Do you ever find it difficult to see the torsional component of nystagmus with the Dix-Hallpike test? At times we have, and it can be concerning given the possibility of the vertical nystagmus being indicative of a central vestibular disorder. There is, however, a clinical trick to help tease out any torsional component.
As the video in this blog reviews, the nystagmus with BPPV is in the same plane as the semicircular canal that is affected. So, with being able to understand the orientation of the canals we can bias the nystagmus to reveal the torsional component and if need be the vertical component.
To see more of the torsional component with BPPV affecting either the posterior or anterior canal, all the patient needs to do is simply look in the direction perpendicular to the plane of the affected canal.
The below chart outlines the effect of lateral gaze with Dix-Hallpike testing.
So, with BPPV affecting the right posterior canal the torsional nystagmus will be more noticeable with Dix-Hallpike testing to the right and right gaze.
With BPPV affecting the right anterior canal the torsional nystagmus will be more noticeable with Dix-Hallpike testing (can actually be to either side) and left gaze.
If lateral gaze in either direction does not elicit torsional nystagmus, then a central vestibular disorder should be considered.
We hope that this gives you a simple tool to help you tease out any torsional component of the nystagmus. That being said, any test should not be used alone, but rather compliment the history and other findings.
If you have any questions regarding the above, please feel free to contact us at North 49.