Laboratory Studies
See the list below:
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Cochleovestibular
Standard audiometry (used to document present hearing acuity and, if loss is present, to determine whether it is sensorineural or conductive hearing loss)
Impedance audiometry or tympanometry (used to determine the status of the tympanic membrane and middle ear)
Electrocochleography (summating potential [SP]:action potential [AP] ratio over 0.4 may indicate Ménière disease)
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Electronystagmography or oculomotor testing (The standard ENG test battery is composed of saccadic, gaze, pursuit, optokinetic-eye movement, head-shake nystagmus, positional nystagmus, positioning nystagmus, and bithermal caloric tests. This testing battery is used to determine whether the vertigo is otologic or central in origin.)
Bithermal calorics
Barany introduced the caloric test in 1903. Since then, it has been the time-honored vestibular test in clinical neurotology. The caloric test remains the standard for evaluating unilateral vestibular deficit. However, it is a limited and nonphysiologic test of the vestibular system.
The traditional caloric test is performed with the patient lying with the head elevated; cold (30° C) and warm (44° C) water are used to irrigate each ear, 1 at a time. Cold irrigation is an inhibitory stimulus, and warm irrigation is excitatory. The direction of postcaloric nystagmus is determined by the quick phase direction and is easily remembered by using the mnemonic COWS: cold opposite and warm same (ie, quick phase away from or toward the irrigated ear).
The 3 most important findings from the caloric test are unilateral weakness, bilateral weakness, and failure of fixation suppression (FFS) of caloric-induced nystagmus. The first 2 abnormalities are due to peripheral vestibular disease, and the third is due to central cerebellar disease.
Rotary testing
Barany introduced rotational testing in 1907. In clinical practice, the rotation test lagged behind the caloric test. However, with the advancement of computer technology, rotational chair-test systems were developed in the late 1970s and continue to evolve. They are now used in several vestibular testing laboratories.
The test is used to evaluate the integrity of the vestibulo-ocular reflex (VOR) in the low- (0.1-0.32 Hz) or high-frequency (1-4 Hz) ranges. The measured parameters are VOR gain, phase (latency), and symmetry. The test is most useful in determining residual vestibular function and the degree of central vestibular compensation.
Imaging Studies
See the list below:
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These scans are very useful for identifying temporal bone fractures. [4]
Two kinds of fractures, longitudinal and transverse, are differentiated in relationship to the long axis of the petrous bone.
Transverse fractures extend through the inner ear and are more likely to cause vestibular symptoms.
High resolution with thin cuts is imperative to ensure that the temporal bone and otic capsule are well visualized
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MRI of the temporal bone and internal auditory canal, with and without contrast, can be obtained to rule out abnormal anatomy or lesions (including retrocochlear lesions such as vestibular schwannomas), which are important to exclude.
Procedures
See the list below:
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Dix-Hallpike maneuver
The patient sits upright on an examination table. The head is turned 45° such that the chin is toward the shoulder. The patient is then brought straight back rapidly into a head hanging position. This position is maintained for at least 30 seconds. See the image below.
The nystagmus characteristic of BPPV begins after a latency of 2-10 seconds, increases in amplitude over about 10 seconds, and decreases in velocity over the next 30 seconds.
Transient geotropic rotatory nystagmus (clockwise with left ear down, counterclockwise with right ear down)
Severe subjective vertigo
Fatigability
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Epley maneuver (canalith repositioning maneuver)
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Posttraumatic vertigo. The Dix-Hallpike maneuver.
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Posttraumatic vertigo. The Epley maneuver.
