includes the otolith organs, the utricle and saccule, that contain calcium carbonate crystals(otoconia) that are sensitive to gravity. The crystals may dislodge from the utricle (an otolith organ) and settle within the semicircular canals. When there is motion, the displaced otoconia shift within the endolymph of semicircular canals, causing an unbalanced (with respect to the opposite ear) stimulus, causing symptoms of BPPV. Diagnosis The condition is diagnosed by the person's history, and by performing the Dix–Hallpike test or the roll test, or both. The patient can also be asked to induce vertigo by performing a movement that the patient knows to induce vertigo. The eyes of the patient can then easily be observed for which kind ( horizontal, vertical, or diagonal ) of nystagmus is present, to determine which semicircular canal ( horizontal, superior, or posterior ) is affected. The Dix–Hallpike test is a common test performed by examiners to determine whether the posterior semicircular canal is involved. It involves a reorientation of the head to align the posterior semicircular canal (at its entrance to the ampulla) with the direction of gravity. This test will reproduce vertigo and nystagmus characteristic of posterior canal BPPV. When performing the Dix–Hallpike test, people are lowered quickly to a supine position, with the neck extended by the person performing the maneuver. For some people, this maneuver may not be indicated, and a modification may be needed that also targets the posterior semicircular canal. Such people include those who are too anxious about eliciting the uncomfortable symptoms of vertigo, and those who may not have the range of motion necessary to comfortably be in a supine position. The modification involves the person moving from a seated position to side-lying without their head extending off the examination table, such as with Dix–Hallpike. The head is rotated 45 degrees away from the side being tested, and the eyes are examined for nystagmus. A positive test is indicated by the patient report of a reproduction of vertigo and clinician observation of nystagmus. Both the Dix–Hallpike and the side-lying testing position have yielded similar results, and as such the side-lying position can be used if the Dix–Hallpike cannot be performed easily. The roll test can determine whether the horizontal semicircular canal is involved. The roll test requires the person to be in a supine position with their head in 30° of cervical flexion. Then the examiner quickly rotates the