Common disorders affecting vestibular and balance- 50% of people over 70 have had BPPV. Saccule and Utricle sense forward, back, up and down movement- gravity sensors. Otoconia come from the utricle where they belong. Semi-circular canals are not suppose to sense gravity, just angular movement, but they do when otoconia are displaced. Fall risk goes up 3-fold with BPPV. Can happen at any age- At ABI they have treated patients 8-108. Head injury can cause a chunk of debris to fall off at once. Increased risk of bilateral in patients post-head injury.