Clinical Vignette

A 68-year-old man presented with sudden onset of unilateral right-sided hearing loss. He stated that this was preceded by several months of constant ringing in his right ear. He had a history of hypertension and type 2 diabetes mellitus that was well controlled by oral hypoglycemic agents. He had no recent head trauma or previous surgeries. His only medications included atenolol and glyburide. There was no family history of hearing loss. He did not have a history of excess noise exposure or recent travel. No other otolaryngologic symptoms were reported.

On examination, his tympanic membranes (TMs) were normal. The Weber test lateralized the tuning fork to the side opposite the hearing loss. Rinne’s test results were normal. The rest of the head and neck examination was unremarkable.

Complete blood count was normal, and a fluorescent treponemal antibody absorption blood test was negative. The patient received a baseline audiogram demonstrating a right ear sensorineural hearing deficit predominantly in the higher frequencies. Brain MRI failed to demonstrate any mass lesion. A brainstem auditory evoked response (BAER) study was performed and revealed a prolonged interaural wave I–III latency, compatible with a retrocochlear process.

Sudden unilateral hearing loss, such as in the above vignette, in the absence of a tumor or lesion involving the vestibular nerve and with a history of diabetes is often attributable to microvascular infarction of the auditory nerve. However, sudden unprovoked hearing loss is not uncommon in patients without microvascular risk factors and the cause, in many cases, remains unknown.

Anatomy

The eighth cranial nerve (CN-VIII) is actually composed of two separate portions: the vestibular and cochlear nerves (vestibulocochlear nerve). The vestibular nerve is responsible for efferent and afferent fibers that control balance and equilibrium (see next section). The cochlear nerve, also called the auditory nerve, carries efferent and afferent fibers for hearing. To understand dysfunction of the auditory nerve, a brief description of the human hearing mechanism is required.

Sound waves travel through the external auditory canal and vibrate the TM, which in turn produces motion of the middle ear ossicles (incus, malleus, and stapes). The vibrations are transmitted through the oval window at the footplate of the stapes, causing a wave to travel through the endolymphatic fluid of the cochlea of the inner ear. The fluid waves vibrate the organ of Corti’s basilar membrane, stimulating inner and outer hair cells (Fig. 8-1). Hair cells, receptors of the sensorineural system, transmit action potentials to bipolar neurons, the bodies of which are in the spiral ganglion.

Figure 8-1 Pathway of Sound Reception.

Afferent fibers projecting toward the CNS comprise the auditory nerve (Fig. 8-2). They travel to the dorsal and ventral cochlear nuclei located in the caudolateral pons. Most of the secondary neurons project contralaterally across the midline to the superior olivary nucleus and then travel up the lateral lemniscus into the inferior colliculus of the midbrain. Decussating fibers from the cochlear nucleus to the superior olivary nucleus are located in the trapezoid bodies and also in the base of the pons. Fibers from the inferior colliculus continue to travel rostrally to the medial geniculate body of the thalamus and then terminate in the auditory cortex located in the transverse temporal gyri of Heschl.

Figure 8-2 Afferent Auditory Pathways.

Clinical Presentation

Physical Examination

Cerumen impaction or foreign bodies are easily identified on inspection of the external auditory canal. Pneumatic otoscopy is used to assess quality (color, lucency, and mobility) of the TM and defines conductive hearing loss as a reason for hearing deficit. Decreased TM mobility can be attributed to ossicular fixation, such as in otosclerosis, or middle ear effusion, as in otitis media. Middle ear or expanding jugular foramen tumors can present as a mass behind the TM causing conductive hearing loss.

Tuning fork tests assess whether the hearing loss is conductive or sensorineural (Fig. 8-3). During the head and neck examination, a complete cranial nerve examination must also be performed to assess other potential cranial nerve abnormalities. Facial nerve weakness may be attributed to viral infections, such as herpes zoster oticus, or expanding neoplasms in the internal auditory canal or cerebello-pontine angle, such as meningiomas or facial neuromas. Auscultation of the areas around the orbit and ear may detect pulsatile tinnitus. The type of SNHL can assist in the localization of the lesion. Ototoxic drugs, excess noise exposure, and autoimmune diseases affect the hair cells within the cochlea, the primary sensory organ of hearing, and lead to hearing loss usually described as decreased sensitivity to pure tones but preserved speech discrimination. Hearing loss caused by retrocochlear lesions of the nerve fibers of CN-VIII or its central auditory projections begins as decreased speech discrimination with relatively normal pure-tone sensitivity. However, decreased speech discrimination is not exclusive to retrocochlear lesions; it is also observed with extensive hair cell damage.

