In addition to serving as the organ of hearing, the ears have a significant role in the control of balance. The inner ears house the semicircular canals and otolithic organs - the sensory organs of the vestibular system - the most rapid sensors of the body's motion.
As the ears sense movement, they send signals to the muscles of the eyes, neck, trunk, arms and legs. These signals allow those organs to maintain a stable position even as the body and head undergo complex motions. Were it not for the vestibulo-ocular reflex (the reflexive control of eye position in response to signals from the ear) we would not be able to keep our gaze fixed on an object as we moved about. In fact, certain patients with loss of inner ear function experience oscillopsia, i.e. the abnormal perception of movement of their visual field as they move about in their daily activities.
A more common symptom that arises from disturbances of the inner is vertigo. Vertigo is either the perception of motion when no movement is present, or the abnormal perception of motion in response to movement. When the vestibular system functions improperly, a person may feel like they are moving even when they are not. There may also be unsteadiness while moving, because the experience of each movement - and the sensation that is felt - is not what the body and brain are used to feeling.
Vertigo is not a disease; it is a symptom of disease. Just like pain in your leg can be caused by many different things - bumping into something, fracture of the bone, clogged blood vessels”¦ - so too can the sensation of vertigo be produced in many different ways.
There are scores of disorders that can cause vertigo. These are some of the more common ones:
Some less common causes of vertigo are:
- Otosclerosis - Changes in the dense bone that houses the inner ear, causing alterations in inner ear function. This is usually, though not always, associated with some type hearing loss. Certain medications have been used successfully to control the symptoms of otosclerotic inner ear disease.
- Superior semicircular canal dehiscence - Loss of bone over the uppermost of the inner ear balance canals causes the symptoms of this syndrome. Vertigo with this syndrome can be provoked by loud sounds (Tullio phenomenon) or pressure in the ear. Not uncommonly, this can be experienced as a sensation of spinning or being pushed to the side when hitting specific notes while singing or playing a wind instrument.
Sometimes there can be spontaneous episodes of vertigo, such as those characteristic of Meniere's disease. Many patients experience a generalized sense of imbalance in between the more distinct episodes of vertigo.
There may also be hearing loss in the affected ear. The diagnosis is usually suspected on office examination, and is confirmed with a combination of hearing and balance tests, and a specially formatted CT (“CAT”) scan.
Many people with this problem are happy simply to have identified the cause, often after a long search for an explanation to their troubling symptoms. In those for whom the symptoms are sufficiently severe, surgical repair or ablation of the affected canal can be curative.
- Perilymphatic fistula - Abnormal connection from the inner ear to the middle ear allowing leakage of the inner ear fluids. This problem most commonly occurs in the setting of ear trauma, either from a head blow, penetrating wound or rapid pressure change. There is no definitive test to reliably diagnose fistulae pre-operatively. Surgical exploration and repair of the fistula site should be undertaken in most cases, though vestibular rehabilitation has been shown to help in some cases of suspected fistula.
- Cervical vertigo: In this poorly understood disorder abnormalities of the bones and muscles of the neck lead to vertigo with certain head movements. Vestibular therapy with attention to physical therapy of the neck muscles is the indicated treatment.
- Cerebrovascular accident (Stroke) - Although strokes can commonly cause vertigo, vertigo is less commonly the only symptom of a stroke
- Vertebrobasilar insufficiency - Decreased blood flow through the major blood vessels that go to the lower areas of the brain can produce vertigo with extension of the neck. However, vertigo provoked by that movement is much more commonly due to BPPV (see above).
- Multiple sclerosis - Although many people with multiple sclerosis will experience vertigo at some point, a few will have episodes of vertigo as the initial symptom of the disease. Vestibular testing and MRI can suggest the diagnosis.
- Chiari malformations - An anatomic abnormality at the base of the skull can lead to vertigo. This can be screened for with an MRI. In severely symptomatic cases, decompression of the base of the skull may be performed by a neurosurgeon.
After injury to the inner ear, the brain undergoes a complex set of changes that allow it to adapt to the altered sensory input and abolish the perception of vertigo. This process is called “vestibular compensation.” After a sudden injury to the inner ear, the continuous perception of vertigo is usually controlled in about 3 days. It can take another 4-6 weeks, on average, for the brain to adapt to the new input with motion.
In some people this process is never completed, and they have vertigo due to incomplete vestibular compensation. It is important to distinguish this process from ongoing alterations and fluctuations in the inner ear itself, in order to properly tailor the treatment.
Certain patients can achieve complete compensation initially only to have episodes of “decompensation” later in life, frequently in response to new physical or emotional stresses. It is likewise important to distinguish this “central decompensation” from a recurrence of the original ear problem that precipitated it.
Treatment of vertigo depends on its cause. If a specific causative disease is identified, therapy can be tailored for that disorder. Frequently there can be multiple, coincident causes of vertigo, and each needs to be treated individually. Surgery can be helpful and even curative for many causes of vertigo. There are a number of different operations that can eliminate vertigo from various inner ear diseases. In general, surgery is reserved for patients in whom more conservative treatments have failed to control the symptoms. Medications are often helpful in controlling the acute symptoms of vertigo, but can frequently be counter-productive for people with more chronic problems.
In certain cases, one specific cause of vertigo cannot be identified, but, depending on the nature of the vertigo treatment may still be provided with good hope for improvement. In many such instances, vestibular rehabilitation therapy (VRT) is the recommended approach.
VRT is a specialized mode of physical therapy that strengthens the vestibular sensory system. This contrasts with traditional physical therapy which strengthens motor systems. VRT has three different general approaches to improving balance:
- Disease specific- In certain cases, VRT can offer specific treatment directed at a well-defined and identifiable disorder. The classic example of this is the particle-repositioning maneuver for Benign Paroxysmal Positioning Vertigo (BPPV).
- System specific- VRT exercises can strengthen the vestibular system and its reflexes, thereby improving residual function in patients who have had an injury to the inner ears or central vestibular pathways. These exercises can be generic, or- as with customized VRT- tailored specifically for the deficits that each individual patient has. Customized VRT has been shown to provide superior rehabilitation results in patients with chronic inner ear disorders, though many other patients can benefit from it as well.
- General conditioning exercises- Many patients with chronic imbalance adopt a relatively sedentary lifestyle in order to avoid the distressing symptoms that result from too much movement. An important element in recovery of function is general muscle and fitness conditioning. A comprehensive VRT program should include appropriately tailored general conditioning exercises.
Other conditioning programs such as Tai Chi have also been shown to benefit people with chronic vestibular and balance disorders. Although they can be helpful, since they may not take place in a closely supervised setting, people who are at risk for falls should use caution when trying such approaches.
If you would like to make an appointment or talk to an Audiologist, please call the Hearing and Balance Center at 410-328-5947.