| Labyrinthitis | |
|---|---|
| Classification and external resources | |
| ICD-9 | 386.3 |
| MeSH | D007762 |
Labyrinthitis is an inflammation of the inner ear,[1] and a form of unilateral vestibular dysfunction. It derives its name from the labyrinths that house the vestibular system (which sense changes in head position). Labyrinthitis can cause balance disorders.
In addition to balance control problems, a labyrinthitis patient may encounter hearing loss and tinnitus. Labyrinthitis is usually caused by a virus, but it can also arise from bacterial infection, head injury, extreme stress, an allergy or as a reaction to a particular medication. Both bacterial and viral labyrinthitis can cause permanent hearing loss, although this is rare.
Labyrinthitis often follows an upper respiratory tract infection (URI).
Contents |
A prominent and debilitating symptom of labyrinthitis is severe vertigo. The vestibular system is a set of sensory inputs consisting of three semicircular canals, sensing changes in rotational motion, and the otoliths, sensing changes in linear motion. The brain combines visual cues with sensory input from the vestibular system to determine adjustments required to retain balance. When working properly, the vestibular system also relays information on head movement to the eye muscle, forming the vestibulo-ocular reflex, in order to retain continuous visual focus during motion. When the vestibular system is affected by labyrinthitis, rapid, undesired eye motion (nystagmus), often results from the improper indication of rotational motion. Nausea, anxiety, and a general ill feeling are common due to the distorted balance signals that the brain receives from the inner ear.
This can also be brought on by pressure changes such as those experienced while flying or scuba diving.[2][3][4]
Recovery from acute labyrinthine inflammation generally takes from one to six weeks; however, it is not uncommon for residual symptoms (dysequilibrium and/or dizziness) to last for many months or even years[5] if permanent damage occurs.
Recovery from a permanently damaged inner ear typically follows three phases:
When the balance system is damaged, it has little ability to repair itself. The body recovers from the injury by having the part of the brain that controls balance re-calibrate itself to compensate for the unmatched signals being sent from the damaged and well ears. This compensation process occurs naturally in most people. Some patients require help from vestibular rehabilitation therapy in order to recover from an injury to the balance system.
Acute (Immediate) Compensation
When a sudden injury occurs to one side of the balance system, the patient may feel very sick for hours to a few days with a spinning feeling, unsteadiness, lightheadedness, and often sweating, nausea, and vomiting. This is because the signals being sent from the two balance organs are no longer equal and opposite, and the brain interprets the difference as constant movement. Researchers theorize that after this initial period, the brain recognizes that the signals being received from the ears are incorrect and turns the signals off through a process called the cerebellar clamp. When the clamp is in place, the spinning and much of the 'sick' feeling improve. The patient feels unsteady while standing though, because the balance organ signals normally used to maintain balance have been turned off. The patient may also report dizziness or blurred vision with movements. Vision and proprioception (the sense of pressure at the bottom of the feet) are also used to maintain balance, so the patient can walk but will feel unsteady and may fall in the dark or on soft or bumpy floors like thick carpet, grass, or gravel.
At this point, most patients are well enough to get out of bed and visit a doctor. The doctor sees a person who is not spinning but whose gait is ataxic. If the patient is not given an opportunity to clearly describe what has happened, he or she may be immediately referred to neurology to rule out stroke because of this ataxic gait. If balance testing is performed during the acute (immediate) compensation phase, test results may incorrectly suggest that the patient has damage to both sides of the balance system, because the cerebellar clamp reduces the eye movements that are looked for during balance testing. The cerebellar clamp may persist for days to a few weeks after the initial injury.
Chronic (Long-Term) Compensation
During the acute compensation phase, the cerebellum slowly releases the clamp, gradually allowing more signals from the balance organs to pass to the balance areas of the brain. As the brain receives these signals, it fine-tunes the mathematics performed to interpret the information, in order to account for the difference between the ears. The brain must receive signals from the balance organs to be able to modify its interpretation of these signals.
For most patients, the movements made during normal daily activities are enough to achieve chronic (long-term) compensation, usually in two to four weeks after the injury has occurred. Once the chronic compensation process is complete, the patient is essentially symptom-free. If unsteadiness and/or motion provoked dizziness persist after that time, compensation is not complete and the physician may prescribe a program of vestibular rehabilitation therapy (VRT).
VRT is a treatment program administered by a specially-trained physical therapist. It is designed to provide small, controlled, and repeated 'doses' of the movements and activities that provoke dizziness in order to (1) desensitize the balance system to the movements, and (2) enhance the fine-tuning involved in long-term compensation. VRT is most effective when administered by a physical or occupational therapist who has special training and specializes in this unusual form of therapy.