Figure 8-3 Hearing Tests: Weber and Rinne.

Diagnostic Approach

Standard laboratory blood tests are not routinely obtained for hearing loss unless a particular cause is suspected by history and physical examination. However, the fluorescent treponemal antibody absorption blood test or the microhemagglutination test for Treponema pallidum or both are usually ordered, as syphilis may often be relatively asymptomatic and is a treatable cause of SNHL.

A basic audiogram with pure tones and speech discrimination evaluation determines the type and amount of hearing loss. Unilateral decrease or asymmetry in speech discrimination, high-frequency hearing loss, or acoustic reflex abnormalities suggests a retrocochlear lesion, warranting further testing.

Gadolinium-enhanced MRI is specifically indicated when history, symptoms, and audiometric tests strongly suggest retrocochlear disease. MRI is the diagnostic “gold standard” for tumors causing hearing loss. For patients presenting with asymmetric hearing loss—especially if sudden—MRI is warranted to exclude acoustic neuromas or other cerebellopontine tumors. MRI with gadolinium can detect 2- to 3-mm tumors within the temporal bone. It is also sensitive for acute and chronic vascular disease or infarction as well as demyelinating lesions.

Brainstem auditory evoked response (BAER) is a useful objective and quantitative test when a retrocochlear deficit is suspected. It can suggest the site of lesion from the cochlea to the inferior colliculus at the pontine mesencephalic junction. BAER studies were initially considered highly sensitive for retrocochlear causes; however, as with most tests, false-negative and false-positive results are possible. The BAER uses electrodes attached to the patient’s head and clicking sounds emitted through earphones. The sounds elicit action potentials through the peripheral and central auditory pathways, and the EEG activity is measured and averaged by a computer. Right and left ear waveform morphologic appearance and latencies are compared. Interaural differences suggest pathologic conditions. Five wave peaks characterize the BAER, corresponding to specific anatomic points within the auditory pathway: I, CN-VIII action potential; II, cochlear nucleus; III, olivary complex; IV, lateral lemniscus; and V, inferior colliculus. A change in peak morphology and latency helps localize the pathologic condition.

Differential Diagnosis

Idiopathic, sudden SNHL is generally defined as loss that develops over 12 hours or less. However, a broad differential of sudden SNHL includes Ménière disease, neoplasms, vascular disorders, viral infections, MS, and rarely, hematologic disorders.

Neoplasms

In any case of sudden, unilateral hearing loss, neoplastic lesions, although rare, should be considered in the differential until excluded by diagnostic or radiologic testing. Vestibular schwannomas (also known as acoustic neuromas) are benign tumors arising from the Schwann cells of CN-VIII and account for 6% of all intracranial tumors (Fig. 8-4). These occur on the vestibular portion of CN-VIII and involve the adjacent cochlear division by compression against the bony walls of the internal auditory canal. Less commonly, neuromas can also arise directly from the cochlear nerve.

Figure 8-4 Vestibular Schwannoma.

Hearing loss is the most commonly reported symptom, occurring at some point in approximately 95% of patients with vestibular schwannoma. Progressive hearing loss generally results from stretching or compression of the cochlear nerve as the tumor grows. In contrast, when hearing loss is precipitous, it is thought to be secondary to occlusion of the internal auditory artery supplying the cochlea. Tinnitus with acoustic neuromas is typically high pitched, continuous, and unilateral. Paradoxically, vestibular symptoms are not frequently seen with vestibular nerve schwannomas because as these lesions grow, the contralateral vestibular system gradually adjusts to the imbalance, preventing any significant or longstanding vestibular symptomatology. Larger tumors occasionally lead to facial or trigeminal nerve involvement with symptoms of facial paralysis or paresthesias, respectively.

