Introduction
Benign paroxysmal positional vertigo (BPPV), characterised by transient vertigo and nystagmus provoked by changes in head position, is the most common cause of vertigo.Reference Kim and Zee1,Reference Bhattacharyya, Gubbels, Schwartz, Edlow, El-Kashlan and Fife2 Recent advances in understanding its pathophysiological mechanisms and nystagmus patterns have facilitated the diagnostic accuracy of BPPV subtypes. Benign paroxysmal positional vertigo subtypes are determined by the canals involved, and BPPV involving the posterior semicircular canal is the most common type, constituting approximately 85–95 per cent of BPPV cases.Reference Bhattacharyya, Gubbels, Schwartz, Edlow, El-Kashlan and Fife2,Reference Parnes, Agrawal and Atlas3 Benign paroxysmal positional vertigo involving the horizontal semicircular canal accounts for 5–33 per cent of cases.Reference Parnes, Agrawal and Atlas3–Reference Honrubia, Baloh, Harris and Jacobson9
Although the reported incidence of horizontal semicircular canal BPPV has consistently been much lower than that of posterior semicircular canal BPPV, recent studies demonstrated that the incidence of the former may be higher.Reference Kong, Song and Shim10–Reference Chung, Park, Ko, Jeon, Choi and Cho12 However, it may be difficult to assess the real incidence of BPPV by subtype without controlling for factors affecting the estimated overall incidence of BPPV. Benign paroxysmal positional vertigo may resolve spontaneously, and the natural course of positional vertigo remission is reportedly quite short.Reference Imai, Ito, Takeda, Uno, Matsunaga and Sekine4,Reference Shim, Ko, Lee, Park and Song13,Reference Imai, Takeda, Ito and Inohara14 The spontaneous remission rate of positional vertigo within one week was higher for horizontal semicircular canal BPPV than for posterior semicircular canal BPPV.Reference Imai, Ito, Takeda, Uno, Matsunaga and Sekine4 Thus, the time interval between symptom onset and specialist evaluation should be considered when assessing the actual incidence of BPPV subtypes. Moreover, because of the patient referral system, patients with BPPV may have a long wait for evaluations in the out-patient clinics of tertiary referral centres, which have reported most studies of BPPV incidence to date.
The present study aimed to investigate the incidence of BPPV subtypes by hospital visit type (i.e. out-patient department vs emergency room), in a single tertiary referral centre.
Materials and methods
The medical records of the patients who sought evaluation for dizziness in our out-patient department or emergency room were retrospectively reviewed, and 772 consecutive patients diagnosed with typical idiopathic BPPV between January 2017 and December 2019 were enrolled. Neurological examinations, including cerebellar function tests, were performed on all patients. Patients with a focal neurological deficit or isolated vertigo, accompanied by central ocular movements, limb ataxia and severe imbalance, underwent magnetic resonance imaging (MRI) of the brain to rule out central nervous system disorders. Spontaneous, head-shaking and positional nystagmus were examined using the video-Frenzel goggle system in all patients with dizziness who sought an evaluation.
In this study, BPPV subtype was determined, in accordance with the standard clinical guidelines for BPPV, as: canalolithiasis posterior semicircular canal BPPV, geotropic horizontal semicircular canal BPPV or apogeotropic horizontal semicircular canal BPPV.Reference Bhattacharyya, Gubbels, Schwartz, Edlow, El-Kashlan and Fife2,Reference Bhattacharyya, Baugh, Orvidas, Barrs, Bronston and Cass15 Benign paroxysmal positional vertigo was diagnosed according to American Academy of Otorhinolaryngology – Head and Neck Surgery clinical practice guidelines.Reference Bhattacharyya, Gubbels, Schwartz, Edlow, El-Kashlan and Fife2,Reference Bhattacharyya, Baugh, Orvidas, Barrs, Bronston and Cass15 Posterior semicircular canal BPPV was confirmed if typical upbeating-torsional nystagmus was induced by the Dix–Hallpike test. Geotropic horizontal semicircular canal BPPV was confirmed if typical geotropic direction–changing positional nystagmus lasting less than 60 seconds was induced by the supine roll test. Apogeotropic horizontal semicircular canal BPPV was confirmed if typical apogeotropic direction–changing positional nystagmus lasting longer than 60 seconds was induced by the supine roll test.
