head 90° to the left side, and checks for vertigo and nystagmus. This is followed by gently bringing the head back to the starting position. The examiner then quickly rotates the head 90° to the right side and checks again for vertigo and nystagmus. In this roll test, the person may experience vertigo and nystagmus on both sides, but rotating toward the affected side will trigger a more intense vertigo. Similarly, when the head is rotated toward the affected side, the nystagmus will beat toward the ground and be more intense. As mentioned above, both the Dix–Hallpike and roll test provoke the signs and symptoms in subjects with archetypal BPPV. The signs and symptoms people with BPPV experience are typically a short-lived vertigo and observed nystagmus. In some people, although rarely, vertigo can persist for years. Assessment of BPPV is best done by a medical health professional skilled in the management of dizziness disorders, commonly a physiotherapist, audiologist, or other physician. The nystagmus associated with BPPV has several important characteristics that differentiate it from other types of nystagmus. Latency of onset: there is a 5–10 second delay prior to onset of nystagmus Nystagmus lasts for 5–60 seconds Positional: the nystagmus occurs only in certain positions Repeated stimulation, including via Dix–Hallpike maneuvers, cause the nystagmus to fatigue or disappear temporarily Rotatory/torsional component is present, or (in the case of lateral canal involvement) the nystagmus beats in either a geotropic (toward the ground) or ageotropic (away from the ground) fashion Visual fixation suppresses nystagmus due to BPPV Although rare, CNS disorders can sometimes present as BPPV. A practitioner should be aware that if a person whose symptoms are consistent with BPPV, but does not show improvement or resolution after undergoing different particle repositioning maneuvers — detailed in the Treatment section below — need to have a detailed neurological assessment and imaging performed to help identify the pathological condition. Differential diagnosis Vertigo, a distinct process sometimes confused with the broader term, dizziness, accounts for about six million clinic visits in the United States every year; between 17 and 42% of these people are eventually diagnosed with BPPV. Other causes of vertigo include: Motion sickness/motion intolerance: a disjunction between visual stimulation, vestibular stimulation, and/or proprioception Visual exposure to nearby moving objects (examples of optokinetic stimuli include passing cars and falling snow) Other diseases: (labyrinthitis, Ménière's disease, and migraine, etc.) Treatment Repositioning maneuvers A number