Before MRI, BAERs were the diagnostic test of choice for acoustic neuromas, with a sensitivity of 93–98%. The sensitivity is significantly lower with tumors less than 1 cm (58%). MRI will detect smaller tumors in patients who have had normal BAERs.

Treatment

When the primary cause of hearing loss is identified, such as an acoustic neuroma or syphilis, therapy is straightforward and potentially remediable depending on when the lesion is diagnosed in the illness course. There is no treatment of vascular lesions with infarction of the auditory nerve. However, for common disorders such as presbycusis, a variety of high-technology hearing-enhancing modalities can be designed, with the aid of an otologist, to meet the patient’s needs.

Clinical Vignette

A 65-year-old woman came to the emergency department with a chief complaint of “dizziness.” At 3:00 AM, she had awoken to an odd feeling in her head, which was accompanied by nausea. As she turned to her right to ask her husband for help, she experienced a severe spinning sensation with increased nausea followed by vomiting. The symptoms lasted for a few minutes. However, in the car and subsequently in the emergency department, any head and neck movement precipitated recurrent symptoms. Her medical history included diabetes mellitus, hypertension, and a remote TIA manifested by right-sided weakness.

Her blood pressure was 180/90 mm Hg. She appeared pale and uncomfortable and refused to open her eyes or move her head during the examination. The findings of her neurologic examination were normal, with the exception that she was hesitant to get off the examining cart to allow gait testing. Brain MRI results were normal. Subsequently, otolith particle-repositioning (Epley) maneuver successfully alleviated her symptoms.

This vignette describes a classic case of an individual with acute benign paroxysmal positional vertigo (BPPV). In most patients, this annoying disorder can be successfully treated by a simple maneuver. However, the possibility of a stroke, especially in those with cerebrovascular risk factors, or other cerebellar lesions must be considered before making this diagnosis.

Dizziness is a common nonspecific symptom. In patients older than 75 years, it is the most common medical complaint that brings individuals to a physician; dizziness is the third most common symptom among all age groups. In the United States, there are 8 million visits annually for dizziness; chronic dizziness affects 16% of the self-reported population.

When patients report dizziness, one of the primary challenges is to define its precise character. Feeling lightheaded, experiencing loss of equilibrium, vertigo, unsteady gait, and fainting can all be grouped under a patient’s ill-defined description of “dizziness,” although these symptoms often suggest different etiologies. Clarification of the precise historical details—onset, duration, positional and other exacerbating factors, and associated symptomatology—is essential to determine the likely cause.

Vertigo is the illusory perception of motion. Patients describe it as a sensation similar to that experienced on a merry-go-round. An inquiry as to whether things actually move in front of the patient’s eyes or a sense that they themselves are moving helps the patient define this symptom. Typical associated clinical findings include sudden precipitous onset, nausea and vomiting, nystagmus, and postural dysequilibrium during the vertiginous symptoms.

Gaze-dependent nystagmus occurs in processes that affect the ipsilateral cerebellum. Vertical nystagmus seen with upward gaze is often the result of disease in the cerebellum or tegmentum. Downward gaze vertical nystagmus is most often found in processes at the foramen magnum level, especially Chiari malformations. Optokinetic nystagmus refers to a normal phenomenon of reflexive slow movement of the eye in pursuit followed by a cortically driven corrective fast movement or saccade. Patients with parietal lobe lesions lose the fast, saccadic elements of the optokinetic response when the strip is moved in the direction of the abnormal hemisphere.

Anatomy

The vestibulocochlear nerve, CN-VIII, is actually composed of two nerves: the vestibular and cochlear nerves. The vestibular nerve is responsible for efferent and afferent fibers that control balance and equilibrium. The cochlear nerve, also called the auditory nerve, carries the efferent and afferent fibers for hearing. The vestibular system provides specific sensory input that influences motor function in reference to postural control (Figs. 8-1 and 8-5); the latter depends on interrelated mechanisms, including perception of position and motion in relation to gravity and orientation of the head and body in relation to the vertical axis during quiet stance. Other vestibular functions include integrating selected postural and orientation sensory cues in various environments; this aids in controlling the center of gravity when the body is static or moving and stabilizes the head during bodily movements. Because the vestibular system primarily provides sensory information about the head on the body, the CNS must rely on other sensory modalities to determine overall body position and movement.

