Vestibular System Function and Dysfunction
The human vestibular system has four primary functions. Thereby, vestibular dysfunction causes four primary problems. In this blog, I will discuss four functions of the vestibular system. For each function, I will describe the associated dysfunction when something has gone wrong.
Steady Upright Posture
The vestibular system allows vertebrates – including humans, to orient themselves upright considering the pull of gravity. Another term for a steady upright posture is postural stability.
This postural stability driven by vestibular system function occurs whether we are sitting upright or standing up. Vestibular function senses the constant pull of gravity when we are at rest. The vestibular system also senses the gravito-inertial forces we experience when we are in motion within a gravitational field.
My surfer and skater patients affectionately call these “G-forces.”
By sensing all these G-forces, our vestibular system function allows us to sit up straight or stand upright steadily. Proper vestibular system function assures our stable, steady, upright postural stability. Steady standing driven by proper vestibular system function can be affected if our vestibular system is not working properly.
For example, patients with vestibular dysfunction may feel tilted when they are upright, or conversely, they may feel like they are straight upright when we can see that they are holding themselves tilted at an angle.
Patients with vestibular dysfunction may feel wobbly or experience disequilibrium when upright.
This is called postural instability. If the vestibular problem is significant, the patient may not be able to hold themselves upright without help while sitting or standing.
Other patients with postural instability are alright when left alone, but become unstable when challenged under certain conditions. Some examples of challenging conditions include visually complex or moving environments and uneven surfaces.
Vestibular rehabilitation or vestibular rehab is effective in improving postural instability.
Walking a Straight Path
Vestibular system function allows us to walk straight from Point A to Point B, without going off our intended straight path. We feel the equilibrium that we have from postural stability is still present while we are in motion walking.
This vestibular system function is called gait stability or steadiness with walking. With normal vestibular system function, most people can walk straight with a normal step length and keep their feet a normal distance apart.
In contrast, vestibular patients will frequently state that they feel like they are drunk when they are walking. They may notice that they veer right or left. Patients with vestibular problems may have trouble walking a straight path. They often express worry about getting pulled over while driving and failing a field sobriety test if administered by police.
To compensate for vestibular dysfunction, patients may shorten their step length or spread their feet wider apart. These are strategies some patients use to compensate for gait instability or unsteadiness with walking. Some patients may even use an assistive device like a cane or walker, or walking poles (trekking poles) to prevent falls.
Vestibular rehab, or vestibular physical therapy, can help with unsteady walking or gait instability.
Seeing Clearly when Moving Quickly
The vestibular system functions in pairs of end organs in the inner ear. Some of these pairs of vestibular end organs are likewise paired with muscles that control the movement of our eyes. Within these vestibular and eye muscle pairs, the pull of G-forces affects the position and motion of muscles that control the position of our eyes within the orbit.
This allows us to see clearly, especially when we are moving fast. These sensory end organs are therefore able to affect the way we position our eyes when we are moving. This vestibular system function is called gaze stability or gaze stabilization.
For example, when we turn our heads quickly to track a baseball on the way over home plate, it should not get out of focus. This ability to see clearly when our head is moving is a vestibular system function.
Another example is when a ballerina or figure skater is twirling their whole body during a fast move. The ability to keep the vision in focus when moving the whole body quickly is a vestibular system function.
The vestibular system allows us to see clearly whether our head alone is moving quickly or our whole body is moving quickly. When the vestibular system dysfunction is present, vision may get out of focus while we are moving. This specific problem is called oscillopsia and is a symptom of vestibular impairment. This may also be described as an unstable gaze or gaze instability.
Some patients experience blurry vision. Other patients describe a vision lag or visual echo effect. This problem can feel like their vision is just catching up to their head after they stop moving.
Some patients even see wavy lines when they know their visual target has straight lines. Stationary objects can also appear to be moving. All of these visual problems are descriptions of vestibular dysfunction that can be improved with vestibular rehab, or vestibular PT.
Navigating our Direction when on the Move
The vestibular system gives us a sense of direction, as well as our current position and perception of our motion in space. This is all accomplished by sensing the G-forces as they pull on our vestibular system sensory organs within our inner ears.
For example, if you get up to go to the bathroom in the dark, you may be able to tell which way you are walking even though you cannot see your path. This example partly relies on the vestibular system to help us delineate where we are and which way we are going when we cannot see.
This task would be even further complicated if our bedroom has a shag carpet that is soft on the bottom of our feet. Walking on a shag carpet in the dark is a demanding vestibular task. I do not recommend walking to the bathroom in the dark due to the risk of falling.
I was just giving you an example so you can understand how the vestibular system helps us navigate our direction when we are on the move.
The vestibular system senses our position and perceives our motion to help us navigate. In contrast, vestibular dysfunction may result in difficulty navigating to locations due to impaired vestibular perception of position and motion.
Many patients with vestibular dysfunction unconsciously learn to rely on their vision as compensation to help them navigate. However, since vision declines with normal aging, this may not be the best long-term solution. Vestibular physical therapy, also known as vestibular rehab and vestibular rehabilitation, can help patients learn to navigate more effectively.
Summary of Key Points
In conclusion, vestibular dysfunction can result in feeling wobbly when upright, unsteadiness with walking, blurry vision with quick turns, and difficulty navigating our direction. Vestibular problems can also cause dizziness and vertigo, in addition to dysequilibrium.
Vestibular physical therapy can help with all these symptoms! Yay! Yet even so, most patients with signs and symptoms of vestibular problems are tragically NEVER referred to vestibular PT. Yikes!
To learn more about why your doctor may not recognize a vestibular problem, check out this blog.
Click here to read the benefits of working with me.
To search for a provider of vestibular rehab in your local area, click here to find a blog on that topic.
Acknowledgments: Special thanks to Colin R. Grove, PT, DPT, PhD, one of the faculty of the Johns Hopkins University Vestibular Competency Certification course which I attended in 2023 for his excellent lecture on postural control and gait impairment in patients with vestibular problems, which inspired this blog article. Clinicians interested in furthering their education in vestibular medicine can learn more about the JHU vestibular competency certification course and register here.
This blog is provided for informational purposes only. The content and any comments by Dr. Kim Bell, DPT are not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. The details of any case mentioned in this post represent a typical patient that Dr. Bell might see and do not describe the circumstances of a specific individual.