Natural course of the remission of vertigo in patients with benign paroxysmal positional vertigo

Benign paroxysmal positional vertigo (BPPV) was initially thought to affect only the posterior semicircular canal (P-BPPV),¹ but in recent years, another type of BPPV has been reported, in which the horizontal semicircular canal is affected (H-BPPV).² The canalith repositioning procedure (CRP) was introduced to treat BPPV based on the canalolithiasis hypothesis.^1,2 On the other hand, it is widely accepted that BPPV is spontaneously resolved in most cases.³ Although there are many clinical investigations about BPPV, few studies have investigated the duration of BPPV without CRP.^4,5 In the present study, we assessed the natural course of the remission of positional vertigo in patients with BPPV.

Methods.

We enrolled 108 sequential patients who were diagnosed with BPPV in the Department of Otolaryngology, Kansai-Rosai Hospital, between April 2001 and November 2003. All patients who had dizziness or vertigo were tested by the Dix-Hallpike maneuver⁶ and then returned to the sitting position. They were then tested by lateral head rotation in supine position. The positional nystagmus was recorded by an infrared CCD camera (RealEyes, Micromedical Technologies) in all subjects. P-BPPV was diagnosed on the basis of the following criteria: 1) a history of brief episodes of positional vertigo, 2) absence of an identifiable CNS disorder able to explain the positional vertigo following neurologic and neurophysiologic studies, and 3) a direction-changing torsional nystagmus triggered by Dix-Hallpike maneuver. H-BPPV was diagnosed based on the following criteria: 1), 2), and 3) a direction-changing horizontal positional geotropic nystagmus triggered by lateral head rotation in the spine position. The patients were asked about the onset time of positional vertigo through a detailed interview. After the patients were informed about CRP and that no long-term effects were evident based on previous reports,⁷ their written informed consent of no treatment was obtained. All patients were required to return to the hospital at least every 2 weeks after the initial visit. At every visit, they were interviewed and examined using the Dix-Hallpike maneuver and lateral head rotation in the supine position. After the disappearance of positional nystagmus, patients were asked to indicate the time at which the positional vertigo disappeared.

As statistical analysis, we used the Mann–Whitney U test. p Values less than 0.05 were considered significant.

Results.

Epidemiology.

P-BPPV was diagnosed in 70 patients (65%) and H-BPPV in 36 patients (33%). In patients with P-BPPV, 32 patients showed positional nystagmus triggered by the left Dix-Hallpike maneuver and 38 patients showed positional nystagmus triggered by the right Dix-Hallpike maneuver. Transition between P- and H-BPPV was found in 2 cases (2%).

Females outnumbered males 43 to 27 (61%) in P-BPPV and 21 to 15 (58%) in H-BPPV.

The peak age of patients was in the sixth decade in both P- and H-BPPV groups and there was no difference in age distribution between P- and H-BPPV groups. Patients in the age bracket between 51 and 80 years accounted for 77% (figure 1).

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Figure 1. The age distribution of patients with posterior semicircular canal benign paroxysmal positional vertigo (P-BPPV) and horizontal canal BPPV (H-BPPV).

Time courses of the remission of positional vertigo.

In 30% of patients with P-BPPV and 53% with H-BPPV, the vertigo disappeared within 7 days. In 36% of patients with P-BPPV and 11% with H-BPPV, the vertigo lasted more than 1 month. The average number of days from the onset to remission of the vertigo in patients with P-BPPV was 39 ± 47 days (n = 69). This number was 16 ± 19 days (n = 34) in H-BPPV (figure 2). The difference was significant (p = 0.0103).

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Figure 2. The number of days from the onset to remission of positional vertigo in patients with benign paroxysmal positional vertigo (BPPV). Open circles represent the number of the days of each case in the left side. The average number of days (filled circles), the median (horizontal bar), 25th and 75th percentiles (box), and extreme points (open circles) are indicated in the right side. P = positional vertigo; H = horizontal canal.

Discussion.

In the present study without CRP, the average number of days from the onset to the remission of the vertigo in patients with P-BPPV was 39 and with H-BPPV was 16. Thus, H-BPPV resolved significantly faster than P-BPPV. The spontaneous remission of BPPV is understandable from the viewpoint of the orientations of the canals. Indeed, according to the canalolithiasis hypothesis, movement of the head causes the otoconial particles to move in an ampullofugal direction, producing ampullofugal displacement of the cupula due to the plunger effect of the particles moving within the narrow canal.^1,2 Moreover, the posterior canal is inferior to the vestibule and has its copular barrier at its shorter, more dependent end. Any otoconial particle entering the canal becomes essentially trapped within it. In contrast, the lateral canal slopes up and has its cupular barrier at the upper end. Therefore, free-floating otoconial particles in the lateral canal would tend to float back into the utricle as a result of natural head movements.⁸ Another possible contributing factor to the spontaneous remission of BPPV is that endolymph, with its low calcium content (20 μM), is able to dissolve otoconia.³

In the present study, H-BPPV was not rare, and accounted for 33% of BPPV. We had recently reported a high incidence of H-BPPV, which accounted for 31% of BPPV, in another hospital in Japan.⁵ However, other reports have shown much lower frequency of the horizontal canal variant among BPPV patients, accounting for about 5 to 20% of all patients presenting with BPPV.^8,9 Differences between countries are unlikely, since the incidence of BPPV in vertigo patients, the age distribution, and the sex ratio reported previously from both Japan and other countries were almost the same.^4,8 However, the difference in the type of hospital might be a reason. Indeed, the two hospitals we investigated were both city hospitals, where most patients visit before consulting their home doctors and where emergency patients are also accepted 24 hours/day. In fact, over 50% of the patients with BPPV visited our hospital within 3 days of disease onset. Moreover, in most cases, H-BPPV resolved within 7 days and faster than P-BPPV. Therefore, it is possible that previous studies underestimated the number of patients with H-BPPV. There is also the possibility that previous findings may be biased by the long waiting period before the clinical assessment.⁸

The transition between P- and H-BPPV was found in two cases. Such canal transitions have been already reported.⁵ BPPV that involved both posterior and lateral canals in the same inner ear has also been reported.^8,10 These findings suggest that etiologies of both types of BPPV are essentially the same.^1,2,8