Patients with anterior semicircular canal or multiple canal BPPV, or BPPV recurrence, were excluded from the study. Patients with central paroxysmal positional vertigo were excluded. In addition, to include only patients with idiopathic BPPV, patients with otological symptoms suggestive of other labyrinthine diseases and those with a recent history of labyrinthine disorders, including sudden sensorineural hearing loss, vestibular neuritis, labyrinthitis and Ménière's disease, were excluded. Patients with head trauma or post-operative conditions were also excluded. Patients with leptomeningeal metastasis of primary cancer and those with severe medical conditions resulting from chemotherapy, heart disease or haemodialysis were excluded.
Although 16 patients reported having co-morbid migraine among 772 patients included in the present study, none of them met the diagnostic criteria for vestibular migraine. Diffusion-weighted brain MRI, which was conducted in 66 patients with apogeotropic horizontal semicircular canal BPPV who were diagnosed in the emergency room, showed no abnormality. Routine brain MRI, which was conducted in only one patient with apogeotropic horizontal semicircular canal BPPV who was diagnosed in the out-patient department, demonstrated no abnormal finding.
Statistical analyses were performed using SPSS software (version 24.0; IBM, Armonk, New York, USA). Categorical variables were analysed using chi-square tests and continuous variables were analysed using student's t-tests. A significance level of 0.05 was adopted. The study was approved by the local institutional review board (approval number: 2021-03-091).
Results
A total of 772 patients aged 14–85 years (mean ± standard deviation (SD), 54.9 ± 12.8 years) were included in this study. Female patients outnumbered male patients (male-to-female ratio of 214:558). The right side was involved more frequently than the left side (right-to-left ratio of 395:377).
Among the 772 patients with idiopathic BPPV, 290 (38 per cent) were diagnosed with posterior semicircular canal BPPV, 143 (19 per cent) with geotropic horizontal semicircular canal BPPV and 339 (44 per cent) with apogeotropic horizontal semicircular canal BPPV (Table 1).
Table 1. Total patients, BPPV subtype, and duration between symptom onset and evaluation according to hospital visit type
BPPV = benign paroxysmal positional vertigo; SCC = semicircular canal; SD = standard deviation
Of the 772 patients with BPPV, dizziness was evaluated in the out-patient department in 285 (37 per cent) and in the emergency room in 487 (63 per cent) (Table 1). More patients with posterior semicircular canal BPPV were evaluated via the out-patient department (161 out of 290 (56 per cent)) than via the emergency room (129 out of 290 (44 per cent)). More patients with geotropic horizontal semicircular canal BPPV (106 out of 143 (74 per cent) vs 37 out of 143 (26 per cent)) and apogeotropic horizontal semicircular canal BPPV (252 of 339 (74 per cent) vs 87 out of 339 (26 per cent)) were evaluated via the emergency room than via the out-patient department (Table 1). Compared with posterior semicircular canal BPPV patients, significantly higher proportions of geotropic horizontal semicircular canal BPPV patients (p < 0.001) and apogeotropic horizontal semicircular canal BPPV patients (p < 0.001) were evaluated via the emergency room (Figure 1).
