Mobile phone app Vs bucket test as a subjective visual vertical test: a validation study:
Abstract
Background.The SVV tests the ability of a person to perceive the gravitational vertical. A tilt in SVV indicates vestibular imbalance in the roll plane, and thus injuries to the utricle or its connecting nerves. A validated bedside method (et, al., 2009, 72(19):1689–1692, Neurol, Zwergal) is the bucket method, in which the subject estimates the true vertical by attempting to properly align a straight line visible on the bottom of a bucket that is rotated at random by the examiner. In our study, the subjects need to align the plumb line on the Visual Vertical iOS app to the vertical direction.
Methods.Measurements of the SVV were made in 22 healthy subjects (16 females and 6 males). Each subject conducted 10 iterations of bucket test and 10 iterations of iOS app test. The reliability and validity of the iOS app was analyzed by SPSS21.
Results.Cronbach’s α for the plumb line method was 0.976, and the iOS app was 0.978. Statistical comparison of SVV values measured by the iOS app and the bucket method showed no significant difference in distribution (Mann Whitney U test U = 0.944).
Conclusion
The Visual Vertical iOS app is an effective and accessible substitute to the plumb line for the measurement of the validated bucket test.
Subjective Visual Vertical (SVV) and the Dizzy Patient
Subjective Visual Vertical (SVV) and the Dizzy Patient
Tech Topic | November 2017 Hearing Review
The measurement of subjective visual vertical (SVV) can serve as a diagnostic indicator of utricular otolith (dys)function, and involves an individual’s ability to adjust a vertical line to be parallel with gravity in the absence of visual cues. Measurement of SVV can take many forms, from inexpensive conventional tests to more involved clinical tests. This article reviews three of these tests with particular focus on the Virtual SVV goggle.Indeed, many of these symptoms can overlap, and the definitions of “dizziness,” “vertigo,” and “unsteadiness” vary. Dizzy patients are sometimes so ill when they experience their debilitating symptoms that they are unlikely to present in the office. Further, if they do present, they may be unable to endure the rigor of clinical tests to indicate or rule out a specific differential diagnosis via a rotary chair, videonystagmography (VNG), marching in place with eyes closed, etc.
Unfortunately, many of the tests used in clinical practice cannot directly diagnose Acute Vestibular Syndrome (AVS), Ménière’s disease, vestibular migraine, and many central pathologies. Specifically, the tests used point us toward/away from a particular diagnosis. Beck, et al1 note the professional is “tasked with relying on and interpreting the patient’s history and physical findings, combined with subjective reports and non-exclusive test findings…” from which an eventual differential diagnosis emerges.
Michelson et al2 report true vertigo is generally associated with the peripheral vestibular system, such as a weakness or malfunction of the semicircular canals (SCCs) which detect angular acceleration. They report malfunction of the otolith organs (ie, saccule and utricle) may be contributory or responsible for unsteadiness as the saccule primarily detects vertical acceleration and the utricle primarily detects horizontal acceleration while upright. The otolith organs function such that linear acceleration displaces the otoconial mass, thus shearing the embedded sensory hair bundles against the otolith maculae, resulting in a potential change in the neuron and, consequently, a change in the afferent discharge rate.
Because the earth’s gravity constitutes a constant linear acceleration, the orientation of the head, relative to gravity, is constantly signaled from the otolith organs to the central nervous system. Therefore, individuals can accurately measure the so-called subjective visual vertical (SVV) without visual reference. Any dysfunction of the otolith apparatus is usually accompanied by incorrect spatial orientation and postural instability. The measurement of the SVV thus serves as a diagnostic indicator of utricular otolith dysfunction.
To measure utricular function, two tests are often used, subjective visual vertical (static or dynamic), and ocular vestibular evoked myogenic potential (oVEMP). This article addresses SVV.
