|Year : 2017 | Volume
| Issue : 2 | Page : 63-66
Investigating a patient of vertigo: Where do we stand today?
Department of ENT, Smt. Kashibai Navale Medical College and General Hospital, Pune, Maharashtra; Vertigo Clinic, Ghaisas ENT Hospital, Pune, Maharashtra, India
|Date of Web Publication||14-Jun-2017|
Department of ENT, Smt. Kashibai Navale Medical College and General Hospital, Pune, Maharashtra; Vertigo Clinic, Ghaisas ENT Hospital, Pune, Maharashtra
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Naik C. Investigating a patient of vertigo: Where do we stand today?. Indian J Otol 2017;23:63-6
Vertigo is an enigma in the field of medicine often misdiagnosed and mistreated. This is so, due to vague symptoms with which a patient often presents with. Moreover, the treating clinician is not able to dedicate enough time for thorough evaluation.
A thorough neurotological history and clinical examination give a definitive diagnosis in more than 60% of cases of vertigo. Yet, in some cases, it is imperative to carry out certain investigations to confirm the diagnosis and plan the further management as per the diagnosis.
Today, a neurotologist has at his/her disposal an armamentarium of various diagnostic tools to investigate a patient of vertigo. It is important for a clinician to be aware of these investigative procedures and their significance in the management of vertigo.
The objectives of investigations are as follows
- To assess the functional integrity of vestibulo-ocular system
- To assess the functional integrity of vestibulospinal system
- Audiological tests to assess hearing thresholds
- Computed tomography scan and magnetic resonance imaging (MRI) to assess the structural integrity of central nervous system (CNS) pathways and positron emission tomography, single photon emission computed tomography, and functional MRI for functional aspects
- Allied tests such as hemogram, biochemical tests for Vitamin B12 and D, tests for Cardiovascular System (CVS), and electroencephalography.
Objectives of these tests are to ascertain that a patient has a definite balance disorder, if so, then to document the degree of functional impairment, to localize the lesion topographically, to arrive at an etiological diagnosis, and to accordingly establish a management protocol. Each of these investigations individually assesses only a part of the complete system. The total picture of the different investigative modalities put together is the key to the diagnosis.
Vestibular function tests include the following:
- The electronystagmography (ENG), videonystagmography (VNG), and video head impulse test (VHIT) to evaluate the vestibulo-ocular reflex (VOR).
- The craniocorpography (CCG), computerized dynamic posturography, and vestibular-evoked myogenic potential (VEMP) to evaluate the vestibulospinal reflex.
| Tests for Vestibulo-Ocular Reflex|| |
VOR plays an important role in stabilizing the image on the retina during head movements without causing a retinal slip. Thus, any defect in this reflex pathway would lead to subjective sense of rotation or dizziness and would manifest clinically in the form of nystagmus. Hence, the assessment of VOR forms an important part of evaluating the balance system.
ENG and VNG are the most popular investigations used for recording and analysis of abnormal eye movements, i.e., VOR and allied reflex systems such as the smooth pursuit, optokinetic, and saccadic.
ENG is nothing but the recording of eye movements. It is a routine investigation done in the management of patients with balance disorders. It gives qualitative and quantitative information of eye movements, more importantly, even with eyes closed. Even s mall nystagmus beats can be recorded.
A single channel machine will record only horizontal nystagmus or vertical one. However, a multichannel machine records both horizontal and vertical nystagmus and also of each eye separately which may be useful in cases of conjugate or deconjugate nystagmus. The digital ENG machine is attached to a computer for receiving, analyzing, and storing digitalized signals. A light bar with LEDs is used to perform calibration and various tests such as gaze test, pendular tracking, and optokinetic.
Spontaneous nystagmus is measured with eyes open and eyes closed to remove the optic fixation. During the analysis of nystagmus, the various parameters studied are configuration, amplitude, frequency, direction, and slow phase velocity (SPV). The amplitude should be 20 microvolts, i.e., 1 mm at least. The direction is determined by the fast phase. SPV is the average speed in degrees of slow phase nystagmus during culmination phase. Culmination phase is the 30 s period where the maximum frequency of nystagmus is seen.
