During the Dix-Hallpike maneuver in BPPV, the patient will exhibit which type of nystagmus?

In Benign Paroxysmal Positional Vertigo (BPPV), the Dix-Hallpike maneuver is utilized to provoke symptoms and observe the nystagmus that occurs in response to changes in head position. In cases of BPPV, particularly when involving the posterior semicircular canal, the nystagmus you would expect to observe is predominantly a horizontal and torsional pattern.

The horizontal component of the nystagmus is due to the way the otoliths (calcium carbonate crystals) become displaced and interact with the fluid in the semicircular canals, thus causing abnormal stimulation of the vestibular apparatus. The torsional component is also commonly observed because of the orientation of the canal and the nature of how the nystagmus manifests as the patient’s head is positioned.

This knowledge of the characteristic nystagmus during the maneuver is critical for the accurate diagnosis of BPPV and differentiating it from other vestibular disorders. Other types of nystagmus, such as purely vertical or different combinations of movements, would suggest other vestibular pathologies rather than classic BPPV involving the posterior canal.