Figure 8-5 Vestibular Receptors.

The visual system provides multiple information modes about head position and movement with respect to the environment, the direction of the vertical axis, and low frequency information regarding slow or static tilts. Joint position and muscle stretch contribute somatosensory information about the relative alignment of body segments with each other and the supporting surface. Postural control involves the combination of the complex organization of this sensory information, a “central set” based on previous experience and biomechanical constraints. Normally, to maintain proper body alignment over the support base, the individual generates a motor output via the vestibulospinal and corticospinal systems.

There are numerous central as well as peripheral processes that cause symptoms of vertigo (Fig. 8-6). During the patient’s initial evaluation, it is important to differentiate a CNS lesion from a peripheral localization by determining whether any associated neurologic deficits are present and their exact characteristics.

Figure 8-6 Causes of Vertigo (Classified by Region).

CNS Disorders

Brainstem dysfunction typically includes prominent dysmetria, diplopia, dysphagia, dysarthria, perioral numbness, or weakness. Twenty-five percent of patients with stroke risk factors who present to emergency medical settings with isolated vertigo, nystagmus, and postural instability have an infarction within the territory of the posterior inferior cerebellar artery (PICA). The acute postural instability with a PICA infarction is usually so severe that independent ambulation is not possible. Other than difficulty walking, there may be no cerebellar or central findings with a posterior inferior cerebellar artery infarction. This diagnosis is particularly important because acute postinfarction swelling or hemorrhage within the cerebellar hemisphere may cause brainstem compression and death (see Chapter 55).

Similarly, multiple sclerosis patients with demyelinating lesions in the brainstem may present with acute vertigo and gait dysfunction.

In contrast, patients with peripheral vestibular disorders have preserved ambulation, although they may have feelings of dysequilibrium and be frightened to move as noted in the vignette. If carefully brought up into the upright posture, most of these individuals can ambulate well and do not exhibit cerebellar ataxia or limb dysmetria.

Therefore, for patients presenting with vertigo who cannot ambulate independently, and particularly those with vascular risk factors, brain imaging is mandatory to rule out cerebellar infarction or multiple sclerosis.

Peripheral Nervous System Disorders

The matched tonic input of both vestibular end organs is processed centrally to mediate head stability. Unilateral reduction or differential in vestibular input is interpreted as turning. Acute peripheral vestibular dysfunction causes vertigo by interrupting the normal tonic discharge of one labyrinth. In the intact vestibular system, upright head rotation causes a reduction in horizontal semicircular canal firing rate on one side, paired with an increased firing rate on the other side. With acute unilateral vestibular loss, the reduced firing rate simulates the normal response to turning, generating fast phase nystagmus away from the affected ear. The nystagmus is usually more pronounced in gaze toward the affected side and reduced in gaze away from the affected side (law of Alexander). Veering or tilting toward the side of lesion may be present, through effects on the vestibular–spinal, vestibular–ocular, and vestibular–cerebellar pathways.

Etiologic Classification of Peripheral Vestibulopathies

Etiologic classification of peripheral vestibulopathies is initially based on symptoms and the presence of hearing loss. When symptoms persist for days to weeks with concomitant cochlear symptoms, such as hearing loss and tinnitus, a diagnosis of labyrinthitis is made once other causes are excluded. Although labyrinthitis is presumably of viral origin, certain structural pathologic conditions, including erosive cholesteatoma, temporal bone trauma or fistula, and central pathophysiologic mechanisms, need to be excluded.

Ménière disease is characterized by recurrent vertigo, fluctuating sensory neural hearing loss, tinnitus, and aural fullness. The prevalence of the disease ranges from 500 to 1000 per million, with no difference in regard to gender. Patients often present in their fourth decade, usually with unilateral symptoms, although many will develop bilateral symptoms within a few years. Initial presentation can simply be aural fullness or short bouts of vertigo that resolve spontaneously. Vertigo, even in advanced stages, rarely lasts more than 2 hours and is nonpositional. Patients can have multiple attacks per month or only one every few years. In the early stages of the disease, symptoms often appear in isolation, and the hearing deficit is not initially noticeable, rendering diagnosis difficult. As the disease progresses, prominent low-frequency hearing loss appears, and the symptoms are more prolonged and recur more frequently. Some patients are left with a chronic sense of imbalance.

