Understanding Vestibular and Balance Disorders

Transcription

1 Understanding Vestibular and Balance Disorders Common Vestibular Disorders Diagnostic Tests Vestibular Rehabilitation Glossary of Common Vestibular Terms Dizziness is one of the most difficult complaints to assess because it is a subjective sensation that cannot be directly and objectively measured. Dizziness frequently represents many separate overlapping sensations that can be caused by a multitude of different pathophysiologic processes. Dizziness also is one of the most common patient complaints seen in ambulatory care today and therefore clinicians in almost all disciplines will be faced with evaluating this difficult problem. Evaluation and treatment of patients with dizziness will differ significantly once the category of dizziness has been determined. It is imperative that clinicians take a careful history to determine the type of dizziness prior to initiating further workup. These patients are typically challenging from a diagnostic standpoint. Their own difficulty in providing a clear and succinct history adds to this challenge. It is helpful to have a solid understanding of the various types of dizziness in order to help obtain an informative history from patients. TRUE VERTIGO VERSUS OTHER TYPES OF DIZZINESS While the description alone cannot make this important distinction between vertigo and other forms of dizziness, there are certain terms that are frequently associated with the description of different forms of dizziness. A vestibular disorder is almost always described as a sensation of spinning and is accompanied by nystagmus that patients may report as a feeling that their eyes were rapidly snapping or jerking to and fro. This will relate to a sensation that the environment around them is moving. Patients with nonvestibular dizziness may describe a spinning sensation inside the head; they do not have nystagmus and thus do not report movement of the environment. Those patients with vestibular dysfunction may equate the feeling to a sensation of having motion sickness and describe feelings of imbalance, as though they were falling or leaning to one side. Those patients describing their symptoms with terms such as lightheaded... swimming... giddiness... floating most often have a nonvestibular etiology for their dizziness. Psychophysiologic dizziness is suggested by a description of a feeling that they have left their body. True vertigo is an episodic phenomenon compared to nonvestibular dizziness that is often described as a continuous sympton.

2 Vertigo is often aggravated by head movements, while nonvestibular dizziness can be aggravated by movement of targets in the visual field. This is often obvious in patients who complain of dizziness stimulated by specific situations such as driving in traffic or shopping in a busy supermarket. In cases where the dizziness is primarily related to positional changes, and postural hypotension has been ruled out, a vestibular lesion should be suspected. The association of symptoms, such as nausea and vomiting or auditory or neurologic symptoms, is more likely to be seen with vestibular causes of dizziness. DIFFERENTIATING AMONG COMMON CAUSES OF VERTIGO Typically, peripheral vertigo is more severe than central forms and is more likely to be associated with auditory symptoms (e.g., tinnitus, hearing loss), as well as nausea and vomiting. Other neurologic symptoms are generally associated with vertigo of central origin. Such symptoms might include diplopia, weakness, numbness, or incoordination. One of the original point mentioned was the importance of determining the basic characteristics of the patient s dizziness, including the length of time that the episodes last. Such information is now even more helpful in leading the clinician to a diagnosis. Episodes of dizziness lasting only seconds in duration are suggestive of benign positional vertigo. This is often preceded by an initial period or episode with complaints of a nonspecific sense of disorientation and imbalance associated with nausea and vomiting that may last for hours or days. When describing more recent recurrent attacks, the patient clearly can separate out brief (seconds) episodes of positional vertigo. A vertiginous episode beginning abruptly and lasting minutes in duration is more characteristic of a vascular etiology, such as vertebrobasilar insufficiency or migraines. Meniere s disease is often responsible for episodes of vertigo that heighten in severity over a period of minutes, but last for several hours with a gradual improvement during another period of several hours. Vestibular neuronitis and episodes of labyrinthitis typically present with fairly abrupt onset vertigo (over a period of hours) with resolution of the acute phase over the next several days. Traumatic injuries or vascular infarction of the labyrinth cause a sudden onset of symptoms with a slow recovery from the acute phase over a period of days to weeks, often with residual effects over a period of 12 to 18 months. COMMON VESTIBULAR DISORDERS Benign Positional Vertigo

