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| ORIGINAL ARTICLE |
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| Year : 2018 | Volume
: 24
| Issue : 3 | Page : 162-167 |
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Subjective visual vertical in different peripheral vestibular disorders
Mostafa El Khosht Mahmoud, Maha Hassan Abou-Elew, Rasha Soliman, Aliaa Aly Moustafa El Brequi
Department of Audiology, Faculty of Medicine, Cairo University, Giza, Egypt
| Date of Web Publication | 11-Jan-2019 |
Correspondence Address:
Prof. Aliaa Aly Moustafa El Brequi
37 Ibrahim El Refai, Nasr City, Cairo
Egypt
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/indianjotol.INDIANJOTOL_92_17
Context: The subjective visual vertical (SVV) is considered to be a functional measure of otolith-mediated verticality perception. Aims: This study aims to detect the normative data of SVV and to analyze SVV changes in peripheral vestibular disorders. Settings and Design: This was a observational, cross-sectional study. Subjects and Methods: Forty-five adult patients with chronic peripheral vestibular disorders endolymphatic hydrops, vestibular neuritis, and benign paroxysmal positional vertigo and 20 normal individuals were included in this study. After full history taken, SVV deviations and caloric tests were completed. Statistical Analysis Used: Independent Student's t-test for independent sample when comparing 2 groups. ANOVAs test compared three or more means for statistical significance. Tukey's test compared the means of every treatment to the means of every other treatment. Chi-square test was performed. Normal cutoff value was calculated by mean +2 standard deviation (SD) as high limit and mean −2 SD as low limit. Results: The normative data of SVV ranged from −0.2° to 1.26° in clockwise direction and from −0.04° to 0.95° in the counterclockwise direction. SVV in counterclockwise direction were significantly deviated among the three groups of Peripheral vestibular disorder (PVD) patients when compared with controls. It revealed a significant deviation in counterclockwise tilt between left diseased ears in relation to controls. Conclusions: Normal adults displayed a narrow range of one-degree SVV deviation (1.06° and 0.91°) in clockwise and counterclockwise direction, respectively. The three vestibular disorders significantly deviate the SVV in counterclockwise direction compared to control with no gender difference. SVV test alone cannot differentiate between different PVD.
Keywords: Peripheral vestibular disorders, subjective visual vertical, verticality
How to cite this article:
Mahmoud ME, Abou-Elew MH, Soliman R, El Brequi AA. Subjective visual vertical in different peripheral vestibular disorders. Indian J Otol 2018;24:162-7 |
| Introduction | |  |
Dizziness is one of the most common presenting symptoms to the primary care physician.
In diagnosis of dizzy patients, videonystagmography (VNG) and rotator chair are used as routine tests. Patients suffering from dizziness with no abnormal findings on routine tests may be diagnosed as having dizziness of unknown origin. However, above-mentioned tests are limited in evaluating semicircular canal functions; therefore, the possibility of disturbance in the otolithic organs cannot be excluded.[1]
The subjective visual vertical (SVV) is considered to be a functional measure of otolith-mediated verticality perception, also posterior canal may contribute.[2] Healthy participants make errors within two degrees to either side.[3]
| Subjects and Methods | | |
Subjects
The study was designed as an observational case–control study. The study was approved by the Research Ethical Committee and otolaryngology department of Faculty of Medicine, Cairo University. Informed consent was assigned by all participants for participation in the study.
Sixty-five participants were included in the study, 45 patients as a study group, and 20 participants as a control group.
Study group
All patients in the study group fulfilled the following.
Inclusion criteria
Adults diagnosed previously as having peripheral vestibular disorders and complaining of vertigo, dizziness, and imbalance >6 months. They were classified according to the etiology into three groups of peripheral vestibular disorders:
- Endolymphatic hydrops
- Vestibular neuritis VN
- Benign paroxysmal positional vertigo (BPPV).
They were selected from Audio-Vestibular Outpatient Clinic in Kasr Al-Ainy Hospital, Cairo University during the period from March 2014 to March 2015.
Exclusion criteria
- Signs of central vestibular disorders (abnormal oculomotor testing, gaze nystagmus, or abnormal caloric fixation index) and any neurological disorders (especially cerebellar)
- Severe visual disturbance, abnormal ocular motility or with lens implanted after cataract operation were excluded due to difficulty in recording
- Elder patients more than 65-years-old
- Control group: Normal adults selected from persons accompanied the patients to the outpatient clinic. They were not complaining of otological symptoms. They were selected randomly to match the age range and gender distribution in the study group.
Methodology
Methods
All participants included in the study were submitted to the following assessment protocol:
- Full history of taking
- Detailed history of vertigo
- History of general diseases.
- Full ear, nose, and throat examination.
