, and severity of hearing loss varied significantly among researchers, all of which may have skewed the final results. This is a problem that cannot be avoided in this study. Therefore, additional clinical studies are needed to support subsequent researchers and obtain new conclusions.
CONCLUSION
Vertigo may be a negative factor in the hearing prognosis of people suffering from SSHL. Moreover, the correlation between poor prognosis and vertigo according to the SSHL became significantly reduced in both subgroups after the combined treatment. The combination of hyperbaric oxygen chamber therapy, intradermal injection of steroid hormone therapy and medication had a significant effect on hearing prognosis in patients with SSHL with vertigo.