Subjective Visual Vertical (SVV)
The SVV represents a method to test an individual’s ability to adjust a vertical line to be parallel with gravity in the absence of other visual cues. The sensory information required to perform this task is provided predominantly by the vestibular organs of the inner ear, and, in particular, by the utricles.In principle, the SVV is determined by presenting the patient with a luminous line in otherwise total darkness and requesting that she/he rotate it to be parallel to gravity in a vertical alignment. In the case of a healthy patient, correct estimation of the direction of gravity is easily accomplished. The SVV is determined by measuring the deviation of the set angle of the luminous line from the tilt angle of the head. With the head in the upright position this tilt angle will effectively be zero, parallel to gravity. It is possible to test the SVV during unilateral centrifugation, which permits exclusive stimulation to the right or left utricle.
There are several common methods used to measure a person’s SVV response:
1) Bucket Test (conventional and inexpensive)
The simplest and least expensive measure is using a bucket placed over the patients head (Figure 1a). Inside the bucket is a line or rectangular object. Figures 1b and 1c show the protractor on the back of the bucket and the line inside a typical bucket.
The clinician rotates the bucket around the patients head until the patient believes the line is completely vertical. The clinician then reads the angle of deviation on the back of the bucket.
This is considered a static test because the patient is not moving during the testing. On average, investigators reported individuals with normal utricular function rotated the bucket within 2° from true vertical, while those with vestibular lesions rotate the bucket within 20°of true vertical.3
2) OVAR Rotational Chair (clinical)
SVV can be accurately measured using a rotary chair with a completely dark enclosure that can rotate up to 300°/sec while migrating off center at 1 cm/sec (Figure 2). While rotating, the patient is asked to manipulate a laser line on the wall (using a handheld remote) to position it such that they perceive “perfectly vertical.” This test is very carefully controlled by the software and provides extremely accurate results. An important advantage of this method is it allows you to test each utricle independently.
3) Virtual SVV™ Goggle (clinical and less expensive)
Recent advances in technology have allowed for a simpler and more portable clinical device for measuring SVV. The light occluding goggle has a built in accelerometer to measure head movements and a “candle- like” target to adjust for verticality. The patient simply moves the target inside the goggle using a handheld remote control. It’s so simple even young children can perform the task (Figure 3). An added feature of this method is one can test subjective verticality with the head tilted up to 45° left or right (Figure 4).
In all cases, the SVV is determined by measuring the deviation of the set angle of the target line from the tilt angle of the head. In a static test, the patient’s head is at zero of fixed degrees of head tilt. A person with a normal vestibular system should align the target very precisely with very little deviation from zero. When you tilt the head, the task is more challenging and a larger deviation occurs for head tilted versus head straight up.
A person with a healthy vestibular system will experience equal stimulation to both utricles when the head is straight up, and they will position the line very near zero. In the acute phase of vestibular disease, the healthy labyrinth correctly detects the stimulation but the diseased labyrinth will provide a deficit. The central nervous system most often interprets this discrepancy as a head tilt to the side of the healthy vestibule, and the patient would set the projected line to a corresponding degree towards the diseased labyrinth.
In the Virtual SVV system, suggested threshold data is presented (Figure 5). The dark-green shaded areas represents the normal range between the 25th-75th percentiles, while the light green shaded area represents the normal range between the 5th and 95th percentiles. These ranges are based on data from a population of normal-testing subjects at the Vestibular Research Lab of the Charité Berlin, Campus Benjamin Franklin.
Most patients with a peripheral deficit show an underestimation during the tilt to the lesioned side and normal values in tilt positions to the healthy side. The SVV test is also sensitive to central vestibular abnormalities (Figures 7a-b).
