The Chinese Medical Association Branch of Otolaryngology and the Editorial Committee of the Chinese Journal of Otolaryngology-Head and Neck Surgery formulated the diagnostic basis of BPPV at their 2006 meeting in Guiyang as follows: I. Variable position test for diagnosing BPPV 1. Dix-Hallpike or Side-lying test: It is a common method to determine BPPV in the posterior or anterior semicircular canal. 2.Rolling test (roll maneuver): It is the most common method to determine the BPPV of the external hemiregular canal. 1. Nystagmus characteristics of BPPV in posterior hemiregular canal BPPV: the patient’s head is turned 45° to the affected side and then quickly lies down, so that the head hangs under the bed and makes an angle of 20°~30° with the bed plane, and the vertical torsional line nystagmus (vertical component to the upper pole of the eye, torsional component to the ground), which is marked by the upper pole of the eye, appears when the affected ear is turned toward the ground; the direction of nystagmus is reversed when the patient returns to the sitting position. The duration of nystagmus is <1min in tubular calculi; the duration of nystagmus is ≥1min in crestal cap calculi. 2. Characteristics of nystagmus in anterior hemianopia BPPV: The patient's head is turned 45° to the affected side and then quickly lies down, so that the head hangs under the bed, making an angle of 20°~30° with the bed plane, and vertical torsional nystagmus (vertical component to the lower pole of the eye, torsional component to the ground) occurs when the affected ear is directed to the ground, marked by the upper pole of the eye. The direction of the nystagmus is reversed when the patient returns to a sitting position. The duration of nystagmus in tubular calculi is <1min; in crestal cap calculi, the duration of nystagmus is ≥1min. 3. Characteristics of nystagmus in external hemianopia BPPV: tubular calculi can induce groundward or dorsal horizontal nystagmus in bilateral varus examination, and the duration of nystagmus is <1min; in crestal cap calculi, dorsal horizontal nystagmus can be induced in bilateral varus examination, and the duration of nystagmus is ≥1min. 3. Diagnostic basis 1. The history of transient vertigo with head movement to a specific position; varus nystagmus test shows the above nystagmus characteristics with short latency (<30s) and fatigue.