The underlying pathophysiology of Ménière disease is presumably related to either excessive production or decreased absorption of endolymph. An autoimmune etiology has been proposed, but the exact mechanism remains unclear. Diagnostic tests such as glycerol dehydration test and audiometry have high sensitivity for Ménière disease, especially if performed during an attack. Other tests such as electrocochleography and vestibular evoked myogenic potentials can be helpful for diagnosis or staging the disease. Serologic tests to exclude co-morbid conditions include thyroid function test, antinuclear antibody, rheumatoid factor, complement antibodies, serum immunoglobulin levels, anticardiolipin antibodies, C-reactive protein, syphilis, and Lyme treponemal titer. Symptomatic treatment includes antiemetics, benzodiazepines, diuretics, and a low salt diet. Avoidance of alcohol, caffeine, nicotine, and stress may help. Reports have suggested a role for antiviral medications and immunosuppressant drugs, at least for short-term control of symptoms. Intratympanic instillation of drugs such as dexamethasone may be helpful to control vertigo for months but has less effect on hearing loss. Intratympanic gentamicin and streptomycin, strong vestibular toxins, are used as a last resort to eliminate residual vestibular function in cases of intractable vertigo. Endolymphatic sac decompression and shunting, as well as surgical labyrinthectomy and vestibular neurectomy, have also been used in refractory cases.

Vestibular neuritis is characterized by prolonged vertigo without hearing loss. This is a cranial mononeuropathy limited to the vestibular division of CN-VIII. Diagnosis is often difficult in patients with recurrent true vertiginous episodes lasting hours, without associated cochlear symptomatology.

Initially, it is important to exclude vertebrobasilar TIAs, particularly in those with vascular risk factors or in young persons with associated recent neck injury and possible vertebral artery dissection. However, it is rare for vertigo to be the sole manifestation of a TIA, emphasizing the importance of a careful history, as patients may overlook seemingly less important symptoms that could lead to a central diagnosis and may focus on the vertigo. Occasionally, early Ménière disease is diagnosed in some patients when hearing loss eventually develops.

Types of Vertigo and Disorders

Benign paroxysmal positional vertigo (BPPV) is the most common cause of vertigo in the elderly. The typical presentation is that of recurrent bouts of position-dependent vertigo with either a transient spinning sensation or an illusion of side to side movement. Spells are brief, lasting seconds to minutes, and often associated with nausea and sometimes vomiting. Symptoms occur with sudden shift in position, when turning in bed, or with neck extension, as while looking up or while in a dentist or hairdresser chair. Often patients become anxious and guard against fast movements. Episodes become gradually shorter and symptoms improve over 72 hours but can occasionally linger for many days. BPPV results from otolith debris errantly entering the semicircular canals, usually the posterior canal, rendering them gravitationally sensitive with the solid material acting as a plunger or weight within the fluid-filled system. Symptoms become less defined when the horizontal or superior canal is involved or bilateral vestibular disruptions are present. Although many cases can be diagnosed in the emergency department or outpatient clinic, BPPV patients are often referred either to neurology or otolaryngology specialists. When the presentation is not typical, tests such as brain MR and electronystagmograms are done to exclude other pathology. Recurrent symptoms can lead to vascular evaluations to rule out possible vertebral artery compromise. Although unusual, vertigo as the sole manifestation of vertebrobasilar disease has been reported, especially with posterior inferior cerebellar artery ischemia, and caution is advised when vascular risk factors are present in those with atypical presentations. However, distinct positionally inducible isolated vertigo remains more a feature of a peripheral vestibulopathy than of cerebral ischemia.