Discussion
The vestibular practitioner has many tools available to test the individual and cumulative responses of the vestibular system. For example, vHIT4 and caloric tests are particularly well suited to test the integrity of the semi-circular canals (SCCs). Further, the cVEMP and the oVEMP are objective tests. The cVEMP is useful to determine the integrity of the saccule, and the oVEMP is useful with regard to determining utricular function. However, some people do not have oVEMP responses, and, in those cases, SVV may serve as a reasonable substitute or addendum to assess utricular function. Of note, SVV is relatively inexpensive, takes only a few minutes to complete, and is generally not unpleasant for the patient.Measurements of SVV are useful in the clinical test battery to assist in the differentiation between central and peripheral vestibular disorders, and SVV can help identify potential abnormalities in the utricle and the pathways of the superior vestibular nerve. SVV can also be used to help monitor positive and negative changes in recovery and compensation during vestibular rehabilitation. Finally, despite the clinical efficacy of the SVV, we believe it should not be relied upon as a “stand-alone” test. Rather, the SVV is a “piece of the puzzle,” and it is best used in conjunction with other vestibular tests to help render a differential diagnosis.
Correspondence can be addressed to HR or Dr Beck at: DBEC@oticon.com
Original citation for this article: Beck DL, Petrak MR. Subjective visual vertical (SVV) and the dizzy patient. Hearing Review. 2017;24(11):30-32.
Screen Shot 2017-10-31 at 4.26.39 PM
References
- Beck DL, Petrak MR, Smith AG. Migraine, Ménière’s disease, and vestibular migraine. Audiology Today. Mar/Apr 2013.54-60. Available at: http://www.hearingloss.org/sites/default/files/docs/Migraines_Beck-Petrak-Smith.pdf
- Michelson P, McCaslin D, Jacobson G, Petrak M, English L, Hatton K. Assessment of subjective visual vertical (SVV) using the “bucket test” and the Chronos system. 2017. In review.
- Akin FW, Murnane OD. Subjective visual vertical test. Semin Hear. 2009; 30(4): 281-286. DOI: 10.1055/s-0029-1241128
- Petrak MR, Bahner C, Beck, DL. Video Head Impulse Testing (vHIT): VOR analysis of high frequency vestibular activity. Hearing Review. 2013;20(10):46-50. Available at: http://www.hearingreview.com/2013/08/video-head-impulse-testing-vhit-vor-analysis-of-high-frequency-vestibular-activity
Indian J Otolaryngol Head Neck Surg. 2015 Jun; 67(2): 180–184.
Published online 2014 Aug 8. doi: 10.1007/s12070-014-0760-0
PMCID: PMC4460102
PMID: 26075175
Subjective Visual Vertical in Various Vestibular Disorders by Using a Simple Bucket Test
Naik Chetana and Rane Jayesh
Author information Article notes Copyright and License information Disclaimer
Naik Chetana, Phone: +919765386084, Email: moc.liamg@17anatehcrd, Email: ku.oc.oohay@17anatehcrd.
Contributor Information.
Corresponding author.
Received 2014 Jun 14; Accepted 2014 Aug 1.
This article has been cited by other articles in PMC.
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Introduction
Subjective Visual Vertical (S.V.V.) is the ability of a person to perceive verticality. The purpose of S.V.V. test is to detect abnormal subjective tilt. In normal persons, the ability to perceive verticality is quite good. This ability is dependent on input from visual, vestibular and somatosensory systems. The otolithic organs in the vestibular system sense gravity. 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, judgement of vertical may be altered, which literally tilts ones 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. A commercial method of measuring S.V.V. is a device that projects a laser line onto a screen. The angle of the line with respect to a reference can be read out by the tester. By allowing a subject to repeatedly set the line to vertical, one can measure S.V.V. Tests for S.V.V. are many viz; Maddox rod, vertical beam projected on screen, motor driven hemisphere with dots, etc. which are used in most research labs across the world.
Despite being easy to perform and interpret, the evaluation of S.V.V. is not routinely carried out in vertigo clinics across India. This is probably because of lack of expensive equipment in clinics and the motivation to carry out the test due to time constraints in a busy out-patient department. The bucket test, first described by Zwergal [1], used in our study is simple and quick to perform routinely in daily OPD. In our study we have assessed the results of S.V.V. in various vestibular disorders, its value in diagnosis and prognosis of the disease.
