Abstract
Objective: To evaluate horizontal semicircular canal (HSC) effects according to Ewald's law and nystagmus characteristics of horizontal semicircular canal benign paroxysmal positional vertigo (HSC-BPPV) in the supine roll test.Methods: Patients with HSC-BPPV (n = 72) and healthy subjects (n = 38) were enrolled. Latency, duration, and intensity of nystagmus elicited by supine roll test were recorded using video nystagmography.Results: In patients with HSC-BPPV, horizontal nystagmus could be elicited by right/left head position (positional nystagmus) and during head-turning (head-turning nystagmus), and nystagmus direction was the same as that of head turning. Mean intensity values of head-turning nystagmus in HSC-BPPV patients were (44.70 ± 18.24)°/s and (44.65 ± 19.27)°/s on the affected and unaffected sides, respectively, which was not a significant difference (p = 0.980), while those for positional nystagmus were (40.81 ± 25.56)°/s and (17.69 ± 9.31)°/s (ratio, 2.59 ± 1.98:1), respectively, representing a significant difference (p < 0.0001). There was no positional nystagmus in 49 HSC-BPPV patients after repositioning treatment, nor in the 38 healthy subjects. No significant difference in head-turning nystagmus was detected in HSC-BPPV patients with or without repositioning.Conclusions: The direction and intensity of nystagmus elicited by supine roll test in patients with HSC-BPPV, was broadly consistent with the physiological nystagmus associated with a same HSC with single factor stimulus. Our findings suggest that HSC-BPPV can be a show of Ewald's law in human body.
Highlights
Benign paroxysmal positional vertigo (BPPV), the most common peripheral vestibular disorder, is characteristic by recurrent attacks of brief positional vertigo and nystagmus elicited by a change in head position relative to gravity [1]
HSC-BPPV could reflect the direction and intensity of the nystagmus elicited by equal excitation and inhibition on a single horizontal semicircular canal, and clarify the gradient of those effects, which will be helpful in understanding the functional status of single horizontal semicircular canals
The supine roll test was performed on both sides for all patients with HSC-BPPV and controls, among which 49 cases with HSC-BPPV underwent successful repositioning using the barbecue maneuver
Summary
Benign paroxysmal positional vertigo (BPPV), the most common peripheral vestibular disorder, is characteristic by recurrent attacks of brief positional vertigo (dizziness) and nystagmus elicited by a change in head position relative to gravity [1]. Richard Ewald conducted more elaborate experiments in 1892 [4]. He observed the intensity and direction of nystagmus by inserting a small tube into the semicircular canal of the pigeon and applying positive and negative pressure. Flourens’ and Ewald’s Laws play an important role in our understanding of the physiology of human semicircular canals and the diagnosis of vestibular disorders. Both were derived from animal experiments, while a functional model of a single semicircular canal has not been established in human body
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