Residual Dizziness Characteristics of Idiopathic Sudden Sensorineural Hearing Loss Patients with Benign Paroxysmal Positional Vertigo

Idiopathic sudden sensorineural hearing loss (ISSNHL) is defined as an otologic emergency in which hearing thresholds for two or more consecutive frequencies abruptly increase by 20 dB or more within 72 h, often accompanied by tinnitus and vestibular symptoms in some cases [1]. Clinically, about 30% of patients with ISSNHL also experience vestibular symptoms, such as vertigo or imbalance [2]. These vestibular symptoms can manifest as an acute vestibular syndrome (similar to vestibular neuritis) [3] or an episodic vestibular syndrome, such as benign paroxysmal positional vertigo (BPPV) [4]. BPPV is believed to be caused by detached otoconia from the utricular maculae, which migrate into the semicircular canals (SCCs) and may either move freely in the endolymph (canalithiasis) or become attached to the cupula (cupulolithiasis). Although its etiology remains elusive, BPPV falls into idiopathic and secondary categories based on causative factors. The latter includes trauma, Ménière’s disease, SSNHL, vestibular neuritis, etc. Recently, studies have explored BPPV associated with ISSNHL regarding its possible pathophysiological mechanism, clinical characteristics, treatment outcomes, and prognosis [4, 5].

BPPV is the most common peripheral vertigo, accounting for about 40% of cases [6]. Statistics show a lifetime prevalence rate of 3.2% for women and 1.6% for men, with an overall rate of 2.4% in adults that increases with age [7, 8]. The disease is characterized by transient vertigo attacks and specific nystagmus triggered by changes in body position (getting up, turning over, turning head). Each attack lasts for several seconds, and the patient often complains of a sense of rotation, accompanied by nausea and vomiting in severe cases [9, 10]. Canal repositioning procedures are currently the most effective treatment for BPPV, with most patients recovering fully after a single treatment [11, 12]. However, clinical studies have found that 31–60% of patients still experience symptoms like dizziness,floating, unstable walking, neck tightness, and others after receiving treatment. These symptoms, though not accompanied by vertigo, specific nystagmus, or positive position-induced test results, are classified as residual dizziness (RD) [13‒15].

Vaduva et al. [16] found that 47.2% of RD patients had balance disorders, and older people over 65 years were more likely to experience RD. RD symptoms significantly impact patients in their daily lives, potentially leading to accidental falls in some elderly patients and increasing the medical economic burden. Additionally, RD can cause anxiety and depression in some patients [17] and even develop into persistent postural perceptual dizziness [18, 19]. Although the detrimental effects of RD are recognized, the pathogenesis of RD remains unclear at present. More clinical studies are urgently needed to explore this condition.

ISSNHL, a common clinical condition, can be accompanied by vertigo. Initially, research on sudden deafness primarily focused on the hearing loss itself, with less emphasis on episodic vertigo. However, as vertigo research has advanced, it has been recognized that BPPV is a frequent accompaniment to ISSNHL-associated vertigo. Even after treatment, some patients may experience RD. This study investigates the characteristics of patients with ISSNHL accompanied by BPPV and the impact of RD on their lives.

We conducted a retrospective observational study on adult inpatients with ISSNHL accompanied by BPPV who were treated by otolaryngologists at Tongde Hospital of Zhejiang Province between January 2023 and January 2024. Patients were included if they met the following criteria: (1) fulfilled the diagnostic criteria for ISSNHL published by the Chinese Medical Association (CMA) [1]; (2) fulfilled the diagnostic criteria for BPPV published by the CMA [20]; (3) did not receive steroid treatment before hospitalization; (4) completed the entire treatment course without interruption; and (5) had complete medical records including pure tone audiometry, Dizziness Handicap Inventory (DHI), and Hamilton anxiety scale (HAMA) scores. Acoustic neuroma and other immune-inflammatory inner ear diseases were excluded using auditory brainstem response testing, internal auditory canal MRI scans, and other laboratory tests. Exclusion criteria were (1) history of genetic disorders associated with familial deafness; (2) sensorineural hearing loss caused by noise exposure or ototoxic drugs; (3) space-occupying lesions of the internal auditory canal, central organic pathology, external or middle ear disease, or malignant tumor; and (4) severe cardiovascular and cerebrovascular diseases, diabetes mellitus, hypertension, or liver and kidney diseases.

