This person has benign paroxysmal positional vertigo (BPPV), which is characterized by sudden-onset brief episodes of vertigo lasting less than a minute. The symptoms are usually brought on by head movement. The cause is commonly attributed to calcium debris in the semicircular canals, known as canalithiasis. The debris is loose otoconia (calcium carbonate) within the utricular sac. Although BPPV can occur after head trauma, there is usually no obvious precipitating factor. It generally abates spontaneously and can be treated with vestibular rehabilitation. Basilar migraine can cause vertigo, but it is not brought on by movement, there is an associated headache and lasts longer than the 30 seconds noticed in this patient. Brainstem ischemic events or cerebellar tumors can cause vertigo but the symptoms are persistent and not intermittent. Finally, Meniere disease also causes vertigo but there is associated hearing changes, and the symptoms last longer than in BPPV.