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Objectives
1. To present a simple inexpensive clinical test to assess S.V.V. in patients of vertigo. 2. To analyze the results of S.V.V. values in various vestibular dysfunctions.
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Material and Methods
A prospective cross sectional cohort study was carried out in 100 patients in age group of 18–77 years, presenting to a private vertigo clinic of an E.N.T. hospital with complaints of rotatory vertigo of vestibular cause over 1 year, 2 months (Nov 2012–Dec 2013). Inclusion criteria: 1. Patients with history of rotatory vertigo. 2. Patients diagnosed with vestibular cause viz; B.P.P.V., Meniere’s syndrome, Vestibular Neuritis, Vestibulopathy, labyrinthitis, Migrainous vertigo, vestibular paroxysmia and semicircular canal dehiscence. Exclusion criteria: 1. Patients with non vestibular cause for vertigo. 2. Patients with poor uncorrected vision.
All the patients presenting with vertigo were subjected to Neurotological history taking & examination, including the Unterbergers stepping test, Head Impulse Test, Dix- Hallpike test, E.N.G with Caloric tests, Audiometry & MRI in indicated cases and all underwent S.V.V. measurement by “Bucket test”.
Patients were given conventional treatment for the underlying disease and asked to follow up at 1 week, 2 weeks and one month intervals and reassessed clinically by above tests.
The patients were classified into definite diagnosis of vestibular disease based on clinical findings and investigations. Criteria for vestibular neuritis were acute vertigo with spontaneous nystagmus or old history of the same, a viral prodrome, canal paresis on caloric test and no hearing loss. Criteria for Meniere’s disease according to the A.A.O.O. guidelines were followed viz, episodes of rotatory vertigo, lasting for at least 20 min, documented sensorineural hearing loss and tinnitus with aural fullness. B.P.P.V. was confirmed with history of rotatory vertigo lasting for few seconds in changes of head position and a positive Dix- Hallpike test. Migrainous vertigo was diagnosed in patients with vertigo of variable durations with past history of migrainous attacks and who improved on treatment protocol for migraine. Patients suspected with labyrinthitis, perilymph fistula and semicircular canal dehiscence were place in a group termed “others”.
Bucket test: A simple plastic bucket is modified for the test. On the inside of its bottom is a vertical line drawn with Radium ink. On the outside of the bottom is a protractor print (showing angles in degrees) pasted, so that the zero of this scale is in line with the vertical line drawn inside. A string with a weight is fixed in a way that it hangs from the centre outside over the scale. As the bucket is rotated the string with the weight moves over the scale indicating the degree of deviation from vertical. (Fig. 1).The subject looks into the bucket holding it in his hands. The examiner rotates the bucket clockwise and anticlockwise for six trials and fixes at one position, asking the subject to re-rotate it till he perceives that the radiant line is vertical. The angle of deviation is measured on the outside indicated by the string on the scale as in degrees away from 0°. A mean of the result of six trials is taken as absolute value. Normal range of deviation is 0 ± 2° [1].
Fig. 1
S.V.V. measurement done with the bucket
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Observations
The distribution of the 100 patients as per their etiology is shown in Table 1.
Table 1
Distribution of subjects with vestibular dysfunction N = 100
Vestibular disorderNumber of patientsB.P.P.V 42
Vestibular neuritis 23
Meniere’s disease 11
Others 24
Out of 23 patients diagnosed as Vestibular Neuritis (Fig. 2) 19 had abnormal deviation of S.V.V. at first visit, four did not show any deviation. S.V.V. value of more than two degrees to the right or the left was considered abnormal. More 85 % 0f the patients with abnormal S.V.V. (range was from >2 to 7°) showed deviation to same side as hypoactive labyrinth on caloric test, whereas in 15 %, the deviation was to opposite side as that of hypoactive labyrinth on calorization. On follow up after 2 weeks, 15 patients still had abnormal S.V.V. and eight had normal values. All the patients were on vestibular rehabilitation therapy. At 1 month follow up 18 patients showed a normal S.V.V. where as only three had abnormal S.V.V., two patients did not follow up.