Decompensation
It's important to remember that even after the symptoms go away, the balance system remains injured, and the brain has simply adapted to the injury. For many patients, dizziness will return months or years after compensating for a balance system injury. It is critical for the physician to find out what type of dizziness the patient has. If the patient describes another severe attack of spinning with unsteadiness and nausea lasting hours to days, this suggests that a second injury has occurred to the balance system, such as another viral infection or an attack of endolymphatic hydrops. These conditions require diagnosis and medical treatment. If the patient reports that dizziness occurs after particular movements and lasts seconds to a few minutes, this suggests decompensation. Decompensation simply means that the brain has 'forgotten' the fine-tuning procedure it developed during the chronic compensation phase described above.
Events that can provoke decompensation include a bad cold or the flu, minor surgery, long vacations, or anything that stops normal daily activity for a few days. Recovery after decompensation is exactly like the recovery that occurs during the chronic compensation phase. Movements and activities are the stimuli the brain needs to fine-tune the system. In our balance center, we routinely counsel patients to keep their VRT exercise program instructions in a drawer even after they recover so that they can begin the exercises immediately if symptoms return. Usually recovery after decompensation is quicker than the recovery after the initial injury to the balance system.
Failure to Compensate
Two things are required in order to compensate for an injury. First, the brain must receive signals from the balance organs. This means that movements must not be avoided, because movements create the signals the brain needs to compensate for the injury. Secondly, the balance areas of the brain must be capable of change.
During the early stages of dizziness, many physicians counsel their patients to avoid quick movements and reduce their activities. Most patients will be prescribed one or more anti-dizziness medications such as Antivert (meclizine), Valium (diazepam), Xanax, Phenergan, or Compazine. This is fine during the acute stages of a dizziness problem in order to reduce the dizziness symptoms that persist for hours or days even when the patient is not moving. However, once the acute phase is past, inactivity and medications can interfere with the long-term compensation process. Any medication that makes the brain sleepy, including all of the anti-dizziness medications, can slow down or stop the process of compensation, so they are often not appropriate for long-term use. Most patients who fail to compensate are found to either be strictly avoiding certain movements, using anti-dizziness medications daily, or both. Treatment includes VRT, gradual reduction, and eventual elimination of these medications.
Chronic anxiety is a common side effect of labyrinthitis which can produce tremors, heart palpitations, panic attacks, derealization and depression. Often a panic attack is one of the first symptoms to occur as labyrinthitis begins. While dizziness can occur from extreme anxiety, labyrinthitis itself can precipitate a panic disorder. Three models have been proposed to explain the relationship between vestibular dysfunction and panic disorder:[6]
Vestibular rehabilitation therapy (VRT) is a highly effective way to substantially reduce or eliminate residual dizziness from labyrinthitis. VRT works by causing the brain to use already existing neural mechanisms for adaptation, plasticity, and compensation.[7]
Rehabilitation strategies most commonly used are:[7]
These exercises function by challenging the vestibular system. Progression occurs by increasing the amplitude of the head or focal point movements, increasing the speed of movement, and combining movements such as walking and head turning.
One study found that patients who believed their illness was out of their control showed the slowest progression to full recovery, long after the initial vestibular injury had healed.[5] The study revealed that the patient who compensated well was one who, at the psychological level, was not afraid of the symptoms and had some positive control over them. Notably, a reduction in negative beliefs over time was greater in those patients treated with rehabilitation than in those untreated. "Of utmost importance, baseline beliefs were the only significant predictor of change in handicap at 6 months followup."
Prochlorperazine is commonly prescribed to help alleviate the symptoms of vertigo and nausea.
Because anxiety interferes with the balance compensation process, it is important to treat an anxiety disorder and/or depression as soon as possible to allow the brain to compensate for any vestibular damage. Acute anxiety can be treated in the short term with benzodiazepines such as diazepam (Valium); however, long-term use is not recommended because of the addictive nature of benzodiazepines and the interference they may cause with vestibular compensation and adaptive plasticity.[8] Benzodiazepines and any other form of mind or mood altering addictive drug should not be used on patients with addictive history.
Evidence suggests that selective serotonin-reuptake inhibitors may be more effective in treating labyrinthitis. They act by relieving anxiety symptoms and may stimulate new neural growth within the inner ear, allowing more rapid vestibular compensation to occur. Trials have shown that SSRIs do in fact affect the vestibular system in a direct manner and can decrease dizziness.[9]
Some evidence suggests that viral labyrinthitis should be treated in its early stages with corticosteroids such as prednisone, and possibly antiviral medication such as valacyclovir and that this treatment should be undertaken as soon as possible to prevent permanent damage to the inner ear.
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