Conversion of canalolithiasis to cupulolithiasis in the course of a horizontal benign paroxysmal positional vertigo case.

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.