A number of tools can be used to assess the patient with complaints of dizziness and imbalance to help determine the management path for these symptoms. The most critical investigative tool available is the neurotologic history—the patient's past and presenting symptoms. The three major descriptors of the symptom presentation can be very useful in determining the lesion site, diagnostic possibilities, and whether vestibular and balance rehabilitation therapy should be recommended.
These descriptors are: characteristics of symptoms, temporal course of symptoms, and circumstances of presentation.
Characteristics of Symptoms
The term "dizziness" is all-encompassing and can imply vertigo (a true sense that the person or the environment is moving in an angular manner), lightheadedness (sensation that if it worsens the person will faint), imbalance, or any combination of these sensations. It becomes important, therefore, first to establish the character of the patient's symptoms: do they involve vertigo or are they restricted to lightheadedness and imbalance?
In sudden-onset vertigo without complaints that suggest a posterior fossa lesion site (e.g., diplopia [double vision], dysarthria, dysphasia, dysmetria, or asymmetrical muscle weakness), labyrinthine involvement is most likely. However, the production of vertigo is restricted to lesion sites from the labyrinth through the pons and posterior cerebellar region. It is highly unlikely that lesions superior to these regions result in vertigo. It is also unlikely that lesions resulting from areas served primarily by the anterior circulation (carotid-fed regions) would produce vertigo as a primary symptom. Therefore, the symptom of rapid-onset vertigo suggests a lesion site in the posterior fossa—that area served by the posterior circulation involving the vertebral arteries, the basilar and their branches—ranging from the medulla to the pons and posterior cerebellum, versus involvement in the labyrinth or directly on the VIIIth cranial nerve.
Temporal Course of Symptoms
Symptoms can present as paroxysmal or continuous with paroxysmal exacerbations. Another common presentation is a sudden-onset vestibular crisis event with continuous symptoms that slowly improve over the course of one to five days, changing to paroxysmal symptoms provoked by head position or movement. An important factor is whether paroxysmal symptoms occur in intervals measured in seconds, minutes, hours, days, or weeks.
Circumstances of Symptom Presentation
The focus here is on how symptoms initiate. Are they spontaneous, or provoked by head position or head or visual motion? A patient may also experience both spontaneous and motion-provoked symptoms. The quintessential example of a disorder with spontaneous symptoms is Meniere's syndrome; in contrast, symptoms of benign paroxysmal positional vertigo (BPPV) are strictly related to head position and head movement.
The initial decision point concerning possible treatment options is reached during the discussion of the circumstances of symptom presentation. The use of vestibular and balance rehabilitation therapy (VBRT), for example, is based principally on symptom presentation, not through direct office or laboratory examinations. The patient with only spontaneous onset of symptoms would not be a likely candidate for VBRT. Patients whose symptoms are provoked by head or visual motion are typically the most appropriate. Patients can have spontaneous events and also experience symptoms provoked by head movement, head position, or visual motion. This group would also be appropriate for VBRT; its effectiveness in helping symptoms provoked by movement or visual motion, however, is inversely related to the frequency of spontaneous symptoms (on which the therapy usually will have no impact).
Two test findings suggest the need for therapy intervention: those related to the functional evaluation of postural control through computerized dynamic posturography, and those related to the functional evaluation of the vestibulo-ocular reflex (VOR) via the dynamic visual acuity test. At this point in the history acquisition, therefore, the clinician should already be considering the possible use of a VBRT program.
Another aspect of the circumstances of symptoms is possible auditory system involvement, indicated by any perceived changes in the patient's hearing, unilaterally or bilaterally; tinnitus; and/or sensation of aural fullness.
A limited example of the use of the three symptom descriptors—characteristics of symptoms, temporal course of symptoms, and circumstances of presentation—is given in Table 1 [PDF] (see page 16). This table contrasts four combinations of symptom presentation.
After the symptoms have been established, it is time to consider direct examination and laboratory studies. We need to look for signs that-when interpreted in the context of the symptoms-offer a more definitive lesion site, narrow the etiological possibilities, and present information about the functional impact of the disorder.