- Full neurological examination (cranial nerves, sensory system, motor system, deep reflexes, and coordination)
- Gait examination
- Visual acuity testing
- Basic audiological evaluation was done to confirm the diagnosis including; pure tone audiometry, and immitancemetry
- Clinical bedside examination including:
- Posture and gait testing
- Spontaneous nystagmus
- Gaze-evoked nystagmus
- Ocular motor examination (smooth pursuit and saccadic eye movements)
- Head-shaking test
- Head thrust test
- Vestibulo-ocular reflex fixation suppression
- Positional and positioning testing.
- VNG test including:
- Spontaneous nystagmus
- Gaze-evoked nystagmus
- Oculography testing (smooth pursuit, saccadic, and optokinetic eye movements)
- Positional and positioning testing
- Water bithermal caloric irrigation testing, with 30 s irrigation for each ear, order of irrigation: Right cool, left cool, right warm, and finally left warm. Canal response was calculated based on average of maximum slow peak velocity in degrees/second.
Unilateral weakness (UW) was expressed as a percentage and is calculated using the following Fitzgerald formula:
The normal limit of caloric asymmetry is 20% in our laboratories.
And the formula of directional preponderance (DP) is as follows:
The normal values for DP in our laboratories are <30%.
7. SVV.
The patient sited in a dark room in front of a screen, on which an infrared line was projected on the right or on the left side. The laser beam was the only landmark of the patient. Gravitational definition of the vertical was given to the patient. The patient used infrared remote control to adjust the line to the vertical. Before testing, a trial session was performed which was not included in the statistical analysis. The SVV readings were taken from the liquid crystal display starting unit for 6 CW then 6 CCW start positions of the linear marker, giving a total of 12 values for each task. Familiarization trials were allowed, and no time limit was set for the adjustments.[4]
Equipment
- Pure tone audiometer – Two channel audiometry, Grason- Stadler Inc model 61 connected to a CD player, using headphones TDH 39 and bone vibrator radio B71
- Sound-treated room – The sound-treated room used was amplisilence model E
- Immitancemeter – Interacoustic AZ 26 with a probe tone 220 Hz, calibrated according to the ISO standards. Acoustic reflexes were presented contralaterally using headphones TDH 39, testing the frequency range from 500 to 4000 Hz.
Difra Instrumentation Visostar II, software Disoft version 1.30.04, NYSSTAR I camera. Windows 7 Ultimate, Processor Intel® Core™ i3-2120 CPU at 3.30 GHz. RAM 4 GB, 32-bit operating system.
Statistical methods
Data were statistically described regarding range, mean ± standard deviation (±SD), frequencies (number of cases), and percentages when appropriate. Comparison of numerical variables between the study groups was done using independent Student's t-test for independent sample when comparing 2 groups. ANOVAs were used to compare (testing) three or more means (groups or variables) for statistical significance. Tukey's test is a single-step multiple comparison procedure which compares the means of every treatment to the means of every other treatment. For comparing categorical data, Chi-square test was performed. All statistical calculation was done using IBM personal computer program Statistical Package for the Social Science version 21.
Normal cutoff value was calculated by mean +2 SD as high limit and mean −2 SD as a low limit.
| Results | | |
This is an observational cross-sectional study involving 45 individuals divided according to diagnosis into three groups: Group I: Endolymphatic hydrops, Group II: VN, Group III: BPPV, the three groups were equally distributed in this study i.e., 15 patients were assigned to each group. The study sample included 19 (42.22%) males and 26 (57, 78%) females. Females constituted 66.67%, 53.33%, and 53.33% in the three groups, respectively [Figure 1], gender distribution was almost equal in three groups (P = 0.691). Their age distribution is illustrated in [Table 1]. There were 28 left diseased ear patients and 17 right diseased ear patients. | Figure 1: Gender distribution in different 3 groups of peripheral vascular disease
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 | Table 1: Age distribution in different three groups of peripheral vascular disease
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Subjective visual vertical
[Table 2] and [Table 3] illustrate age and gender distribution in the different three groups, and the control group, respectively. Both age and gender were matched (P = 0.989 and 0.864), respectively. | Table 2: Age distribution in the three different groups and the control group
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 | Table 3: Gender distribution in the three different groups and the control group
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The mean value and SD of SVV in the clockwise and counterclockwise direction in the three different groups and the controls included in the study were displayed in [Table 4] and [Figure 2]. The same values of SVV in clockwise and counterclockwise among the three different groups were illustrated in [Table 5]. There was a significant difference between the three different groups and the controls in the SVV-CCW (P = 0.042) and a non (borderline) significant difference in the clockwise direction (P = 0.055). There was no statistically significant difference among the three different groups [Table 5]. | Table 4: Comparison between the subjective visual vertical in the clockwise and counterclockwise in the 3 different groups and the control group
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 | Figure 2: Comparison between the subjective visual vertical in the clockwise and counterclockwise in the 3 different groups and the control group
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 | Table 5: Comparison between three different groups in subjective visual vertical-clockwise
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The mean and SD of SVV clockwise and counterclockwise direction of patients with right and left diseased ear and the control group included in the study were summarized in [Table 6]. | Table 6: Comparison between the values of subjective visual vertical (clockwise and counterclockwise) in patients with right diseased ear, left ear diseased, and the control group
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There was a statistically significant difference between the left diseased ear and the controls in the counterclockwise direction (P = 0.001). The clockwise direction showed no significant difference.
