Otolith dysfunction common among patients with dizziness

Among patients who present to the hospital with dizziness, the prevalence of isolated otolith dysfunction (iOD) is high, according to a recent Singapore study, which emphasizes the need for a more routine performance of laboratory tests of otolith function.

“This can be done in a sequential way to optimize cost effectiveness in countries with no insurance reimbursement,” the researchers said. “Prospective cohort studies on isolated otolith dysfunction will lay the groundwork for achieving diagnostic consensus and formulating rehabilitation plans to aid this group of patients.”

The retrospective chart review included 206 patients (age 17–82 years, 139 men) who presented with dizziness to the Otolaryngology Clinic of the Changi General Hospital in Singapore. Following vestibular laboratory investigation, more than half (52.4 percent; n=108) were found to have either iOD or probable iOD. [J Otol 2022;17:5-12]

OD was diagnosed either symptomatically (SxOD), marked by the presence of disequilibrium, floating, rocking, or swaying, or through laboratory (LabOD) findings using vestibular evoked myogenic potential (VEMP). Patients positive for SxOD and LabOD were given a definitive diagnosis, while those who were positive for only SxOD or LabOD were said to have probable iOD.

Of the 108 patients, 25 were positive in both SxOD and LabOD and were identified to have definite iOD. In comparison, 52 had abnormal VEMP but showed no symptoms, while 56 were symptomatic for iOD but had unremarkable lab findings.

Notably, there was a significant link between being symptomatic for iOD and showing abnormal VEMP results. Patients who were positive in SxOD were >60 percent more likely to also be positive in LabOD (odds ratio, 1.62, 95 percent confidence interval, 1.25–4.13; p=0.01).

“It is not uncommon to find patients presenting clinically with complains of swaying, rocking, tilting, floating, and disequilibrium,” the researchers said. Though such symptoms are not automatically indicative of OD, they may be warning signs of an isolated deficit of the otolith organs, particularly when backed by laboratory findings.

The present study confirmed that this is a relatively common scenario, detected in about half of patients with such symptoms despite VEMP not being a routinely performed test. “If VEMP were deferred, diagnosis of probable or definite iOD in more than half of the 206 patients would have been missed,” said researchers.

However, they recognized that not all medical systems may be able to handle the economic impact of routine VEMP. “Hence, clinicians have to be prudent with selection of procedures to minimize the patients’ out-of-pocket cost,” the researchers said. “It is therefore advisable in our local context to sequentially carry out vestibular assessment based on the test results obtained at each stage to optimize cost-effectiveness and time.”

For instance, when a patient shows unremarkable findings in most tests, including videonystagmography, it may not be worth undergoing VEMP, as the likelihood of iOD is low. But since clinical signs of iOD are linked with a significantly higher likelihood of abnormal lab findings, VEMP may be beneficial in these cases.

“Continuous and further refinement of iOD diagnosis will lay the groundwork for the eventual conceptualization and development of rehabilitation strategies for patients with OD,” they said. “Further refinement of iOD should also include the concept of isolated otoconia loss as a possible explanation.”