The observation of the signs related to dizziness (when the term is used in its broadest context) can be accomplished through office examination techniques, formal laboratory studies, or a combination of the two. The following discussion will be limited to laboratory studies. (Major sections of the remainder of this article appear in another publication to which the reader is referred for further details and clinical examples of this discussion [Shepard, 2007].)
Vestibular and Balance Studies
The different information provided by each of the vestibular and balance studies available helps establish which would be the most useful for a given patient and how they may be used together.
Extent and Site-of-Lesion Studies
- Ocular motor testing with saccade, pursuit, and gaze provide for evaluation of cerebellar/brain stem involvement
- Spontaneous and positional nystagmus—non-localizing but suggestive of peripheral involvement when ocular motor studies are normal
- Caloric irrigation testing—localization to right or left peripheral horizontal semicircular canal system
- Note that the Dix-Hallpike requires direct visualization of the eye and cannot be analyzed from a two-dimensional recording after the test. Therefore, this is more of a direct clinical examination and will not be considered in this context.
- Rotational Chair (via step tests or sinusoidal protocols)
- Expands the review of the peripheral vestibular system, typically the horizontal canals in routine protocols. Provides evidence for possible peripheral involvement when the time constant is abnormally low.
- Suggestions for right/left localization can be noted.
- Special paradigms may be used to review cerebellar nodulus involvement.
- Computerized Dynamic Posturography
- Motor Control Testing—suggests possible involvement in the long loop pathways for stimulation of motor response activation in the lower limbs
- Postural Evoked Responses (surface EMG recordings of muscle activity of the lower limbs)—provides for site-specific localization of lesions within the long loop pathways and a first approximation differentiation between certain central nervous system disorders
- Otolith function (via vestibular evoked myogenic potentials [VEMP] and subjective visual vertical [SVV])
- Allows for evaluation of individual saccular function and the integrity of the inferior division of the vestibular portion of the VIIIth cranial nerve via the use of an auditory stimulus (VEMP).
- Evaluation of the utricular organs in a global manner can be investigated in the more acute patient by the patient's ability to set a projected line in absence of ambient light to his or her perception of vertical (or horizontal)—the SVV test.
Functional Performance/Objectify Complaints
- Presence of spontaneous or positional nystagmus when the patient reports vertigo is an objective sign consistent with that complaint
- Dynamic visual acuity testing (DVA)—objectifies and quantifies the magnitude of oscillopsia and is a functional manifestation of VOR gain reduction unilaterally or bilaterally
- Sensory Organization Tests (SOT)—strictly a functional evaluation of static and dynamic balance and the only quantitative assessment of aphysiologic performance
- Disability/functionality scales—Dizziness Handicap Inventory/SF-36/visual analog scales (VAS), among others, improve ability to assess a patient's overall functional and disability status
Indications for Status of Central Compensation Process
- Physiologic status relative to nystagmus—spontaneous and positional nystagmus/directional preponderance from caloric/asymmetry from rotary chair sinusoidal or step test protocols
- Functional status—SOT/DVA/VAS all give indications of functional performance change over time and hence compensation. It is important to note that the functional and physiologic indications of compensation may vary in an independent manner.
Indications, Prognosis, and Design for Vestibular and Balance Rehabilitation Programs (VBRT)
- Symptom presentation is the primary indication for use of VBRT.
- SOT can indicate functional deficits in postural control not reported in the history that would indicate the need for VBRT when symptom presentation is not strong in that manner. This study can be used for assistance in design and monitoring performance for VBRT.
- DVA indicates the need for specific type of exercises (adaptation) and provides a means for monitoring the effectiveness of therapy in improving the VOR on a direct functional basis
- Caloric irrigations, rotational chair time constant, and asymmetry abnormalities provide indications of VOR gain deficits and if symptom presentation is appropriate also would support the use of adaptation type of exercises in a VBRT program. These are of minimal use in monitoring the outcome of the therapy program unless the patient is worsening.
Although these tests are presented individually to highlight their designed use, a combination of test findings are typically used to develop a final impression from the evaluation.