The diagnosis of BPPV in large part depends on the clinical history and bedside testing. The Dix-Hallpike maneuver, when performed and interpreted properly is diagnostic. Studies suggest that the Dix-Hallpike maneuver has a sensitivity and specificity of approximately 75%. In our experience the ability to perform the maneuver properly in anxious patients fearful of provocative maneuvers is a major limiting factor for accurate evaluation. Risk factors for BPPV include recent head trauma (which can be relatively minor); otologic surgery or disease; habitual unusual positioning such as is a daily occurrence for plumbers, mechanics, and yoga enthusiasts; or advanced age. Particle repositioning maneuvers or canalith repositioning maneuver is the main treatment for benign paroxysmal positional vertigo (Fig. 8-7). Another maneuver known as the liberatory maneuver, developed by Semont et al., relies on rapidly swinging the patient from lying initially on the involved side through 180 degrees to the opposite, uninvolved side. Unfortunately any repositioning maneuver can be limited by the inability of the patient to physically participate (musculoskeletal and orthopedic limitations, especially of the head and neck) or when induced symptoms are intolerable. In 5% of patients, symptoms may worsen with repositioning maneuvers in part due to conversion from posterior to horizontal canal involvement. Outcome studies regarding the effectiveness of the canalith repositioning maneuver provide a range of reported success, as most studies rely on subjective reporting, which is inherently unreliable because patients quickly develop adaptive behavior spontaneously. Overall, however, there is evidence to favor repositioning maneuvers, with some studies demonstrating resolution of symptoms in 90% of patients after only one treatment. Self-administered maneuvers in combination with guided treatments can often help expedite improvement in the remaining patients. Successful treatment with the repositioning maneuvers does not influence recurrence rate, which averages around 20% over a 20-month period. Persistent vertigo or frequent recurrences of BPPV is uncommon, but under such circumstances surgical occlusion of the posterior semicircular canal with bone grafts and fibrin glue is an effective treatment. Medications can provide temporary relief by controlling nausea and suppressing the vestibular responses. Meclizine and benzodiazepines are the most frequently prescribed medications but can be sedating and should be used only for a few days.

Figure 8-7 Canalith Repositioning (Epley) Maneuver.

Chronic vestibulopathies are less likely to cause vertigo, because their duration allows for CNS compensation. Acoustic neuromas and other slow-growing neoplasms affecting CN-VIII may cause unilateral tinnitus, hearing loss, and abnormal hypoactive caloric responses on electronystagmogram. However, these tumors rarely present with vertigo.

Bilateral vestibulopathy typically do not cause vertigo or a sensation of turning. However, bilateral vestibular disruption does affect the vestibular–ocular reflex, which stabilizes visual perception during head motion. The main symptoms in these cases are a sense of imbalance, especially when visual cues are altered (unequal surface, dim illumination, and quick head movements), and oscillopsia (see below). Vestibulotoxic agents, such as aminoglycosides, alcohol, and heavy metals, can lead to transient or permanent vestibular damage, but bilateral vestibular hypo-function can also occur in otherwise healthy adults (idiopathic) or can result from a genetic predisposition.

Oscillopsia, or failure to stabilize vision during head movement, can cause bobbing visual perception and loss of dynamic visual acuity while walking. Because some patients call this “dizziness,” a close history is needed to help differentiate it from true vertigo. In addition to bilateral peripheral vestibulopathies, oscillopsia can be seen with central lesions involving the brainstem and cerebellar, particularly mass lesion around the foramen magnum. It is typically seen in patients with the Arnold–Chiari syndrome, a developmental condition often associated with syringomyelia and syringobulbia, and is rarely observed in patients with multiple sclerosis. This phenomenon is usually binocular, and monocular symptoms raise the possibility of ocular muscle myokymia instead.

Canal dehiscence syndrome, first described in 1998 by Lloyd B. Minor, is caused by thinning or developmental absence of part of the temporal bone overlying the superior semicircular canal leading to an extra direct conduit for impulses into the inner ear in addition to normal conduction through the oval window. Canal dehiscence presents with a variety of symptoms including a sensation of ear blockage that is relieved with Valsalva maneuver, hyperacusis, sound distortion, conductive hearing loss, and chronic imbalance. Abrupt vertigo, disequilibrium, nystagmus, oscillopsia, and nausea induced by external sounds and even one’s own voice or pulsations occur in some cases and is known as the Tullio phenomenon. Clinical diagnosis, however, can be difficult, as symptoms may often be nonspecific or occur in isolation. Some seemingly bizarre complaints, such as hearing louder than usual gastric noises and being aware of the eyeballs moving in the socket, are reported. Pulsatile tinnitus is also common and often leads to a suspicion of vascular causes.

