Fig. 2.

Left posterior cupulolithiasis. The otoconia adhere to the cupula of the left posterior canal creating a heavy cupula. This patient had an acute vestibular syndrome and secondary BPV. In the upright position, low velocity right-beating nystgamus is seen, consistent with the left unilateral vestibular loss. During the left Dix-Hallpike test, the cupula is deflected away from the ampulla due to its increased mass, causing excitation of the left posterior canal and generating an upbeating leftward torsional nystagmus. The nystagmus slow phase velocity (SPV) profile shows an immediate onset of nystagmus that rises to a peak, gradually decays but persists for more than one minute.