Abstract
The benign paroxysmal positional vertigo of the horizontal semicircular canal is manifested with either geotropic or apogeotropic horizontal nystagmus. A 61-year-old male patient who experienced repeated episodes of positional vertigo is presented in this study. The vertigo was reported to be more severe while rotating his head to the left and then to the right. The initial examination revealed a geotropic purely horizontal nystagmus at the lateral positions of the head compatible with canalolithiasis of the left horizontal semicircular canal. In this case, the otoconia debris migrates from the vestibule into the horizontal semicircular canal through its nonampullary end, where they float freely (canalolithiasis). Five days later, the geotropic nystagmus transformed to apogeotropic. Thus, it may be assumed that the otoconia debris adhered to the cupula and converted the canalolithiasis to cupulolithiasis of the horizontal semicircular canal on the same side. With rotation of the head to the left while the patient was in the supine position, gravity causes the weighted cupula to deflect ampullofugally, resulting in apogeotropic nystagmus; the opposite was noticed when the head was rotated to the right. The so-called barbecue maneuver was initially effective curing the geotropic form of the condition and consequently the modified Semont maneuver for the apogeotropic form.
1
Case report
A 61-year-old male patient complained of repeated episodes of positional vertigo, nausea, and vomiting. Vertigo was more severe when he turned his head to the left. Clinically, in the supine position, he exhibited geotropic horizontal nystagmus when his head was rotated 90° to both lateral positions. Magnetic resonance imaging of the internal auditory canals and cerebellopontine angles (CPAs) did not show any abnormality. The patient underwent videonystagmography (VngPlusSC; Ecleris, Buenos Aires, Argentina). Spontaneous and gaze nystagmus were not noticed. While the patient was in supine position, turning the head to the left by 90°, a purely horizontal geotropic nystagmus was revealed with a slow-phase velocity (SPV) average of 3.21°s −1 ; turning the head to the right, a less intense geotropic nystagmus was revealed with SPV average 3.02°s −1 . The diagnosis of canalolithiasis of the left horizontal semicircular canal was thus confirmed, and the so-called barbecue maneuver was performed.
On reexamining the patient 5 days later, the positional nystagmus changed from geotropic to apogeotropic. On videonystagmography, when the patient turned his head to the right, the SPV average of the apogeotropic nystagmus was 8.28°s −1 and the SPV average of the nystagmus provoked by turning the head to the left was 5.05°s −1 . The duration of the nystagmus provoked by turning the head to the right was shorter than the other side (right, 17 seconds; left, 25 seconds). This finding suggested cupulolithiasis of the left horizontal semicircular canal. The modified Semont maneuver was then applied. The following day, the Hallpike test showed a brief torsional downbeating nystagmus compatible with left posterior benign paroxysmal positioning vertigo (p-BPPV); this nystagmus was immediately followed by horizontal apogeotropic nystagmus.
At the follow-up 1 month later, the patient was free of vertigo, and any nystagmus.
2
Discussion
In horizontal BBPV (h-BPPV), the geotropic nystagmus implicates the canalolithiasis mechanism. Rolling the head to the affected side while in the supine position results in displacement of the otoconial debris, which float into the horizontal semicircular duct, from its posterior part toward the anterior part. This movement produces utriculopetal endolymphatic current in the horizontal canal and results in a stronger response ( Fig. 1 B ) and vice versa when rolling the head to the healthy side ( Fig. 1 C). The geotropic postmaneuver nystagmus is usually more intense when the head is rotated to the pathologic side.
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