A combination of tests helps establish the diagnosis of canal dehiscence and differentiates it from conditions such as Ménièe disease or perilymphatic fistulas. A normal vestibular-evoked myogenic response in the presence of temporal bone abnormalities seen on high-resolution CT scan has more than 90% sensitivity and specificity. Low frequency conductive hearing with normal tympanometry and an intact acoustic reflex provides further support. A variety of surgical techniques to repair or plug the bone around the superior semicircular have been developed.

Diagnostic Approach

A complete neurologic examination is of the utmost importance in the evaluation of dizziness or vertigo. When one sensory vestibular mechanism is absent, the remaining sensory inputs are used to elicit corrective postural reactions. Superimposed neurologic disorders, including stroke, Parkinson disease, cerebellar pathology, or peripheral neuropathy, may affect the potential of the nervous system to compensate, and symptoms are amplified significantly.

Electronystagmogram (ENG): This test is intended to evaluate the effects of vestibular input on the ocular system. Disorders of both the otoliths and the vestibular nerve can cause abnormalities on the ENG. The two basic elements of the ENG include the equivalent of cold calorics and the second is rotatory chair testing. Vestibular nerve abnormalities can manifest as a delay in conduction of the vestibular–ocular reflex via the medial longitudinal fasciculus. Otolith dysfunction is not easily detected by this test, however, and false-negative results are common. Rotatory chair testing, on the other hand, may elicit abnormal responses in patients with otolith dysfunction as well as in those with vestibular nerve dysfunction. The tests are affected by medications and patient cooperation and depend on comparison to standard tables or to the normal side. The results should be interpreted with the clinical presentation and potential confounding variables taken into account.

Dynamic posturography is a complex testing modality that defines the extent to which a patient is able to use visual, somatosensory, and vestibular input for postural control. The patient stands on a shifting platform in front of a simulated visual field presented at different angles. The postural response to various shifts can be assessed and quantitated. To date, however, the value of this test is still questionable, although it is sometimes used for designing rehabilitation strategies.

The clinical test of sensory interaction and balance uses a combination of two visual (eyes open or closed) and two support surface (soft unstable, firm stable) conditions to clinically measure a patient’s sensory interaction for postural stability. The Romberg (stationary) and sharpened Romberg (tandem stance) test with eyes open and eyes closed, and unilateral standing with eyes open and eyes closed are not specific for postural deficits secondary to vestibular pathologic conditions. However, patients with vestibular damage may demonstrate increased sway or falling during these tests.

Dynamic tests, such as floor walking with the eyes closed, measure tandem walking for up to 10 steps. Persons with acute or chronic vestibular disorders may fail this test based on established age-related norms.

Several performance tests are used to establish a baseline function analysis and measure outcome in individuals with impairments of static and dynamic postural control. These include the Timed Up and Go Test, the Dynamic Gait Index, and the Berg Balance Scale.

The Timed Up and Go test measures the time required to rise from a standard chair, walk 10 feet, return to that chair, and sit. The norm for neurologically intact older adults is 10–12 seconds. The results may be a predictor for falls in community-dwelling elders. There is a maximum of 14 seconds for elders at minimal risk for falls and less than 30 seconds for elders who are dependent on assistance for ambulation in the community. There is no threshold established for patients with vestibular disorders.

The Dynamic Gait Index measures the ability to modify gait in response to eight different tasks during ambulation. Each task is given a score of 0 to –3. A score of 11 ± 4 is found in older adults with a history of falls but no neurologic disorders.

The Berg Balance Scale uses 14 test-specific items rated 0–4 that measure postural control during functionally related tasks. These require anticipatory abilities and are performed only while sitting and standing. Test scores are a good predictor of elderly fall risk. Scores less than 45 were associated with an increased risk for falls; scores less than 36 were associated with a 100% risk of falls.

General Treatment Considerations