Fig. 1. Proportion of patients with posterior semicircular canal (PSCC) benign paroxysmal positional vertigo (BPPV), geotropic horizontal semicircular canal (HSCC) BPPV, and apogeotropic horizontal semicircular canal BPPV by hospital visit type. Geo = geotropic; Apo = apogeotropic; OPD = out-patient department; ER = emergency room
The mean (± SD) time interval between symptom onset and the first evaluation for dizziness was: 13.43 ± 20.08 days (range, 0–180 days) for patients with posterior semicircular canal BPPV, 1.76 ± 5.38 days (range, 0–52 days) for patients with geotropic horizontal semicircular canal BPPV, and 2.84 ± 9.97 days (range, 0–120 days) for patients with apogeotropic horizontal semicircular canal BPPV (Table 1 and Figure 2). The mean time interval was significantly longer in patients with posterior semicircular canal BPPV than in those with geotropic horizontal semicircular canal BPPV (p < 0.001) or apogeotropic horizontal semicircular canal BPPV (p < 0.001) (Figure 2). The mean (± SD) time interval of the patients who were evaluated via the out-patient department versus the emergency room was: 15.41 ± 25.19 days versus 1.29 ± 2.79 days for posterior semicircular canal BPPV, 5.65 ± 9.49 days versus 0.41 ± 1.00 days for geotropic horizontal semicircular canal BPPV, and 9.39 ± 17.91 days versus 0.59 ± 2.02 days for apogeotropic horizontal semicircular canal BPPV, respectively (Table 1). Regardless of subtype, the mean time interval was significantly longer in BPPV patients evaluated via the out-patient department than via the emergency room (Figure 3).
Fig. 2. Mean time interval between symptom onset and clinical evaluation according to benign paroxysmal positional vertigo (BPPV) subtype. PSCC = posterior semicircular canal; Geo = geotropic; HSCC = horizontal semicircular canal; Apo = apogeotropic
Fig. 3. Differences in mean time intervals between symptom onset and clinical evaluation according to benign paroxysmal positional vertigo (BPPV) subtype by hospital visit type. PSCC = posterior semicircular canal; Geo = geotropic; HSCC = horizontal semicircular canal; Apo = apogeotropic; OPD = out-patient department; ER = emergency room
Discussion
Because the posterior semicircular canal was the only canal involved in BPPV when Bárány first reported on it in 1921, posterior semicircular canal BPPV was the only BPPV subtype until McClure described horizontal semicircular canal BPPV in 1985.Reference McClure16 This might have led to the supposition that BPPV is a disorder of the posterior semicircular canal; accordingly, patients with positional vertigo have been evaluated only by the Dix–Hallpike test for a long time, even after the introduction of horizontal semicircular canal BPPV.Reference McClure16 Furthermore, because the posterior semicircular canal is the most gravity-dependent part of the vestibular labyrinth in most positions in daily life, including upright and supine positions, the belief that BPPV is a disease associated with the posterior semicircular canal persisted. This might have caused some proportion of horizontal semicircular canal BPPV patients to be unrecognised, leading to underestimation of the true incidence of horizontal semicircular canal BPPV. The incidence of horizontal semicircular canal BPPV is reportedly 1.9–33 per cent,Reference Parnes, Agrawal and Atlas3–Reference Honrubia, Baloh, Harris and Jacobson9,Reference Wolf, Boyev, Manokey and Mattox17 and the incidence of anterior semicircular canal BPPV was higher than that of horizontal semicircular canal BPPV in some reports.Reference Cakir, Ercan, Cakir, Civelek, Sayin and Turgut5,Reference Wolf, Boyev, Manokey and Mattox17
Here, we assessed the incidence of BPPV subtypes according to hospital visit type in a single tertiary referral centre. We found that a significantly higher proportion of patients with horizontal semicircular canal BPPV than posterior semicircular canal BPPV visited the emergency room. There are several speculative reasons why patients with horizontal semicircular canal BPPV visit the emergency room more often than those with posterior semicircular canal BPPV; these are outlined below.
Patient-perceived disability is reportedly more severe in patients with horizontal semicircular canal BPPV than in those with posterior semicircular canal BPPV,Reference Martens, Goplen, Aasen, Nordfalk and Nordahl18 and a relationship was observed between horizontal semicircular canal BPPV and increased symptoms of functional, emotional and physical limitations.Reference Kim, Kim, Joo, Park and Han19
Patients with horizontal semicircular canal BPPV may experience more intense symptoms during the daytime, when the head is mostly in the upright position,Reference Martens, Goplen, Aasen, Nordfalk and Nordahl18 while those with apogeotropic horizontal semicircular canal BPPV may, despite symptoms being aggravated by a position change, feel persistent dizziness because of the constant influence of gravity. This can cause greater anxiety and motivate these patients to visit the emergency room.