This single-center, retrospective cohort study was approved by our hospital’s Ethics Committee and Institutional Review Board (the number of the ethical approval: 2022-244(K); the date of the ethical approval obtained: December 6, 2022). All patients were informed and provided written informed consent. The study adhered to the Consolidated Standards of Reporting Trials guidelines and the Declaration of Helsinki. We ensured participant privacy throughout the study.

A total of 54 patients were enrolled in the study. All participants underwent pure tone audiometry, DHI, and HAMA assessments before and after treatment. All patients received a 5-day course of intravenous prednisolone (50 mg daily) and hemodilution agents for 10 days. Hemodilution therapy included intratympanic methylprednisolone injections every other day for a total of five times and intravenous batroxobin (Beijing Tobishi Pharmaceutical Co.) at a dose of 5 BU. The initial dose of batroxobin was doubled, followed by adjustments based on subsequent fibrinogen levels. Fibrinogen levels were typically re-evaluated the day after the first batroxobin dose. If the level remained below 100 mg/dL, batroxobin was repeated until the level exceeded 100 mg/dL.

Concurrently, all patients received BPPV repositioning maneuvers performed by the same therapist using the SRM-IV vertigo diagnostic and treatment system (Beijing SRM Medical Technology Co.). The specific maneuver used depended on the type of otolithiasis identified. For posterior canalithiasis, the Epley maneuver or posterior canal roll maneuver was used. Posterior cupulolithiasis was treated with the Semont maneuver or combined repositioning therapy. Horizontal canalithiasis was treated with the barbecue maneuver and horizontal cupulolithiasis with the Gufoni maneuver combined with the barbecue maneuver. Patients underwent repositioning maneuvers every other day until their nystagmus resolved, as determined by a positioning test. Upon discharge, patients were categorized into two groups based on the presence or absence of RD: the group without RD and the group with RD.

To assess treatment efficacy, an otolaryngology assistant performed a comprehensive audiologic examination before treatment and 1 month later. This evaluation assessed the severity of hearing loss. We also confirmed that participants did not receive any changes to their Western medications during the study period. The following definitions were used to categorize hearing improvement attributable to treatment [1]:

• a.

  Recovery: hearing is restored to within 10 dB of the pure tone average in the unaffected ear or returns to pre-disease levels.

• b.

  Marked relief: average hearing improvement exceeds 30 dB.

• c.

  Relief: average hearing improvement is between 15 and 30 dB.

• d.

  Invalid: average hearing improvement is less than 15 dB.

To evaluate treatment efficacy across the three groups, we calculated the overall effective rate using the following formula: overall effective rate = [(number of patients with recovery + marked relief + relief)/total number of patients] × 100%. This study utilized a set of scales to collect relevant data on dizziness, one of which was the Dizziness Handicap Inventory [21].

The DHI is a 25-item questionnaire that assesses the impact of dizziness on a person's daily life across three dimensions: physical, functional, and emotional. While a validated version of the DHI exists [22], this study employed the Chinese version validated in 2015 [23]. The DHI consists of 25 items divided into three domains believed to encompass the impact of the disease: functional (DHI-F, 9 questions), emotional (DHI-E, 9 questions), and physical (DHI-P, 7 questions) (Table 1). Each item is scored 0, 2, or 4 points, resulting in a possible total DHI score ranging from 0 to 100. In this study, both the total DHI score and the score for each domain were calculated.

We performed statistical analyses using IBM SPSS Statistics version 21 (IBM, Armonk, NY, USA). Demographic data are presented as means ± standard deviations, while clinical characteristics are expressed as percentages. To compare the efficacy of treatment between the two groups, we used the Kruskal-Wallis rank-sum test for differences in DHI and HAMA scores before and after treatment. The χ² test was used to compare hearing improvement between the groups.

The group with residual symptoms included 24 participants (10 males and 14 females, 58.33% female). Their mean age was 46.75 years (standard deviation ±13.80 years). The group without residual symptoms consisted of 30 participants (13 males and 17 females, 56.67% female) with a mean age of 45.77 years (standard deviation ±11.86 years).

