By Tony Friese, PT
Competency Certificate in Vestibular Rehabilitation
“Theoretically, if “vestibular exercises” were ordered for a patient you were ostensibly in charge of, what would you do?”
This hypothetical question was posed by Barrett Dorko, PT at somasimple.com about six months ago. (The thread can be found here) The question brought back memories of my first exposure to the world of vestibular rehabilitation a little over 10 years ago. At that time, an ENT physician in my local area was seeking PT departments willing to develop a “balance program” and had begun to send patients to our department, a general, hospital-based outpatient PT department, for “balance rehabilitation”.
In those days, my clinical practice was focused primarily on orthopedics and we were, at my facility, just beginning to be hounded about “productivity”-meaning basically the pressure was being applied to stay busy. My own schedule tended to be only moderately full, and I wasn’t really enthusiastic about some of the other specialties being developed (industrial rehab, lymphedema, aquatics, spinal cord rehab, etc) so when the opportunity came about for “balance rehabilitation” I thought it was something I’d better at least consider looking into.
My knowledge of the subject matter was scarce. I attended PT school in the late 1980s when Bachelor’s programs were still the norm, and balance in general was barely covered in neuro class, let alone any specifics on the vestibular system. I do have vague recollections of my “Vertebrate zoology” professor mentioning “stones” in the inner ear that could cause dizziness if they went out of place, an idea that I found fascinating and may have been a foreshadowing of my affinity for treating benign paroxysmal positional vertigo (aka “BPPV”), and remember having an image in my head from PT school about vestibular being equal to bouncing a child up and down on a physioball or spinning them on a stool. I wasn’t really interested in treating kids at the time so maybe that explains why it took over 10 years to get on board with anything vestibular. (Note: incidentally, to this day, after 10 years of vestibular experience, I have yet to either bounce anyone on a ball or spin them in a chair in the context of my daily practice!) Basically, my knowledge of balance was basically have someone stand there and try to not fall down, and maybe nudge them around a bit as an extra challenge, and if they were really advanced put them on a tilt board or have them stand in tandem or on one leg.
This is the approach I took with one of my first new patients referred by the ENT for “balance rehabilitation”. After giving the patient what I thought was a well designed home program of standing balance exercises, the patient remarked something to the effect of “my doctor said you were going to give me exercises to strengthen my inner ear” to which I am sure I appeared like a dumbfounded idiot-I know I felt that way! I had never heard of such a thing! “Inner ear strengthening”??? How do you strengthen the inner ear? Apart from that idea of the stones in the ear going in the wrong place that I heard about in that class in school, I didn’t even really know what could go wrong in the inner ear, let alone how to “strengthen” it.
Now, over a decade and several continuing education programs later, I *know* what “inner ear” strengthening is *supposed* to mean, but those early memories of mine help me understand the confusion and uncertainty that could accompany a request for “vestibular exercises” presented to clinicians unfamiliar with the territory. The purpose of this blog post is to try to shed some light, for the uninitiated, on the potentially mystifying field of vestibular rehabilitation, and, in the process, hopefully inspire some readers who may be feeling frustrated by the field of treating painful disorders that there may be an unexplored area of practice that might be a surprisingly good fit for them as it has been for me.
First, a little bit about the inner ear…
Maintaining balance is a complex bodily function that occurs mostly unconsciously through an input-processing-output process involving several bodily systems.
Sensory INPUT for balance mainly comes from three types of sensory input. Somatosensory input involves sensation of the body relative to the support surface or of body segments relative to each other. In oversimplified terms, is often thought of as feet feeling the ground. Visual input allows the CNS to know where the body is by comparing its position to the position of stable objects seen in the environment. Somatosensation and vision help us to stay stable on our feet most of the time. There are times, however, where these two systems may not be adequate to keep us upright. For example, walking on a beach at night, or in a room with thick carpeting with the lights off. In these circumstances, additional sensory information is needed to maintain stable upright balance which is where the inner ear comes in.
