Evaluation Guidelines Tables125 and 126

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Numerous laboratory procedures are commonly used for evaluation of patients with vertigo and dizziness. For efficiency and cost, procedures should be selected according to specific symptom complexes present in the patient.

Neuroimaging. Skull films, cervical spine films, computed tomography (CT) scans of the head, and CT scans of the sinuses are not routinely recommended in the evaluation of vertigo or hearing disturbances. Magnetic resonance imaging (MRI) of the head can be used to evaluate

TABLE 12-5 -- USEFUL STUDIES IN THE EVALUATION OF DISORDERS OF CRANIAL NERVE VIII

Syndrome

Neuroimaging

Electrophysiology

Fluid and Tissue Analysis

Neuropsychological Tests

Other Tests

Central hearing disorders

Temporal cortex lesion: MRI, CT

N/A

N/A

Abnormal

Poor word recognition on audiometry

Peripheral hearing loss

Usually normal MRI, CT

BAER ECOG MLR

N/A

N/A

Audiogram abnormal

CPA syndrome

Lesion in CPA: MRI, CT

BAER

CSF

N/A

Audiogram abnormal

Central vertigo

Brain stem or cerebellum lesion: MRI, CT

BAER

CSF Blood

N/A

Rotatory chair test

Peripheral vertigo: BPPV

Normal

Normal

N/A

N/A

ENG

Meniere's disease

Normal

BAER ECOG

N/A

N/A

Audiogram ENG

Vestibular neuritis

MRI may show enhancement of vestibular nerve

N/A

N/A

N/A

ENG

Bilateral vestibular

Normal

N/A

N/A

N/A

ENG

loss

Rotatory chair Audiogram

MKI, magnetic resonance imaging; CT, computed tomography; MLR, middle latency response; BAER, brain stem auditory evoked responses; ECOG, electrocochleography; N/A, not applieable; ENG, electronystagmography.

the structural integrity of the brain stem, cerebellum, periventricular white matter, eighth nerve complexes, and sinuses. The T1 MRI with gadolinium contrast is the most useful study. MRI is not routinely needed to evaluate vertigo or hearing disturbance without accompanying neurological findings. Although the MRI may show enhancement of the vestibular nerve in vestibular neuritis, the expense of this study should be considered when attempting to document the existence of this self-limited condition. MRI with contrast is preferred to brain stem auditory evoked responses (BAER) testing, when acoustic neuroma is suspected, because it detects tumors at an earlier stage. CT of the temporal bone provides higher resolution than MRI and is preferred in the evaluation of lesions involving bone, particularly when otosclerosis or cholesteatoma is suspected.

Electrophysiology. Electroencephalography has a low yield in most disorders related to cranial nerve VIII but is indicated when there is unexplained vertigo after head trauma or for the "quick spin" symptom complex. The BAER test, also known as auditory brain stem response test, assesses the auditory nerve and brain stem pathways. This test is usually ordered to rule out an acoustic neuroma, and this study has roughly a 90 percent sensitivity. Because BAER results may be inaccurate in patients who have no high-frequency hearing, audiometry is recommended before BAER testing. The presence of abnormal BAER results is an indication for a MRI evaluation of the posterior fossa (T1-weighted image with contrast). For cost efficiency, BAERs need not be obtained if an MRI is planned, and the MRI is generally the preferred test in most instances. Electrocochleography (ECOG) is a variant of the BAER in which needle electrodes are placed in the ear drum to obtain better definition of the cochlear potential. ECOG is sometimes helpful to confirm a diagnosis of Meniere's disease.

Numerous more unusual electrophysiological tests can be used to infer the integrity of central auditory pathways. The middle latency response, or MLR, is generated by thalamocortical pathways. The "mismatch" response is a test of higher order auditory discrimination. The role of these tests in clinical practice is uncertain.

Fluid and Tissue Analysis. Blood tests are triggered by specific symptom complexes, and there is no routine set of values obtained in every patient. In particular, chemistry panels, complete blood counts, glucose tolerance tests, and allergy tests need not be routinely ordered. Similarly, urine testing is rarely productive in disorders of cranial nerve VIII.

Cerebrospinal Fluid. Lumbar puncture has limited usefulness in disorders of cranial nerve VIII. Occasionally, it may be indicated in pursuit of the diagnosis of neurosyphilis, Lyme disease, and meningeal carcinomatosis.

Neuropsychological Tests. Neuropsychological testing of speech and language may be helpful in patients in whom the diagnosis of a central hearing disturbance is being entertained. Otherwise, these procedures have limited usefulness in the evaluation of disorders of cranial nerve VIII. The Minnesota Multiphasic Personality Inventory has some usefulness when the diagnosis of malingering is being considered. Neuropsychological testing may also be useful in determining how much anxiety is associated with the patient's symptom complex.

Other Tests. The audiogram is the single most useful test in the patient with a hearing disorder and/or vertigo. In hearing disorders, the audiogram is crucial in defining the degree and type of loss. In patients with vertigo, abnormalities in the audiogram usually narrow the differential diagnosis down to otological vertigo. Accompanying the audiogram is a battery of related measures. The tympanogram measures middle ear pressure, and tympanometry is helpful in identifying a perforated ear drum or middle ear infection. Acoustical reflexes measure the stapedius and tensor tympani reflex-generated ear drum movement in

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