A 60-year-old man presents to his primary care physician complaining that he often feels as if the room is spinning when he gets up from a recumbent position or turns his head. He has not lost consciousness and has had no chest pain. He has no cardiac history, and a recent treadmill test showed no abnormalities. On examination, the sensation can be produced by rapidly turning the head. It can be reproduced many times, but it eventually ceases. Nystagmus is elicited. Hearing is normal. Which of the following is the MOST likely mechanism for this patient's symptoms?
In benign paroxysmal positional veigo, calcium carbonate crystals called otoliths, which are usually fixed in a gelatinous otolithic membrane, float freely in the endolymph. Usually, movement is sensed by the movement of this heavy membrane as it stimulates hair-like projections on sensory hair cells fixed to the membrane in the inner ear. In BPPV, the loose crystals aberrantly stimulate the hair cells with ceain head movements. Thus the sensation of veigo is produced. Hair cell death does not cause veigo. Insufficient cardiac output and cerebral blood flow lead to syncope, not veigo.
Aberrant stimulation of hair cells
Hair cell death in the semicircular canals
Insufficient cardiac output
Insufficient cerebral perfusion