1. “The vestibular system is responsible for sensing motion of the head and maintains stability of images on the fovea of the retina and postural control during that motion”
I am going on a limb here. Vestibular dysfunctions are not my specialty. I will be learning along with you here. If there are folks out there that understand this better than I do, please comment on this article where I am out of place or my thinking is not correct.
In school, we learned about the vestibular system over the course of 2 days. It sounds like a lot of learning, but put it into perspective. This equates to about 4 hours of learning in comparison to about 2,000 hours of overall course work.
The vestibular system detects motion of the head. The apparatus is located behind the eye and is very small. It communicates with the brain in order to indicate where the body is at in space.
2. “The vestibular receptors in the inner ear provide an exquisitely accurate representation of the motion of the head in 3 dimensions”
The system is able to determine tilts of the head in each direction and acceleration of the body.
3. “Disorders of the vestibular function result in abnormalities in these reflexes and lead to sensations that reflect abnormal information about motion from the vestibular receptors”
Remember, this system communicates with the brain regarding tilting forward, backwards, rotating left and right, and acceleration. When this system is not working smoothly, you may be still, but the brain may get a message that you are actually moving. You may be straight, but the brain sees that you are tilting. I can remember going to the fun house at Navy Pier. There is a bridge that is no more than 2 inches off of the ground, but visually, it seems like the bridge is moving. Watching people attempt to cross the bridge is amusing. Unfortunately, this is how people with vestibular dysfunctions perceive daily life. Not so amusing.
4. “Best visual acuity is obtained when images are projected on the fovea of the retina…occupies a small area of the visual field, but movements of an image off the fovea by as little as 1 degree can cause substantial decreases in visual acuity”
The fovea is like a hole that the image from the eye has to fall into in order for the image to be perceived clearly. If the eye doesn’t follow the image perfectly, the image will then become blurry.
5. “Normal activities of daily life (such as running) can have head velocitieis of up to 550 degrees/second, head accelerations of up to 6,000 degrees per second squared, and frequency content of head motion from 0 to 20 Hz. Only the vestibular system can detect head motion over this range of velocity, acceleration and frequency”
The vestibular apparatus is very sensitive to movement. It can react quickly to head motion and if there is a deficit in this system, all of the above descriptions will be limited.
6. “The incidence of dizziness in the United States is approximately 5.5%, which means that more than 15 million people develop the symptom each year”
This is one of the chief reasons for ED visits. As a PT student, one should follow his/her passion. With the pleasantries out of the way, the PT student should become great at treating diseases that are going to keep that PT in business. For instance, if you are in a small town of 10,000, then you will end up seeing about 500 cases of balance issues in the year. Back pain will give you about 2,500 cases per year. If you get really good at treating these two incidences, you will have business for life, assuming that you can get the public to become aware of your services.
7. “For patients over 75 years of age, dizziness is the most common reason they see a physician…it has been reported that more than 70% of patients with initial reports of dizziness will not have a resolution of symptoms at a 2-week follow-up”
Older patients will have more occurrences of dizziness than younger patients. Dizziness is not going to be cleared up rapidly in most patients, but some cases of dizziness can improve within 1-3 visits. It is important that the therapist is trained in treating different types of dizziness.
8. “Many patients and clinicians use the imprecise term “dizziness” to describe a vague sensation of light-headedness or a feeling that they have a tendency to fall…Generally, most complaints of being “dizzy” can be categorized as light-headedness, disequilibrium, vertigo, or oscillopsia”
Not all “dizzinesses” are the same and because of this, they aren’t all treated the same. You will see in the next points.
9. “Light-headedness is often defined as a feeling that fainting is about to occur and can be caused by nonvestibular-factors such as hypotension, hypoglycemia, or anxiety”
Someone fainting does not need balance exercises. They require medical attention. The physician needs to be made aware, as this could be a sign that the cardiovascular system is not working correctly. Sometimes it can be as simple as giving advice to sit for a minute before standing and stand for a minute before walking. The physician needs to be aware of this symptom in order to determine which advice is needed prior to treatment.