3 Benign positional vertigo, believed to be the most common type of peripheral vertigo, can be seen following head injury, vestibular neuronitis, stapes surgery, Meniere s disease, or can present alone. The disorder is thought to be related to an abnormality in the association of the otoconia to the cupula within the membranous labyrinth, resulting in abnormal responses to endolymph movement with head motion. Symptoms are typically associated with head movement, such as rolling over or getting in or out of bed. The associated vertigo is brief, lasting only seconds in duration, and can be seen as an acute form only or in an intermittent or chronic form. Labyrinthine Infarction Labyrinthine infarction leads to a sudden profound loss in auditory and vestibular function, and typically occurs in older patients. This phenomenon can be seen in younger patients with atherosclerotic vascular disease or hypercoagulation disorders. Episodic vertigo may herald a complete occlusion in the form of a type of transient ischemic attack. After complete occlusion, the acute vertigo that ensues will subside, often leaving the patient with some residual unsteadiness and dysequilibrium over the next several months while vestibular compensation occurs. Vestibular Neuronitis Vestibular neuronitis presents as a sudden episode of vertigo without hearing loss in an otherwise healthy person. The disorder can occur as a single attack or can present as multiple attacks. It occurs more often in spring and early summer, and as a result is often associated with an upper respiratory tract infection developing around the same time. The onset of vertigo is sudden and is typically associated with nausea and vomiting, and can last for a period of days with gradual improvement over the following weeks. The disorder is often followed by episodes of benign positional vertigo. Labyrinthitis Labyrinthitis is an inflammatory process occurring within the membranous labyrinth that may have a bacterial or viral etiology. Viral infections produce symptoms of dizziness similar to vestibular neuronitis, except that there is cochlear dysfunction as well. Congenital measles, rubella, and cytomegalovirus infections frequently cause no vestibular symptoms. Bacterial labyrinthitis can present in a supparative form with

4 direct involvement of the membranous labyrinth by the pathogen, or in a serous form. The serous form often is seen with acute otitis media when diffusion of bacterial toxins across the round window membrane occurs. Meniere's Disease Meniere's disease is an inner ear disorder characterized by episodic vertigo attacks, sensorineural hearing loss, tinnitus, and pressure or fullness in the involved ear. Initially, the hearing loss involves the lower frequencies and fluctuates, usually worsening with repeated attacks. The attacks are characterized by true vertigo, usually with nausea and vomiting lasting hours in duration. Histopathologically, this disorder is believed to be due to dilation of the endolymphatic spaces (hydrops) with ruptures and subsequent healing of the membranous labyrinth. Variants of the disease do occur, including vertigo without associated auditory symptoms. Migraine The vast majority of migraine variants are made up of the first two categories, migraine without aura, and migraine with aura. The term aura can be defined as a focal neurological disorder. Auras generally are considered to be abnormal sensory perceptions. Visual auras are the most frequent type, and may come in a wide variety of phenomena or hallucinations. It is valuable for healthcare professionals to have at least a basic understanding of migraine and audiovestibular symptoms. Vertigo, tinnitus, photophobia, and phonophobia, and occasionally hearing loss may present in at least 30% of migraine patients. Although hearing loss in migraine patients is less common than in vertigo, tinnitus, photophobia, and phonophobia, it may present as a low frequency fluctuating sensorineural hearing loss. It is possible, however, to have a permanent hearing loss or vestibulopathy (as indicated by caloric weakness) secondary to a migraine attack. The commonality of these symptoms, often make it difficult to distinguish the disorders on clinical grounds alone. This collection of symptoms may first be thought as consistent with Meniere s disease, or other types of inner ear involvement, such as a recurrent vestibular neuronitis, particularly in patients with recurring episodes or attacks. The differential diagnosis of migraine and Meniere s disease, then, may often present as a diagnostic enigma. In addition, 60% will report a lifelong history of motion sensitivity. Interestingly, the incidence of Meniere s disease is twice as prevalent in migraineurs, as in the general population. The diagnostic challenge is further complicated if a differential diagnosis of multiple sclerosis (MS) is included. The initial onset of acute, debilitating vertigo will appear as the initial symptom in 5% of MS patients. As many as 50% of MS patients will experience at least one occurrence of acute vertigo at some time during the course of

5 the disease. This may also be compounded by the fact that one in ten MS patients may present with hearing loss, which may be partial or complete, but often recovers, similar to the migraine or Meniere s patient. Mal de Debarquement Mal de Debarquement, or disembarkment sickness, is actually a common and normal occurence1. It can best be defined as the continued sensation of motion, rocking, or swaying that persists after return to a stable environment following a prolonged exposure to motion, as one would encounter on a cruise, car, bus or train ride. It can be related to any form of conveyance. Most individuals who have enjoyed even a few hours on a fishing boat may have experienced this sensation of still being on the water, after they have returned to shore. This sensation may only last hours or even for a few days. It seems to be most noticeable when standing in the shower shampooing with eyes closed, lying in bed, or perhaps leaning against a stable fixture, as when one is at the sink washing the dishes. The Mal de Debarquement sensation that commonly occurs is independent of any seasickness or motion sickness that may be experienced during the cruise or travel. The individual may not have any ill feelings at all, and only notices the rocking sensation once on solid ground. A survey by Gordon, Sphitzer, and Donavitch, found that of 116 crewmembers of the Israeli naval force, 72% reported this common sensation with 67% reporting a very strong sensation following their initial voyage. REFERENCES 1. Sloane P.D. Dizziness in primary care: results from the National Ambulatory Medical Care Survey. J Fam Pract 1989; 29: Kroenke khz, Arrington MA, Mangelsdorff AD. The prevalence of symptoms in medical outpatients and the adequacy of therapy. Arch Intern Medical 1990; 150: Baloh RW, Honrubia V. Clinical Neurophysiology of 3. the Vestibula To request further information click here Review of Diagnostic Tests