Fig. 2
The findings of S.V.V. in patients of Vestibular Neuritis (N = 23)
Meniere’s disease was diagnosed in 11 patients (Fig. 3), six of whom showed abnormal values of S.V.V. and in five it was normal. Amongst patients with abnormal S.V.V. values, three patients showed deviation to same side as the disease, one to opposite side and two of patients had bilateral disease.
Fig. 3
The findings of S.V.V. in patients of Meniere’s disease (N = 11)
Out of 44 patients of B.P.P.V. (Fig. 4), 36 had unilateral B.P.P.V. of posterior semicircular canal and six had Lateral Semicircular Canal involvement. 30 patients had abnormal S.V.V. to the same side, four to opposite side and in eight patients it was normal. They were all subjected to repositioning maneuvers. On follow up after 1 month out of 32 patients, 30 had a normal S.V.V. and two still had abnormal value. Ten patients did not follow up.
Fig. 4
The findings of S.V.V. in patients of B.P.P.V. (N = 42)
Other causes of vestibular dysfunction included Migraine related Vertigo (10), Idiopathic vestibulopathy (5), Vestibular paroxysmia (2), Labyrinthitis (3) and Superior Semicircular Canal dehiscence (1). 20 of these patients had normal S.V.V. values and four had abnormal values which included all three patients of labyrinthitis and one of idiopathic vestibulopathy.
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Discussion
Various test batteries to assess vestibular system are usually limited to the assessment of semicircular canal functions. Nowadays VEMP is being widely used for testing saccular function. Utricular function can be tested by S.V.V. In our study we used a simple plastic bucket which was modified very easily to measure the S.V.V. Research has shown that there is no difference between results using the bucket test and more expensive testing apparatus [1]. We found this method though not very sensitive, is quick, inexpensive, easy to replicate, re-test and comfortable for the patients in our routine assessment.
In humans, the perception of vertical is provided by input from various sensorineural organs and pathways: vision, eye-movements, and proprioceptive and vestibular cues, particularly from the otolithic organs and graviceptive pathways. Friedman, in 1970, studied subjective vertical in a variety of clinical situations. Normal subjects can adjust an illuminated rod in an otherwise completely dark room to vertical within a mean error of less than 2°. Friedman concluded that severe derangement of this test is confined to brainstem lesions and the immediate postoperative period of peripheral vestibular lesions. The S.V.V. tilts toward the side of lesion [2].
Though well known in several types of brainstem lesions, S.V.V. abnormalities may also be observed after peripheral vestibular lesions, such as surgical de-afferentation, with a deviation directed toward the operated ear. Subjective Visual Vertical abnormalities are presumably related to a lesion of the otolithic organs and/or to changes in the afferent graviceptive pathways. Vibert et al. in their prospective study, measured the S.V.V. and defined the influence of the otolithic organs in patients suffering from various types of peripheral vestibular diseases: unilateral sudden cochleo-vestibular loss, so-called “viral labyrinthitis”, sudden idiopathic unilateral peripheral vestibular loss, so-called “vestibular neuritis” [3]. Data were compared with findings after unilateral surgical deafferentations such as vestibular neurectomy and labyrinthectomy. Subjective Visual Vertical was measured with a binocular test (vertical frame) and a monocular test (Maddox rod). Their results demonstrated that S.V.V. is frequently tilted in acute peripheral vestibulopathies. These findings suggested that otolithic function is implicated in the deficit depending on the extent and/or the localization of the peripheral vestibular lesion [3].