Pendular tracking is used to assess the functional integrity of oculomotor and smooth pursuit system. In normal individuals, a smooth tracing is obtained. Ataxic tracing will be seen in lesion involving the CNS.
Bithermal caloric test involves inducing nystagmus by thermal stimulus. Nystagmus obtained on irrigating the ear canals with warm and cold water is recorded and analyzed. Here, the patient is placed in the supine position with head elevated by 30°so that the lateral semicircular canal assumes vertical position with respect to horizontal. Irrigation of the ear canal with warm and cold water sets up convection currents in the endolymph, resulting in stimulation of the crista in ampulla. For example, warm water (44°C) irrigation of the right ear causes convection currents causing ampullopetal flow of endolymph resulting in the right beating nystagmus. Cold water (30°C) will cause the opposite effect, i.e., opposite beating nystagmus. Fritzgerald and Halpike recorded the duration of nystagmus for analysis, but it had its drawbacks, especially if spontaneous nystagmus was present. Claussen and Desa  have modified this test and also designed the Butterfly Chart for recording and easy interpretation. Right ear is first irrigated with 20 cc warm water of 44°C, over 30 seconds, nystagmus generated is recorded over 2 minutes. This followed by similar irrigation in left ear with warm water, then right ear with cold water (30°C) and lastly left ear with cold water. A gap of 8 minutes is maintained between each irrigation. The culmination phase with maximum nystagmus beats in 30 s period is selected, and the frequency of beats is calculated. The results are then presented on a rectangular quadrant system called the Butterfly Chart. This chart is a rectangular quadrant system. The term hypoactive is used when the result of a caloric test is less than normal range and hyperactive when it is more than normal. Just like the results of audiometry presented in the form of an audiogram for easy interpretation, in the same way, the results of caloric tests are presented in the form of calorigram.
The caloric test thus helps us to differentiate between a peripheral and central vestibular lesion, it determines the side of the lesion and whether the lesion is inhibitory or excitatory. It also helps us calculate canal paresis and directional preponderance by Jongkees formula, and gives an easy interpretation by the Butterfly Chart. The main disadvantage is that it assesses only a small part of vestibular system, i.e., the lateral semicircular canal, and at very low frequency.
More recently, VNG testing is considered the new standard for testing inner ear functions over ENG. It involves the use of infrared goggles to trace eye movements during visual stimulation and positional changes (ENG) because it measures the movements of the eyes directly through infrared cameras, instead of indirect method of measuring electric signals by electrodes around the eyes as in ENG. VNG testing is more accurate, more consistent, and more comfortable for the patient. By having the patient more comfortable and relaxed, consistent and accurate test results are more easily achieved.
VNG testing involves a series of tests designed to document a person's ability to follow visual objects with their eyes and how well the eyes respond to information from the vestibular system. To monitor the movements of the eyes, infrared goggles are placed around the eyes to record eye movements during testing. Thus, there is no problem of electrical interference. Moreover, removal of optic fixation can be achieved without closing the eyes as opposed to the ENG. The software provided does the calibration easily. The various stimuli can be provided on the computer screen itself such as the moving dot for gaze test, optokinetic testing, saccades, smooth pursuit, and even the subjective visual vertical (SVV). After the calibration, various tests done are recording and analysis of spontaneous nystagmus without and with optic fixation. Parameters analyzed are the frequency, SPV, the direction, and type. In addition to the horizontal and vertical nystagmus, torsional/rotatory nystagmus can be recorded and studied. This is advantageous in cases of benign paroxysmal positional vertigo (BPPV).
