During a Dix-Hallpike, what is the typical nystagmus for posterior canal BPPV?

• A. Downbeat nystagmus without torsion
• B. Horizontal nystagmus
• C. Upbeat and torsional nystagmus with the fast phase toward the affected ear
• D. Vertical nystagmus

Answer: (C)

During the Dix-Hallpike test, posterior canal BPPV produces an upbeating nystagmus with a torsional component. The fast phase of the eye movement is toward the ear on the side of the affected canal. This pattern arises because gravity moves the jelly-like debris (canaliths) within the posterior canal when the head is positioned back and turned, stimulating the canal and causing vertical (upbeat) and rotational (torsional) eye movements. Horizontal nystagmus points to horizontal canal involvement, while purely vertical or downbeat nystagmus suggests anterior canal BPPV or other etiologies. Hence, the characteristic response is upbeat and torsional nystagmus with the fast phase toward the affected ear.