In our study of S.V.V. in vestibular disorders we found that 83 % of patients with Vestibular Neuritis had abnormal S.V.V., 71 % of B.P.P.V. cases, 52 % of Meniere’s disease, 100 % of patients with acute labyrinthitis did have abnormal S.V.V. frequently towards the side of lesion (Table 2). We did not have any cases of operated Vestibular neurectomy or Labyrinthectomy.
Table 2
Percentage of cases with abnormal S.V.V. in various vestibular disorders in our study
Vestibular diseasePercentage of cases with abnormal S.V.V. (%)Vestibular neuritis 81
B.P.P.V 71
Meniere’s disease 52
Labyrinthitis 100
Amongst the 23 patients of vestibular neuritis, we found that 83 % had tilting of subjective vertical, in 85 % towards side of lesion, i.e. a hypoactive labyrinth on calorization and Unterberger’s stepping test. In most of patients compensation occurred with vestibular exercises, S.V.V. being abnormal in only 64 % at 2 weeks and at 1 month follow-up, 79 % showed no deviation. Three patients who still had S.V.V. tilt were those who were non compliant with the vestibular rehabilitation therapy. The improvement in S.V.V. tilt correlated very well with the improvement of symptoms in our patients. However, Heil Noh and Sayong Chae in their study of 62 patients with vestibular neuritis found that there was no relation between the canal paresis and the tilt of S.V.V. Yet their results showed that S.V.V. correlated with clinical improvement of dizziness symptoms in vestibular neuritis, thus help evaluate vestibular neuritis during the follow up [4]. S.V.V. is useful in clinical practice in persons with vestibular neuritis [5]. The range of abnormal tilt on either side in our cases was from more than 2 to 7°. Literature mentions that persons with vestibular lesions may orient the bar tilted as much as 10° [6]. The S.V.V. reverts to normal in labyrinthectomy by 1 year. In vestibular nerve section, a small deviation may persist after neurectomy even after 4 years [7].
Literature search was not fruitful in case of S.V.V. done on patients with active or remitted Meniere’s disease except for those who underwent labyrinthectomy or neurectomy. In patients with Meniere’s disease, operated with labyrinthectomy, a marked deviation toward the operated side was found acutely, with resolution over weeks [7]. Our study included 11 cases of diagnosed Meniere’s syndrome, in varying stages of the disease, two of who had bilateral disease. 55 % of these patients had abnormal S.V.V. amongst which again in 50 % the tilt was to same side as the disease. This correlated with the hypoactive labyrinth on caloric test and Unterberger’s stepping test. In bilateral Meniere’s disease S.V.V. is insensitive to lateralization hence of little value.
S.V.V. is slightly biased during eccentric rotation in persons with B.P.P.V. This probably reflects unilateral utricular disturbance [8]. Amongst our 42 patients diagnosed as BPPV. 86 % had posterior SCC BPPV and 14 % had lateral SCC BPPV. At first visit, 71 % did show abnormal S.V.V. towards affected side, 19 % had normal S.V.V. and in rest, the tilt was to opposite side. After treatment by canal repositioning maneuvers, at one month follow up, 17 % showed a normal S.V.V. Amongst the patients grouped as “other causes”, all three patients of labyrinthitis had tilt to affected side, one patient with idiopathic vestibulopathy showed abnormal S.V.V., whereas the patients diagnosed as Vestibular Migraine, Vestibular paroxysmia and Superior canal dehiscence showed normal S.V.V. None of our patients diagnosed as vestibular migraine showed abnormal S.V.V. though literature mentions that S.V.V. maybe altered in vestibular migraine [9].
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Conclusion
Static S.V.V. is a useful measure of utricular dysfunction in acute peripheral disorders especially vestibular neuritis. It has a potential use in measuring compensation, prognosis and recovery in various peripheral vestibular conditions. The bucket test though not very sensitive is a simple, cost effective, easy and quick method to assess S.V.V. in daily practice. It should be made a part of routine neurotological examination while evaluating a patient of vertigo.