Both the residual symptom group (n = 24) and the non-residual symptom group (n = 30) exhibited hearing loss across the spectrum, with distributions of mild (2 vs. 3), moderate (7 vs. 13), severe (12 vs. 11), and profound (3 vs. 3) cases, respectively. The χ² test revealed no significant difference in hearing loss distribution between the two groups (see details in Fig. 1).

The data in Table 1 reveal that among the total cases (54), those with RD showed a slightly higher frequency of recovery (6 cases) compared to those without RD (8 cases), indicating a potential influence of RD on hearing recovery. However, for marked relief, relief, and invalid outcomes, patients without RD displayed higher numbers (9, 6, and 7 cases, respectively) than those with RD (8, 4, and 6 cases, respectively). But the χ² test revealed no significant difference in hearing improvement between the two groups.

Among participants with residual symptoms, the affected canals were posterior semicircular (n = 9), horizontal semicircular (n = 12), and cupulolithiasis (n = 3). In the group without residual symptoms, the distribution of affected canals was posterior semicircular (n = 13), horizontal semicircular (n = 16), and cupulolithiasis (n = 1). The χ² test revealed no significant difference in canal involvement between the two groups (see details in Fig. 2).

The DHI scores showed no significant difference between the two groups before treatment. However, Mann-Whitney U tests revealed a statistically significant difference in DHI scores before and after treatment for both groups. Similarly, the HAMA scores showed a significant statistical difference between the two groups before treatment, as determined by the Mann-Whitney U tests.

It is now understood that residual symptoms may occur even after successful BPPV treatment for several reasons. First, the repositioning maneuver might not be fully completed. Second, BPPV can involve not only the SCCs but also the otoliths, and dysfunction in the otoliths may cause transient mild dizziness. Third, other vestibular problems may coexist with BPPV. Fourth, vestibular function takes time to recover after treatment. Fifth, a patient’s anxiety and depression about vertigo can also hinder rehabilitation [24, 25]. The incidence rate of residual symptoms following BPPV maneuvers is reported to be between 34% and 61% [26].

A study by Vaduva et al. [16] found that 47.2% of patients with RD also experienced balance disorders, with a higher prevalence in older adults over 65 [27]. RD symptoms significantly impact patients’ daily lives, increasing the risk of accidental falls, particularly in elderly patients, and contributing to a higher medical burden. Additionally, RD can lead to anxiety and depression in some individuals and even develop into persistent postural perceptual dizziness [28‒30]. While the detrimental effects of RD are recognized, the underlying mechanisms remain unclear. Therefore, further clinical studies are urgently needed to explore the causes of RD.

Faralli et al. [31, 32] proposed that the generation of RD might be linked to the compensatory mechanism of the vestibular center. Their research also showed that patients who received earlier diagnosis and treatment were less likely to develop RD symptoms. They hypothesized that otolith loss disrupts the functional symmetry of bilateral peripheral vestibular function, triggering the compensatory mechanism in the vestibular center. However, even with canalith repositioning procedures, the brain’s compensatory mechanism is relatively slow and requires time to complete adaptation to the changes in peripheral vestibular function. This delay may contribute to the production of RD symptoms [33].

Some studies focusing on BPPV found that at the time of diagnosis, the DHI subscale scores of the RD group were significantly higher than those of the NRD group, and linear regression analysis demonstrated that the DHI total score before canal repositioning procedures was a predictor for RD. And according to previous studies, high DHI subscale scores and total scores at the first presentation are sensitive factors related to the incidence of RD [34, 35]. Our research indicates that there is no significant difference in the pre-treatment DHI scale scores, which may be related to our study enrolling patients with ISSNHL accompanied by BPPV. This is different from other studies that only included patients with BPPV, and it may also be related to an insufficient number of subjects.

