Question
If horizontal nystagmus is present during positional testing, and also seen during the Dix-Hallpike, (a)what is the correct way to report it? I thought it was not BPPV unless torsional (rotational) nystagmus was seen in the Dix-Hallpike, with a slight delay, and that the patient must perceive vertigo. (b) Must each of these 3 be present for the Dix-Hallpike to be positive? Today's patient had geotropic positional nystagmus, also seen during the Dix-Hallpike. I reported the Dix-Hallpike as negative as it appeared to be just the same positional nystagmus--not torsional, no sensation of dizziness, etc.; the vestibular rehab physical therapist insists patient has horizontal BPPV. (c) How does one diagnose horizontal BPPV? (d) How does one report the finding if positional and a true Dix-Hallpike are present?
Answer
The first thing to do is determine whether the horizontal nystagmus is positional or positioning. In other words, does the nystagmus persist as long as the patient stays in the provocative position (positional), or does the nystagmus decrease within the first minute or two (positioning). If the nystagmus decreases with time, then the high probability is that the nystagmus represents a form of BPPV, probably horizontal canal. If so, the direction of the horizontal nystagmus should change when changing head position. If the nystagmus persists, check to see if it is diminished by visual fixation. If so, this would represent a persistent labyrinthine asymmetry to the provocative position. The nystagmus associated with BPPV is not significantly affected by fixation.
Unfortunately, BPPV takes many forms, and is not quite as simple as the description you have been given. The most common form of BPPV (Posterior canal) fits your description; however, 5 to 10% of BPPV patients have the horizontal canal variant. Additionally, some patients with BPPV will be inactive at the time of exam due to fatiguing of the response. They will have none of the above signs and symptoms, but may still be suffering from BPPV. The provisional diagnosis of BPPV is made based on the patient's description of symptoms, lack of any other identifiable pathology, and positive response to home provocation exercises.
In your particular patient's case, the following questions would need to be answered to have a better idea of specific pathology:
- You say the patient had "geotropic positional nystagmus" which I assume were horizontal. What did you see when the patients head was rolled to the opposite side? In horizontal canal BPPV, you should have seen a direction change. When the horizontal nystagmus is geotropic, the BPPV is suspected to be canalithiasis, occurring on the side with the more intense nystagmus.
- Did the nystagmus diminish on visual fixation?
The second scenario (d), with a typical Dix-Hallpike response might go like this: Dix-Hallpike (dynamic positioning) test to the left elicited rotary nystagmus and subjective vertigo consistent with benign paroxysmal positional vertigo of the left posterior semicircular canal. Following the transient BPPV response, a persistent left beating horizontal nystagmus was present throughout static positional testing.
Alan Desmond, Au.D is the director of Blue Ridge Hearing and Balance Clinic in Bluefield and Princeton, WV. Thieme Medical Publishers released his book Vestibular Function: Evaluation and Treatment in April 2004. He can be reached at BRHBC@comcast.net