Nystagmus with upbeat torsion indicates which canal may be involved in BPPV?

Nystagmus with upbeat torsion is specifically indicative of involvement with the posterior canal in benign paroxysmal positional vertigo (BPPV). This form of nystagmus occurs when the otoliths dislodge from the utricle and migrate into the posterior semicircular canal, leading to unique positional vertigo symptoms characterized by movements triggering episodes of vertigo. The "upbeat" component of the nystagmus signifies that the fast phase of the eye movement is directed upwards, while the torsional aspect indicates that there is a rotational component that tends to be towards the affected side, consistent with posterior canal involvement.

In the context of BPPV diagnosis and treatment, recognizing this type of nystagmus is crucial for clinicians. It helps in confirming that the issue is localized to the posterior canal. Therefore, if a clinician observes upbeat torsional nystagmus during examination, it provides strong evidence to support the diagnosis associated with the posterior canal, guiding appropriate treatment strategies such as the Epley maneuver tailored specifically for this condition.