6 Audiologic Testing Audiology tests can provide information about hearing, middle ear function, cochlear hair cell function and several neural aspects of the hearingbalance system. Although there are many ear related conditions, which cause hearing loss along with vertigo, there are many that do not. So, the presence of an accompanying hearing loss with the vertigo symptoms may help differentiate certain ear disease-disorders from one another. For example, Menieres disease and labyrinthitis typically has both hearing loss and vertigo, whereas vestibular neuronitis and BPPV only have the symptom of vertigo. Audiology testing often includes: Pure tone (air and bone) and word discrimination tests as well as Immittance Audiometry which evaluates middle and inner ear and some neurological pathways. Otoacoustic Emissions is a relatively new test that looks at the outer hair cell function within the inner ear (cochlea). Brainstem Auditory Evoked Response (BAER) tests the neural conductivity of the hearing and balance nerve (CN VIII). Gans Sensory Organization Performance Test (SOP) A combination of the Romberg, clinical test of sensory integration of balance (CTSIB) and Fukuda Stepping Tests provide qualitative information on whether an equilibrium dysfunction exists, whether it is CNS or peripheral and also serves as an indicator of impact on balance function. Whether the is patient surface or visually dependent gives insight into the status of the vestibular system. Recovery of function post treatment may also be documented. Computerized Dynamic Visual Acuity Test (CDVAT)

7 This tests for a change in vision with controlled head movement. Oscillopsia is a breakdown in gaze stabilization during active head movement caused by peripheral or central vestibular disorders. The abnormal vestibulo-ocular reflex (VOR) function of as little as 3 degrees can change vision from 20/20 to 20/200 simple head movements. The vision test is conducted while the patient produces horizontal and then vertical head movement of 2.5 cycles per second. This is in the low-mid range of normal active head movement. The test indicates the function problem caused by the vestibular dysfunction and can be used as a baseline to latter compare improvement post Vestibular Rehabilitation Therapy (VRT) to document the treatment efficacy. Vestibular Autorotation Testing VOR function gain and phase is quantitatively analyzed using this active rotation test for both horizontal and vertical head movements over a frequency range of approximately 2-8 cycles per second. This indicates the direction of head movement, which is most dysfunctional as well as the frequency (speed) of head movement. The patient is required only to look straight ahead while moving their head to an auditory cuing signal. This test as those mentioned above provides diagnostic as well as outcome measurements. This test can be obtained through passive tests like the Rotary Chair, in which the patient simply sits while being harmonically accelerated or active tests, in which the person volitionally moves their head to an auditory cue. Videonystagmography (VNG) The most enduring and commonly used test of vestibular function is the VNG. The latest technology utilizes infrared video cameras recording the movement of each eye. Prior to this technology, the test was called ENG, as it was a recording of the corneoretinal potential. The test is comprised of subsets, which include the following: Dix-Hallpike - tests for BPPV-PC Ocular motor tests - saccadic, pendular and optokinetic pursuit are tests, which provide diagnostic information about the central vestibular and neuropthamologic systems connections within the brain. Gaze testing - tests for the presence of spontaneous nystagmus. High frequency headshake test - dynamically provokes nystagmus in some cases if the patient has an uncompensated or non-stabilized unilateral vestibular dysfunction.