There was no statistically significant difference in SVV for both clockwise and counterclockwise directions between males and females in the three different groups and control subjects [Table 7] and [Figure 3]. | Table 7: Comparison between the values of subjective visual vertical (clockwise and counterclockwise) in different three groups across gender distribution
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 | Figure 3: Comparison between the values of subjective visual vertical (clockwise and counterclockwise) in patients with right diseased ear, left ear diseased, and the control group
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The normative data of SVV in a sample of normal adults based on the mean values in controls (mean ± 2 SD), SVV deviation ranged from 0.2° to 1.26° in the clockwise direction and from 0.04° to 0.95° in the counterclockwise direction, individual results revealed abnormal SVV deviation in 5, 6, and 6 patients, respectively, in the three peripheral vascular disease (PVD) groups in either or both direction.
Audiological assessment
There are 13 patients with unilateral sensorineural hearing loss (SNHL) and two patients with bilateral SNHL in Group I and one patient with unilateral hearing loss and two patients with bilateral SNHL in Group II. Only 1 patient with bilateral SNHL in Group III, otherwise the rest of patients had normal hearing threshold level or mild higher frequencies SNHL according to their ages.
Caloric test
There was unilateral canal paresis in all patients in Group I and II while Group III showed no canal paresis.
Dix-hallpike
There were seven patients with right posterior canal BPPV, six patients with left posterior canal BPPV, one patient with right anterior canal BPPV, and one patient with right horizontal canal BPPV in Group III.
There was only one patient with right posterior canal BPPV in Group II.
| Discussion | | |
In humans, the perception of vertical is provided by input from various sensorineural organs and pathways: Vision, proprioceptive, and vestibular cues, particularly from the otolithic organs and graviceptive pathways. Lesions involving central or peripheral vestibular system or the central integrating system lead to abnormal perception of body orientation in space and abnormal perception of vertical.[5] Recent studies have shown that the awareness of the body orientation may also modulate verticality representation, indicating the importance of the cognitive systems. This means in addition to sensory integration, mental processes play also a role in the sense of verticality.[6]
Both the utricle and saccule contribute to the sense of verticality. After injury to the otoliths, or to the nerve that transmits impulses from the otoliths and other parts the ear to the brain, judgment of vertical may be altered, which literally tilts one's vision. A person with vestibular disease may not perceive a vertical line as vertical resulting in deviation from normal which, can be measured in degrees.[7]
Various test batteries to assess vestibular system are usually limited to the assessment of semicircular canal functions. Nowadays, cervical vestibular-evoked myogenic potential is being widely used for testing saccular function. Utricular function can be tested by SVV. The static SVV is considered to be a functional measure of otolith-mediated verticality perception although vertical semicircular canals, in particular, the posterior canal, may also contribute.[2]
To determine the normative data of SVV in a sample of normal adults based on the mean values in controls (mean ± 2 SD), SVV deviation ranged from −0.2° to 1.26° (i.e., 1.06) in the clockwise direction and from −0.04° to 0.95° (i.e., 0.91) in the counterclockwise direction.
In this study, SVV tilt was compared with age- and gender-matched controls [Table 2] and [Table 3]. SVV in counterclockwise direction was significantly deviated among the three groups of PVD patients when compared with controls. However, in the clockwise direction, a borderline deviation was detected [Table 5], P = 0.055]. Given no significant deviation between the three groups of PVD in the clockwise and counterclockwise direction [Table 5], the three vestibular disorders significantly deviate the SVV compared to control individuals. In the present study, individual results revealed abnormal SVV deviation in 5, 6, and 6 patients, respectively, in the three PVD groups in either or both direction.
