Disorders of the inner ear are, for the most part, not visible through imaging and are not detected through blood tests. We get a limited and indirect view of inner ear function by evaluating the Vestibular-Ocular Reflex (VOR). These tests are fairly sensitive in determining the current status of the inner ear, but they rarely provide the ability to make a diagnosis without significant additional history information or access to other tests such as multiple audiograms.
The only vestibular disorder that can be diagnosed strictly as a result of vestibular testing is BPPV. The pattern, duration, and triggering position for nystagmus can be clearly diagnostic for BPPV.
Most often, the end result of a comprehensive vestibular evaluation (including detailed history) is the ability to determine the most likely cause of the patient’s symptoms, and the ability to determine the most logical next step. We don’t have the ability to be right 100% of the time, but we are also quite far from random speculation. We have to live with the fact that in order to be effective, we will occasionally be wrong. We make this clear to our patients.
Working in a university medical center is quite different from working in a community ENT/Audiology setting (which I did for many years). We don’t see many straightforward patients, or patients who have responded well to standard therapies. Our case load tends to be heavy with complicated patients with multiple issues, undiagnosed or unresolved symptoms. We see many patients who have been through various levels of vestibular diagnostic evaluation and testing.
Common Vestibular Diagnostic and Management Errors
While many of these tests are done properly, we do see some common and repeated diagnostic and management errors. Here are a few:
- Letting the computer pick the peak caloric response – We see tests where the peak response may be marked at 15 seconds following the irrigation in one ear, and 75 seconds in the other ear. The computer does not consider timing and just picks the area of strongest response.
- Telling patients that a vestibular problem has been “ruled out” based on a normal VNG exam- Arriaga and Chen (2005) report that rotational chair is much more sensitive than caloric testing in detecting vestibular dysfunction For more on this topic, click here.
- Telling patients that they have total vestibular loss if they have no response to caloric irrigation – Goebel and Rowdon (1992) reported that 2/3 of a group of patients with bilateral caloric hypofunction had normal high frequency VOR gain.
- Diagnosing “Central Vestibular Dysfunction” based on mild, symmetric ocular-motor abnormalities. Age, inattention, medication or visual deficits are common causes of ocular-motor abnormalities. These would not explain asymmetries, so asymmetries must be considered worrisome.
- Ruling out BPPV as a result of a negative Dix-Hallpike test – We did an in office study several years ago where we had patients with suspected BPPV, but negative Dix-Hallpike tests (D-H), come back the next day after immobilizing their head for a few hours before exam using a soft collar. Forty percent of these patients had a positive D-H on return. Some clinicians have found that repeating the D-H on the same day can increase the likelihood of a positive response in a significant portion of suspected BPPV patients.
- Treating all complaints of positional vertigo with the Epley Manuever – We have noted an increase in patients that have not improved with home Epley exercises, presenting with horizontal canal BPPV. Whether they were misdiagnosed or not diagnosed, or whether the home exercises deposited otoliths in the horizontal canal, is unknown.
- Giving the patient Brandt-Daroff exercises (BDE) for posterior canal BPPV – the home Epley maneuver has been shown to be significantly more effective than the Brandt-Daroff exercises, yet we still frequently see patients that have been given BDE for suspected BPPV. Keep in mind, that the BDE exercises were designed to habituate to the vertigo, not to reposition otoconia. They are not very effective at repositioning.
- Diagnosing patients with Meniere’s disease when they do not have temporally related unilateral auditory symptoms. We see many patients that have complained of episodic vertigo and also complain of bilateral tinnitus, but have no asymmetry on audiometry and have no documentation of fluctuating unilateral hearing loss or tinnitus, yet have been treated for years with diet and diuretics for Meniere’s disease.
- Failing to consider Vestibular Migraine – in 2017 in our clinic, 20% of those evaluated fit the criteria for probable Vestibular Migraine. This was the second largest diagnostic category (BPPV was the most common)
Fortunately, these errors are the exception rather than the rule. We all make errors on occasion, yet we must be open to discussing these issues in hopes of steady improvement and consistency in patient care.