8 Positional testing - documents the presence of static positional nystagmus. Findings are used for differential diagnosis of HC-BPPV and other peripheral type causes vs. CNS lesions. Caloric tests - Thermal convection of inner ear fluids are created by irrigating each ear with warm and cool air, which is above and below body temperature. The test may also be performed with water. The reactivity or responsiveness of each of the respective ears horizontal semicircular canals is calculated through a measurement of the patients induced nystagmus. A difference of 25% or more in the total nystagmus of the two ears indicates a caloric weakness a finding usually attributed to a peripheral or central dysfunction. In some disorders, both ears responses are depressed. Vestibular-Evoked Myogenic Potentials (VEMPs) Vestibular-evoked myogenic potential testing (VEMPs) is based on the reflex, which occurs between the otolith system (specifically the saccule), and the sternocleidomastoid muscle (SCM). The vestibulo-collic reflex (VCR) has been well studied in animals and humans. The benefit of VEMPs is there is no other vestibular function test, which provides information regarding the saccule or its innervation by the inferior branch of the vestibular nerve. As the VCR is a classic reflex arc with a sensory, CNS, and motor output component, it has been used to provide information regarding both the integrity of the saccule and inferior vestibular nerve, as well as the reflex arc through the brainstem. This has provided information on both otologic and neurologic conditions. In the literature, you will see VEMPs reported in studies with patients ranging from otologic conditions such as Menieres, superior canal dehiscence syndrome to neurological disorders such as multiple sclerosis (MS). Vestibular Rehabilitation: Producing Successful Outcomes

9 Vestibular Rehabilitation Therapy (VRT) can best be described as systematic repetitive exercises and protocols which extinguish or ameliorate patients motion provoked symptoms as well as enhancing postural stability and equilibrium. VRT is not new; it dates back to the 1940s. Cawthorne and Cookseys articles began to discuss the benefit of active eye and head movement exercise for patients who experienced labyrinthine problems. This was followed in 1980 by the work of Brandt and Daroff, which became known as the Brandt exercises. Since then, research and clinical experience has greatly advanced the scientific application of this treatment methodology. During the past several years, VRT has been gaining acceptance by physicians, therapists, and audiologists. Both the American Speech-Language-Hearing Assn. (ASHA) 4 and the American Academy of Audiology (AAA) have recognized the role of VRT within the audiologists scope of practice. The American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) 6 has also supported the role of VRT in the management of vestibular patients. Additionally, physical and occupational therapists and their respective organizations have supported this subspecialty within their professions. How does VRT work? The underlying physiological basis for VRT is the plasticity of the central nervous system. VRT does not actually involve a regeneration or treatment of the damaged vestibular end organ itself. Instead, it works by allowing the central nervous system and the brain to acclimate or adapt to asymmetrical/conflicting input coming from the vestibular mechanisms. Theoretically, central compensation should occur within 90 days following dysfunction or loss of one of the vestibular systems. However, many vestibular lesions, particularly those that occur with rapid onset, do not benefit from this compensation phenomenon. Complicating or retarding the phenomenon of central compensation is the reluctance of the patient to do any of those activities involving active head motion which produce symptoms of dizziness. This often is one of the main reasons why central compensation does not occur in so many individuals. To quote David Zee, M.D. of Johns Hopkins, The brain cannot fix what the brain cannot see. Other complicating factors include drugs like Meclizine, Antivert, Valium or other pharmaceuticals which suppress either peripheral vestibular or CNS function. These drugs will also delay or prevent the central nervous system from relearning or adapting to asymmetrical sensory input. Unfortunately, the dizzy patient, in his/her heightened anxiety about becoming dizzy (especially while at work or driving) becomes reliant on those pharmaceuticals that assist in suppressing their symptoms. These pharmaceuticals are often dispensed to patients who would be far better off without them.

10 Benefits of VRT May be the best or only management. Cost effective. Non-invasive. Short course of therapy. User friendly. Returns or restores everyday function. Who is VRT for? Vestibular rehabilitation therapy works best when it is utilized with individuals who are outside of the acute phase of a condition (e.g. symptoms no longer include the acute labyrinthine storm with debilitating vertigo accompanied by nausea, vomiting and diaphoresis). The patient who is in the midst of a labyrinthine storm secondary to labyrinthitis, vestibular neuritis or active Menieres disease will receive little or no benefit from VRT. However, most patients will be in a stabilized condition. This may include any condition which causes a vestibulopathy (weakness or loss of vestibular function), such as a Menieres patient who is in the endstage where there are no longer attacks, and the individuals fluctuating hearing loss is stabilized. This also applies to labyrinthitis, vestibular neuronitis, vertebrobasilar and labyrinthine ischemias. These patients typically present symptoms that are provoked with active head movement often at a particular frequency of motion and in a particular direction. There may also be significant visual provocation as well. The patient may present complaints related to an inability to drive down a particular street if they are looking out the side window where there are numerous telephone poles. It is common for patients to express a sense of motion sickness while they are looking at certain patterns of floor tile or wallpaper. One of the most common patient complaints is difficulty walking down the aisle of a grocery store while turning their head from side to side and up and down while shopping.