Over the years, several studies have identified anxiety and depression as significant predictors of RD, with anxiety emerging as the strongest predictor. This finding suggests that anxiety and depression disorders can influence the presence of RD after successful canalith repositioning procedures. Research has shown that the RD group exhibits significantly higher levels of anxiety and depression compared to the non-RD group at the initial visit. This may be because acute vertigo episodes trigger or exacerbate anxiety and depression in BPPV patients. Kalderon et al. [36] further demonstrated that anxiety in BPPV patients is not a long-term personality trait (trait anxiety) but rather a temporary state (state anxiety) provoked by acute vertigo episodes. Additionally, Jung et al. [37] reported that a low dose of the anti-anxiety medication etizolam could alleviate RD in BPPV patients, particularly for those experiencing functional and emotional difficulties. While rigorous scientific evidence is still needed to generalize the use of this medication in clinical practice, its positive effect lends some support to the role of psychiatric disorders in RD. Consistent with previous research, our study found that HAMA scores before treatment were higher in the RD group compared to the non-RD group.

The shared susceptibility of the posterior SCC, cochlea, and possibly the saccule can be explained by their common blood supply from the inferior labyrinthine artery, a branch of the common cochlear artery [38]. In contrast, the inferior vestibular nerve innervates both the posterior SCC and the saccular macula. Therefore, the pattern of injury (neural vs. vascular) in an acute setting might be suggested by the specific structures affected. For instance, posterior SCC paresis combined with sudden hearing loss on the same side (ipsilateral) could be caused by ischemia of the common cochlear artery [39]. A recent case report described a patient with SSNHL and acute vertigo who exhibited a selective decrease in vHIT gain on the ipsilateral posterior SCC. Inner ear MRI in this patient revealed fibrosis of the posterior SCC, further supporting a vascular etiology [40]. While new instrumental tests like video head impulse test (vHIT) and vestibular evoked myogenic potential can aid in the topographical diagnosis of dysfunction within specific inner ear structures, the underlying mechanisms of vertigo in SSNHL patients require further investigation [40, 41].

Zhong et al. [42] found that patients with sensorineural hearing loss (ISSNHL) accompanied by BPPV exhibited a higher rate of abnormal caloric test results (77.8%) compared to those with ISSNHL alone. This suggests broader inner ear involvement in patients with co-existing BPPV, potentially affecting the cochlea, vestibule, and SCCs. Studies have shown that among patients with BPPV associated with sudden deafness, the horizontal SCC is most frequently affected. This differs from primary BPPV, where the posterior SCC is typically involved [43, 44]. The reason for this difference remains unclear. Kim et al. [43] proposed that the underlying cause of BPPV secondary to sudden deafness might be distinct from that of primary BPPV. It is important to note that our study did not identify any cases with the involvement of multiple SCCs, likely due to our relatively small sample size. Viral infection, a common cause of sudden deafness, can also lead to secondary BPPV. This virus-induced BPPV may preferentially affect the horizontal SCC compared to the vertical canals. However, this hypothesis requires further investigation and remains to be conclusively proven.

In summary, ISSNHL-associated BPPV may be caused by vascular embolism or thrombosis in the cochlear or spiral modiolar artery. This disrupts blood flow, leading to ischemia in the otolithic membrane and subsequent detachment of otoconia. Because this detachment often occurs within 24 h of the initial event, patients experience positional vertigo early in the course of the disease.

The authors would like to thank the participants and the health care team at the otolaryngology department of Tongde Hospital of Zhejiang Province.

This single-center, retrospective cohort study was approved by our hospital’s Ethics Committee and Institutional Review Board (the number of the ethical approval: 2022-244(K); the date of the ethical approval obtained: December 6, 2022). All patients were informed and provided written informed consent. The study adhered to the Consolidated Standards of Reporting Trials guidelines and the Declaration of Helsinki. We ensured participant privacy throughout the study.

The authors have no conflicts of interest to declare.

This work was supported by the Medical Science and Technology Project of Zhejiang Province (Grant No.: 2019KY347 and 201129975) and Zhejiang Traditional Chinese Medicine Administration (Grant No.: 2023ZL348, 2023ZF070, and 2021ZB053). Role of the funding source was as follows: Grant No.: 2023ZL348: study design and the writing of the report; Grant No.: 2023ZF070 and 2021ZB053: the collection of data; and Grant No.: 2019KY347 and 201129975: the analysis and interpretation of data.

Jing Yang: writing – original draft; Gaoyun Xiong: investigation; Hongyi Lu and Xiandan Luo: data curation; Xiaoxing Xie: methodology; and Aoling Shao: writing – review and editing.

All data generated or analyzed during this study are included in this article. Further inquiries can be directed to the corresponding author.