Given that horizontal semicircular canal BPPV spontaneously resolves more quickly than posterior semicircular canal BPPV,Reference Imai, Ito, Takeda, Uno, Matsunaga and Sekine4,Reference Shim, Ko, Lee, Park and Song13,Reference Imai, Takeda, Ito and Inohara14 patients with the latter subtype and with a longer symptom duration may be more likely to visit the out-patient department.
The medical referral system may account for the higher proportion of emergency room visits among patients with horizontal semicircular canal BPPV. Under our healthcare delivery system, patients with BPPV cannot visit the out-patient department of a tertiary medical centre; rather, they are usually transferred to specialists of the tertiary referral centre several days after undergoing an evaluation by a primary care physician. On the other hand, patients with dizziness or vertigo may directly visit the emergency room without paying additional fees. Patients with horizontal semicircular canal BPPV generally have more severe symptoms than those with posterior semicircular canal BPPV,Reference Martens, Goplen, Aasen, Nordfalk and Nordahl18,Reference Kim, Kim, Joo, Park and Han19 meaning that the former may be more likely to urgently visit the emergency room.
Another remarkable finding of this study was that the incidence of horizontal semicircular canal BPPV was higher than that of posterior semicircular canal BPPV. In addition, interestingly, apogeotropic horizontal semicircular canal BPPV was more common than geotropic horizontal semicircular canal BPPV or posterior semicircular canal BPPV (Table 1), which is in contrast with the estimates of most previous studies.
A significantly higher number of patients with apogeotropic horizontal semicircular canal BPPV than with posterior semicircular canal BPPV or geotropic horizontal semicircular canal BPPV were diagnosed in the emergency room. However, a higher number of patients with posterior semicircular canal BPPV than with apogeotropic horizontal semicircular canal BPPV were diagnosed in the out-patient department, as reported in previous studies. Considering that many posterior semicircular canal BPPV patients may be diagnosed and treated by primary care physicians without requiring a tertiary referral centre visit, the true incidence of posterior semicircular canal BPPV might be higher than that estimated here. The mean time interval of the patients who were evaluated via the out-patient department was significantly longer than for those evaluated via the emergency room for all BPPV subtypes. The mean time interval between symptom onset and the first evaluation for dizziness was significantly shorter for horizontal semicircular canal BPPV than for posterior semicircular canal BPPV, a finding consistent with a previous study.Reference Chung, Park, Ko, Jeon, Choi and Cho12
• This study investigated the incidence of benign paroxysmal positional vertigo (BPPV) subtypes by hospital visit type (i.e. out-patient department vs emergency room)
• The proportion of patients who visited the emergency room was significantly higher for horizontal semicircular canal BPPV than posterior semicircular canal BPPV cases
• The mean time interval between symptom onset and clinical evaluation was significantly longer in posterior than horizontal semicircular canal BPPV
The limitations of the present study are as follows. First, patients with recurrent BPPV were excluded as they might have different hospital visiting behaviours than those diagnosed with BPPV for the first time. Patients with anterior semicircular canal BPPV, multiple canal BPPV, post-traumatic BPPV and secondary BPPV were also excluded from the study. Thus, the incidence described in the present study does not represent all BPPV populations. Second, this study was performed at a single tertiary referral centre, which further limits the generalisability of our results.
Conclusion
The present study demonstrated that a significantly higher proportion of patients with horizontal semicircular canal BPPV than those with posterior semicircular canal BPPV visited the hospital via the emergency room, whereas the mean time interval between symptom onset and the first evaluation for dizziness was significantly shorter for those with horizontal semicircular canal BPPV than for those with posterior semicircular canal BPPV. These results suggest that the true incidence of horizontal semicircular canal BPPV might be higher than previously reported. However, further studies that include primary, secondary and tertiary care centres are needed to elucidate the actual incidence of the BPPV subtypes.
Acknowledgement
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (grant number: 2021R1F1A1062019).
Competing interests
None declared