The head shaking test
Head shaking nystagmus (HSN) is a jerk nystagmus that may follow a prolonged sinusoidal head oscillation. HSN was first described in 1907 by Robert Bárány. The patient is positioned upright, and the test is performed using video goggles with both eyes covered to remove fixation. The examiner grasps the patient's head and moves it briskly side-to-side around the vertical axis, with a frequency of about 2 Hz and a displacement of the head of approximately 30°to either side. The head shaking is continued for 20 cycles and then abruptly stopped. In normal subjects or persons with symmetrical vestibular loss (such as bilateral vestibular loss), no nystagmus is expected. In persons with a dynamic imbalance between the ears (such as due to unilateral vestibular neuritis or an acoustic neuroma), a nystagmus is often seen (usually beating toward the “better” ear [Hain et al., 1987; Katsarkas et al., 2000)) which decays over about 30 s.
The patient is asked to follow objects that jump from place to place, stand still, or move smoothly on a screen. Inability to follow visual targets may indicate a central or neurological problem or possibly a problem in the pathway connecting the vestibular system to the brain.
The patient is asked to view a large, continuously moving visual image to look for any slowness, or inaccuracies in his/her ability to follow the visual targets. This may indicate a central problem in the pathway connecting the vestibular system to the brain.
The patient goes through the various positioning and positional tests (Dix–Hallpike test) and the nystagmus elicited in different head positions is recorded. This is of advantage in cases of BPPV. Torsional nystagmus will be recorded with its typical features in the posterior canal BPPV.
Caloric test is carried out as described earlier and the nystagmus is recorded. Water calorization or air calorization can be done. This test assesses the VOR. The VOR gain can be calculated. The canal paresis and directional preponderance are determined. The results are represented on a four-quadrant chart. This is the only test available that can decipher between a unilateral and bilateral loss since we can individually stimulate the two ears separately.
Video head impulse test
VHIT is a documentation of clinical head impulse test of Halmagyi and Curthoys (1988). It evaluates the VOR. The head impulse test finds out if there are any saccadic eye movements when the head is moved suddenly with eyes focused on a target. The presence of catch-up saccades indicates a weak VOR resulting from a weak labyrinth. While doing this test clinically, one is likely to miss out on the saccades. Moreover, any saccadic eye movements occurring while the head is moving will be missed. The VHIT overcomes these limitations and can also measure the gain of VOR.
A goggle with an inbuilt camera is worn by the patient or a camera is placed in front of patient to record the head and eye movements. The examiner stands behind the patient holding head of the patient and moves it with sudden jerks horizontally or vertically in planes of all the semicircular canals. The movements of head and eye positions are recorded graphically and analyzed. The parameters analyzed are as follows:
- Presence or absence of saccades
- The gain of the VOR gain
- Shape of the eye position and velocity tracing.
If saccades are present, then one has to look for consistency, direction, amplitude, and latency. The presence of saccades indicates a weak VOR on that side and the canal. If no saccades are present, the VOR gain is noted (normal range: 0.8–1.2 for the right and left lateral squamous cell carcinoma [SCC] and 0.7–1.2 for the vertical canals). Low VOR gain indicates hypofunctioning of the particular canal.
In defects of the inferior vestibular nerve, VHIT findings of the posterior SCC of that side will be abnormal. In defects of superior vestibular nerve, VHIT findings of the lateral and superior SCC will be abnormal. If the main trunk of vestibular nerve is involved on both sides, VHIT findings will be abnormal for all canals.
| Vestibulospinal Reflex|| |
This reflex is of utmost importance in maintaining the balance. It brings about postural control by exerting the push-pull mechanism of the flexors and extensors of the limbs and neck muscles.
This objective test for the vestibulospinal system consists of photographically recording the patient's head and body movements as he/she performs the Unterberger's stepping test and the Romberg's test.