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Contributor Information
Naik Chetana, Phone: +919765386084, Email: moc.liamg@17anatehcrd, Email: ku.oc.oohay@17anatehcrd.
Rane Jayesh, Phone: +918806790245, Email: moc.liamg@02.enarhseyaj.
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References
1. Zwergal A, Rettinger N, Frenzel C, Dieterich M, Brandt T, Strupp M. A bucket of static vestibular function. Neurology. 2009;72:1689–1692. doi: 10.1212/WNL.0b013e3181a55ecf. [PubMed] [CrossRef] [Google Scholar]
2. Friedmann G. The judgement of the visual vertical and horizontal with peripheral and central vestibular lesions. Brain. 1970;93:313–328. doi: 10.1093/brain/93.2.313. [PubMed] [CrossRef] [Google Scholar]
3. Vibert D, Hausler R, Safran AB. Subjective visual vertical in peripheral unilateral vestibular diseases. J Vestib Res. 1999;9(2):145–152. [PubMed] [Google Scholar]
4. Noh H, Chae S. Change of Subjective Visual Vertical (SVV) in Patients of Vestibular Neuritis. J Korean Balance Soc. 2007;6(2):143–149. [Google Scholar]
5. Min KK, Ha JS, et al. Clinical use of subjective visual horizontal and vertical in patients of unilateral vestibular neuritis. Otol Neurotol. 2007;28(4):520–525. doi: 10.1097/01.mao.0000271674.41307.f2. [PubMed] [CrossRef] [Google Scholar]
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7. Vibert D, Hausler R. Long-term evolution of subjective visual vertical after vestibular neurectomy and labyrinthectomy. Acta Otolaryngol. 2000;120:620–622. doi: 10.1080/000164800750000432. [PubMed] [CrossRef] [Google Scholar]
8. Hong SM, Park MS, et al. Subjective visual vertical during eccentric rotation in patients with benign paroxysmal positional vertigo. Otol Neurotol. 2008;29(8):1167–1170. doi: 10.1097/MAO.0b013e31818a0f3c. [PubMed] [CrossRef] [Google Scholar]
9. Asai M, Aoki M, Hayashi H, et al. Subclinical deviation of the subjective visual vertical in patients affected by a primary headache. Acta Otolaryngol. 2009;129(1):30–35. doi: 10.1080/00016480802032785. [PubMed] [CrossRef] [Google Scholar]
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Subjective visual vertical
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Subjective Visual Vertical (SVV) is a diagnostic test of the inner ear to assess a patient's perception of verticality and detect if there are signs of an abnormal tilt that can cause dizziness or vertigo. It investigates the function of the utricle, one of two otolith organs located in the vertebrate inner ear, to evaluate the perception of verticality. As its name suggests, the test is subjective and cannot directly diagnose Acute Vestibular Syndrome (AVS), Ménière’s disease, vestibular migraine, vestibular neuritis or other central nervous system pathologies.[1]
Technique and usage[edit]
This test is conducted in various ways. One method involves a dark room where a patient sits and adjusts a remotely controlled laser projection line to his perceived horizontal or vertical position. Sometimes this involves a dynamic element like a rotary chair. Another method, known as the bucket test, uses a bucket over a patient's head. The clinician rotates the bucket until the a line at the bottom of the bucket is perceived to be vertical. The Subjective Virtual Visual goggle is a trademarked method, which employs a goggle displaying a vertical line and a hand-held remote. It allows the clinician to administer the test while tilting the patient's head.[2] It is used for the following objectives:[citation needed]
Diagnosis of vestibular disorders
Assessment of the effectiveness of vestibular rehabilitation in patients suffering from vertigo
Assessment of chronic dizziness and other otolith disorders
Differentiation between peripheral and central vestibular disorders
References[edit]
^ "Subjective Visual Vertical (SVV) and the Dizzy Patient".
^ "Balance And Vestibular Program | Tests and Procedures | Boston Children's Hospital". www.childrenshospital.org. Retrieved 2018-07-11.
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