The inner ear is the location of the peripheral vestibular system, which is the third main source of sensory input for maintaing balance. The vestibular system is located in the temporal bone at about the level of the cheekbone and is about the size of a dime. It is made up of a bony labrynth that contains two types of balance related sensory organs: semicircular canals and ototliths. Each inner ear contains 3 semicircular canals (anterior/superior, posterior/inferior and horizontal/lateral) and 2 otoliths (utricle and saccule).
The three semicircular canals are basically fluid filled tubes sitting at 90 degree angles to each other which function to detect head motion. As the head moves, inertial movement of the fluid inside the canal deforms sensory hair cells in the canal, creating nerve impulses providing sensory information about head movement. Each canal is most sensitive to certain directions of head motion. Having a similar yet mirror-opposite arrangement on both sides of the body provides redundancy which has implications for rehabilitation.
The two otoliths are small chambers in close proximity to the semicircular canals. One of the otolith organs, the utricle, actually has connections to the semicircular canals. Rather than detecting changes in angular head motion as the semicircular canals do, the otoliths function more in the detection of static tilt of the head relative to gravity and acceleration movements such as when riding in an elevator or speeding up/slowing down in a car. The gravity dependent functioning of the otoliths explains the presence in the utricle and saccule of little stone-like particles called otoconia. These are the particles my college professor was referring to. They are made of calcium carbonate and normally adhere to the surfaces of the otolith organs. During head tilting motions or linear acceleration movements, shifting of these little stones on the sensory membrane creates deformation of the sensory hair cells again creating nerve impulses signalling information about head position.
Nerve signals generated by stimulation of the canals and otoliths travel to the CNS via the eight cranial nerve to the vestibular nuclei in the brainstem and to the cerebellum. It is here that PROCESSING occurs, and appropriate motor OUTPUT is generated. Inner ear participation in the input-processing-output loop occurs via two main reflexes: the vestibulo-ocular reflex (VOR) and the vestibulo-spinal relflex (VSR). The VSR is likely familiar to nearly all therapists, as we all had to learn labrinthine reflexes in motor development class, which are all mediated by the VSR. With the VSR, information from the canals and otoliths travels to the CNS, and motor output signals go to the trunk and extremity muscles to maintain postural stability.
The VOR is what was totally new for me in learning about vestibular rehab. With the VOR, information from the inner ear is processed by the CNS, and motor output to the ocular muscles is generated in order to maintain gaze stability. With slow head motions, stable vision can be maintained by basic oculomotor functions such as smooth pursuit. With faster head movements, smooth pursuit alone does not function fast enough allow a visual target to be kept in focus. The VOR, however, being one of the fastest reflexes in the body, will allow a visual target to remain in focus during rapid head movements. Each semicircular canal has neurologic connections to specific eye muscles so that, with movement of the head in a given direction, the nervous system will reflexively generate eye movement in the opposite direction which helps to maintain stable vision. This is one of the ways the inner ear assists with balance-by helping us be able to still use our eyes when our head is moving quickly. Here is an experiment that will help underscore the potency of the VOR in keeping vision stable. Hold one arm stretched out in front of your face with a thumb extended. Keep your eyes focused on your thumb. Now move the arm side to side quickly in front of your face. How fast can you go and still see your thumb clearly? Now, keep the arm still, and, still focusing on your thumb, shake your head side to side. How quickly can you do this and still see your thumb clearly? Thanks to the VOR, you could undoubtedly move the head more quickly than you could your arm.
Great system, that inner ear! BUT….things can go wrong. The vestibular system, as tiny as it is, is vulnerable to several things: trauma, tumors, infections, damage from medications, vascular compromise, fluid balance regulation, stuff breaking loose and going where it doesn’t belong and problems with the processing center (CNS) are just a few of the general categories of problems that can occur to disrupt balance and cause dizziness. Any of these problems (that have technical names like vestibular neuritis/labrynthitis, Meneire’s disease, acoustic neuroma, labrynthine concussion, BPPV, ototoxicity, etc) can affect the normal functioning of the VOR and VSR and result in symptoms that include dizziness, imbalance, blurred vision and sensitivity to motion. Sounds bad, but wait! Many of these things can be helped with movement oriented therapy aka “vestibular rehabilitation”