PP1412 - Otolith Dysfunction May Be More Common than Other Vestibular Disorders in Patients with Chronic Dizziness

Abstract:
We performed a retrospective study on 99 patients who performed our advanced vestibular battery tests. We determined that 1) Unilateral centrifugation (UC) is the most sensitive test, 2) otolith dysfunction may be more common than other peripheral disorders in patients with chronic dizziness, and 3) UC, static subjective visual vertical (SVV), ocular and cervical evoked myogenic potentials (oVEMP/cVEMP), and video head impulse test (vHIT) are important chronic dizziness diagnostic tests. Upon completion, learners will be able to analyze the findings of patients with chronic dizziness and appreciate the importance of comprehensive vestibular testing in the diagnosis of chronic dizziness/vertigo patients.

Summary:
The instructional level was chosen as "advanced" because this content requires understanding of inner ear structures and typical vestibular testing batteries used in clinical practice.

Objective
Most vestibular laboratories in the United States only have rotary chair (RC) and caloric testing in addition to hearing tests. These tests mainly examine the horizontal canal which makes up about one-third of vestibular functions. The current study is to determine if more extensive peripheral vestibular testing (Advanced Videonystagmography-AVG) can help differentiate the underlying etiologies of patients with chronic dizziness. AVG includes unilateral centrifugation (UC-dynamic SVV), subjective visual vertical (static SVV), ocular and cervical vestibular evoked myogenic potentials (oVEMP/cVEMP), and video head impulse test (vHIT) in addition to caloric testing, rotary chair (RC), and computerized dynamic posturography (CDP).

Methods
The study included 99 patients with chronic dizziness (for more than 3 months) who performed AVG (SVV, UC, oVEMP/cVEMP, vHIT, caloric testing, RC, and CDP). Average age of patients was 57.9 years (± 1.57) with 43 males and 56 females. SVV, UC, oVEMP/cVEMP are designed to test otolith function; vHIT, RC, and CDP primarily test semicircular canal and other peripheral vestibular functions. Patients diagnosed with benign paroxysmal positional vertigo were excluded from the study.

Results
38 patients were unable to complete UC testing due to dizziness or fear of dizziness. In 61 patients that completed UC testing, 79% of patients were abnormal, either unilaterally or bilaterally. VEMPs, RC, CDP, Calorics, vHIT, and SVV had abnormal result percentages of 63%, 41%, 32%, 32%, 21%, and 12%, respectively.

UC, SVV, and oVEMP/cVEMP abnormal results are indicative of otolith dysfunction, and their combined abnormal percentage in all 99 patients was 70%. 18 patients (18.2%) could not perform UC testing but had normal results for SVV and oVEMP/cVEMP. There is a high probability that those 18 patients would have an abnormality rate of 79% or more if tests were able to be performed.

In a subgroup of PPPD patients, 30% exhibited otolith dysfunction from UC testing alone, and 50% exhibited otolith dysfunction when combined with SVV and oVEMP/cVEMP abnormalities.

Conclusion
1) UC-dynamic SVV may be the most sensitive vestibular test, producing the highest probability of abnormal results in patients with chronic dizziness.
2) Furthermore, otolith dysfunction may be much more common than other peripheral disorders in patients with chronic dizziness.
3) AVG including UC, SVV, oVEMP/cVEMP, and vHIT testing in addition to traditional caloric testing, RC, and CDP may provide better chances of diagnosing underlying etiologies for patients with chronic dizziness.