Positional vertigo related to semicircular canalithiasis

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Abstract
My clinical and laboratory observations support the theoretical concept that the mechanism of typical nystagmus, and most forms of atypical transient nystagmus, is hydrodynamic drag by gravitating free densities--most commonly displaced otoconia--in the endolymph of a semicircular canal; and that these "canaliths" have a significant mechanical advantage, by virture of the canal/ampulla cross-sectional differential, over densities acting directly on the cupula. Positional vertigo related to apparent canalithiasis (benign paroxysmal positional vertigo) is a common cause of incapacitation. The profile of the concomitant nystagmus localizes the semicircular canal involved. The canalith repositioning procedure, appropriately administered and targeted according to the observed nystagmus, provides a highly effective means for control of symptoms and a valuable resource for diagnostic evaluation of the more complex case. Surgery is rarely indicated.