Experimental study of speed-dependent positional nystagmus in benign paroxysmal positional vertigo.
OBJECTIVE
One of the clinical characteristics of benign paroxysmal positional vertigo (BPPV) is that the more quickly the head position changes, the more severe the vertigo. This suggests that the velocity of the head change is critical in determining the occurrence and severity of vertigo. The aim of this study was to examine factors determining the symptoms of BPPV using models of canalolithiasis and cupulolithiasis.


METHODS
Canalolithiasis and cupulolithiasis models were prepared using the bullfrog posterior semicircular canal (PSC). The ampullary nerve discharges were compared between quick and slow positional changes to examine factors determining the symptoms of BPPV.


RESULTS
In the canalolithiasis model, the acceleration of the otoconia was greater for the quick positional change. This resulted in a greater discharge with a longer duration. With the slow positional change, the discharges were smaller and shorter. In the cupulolithiasis model, the discharges were sustained and their magnitude did not differ between the quick and slow positional changes. The canalolithiasis model influenced the magnitude of discharge of the PSC depending on the speed of the positional change.


CONCLUSIONS
Canalolithiasis is the more likely mechanism of BPPV, which is characterized by various degrees of vertigo upon kinetic positional change.
Furuya
Masayoshi
M
Department of Otolaryngology, Tokyo Medical University, Tokyo, Japan.
Suzuki
Mamoru
M
Sato
Harushiro
H
D000818:Animals; D007758:Ear, Inner / Q000294:innervation / Q000503:physiopathology*; D019416:Head Movements / Q000502:physiology*; D007759:Labyrinth Diseases / Q000503:physiopathology*; D020347:Lithiasis / Q000503:physiopathology; D023421:Models, Animal; D009760:Nystagmus, Physiologic / Q000502:physiology*; D011892:Rana catesbeiana; D014717:Vertigo / Q000503:physiopathology*; D000159:Vestibulocochlear Nerve / Q000502:physiology / Q000503:physiopathology