Abstract
Objective: Direction-changing positional nystagmus (DCPN) had been observed as persistent horizontal apogeotropic and was considered as “cupulolithiasis or heavy cupula. ” Recently, the concept of “light cupula” exhibiting persistent geotropic DCPN has been introduced. However, the light cupula is not systematically described, while the identification and diagnosis of “light cupula” should be improved. Here we investigated the underlying characteristics and therapeutic options designed to the “light” and “heavy” cupula, respectively; and summarized the clinical characteristics and therapeutic effect in the two groups.Methods: A total of 359 cases with vertigo and bilateral DCPN were found in the supine roll test. Only 25 patients with persistent DCPN were enrolled and followed up. According to the direction of nystagmus, we further divided the patients into “heavy cupula” (apogeotropic) and “light cupula” (geotropic) groups. We compared the incidence, characteristics of nystagmus and the efficacy of repositioning maneuver in the two groups.Results: Nine patients with persistent horizontal geotropic DCPN were confirmed as “light cupula,” other 16 patients with persistent horizontal ageotropic DCPN were confirmed as heavy cupula. All 25 patients had null plane; the mean value and standard deviation of the null plane in light cupula and heavy cupula was 25.67 ± 9.31° and 27.06 ± 6.29°, respectively. The mean value and standard deviation of the termination plane in light cupula was 28.78 ± 10.00°, and 30.25 ± 6.53° in heavy cupula. There was no statistical significance between the two groups. We found that the direction of evoked nystagmus in the supine position was toward the intact side in light cupula, while in heavy cupula, it was toward the lesion side. The null plane appeared on the lesion side. For light cupula patients, the effect was not obvious at Day-7 after the treatment, however, treatment for most heavy cupula patients were effective. All patients recovered after 30 days of treatment.Conclusion: The null plane is crucial in determining the lesion side for light or heavy cupula. Although the short-term therapeutic effect of the light cupula is not as promising as the effect seen in heavy cupula, the long-term prognosis in both groups is comparable; with all patients recovered after 30 days of treatment.Study design: This is a retrospective cohort study.
Highlights
Benign Paroxysmal Positional Vertigo (BPPV) is the most frequent episodic vestibular disorder
If the apogeotropic direction-changing positional nystagmus (DCPN) is persistent and lasts for more than 1 min, it is considered as cupulolithiasis or heavy cupula where the otolith debris may attach onto the cupula
We found that the rotational angle from the ceasing of nystagmus to re-appearance was about 2◦ (Figure 3) and was designated as null plane
Summary
Benign Paroxysmal Positional Vertigo (BPPV) is the most frequent episodic vestibular disorder. The BPPV horizontal semicircular canal recognizes two variants, conductolitiasis and cupulolithiasis, with the former being more frequently diagnosed (1). It has been reported that approximately 10–30% of BPPV originate from the horizontal semicircular canal (2). For patients with LSCC BPPV, direction-changing positional nystagmus (DCPN) is typically observed in a supine roll test. LSCC BPPV can be divided into horizontal apogeotropic DCPN and geotropic DCPN. If the apogeotropic DCPN is persistent and lasts for more than 1 min, it is considered as cupulolithiasis or heavy cupula where the otolith debris may attach onto the cupula. The duration of the most of evoked geotropic nystagmus was less than 35 s and relatively gradually weakened or disappeared after positional examination, which is commonly considered as canalithiasis
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