When you think of the five senses, you are probably not thinking “vestibular.” Divya Chari, MD, does, and she wants you to know that the inner ear does more than hear; it’s also critical to how we perceive our body in space. Armed with pilot funding from our Five Senses: Input and Response opportunity, the Massachusetts Eye and Ear otologist is already shining new light on the forgotten child of sensory disorders, vestibular dysfunction.
An estimated 11 to 20 percent of adults have vestibular dysfunction, which can interfere with activities of daily living and worsen quality of life. Diagnosis presents a clinical challenge, and without more exacting diagnostics, treatment is a trial-and-error slog that steals time from patients.
Chari’s approach straps patients into a moving, tilting, rolling chair for a battery of tests designed to pinpoint the precise source of the problem – with the long-term goal of treating it right the first time.
What drives your interest in studying vestibular disorders?
Our goal is to improve the diagnostics of vestibular disorders and tailor treatment. Symptoms of vestibular disorders overlap considerably, so a major focus of our lab is to understand why a patient is having symptoms and to differentiate vestibular disorders from one another.
Vestibular disorders often get ignored in research on sensory dysfunction, even though they affect a significant portion of the population. As an otologist, I spend a great deal of my clinical time treating patients with hearing loss, which affects so many people. But hearing is not the only thing that the inner ear does. Many of those patients also suffer from symptoms of dizziness, imbalance, and vertigo that lead to significant morbidity and reduced quality of life. Paying attention to those symptoms is important.
“Vestibular disorders often get ignored in research on sensory dysfunction, even though they affect a significant portion of the population.”
There’s still so much we don’t know about the inner ear. Acute or chronic vestibular disorders can be more readily identified by the damage they cause, but many vestibular disorders are episodic in nature, meaning that people might have symptoms some days but not on others. The episodic nature of symptoms can make it challenging to come to a definitive diagnosis.
Meniere’s disease and vestibular migraine are two disorders that pose a particular challenge because they have similar symptoms and a high rate of co-occurrence, with an estimated 20 percent of patients meeting diagnostic criteria for both. Although treatments exist for both disorders, the treatments are very different.
How might this work change clinical practice?
That’s the million-dollar question, and I think this is where our test battery has the potential to have a large impact.
Currently, we rely on clinical history for diagnosis. We ask questions about symptoms, then apply a defined set of clinical consensus criteria to the answers. That process is highly variable. It’s very patient-dependent and provider-dependent. We need better diagnostic tools to help us understand, diagnose, and tailor our treatments.
If we can better differentiate definite Meniere’s from definite migraine, we might also be able to identify patients in the middle. Our hope is that this can be more broadly applied to a larger group of patients with vestibular dysfunction and inner-ear disease.
Right now, we have a number of treatments for vestibular migraine, and other treatments for Meniere’s disease, but we often don’t know which one to use. We’ll try one and if that doesn’t work, we try another, and so on. It’s trial-and-error.
Getting to a more definitive diagnosis quicker allows us to tailor treatment more effectively. That has the potential to decrease suffering and improve the patient’s quality of life much more quickly.
Your approach seeks to capture “perceptual thresholds” as clues to vestibular function. How does that work?
Thresholds have long been applied to the auditory system to aid in diagnosis. Someone experiencing hearing loss will typically undergo an audiogram, a hearing test in which the volume of a sound is progressively increased until the patient detects it. That is a measure of the patient’s perceived threshold of hearing.
We don’t have an analogous test for the vestibular system. Conventional vestibular testing is imperfect, because we don’t have a good test that allows us to look at different parts of the inner ear. Our goal is to create a measure of vestibular function from the patient’s perception, using a direct physiologic stimulus.
Practically, how it works is that the patient is strapped into a specially designed, elevated chair that moves in different directions — right and left, up and down, forward and backward – and also can roll or tilt from side to side. As the chair moves, the patient tells us when they perceive movement and in which direction. In that sense, it’s similar to the audiogram, but instead of sound perception, we’re identifying their thresholds for specific motions.
“Getting to a more definitive diagnosis quicker allows us to tailor treatment more effectively. That has the potential to decrease suffering and improve the patient’s quality of life much more quickly.”
There’s fairly good evidence that decreased vestibular function is associated with higher thresholds for certain motions. We can glean information about how each part of the inner ear is functioning based on which movements are more challenging for the patient to identify. That in turn gives us clues to the diagnosis.
We have also been performing specialized inner ear magnetic resonance imaging (MRI) scans on people with Meniere’s disease. These scans have the potential to give us information about anatomic changes within the inner ear due to the disease process. Previously, researchers could only learn this information from cadavers. We can then correlate imaging findings with our perceptual threshold measurements to improve diagnostics and guide treatments for patients.
What clues are you getting about the pathophysiology of these conditions?
Classically, vestibular migraine was thought to be a central diagnosis, meaning that it is produced by the brain. Meniere’s disease is thought to be a peripheral disease process, a problem of the inner ear. We think these perceptual threshold measurements can help sort out differences between the disorders and shed light on the mechanisms involved in the two conditions.
We’ve already found some interesting results. Patients with Meniere’s disease seem to have highly elevated thresholds for certain movements that suggest damage to the otolith organs of the inner ear, which sense movement in certain planes. In addition, these elevated thresholds, which translate clinically to worse inner ear function, seem to correlate with our imaging findings.
In contrast, vestibular migraine patients have difficulty with some of the more complex movements, such as being rotated at the same time they’re being tilted or moved downwards. Their problem seems to be more related to the integration of information coming from the inner ear’s semicircular canals and otolith canals.
You’re a young investigator as well as a young mother. How do you manage work-family balance?
Not without a lot of help! We’re fortunate to have really great childcare, and parents who come visit often and help out immensely. And I think having a supportive spouse who is on the same page is really helpful. My husband and I really work together to make sure that we’re able to achieve our ambitions for our careers and our family.
Outside of science, I like to spend time in the outdoors with my family–my husband, our two-year-old daughter, and our dog Frankie–hiking and biking in the summer and skiing in the winter. We just love Massachusetts!