It is the exception—not the rule—that results of vestibular and balance laboratory tests would drive management of the dizzy patient. It would be extremely rare that these studies return a diagnosis. Therefore, the routine use of these tools to determine how to manage a dizzy patient, without a clinical history, is a false line of reasoning and unproductive in the majority of patients. This conclusion does not imply that the studies have minimal or no value; in fact, they can be very useful in confirming suspected site-of-lesion, verifying certain function abnormalities, and occasionally revealing unanticipated results that can alter management.
The interpretive value of the studies isolated from the clinical history is of limited use, however, when the treating physician is making the initial management decisions involving medication, surgical procedures, VBRT, or a combination of these options. After this first decision is made, isolated test findings from the studies may help design the specifics of treatment and monitor progress. Two case studies illustrate these points.
Case Study 1
A 35-year-old male sought treatment for continuing symptoms which had begun six months prior with a crisis event of vertigo, nausea, and vomiting that lasted continuously for three days with slow, steady improvement. The continuous vertigo resolved into his current head movement-provoked spells of lightheadedness with imbalance and occasional vertigo lasting up to a minute after movement. His audiometric evaluation was completely normal bilaterally, as was his contrast MRI study of the head.
His history, combined with the direct office examination, strongly suggested uncompensated left peripheral vestibular hypo-function, secondary to vestibular neuritis. Laboratory vestibular function testing revealed spontaneous right beating nystagmus with visual fixation removed and a 76% left reduced vestibular response with ocular motor testing and postural control assessment normal. The tests, as is typical in most cases, confirmed the findings from the history and direct office examination.
The initial management decisions--to initiate VBRT and to discontinue vestibular suppressive medication--were not altered by the laboratory findings. The vestibular function and balance tests were well-justified, given the duration of symptoms and the testing's sensitivity (better than the direct examination) to some ocular motor findings--specifically saccade velocity testing and quantification of smooth pursuit. Sensitivity to mild peripheral vestibular function asymmetry is also better with laboratory testing.
Case Study 2
In contrast, a 31-year-old male presented with vertigo provoked by head motion with a relatively constant imbalance with standing and walking. He denied any vestibular crisis event or auditory complaints. His symptoms were more concentrated in sagittal plane movement and when rolling left or right from a supine position. These symptoms had been ongoing for several years, with intervals when the vertigo was resolved and the imbalance reduced but not absent. An MRI from several years prior was normal, as was an audiological examination. Other than the development of mild paresthesia of the right hand and arm over the last year, he had no other neurological complaints and his past medical history was non-contributory.
His direct office examination was remarkable for anterior, semi-circular canal benign paroxysmal positional vertigo (BPPV). The remainder of the examination was normal. He was treated in the office with a Canalith Repositioning Procedure and referred to a formal VBRT program. Secondary to the length of time of the symptoms and the complaints of persistent imbalance (although this is a common report with BPPV), vestibular and balance function testing was requested.
The laboratory studies continued to show anterior canal BPPV with no other indications of peripheral vestibular system involvement. Pursuit tracking tests were normal, but saccade testing was positive for mild right internuclear ophthalmoplegia. Postural control abnormalities were collectively consistent with that seen in demylinating disorders. Secondary to these findings and the patient's report of paresthesia starting in the left foot, a new MRI was obtained that showed multiple hyper-intense spots throughout the brain stem region. He was referred on to neurology and is being followed with a diagnosis of probable multiple sclerosis with BPPV. Unlike the first patient, the management in this case was driven strongly by the results of the vestibular and balance function tests. The test results revealed abnormalities too subtle to be detected in a direct examination and the symptom presentation was, in general, not inconsistent with the BPPV noted.
History and Testing
In the evaluation of the patient with dizziness, using the presenting and past symptoms by means of the history, as the framework around which the laboratory studies and direct office examination are interpreted, is of importance.
The careful consideration of symptoms, together with the results of various studies, provide the opportunity to arrive at lesion-site, diagnosis, functional impact, and management options for the majority of the patients. This systematic approach helps reduce the mystery and frustration involved with patient care for both the health care professional and the patients themselves.