In earlier days, the CCG was carried out in a dark room with a convex mirror attached to the ceiling. The patient with eyes closed wore a headgear with three lights and one light on each shoulder. A Polaroid camera was fixed with its lens directed upward to the convex mirror to record the picture from the mirror. The person performs the Rombergs test and Unterberger's test and his/her movements causing movements of the lights as reflected from the mirror are recorded by the camera. In case of a vestibular lesion, the deviation and the rotation toward the affected side in degrees at the end of the Unterberger's test can be measured from the print out of the recording. Similarly, the abnormal sway (more than 10 cm) in case of a central lesion causing ataxia during Romberg's test can be measured. With the recent developments in technology, the CCG is carried out using USG sensors and computerized analysis. With digital recording cameras, one can do the test without the need for the mirror.
Computerized dynamic posturography
This is available only in more sophisticated laboratories. It involves the overall assessment of balance system by subjecting the patient to various visual and proprioceptive challenges and analyzing the responses.
Vestibular-evoked myogenic potential
Vestibular stimulation causes contraction of certain muscles which can be measured as myogenic potential. This is called the VEMP. The vestibule can be stimulated by loud sounds (Von Bekesy, 1935; Dawson, 1954).
The VEMP tests evaluate the otolithic function. Accurate assessment of the utricular and saccular function can be done safely with the VEMP test. The utricle responds to horizontal displacement and the saccule to the vertical displacement. The VEMP test evaluates the otolith organs, the superior and inferior vestibular nerves, the vestibulocollic reflex, and the maculo-ocular reflex.
VEMPs are of two types, cervical VEMP (cVEMP) and ocular VEMP (oVEMP). cVEMPs are recorded from the ipsilateral sternocleidomastoid muscle on the side of the ear stimulated by auditory stimulus. Similarly, oVEMP is the myogenic response picked up from contralateral inferior oblique muscle. Both air-conducted and bone-conducted sounds can be used. Air-conducted cVEMP evaluates saccular function, and air-conducted and bone-conducted oVEMP evaluates utricular function.
VEMPs are absent in case of conductive deafness whereas sensorineural deafness does not affect the VEMP results. Abnormal cVEMPs are seen in disorders of saccule, inferior vestibular nerve damage (20%–30% of vestibular neuritis), vestibular damage, Meniere's disease, superior semicircular canal dehiscence, and also lesions of lower brainstem. oVEMP is abnormal in utricular disorders and lesions of superior vestibular nerve.
| Subjective Visual Vertical|| |
The purpose of SVV test is to detect abnormal subjective tilt. In normal persons, the ability to perceive verticality is quite good. An individual's perception of verticality is based on a fusion of vestibular, visual, and egocentric references. Bilateral gravitational input from the otolith organs, in particular, the utricles, dominates this perception of verticality. Utricle function is reflected by an individual's ability to adjust an illuminated rod to what they consider to be perfectly vertical, known as their SVV. Comparison of their estimation with the true earth vertical provides important information regarding the utricles and processing of otolithic information in the higher brain center. Similarly, the subjective visual horizontal measures an individual's perception in the horizontal plane. This test also reflects utricle function and can be used as an alternate or additional test to SVV. Tests for SVV are many, namely, Maddox rod, vertical beam projected on screen, and motor-driven hemisphere with dots, which are used in most research laboratories across the world. The bucket test, first described by Zwergal, is simple and quick to perform and can be routinely used in daily outpatient department. Subjects look into a clean bucket with a vertical line on the bottom, which rested on a table. It is rotated, clockwise or counterclockwise, for three trials per direction until the subject indicated that the line was vertical. The dependent measure was the mean absolute value of the deviations from the true vertical. Today, with good technology, accurate measurements of SVV can be done using software of the VNG machine itself by projecting a vertical line on the screen which the subject can manipulate. In peripheral vestibular disorders, the SVV is found to be tilted, especially in vestibular neuritis, vestibular nerve section, and other vestibulopathies.
Thus, in the present scenario, we as the neurotologists can assess a patient of vertigo more objectively and derive at a topognostic diagnosis with a battery of tests. This definitely would guide us in the further management of the patient in a more effective manner.
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