10. “Disequilibrium is defined as the sensation of being off balance…associated with nonvestibular problems such as decreased somatosensation or weakness in the lower extremities”
The somatosensory system is the body’s communication system between where the joints and limbs are in space with the brain. For instance, I can touch my nose or feed myself without seeing either my hand or my mouth. If the somatosensory system is not intact, I would have trouble feeling the ground with my feet and telling whether my weight was on my heels or on my toes. This is a big problem that could lead to falls.
11. “Vertigo is defined as an illusion of movement…tends to be episodic and tends to indicate pathology at one or more places along the vestibular pathways”
This means that you feel that you are moving, even though you are not. Think of being on a boat and how that feels. When you feel like this on land, something is not working correctly. This sensation could be due to BPPV, “ear rocks” that get out of place, or a lesion in the vestibular apparatus.
12. “Oscillopsia is the experience that objects in the visual surround that are known to be stationary are in motion…can occur in association with head movements in patients with vestibular hypofunction because the vestibular system is not generating an adequate compensatory eye velocity during a head rotation”
This isn’t the first time that I heard this term, but I am also not very familiar with this phenomenon either. I am just learning this entire topic of vestibular rehab, but I realize that when you are standing still and you see things moving…something ain’t right!
I have personally never seen this symptom in the clinic, but I am excited to see a patient with this complaint because after taking a course with Evidence CEU, I feel more confident in treating these types of patients.
“…the bedside examination of eye movements can be of primary importance in defining and localizing vestibular pathology”
I have to speak with regards to orthopedics for a second, but there is a slow wave of support coming forth that is negating the need for expensive tests prior to an actual assessment of the patient. This also seems to hold true for vestibular dysfunctions. Much can be learned by listening to the patient’s history and doing examinations while watching the patient’s eyes during different movements. Prior to taking the course with Mickey Shah, PT, DSc, cert. MDT, FAAOMPT, vestibular certified (Emory), I had little understanding of the vestibular system and its effect on function. I have more confidence now in performing a bedside examination, which can give great insight into the patient’s vestibular system.
The next couple of pages go into depth on the special testing that is used to detect vestibular pathology. I won’t go into depth, but when going to see a vestibular therapist, the following tests should be done (assuming there are no contraindications to performing the tests such as cervical instability)
Head thrust test
Head-shaking-induced-nystagmus
Positional testing (such as Dix-Halpike and roll testing)
Dynamic visual acuity
“The most frequent cause of UVH (unilateral vestibular hypofunction) is vestibular neuronitis, which is commonly caused by the herpes simplex virus…may experience vertigo, spontaneous nystagmus, oscillopsia, postural instability and disequilibrium”
Essentially, this means that there is an issue with the vestibular system sending afferent signals to the brain. In short, the balance system in the ear is malfunctioning, but only on one side. This has the potential to cause a patient to feel “off balance”, possibly have blurred vision, and maybe lean to one side.
“The most common cause of vestibular hypofunction on both sides (BVH) is ototoxicity…experience gait ataxia, postural instability and oscillopsia”
This is a patient that I have seen a few times. When you see it, you don’t forget it. These patients look like they have a stroke in the cerebellum. They have trouble walking and initiating gait. They look like they are going to fall (and they typically do without a walker). It’s interesting in that if they are allowed to touch something stable with fingertips, they look absolutely normal. The body’s somatosensory system would then take up the slack for the dysfunctional bilateral vestibular system.
In the end, vestibular rehab can be very beneficial to help patients that have these dysfunctions. If you have any of the above symptoms, do not be satisfied with the statement “you have a weak core”. If you are losing your balance, special testing should be done in order to determine the cause of your balance limitations. If you feel sensations of movement when you are still, or you see things moving, that you know should be still, go see a therapist trained in the methods discussed above. Never be too shy to ask your therapist their qualifications to treat these disorders. I am proud of what I know regarding orthopedics, but also take ownership over the fact that I have much to learn in all of the other aspects that I allowed to play second fiddle while I was studying about spinal conditions and other orthopedic topics.
EXCERPTS FROM:
Schubert MD, Minor LB. Vestbulo-ocular Physiology Underlying Vestibular Hypofunction. Phys Ther. 2004;84:373-385.
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