SVV was tested with a simple innovative device a specially designed bucket. Out of 23 patients with VN 83% showed abnormal SVV. Among 11 patients of MD, 55% and 42 patients of BPPV, 71% had abnormal SVV. Among 24 patients with other causes 15% showed abnormal SVV. The study concluded that SVV is a reliable screening tool in the assessment of vestibular dysfunction along with other clinical tests. It has a prognostic value during recovery following vestibular damage.[7] The deviation of SVV is variable according to the time of testing as all our patients were included with total duration of illness more than 1 year. However, some patients have recent attacks of dizziness few weeks before time of testing. This explains the discrepancy in number of patients with abnormal SVV deviation the present study and previous study. Many studies reported that deviation of the SVV is compensated during the following months; patients with chronic unilateral vestibular loss do no longer differ from normal subjects.[8] They found that there was no correlation between the mean value of SVV or mean value of SVH tilt and the duration of symptoms in either the MD group or the PVD group as abnormal SVV tilts are known to normalize over weeks to years after an acute vestibular insult.[9] In patients with MD operated with labyrinthectomy, a marked deviation toward the operated side was found acutely, with resolution over weeks[10] and months.[11]
In the same way, slowly developing unilateral vestibular disorders usually do not induce significant deviations of the SVV. In a series of 27 patients with an acoustic neuroma, for example, the mean deviation was 1.1° ± 1.5°; only four patients had a SVV more than 2.5 with a maximal value of 4.0. In chronic stages, UVD participants thus can no longer be distinguished by their SVV from normal.[8]
They reported also that a smaller percentage of participants in the PVD group had abnormal mean SVV and SVH values (2 of 9 subjects [22%]).[4] They explained that their findings by the longer duration of symptoms in this group. In addition, they did not include participants with vestibular neurectomy, which may have persistently abnormal SVV and SVH values. These two subjects with abnormal mean SVV and SVH measures had symptoms suggestive of otolithic dysfunction and persistent disequilibrium with slower compensation from otolithic dysfunction.[10] Because both subjects had only a modest canal paresis, this may indicate either a recovery of semicircular canal function or a vestibular insult predominantly involving the otoliths and/or the vertical canals.
On the other hand, they showed that only three patients had abnormal SVV among 44 patients with chronic dizziness without abnormal findings in routine vestibular function tests. The latter three patients had deep white matter hyperintensities on their MRI, probably due to aging. Hence, they concluded their results that the SVV test can detect abnormality of the otolithic organs and the graviceptive pathways present in a group of patients having dizziness; however, presenting no abnormal findings in conventional vestibular function tests.[12]
To study the side of deviation in the present study, all patients start testing with clockwise direction. Although patients got experienced in testing SVV in counterclockwise direction, there was a significant deviation in this direction. To prove this finding, left and right diseased ears were compared to controls; it revealed a significant deviation in counterclockwise tilt between left diseased ears in relation to controls [Table 6]. Trying to explain this finding, we noticed that all our patients were right handed (i.e., all had left dominant hemisphere) so this could be attributed to left side vestibular pathology. Similarly, they found that handedness-related vestibular dominance does concern both lower[13],[14] and higher order vestibular function.[5],[15] However, this does not detract from the hypothesis which focuses on the independent development in the child of hand dexterity and vestibular function.[16]
The SVV tilts toward the side of lesion. Although well known in several types of brainstem lesions, SVV abnormalities may also be observed after peripheral vestibular lesions, such as surgical deafferentation, with a deviation directed toward the operated ear.[3]
Deviations of the SVV in the frontoparallel roll plane are the most sensitive sign of acute unilateral brainstem infarctions. They occur in more than 90% of affected patients in the acute stage and may be helpful when determining not only the level but also the side of the brainstem lesion. If the level of damage is known from the clinical syndrome, the SVV tilt indicates the more severely affected side. Conversely, if the side of damage is clear from the clinical syndrome, the direction of SVV tilt indicates the level in the brainstem. All SVV tilts are ipsiversive in unilateral peripheral vestibular or pontomedullary lesions (vestibular nuclei) below the crossing of the “graviceptive pathways.”[17] All SVV tilts in unilateral pontomesencephalic brainstem lesions are contraversive and indicate the involvement of the medial longitudinal fasciculus or the interstitial nucleus of Cajal. There are two loci, a lesion of which may induce either ipsiversive or contraversive SVV tilts. One locus is the posterolateral thalamus with the involvement of the vestibular thalamic subnuclei;[5] the other is the dentate nucleus, which when spared in acute cerebellar strokes induces ipsiversive tilts and when damaged induces contraversive tilts.[18]
| Conlusion | | |
Normal adults displayed a narrow range of about one SVV deviation (1.06 and 0.91 degree) in clockwise and counter clockwise direction respectively. The three vestibular disorders significantly deviate the SVv in counter clockwise direction compared to control subjects with no gender difference. However, SVV test alone can not differentiate between different PVD. In abscent of vestibular input, endolymphatic hydrops patients relay on somatosensory input while BPPV patients relay on visual cues to maintain balance. Abnormal VEMP results were more likely obtained in endolymphatic hydrops group than in VN and BPPV groups.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]
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