Vestibular Autorotation Test (VAT)

Number: 0467

Policy

Aetna considers vestibular autorotation test (VAT) experimental and investigational for the diagnosis of individuals with vestibular disorders, vestibular migraine, or any other indications because its sensitivity, specificity, reproducibility, and clinical utility have not been demonstrated.

See also CPB 0238 - Chronic Vertigo.

Background

Impairment of the vestibular-ocular reflex (VOR) may result in chronic dizziness and imbalance.  The vestibular autorotation test (VAT) is a high-frequency, active head rotation (AHR) test to subjectively evaluate the VOR and its function.  Patients wear a light-weight head-strap with a velocity sensor on the back. Conventional electro-olfactogram electrodes placed around the eyes measure patients' eye movements, and other electrodes monitor head movements. While following a moving target with the eyes, the individual moves the head back and forth or up and down in time with gradually accelerating computer generated tones.

Although some published studies have suggested that the VAT may be useful in evaluating patients with vestibular disorders/diseases, there are few studies that examined the sensitivity and specificity of the VAT in evaluating patients with suspected vestibular abnormalities.  Furthermore, there is a lack of data supporting the value of the VAT in the management of patients with vestibular disorders/diseases.

In an assessment on vestibular testing techniques in adults and children, the American Academy of Neurology (Fife et al, 2000) stated that AHR testing is not an established technique.  This type of testing does not appear useful in detecting unilateral vestibular loss (e.g., as a consequence of unilateral acoustic neuroma, Meniere's disease or vestibular neuritis).  Furthermore, a recent study (Tirelli et al, 2004) reported that the test-retest of the Vorteq system, a head-autorotation test is not sufficiently reliable and hence can not be used in clinical practice.

Ozgirgin and Tarhan (2008) noted that the head autorotation tests can be affected with the dynamic changes within the semicircular canals caused by benign paroxysmal positional vertigo (BPPV).  The VAT is a method of examining the VOR (especially the VOR that develops at higher frequencies like those that occur in the everyday environment).  In this study, 20 patients who had been diagnosed as having posterior semicircular canal BPPV were evaluated with head autorotation tests before and after Epley maneuver.  The head autorotation tests were performed just before the use of the Epley maneuver and after the resolution of symptoms and the typical nystagmus pattern.  The mean gain values for horizontal rotation tests during the pre-treatment period were 0.823, 0.844, and 0.840 for the frequencies 1, 2, and 3 Hz, respectively.  The mean gain values increased by 0.095 (95 % confidence interval) with Epley maneuver.  But this difference between the pre-treatment and post-treatment values was not statistically significant.  All patients were also evaluated with vertical active tests.  The differences between the pre-treatment and post-treatment values were not statistically significant in the vertical autorotation group.  The phase values were within normal range in the horizontal and vertical rotation tests and remained so after the Epley maneuver.  The stimulation of the VOR caused by BPPV did not affect gain and phase values to a statistically significant degree, and the values noted after the resolution of the patient's symptoms improved slightly but without statistical significance.

Blatt and colleagues (2008) established intra-rater and inter-rater reliability of the VAT in a clinical sample of individuals reporting dizziness.  A total of 98 patients with reports of dizziness referred for vestibular function testing performed repeated trials of horizontal VAT.  A sub-sample of 49 individuals repeated the test for a second rater.  About 66 % of subjects were unable to meet the performance criterion of 6 consecutive trials where data was displayed at frequencies greater than or equal to 3.9 Hz with coherence values held constant trial to trial. There was a good level of intra-rater reliability for gain independent of the effects of practice (intraclass correlation coefficient [ICC] = 0.78 [95 % confidence interval [CI]: 0.69 to 0.87] to 0.95 [(95 % CI: 0.93 to 0.97]).  A significant difference in intra-rater reliability was found when the first 3 trials were compared to the last 3 trials for phase (ICC ranged from 0.04 [95 % CI: 0.00 to 0.31] to 0.96 [95 % CI: 0.93 to 0.97]) and asymmetry (ICC ranged from 0.39 [95 % CI: 0.17 to 0.56] to 0.73 [95 % CI: 0.32 to 0.81]) particularly at frequencies greater than or equal to 4.3 Hz.  Inter-rater reliability was good to excellent across all variables at frequencies less than or equal to 3.9 Hz.  The authors concluded that many patients had difficulty performing the VAT.  The reliability estimates for phase and asymmetry, but not gain, were significantly affected by practice.  They stated that careful attention to patient preparation, instruction, and test monitoring including sufficient patient practice before data collection are likely to be critical factors to ensure quality data.

Gao et al (2010) evaluated the utility of VAT in the diagnosis of BPPV.  Caloric test and VAT were performed on 41 patients with BPPV; VAT results were analyzed according to the affected semicircular canal.  Results of VAT were abnormal in 34 (82.93%) patients with BPPV.  Fourteen cases were found with abnormal vertical phase, 1 case with abnormal vertical gain in a total of 21 vertical semicircular canal BPPV patients.  Six cases with abnormal horizontal phase lead, 5 cases with abnormal horizontal gain, 2 cases with asymmetry were found in 12 patients with horizontal semicircular canal BPPV.  Phase lead was abnormal in all frequencies in 4 patients, and in 2 to 3 Hz in 21 patients; 24 (58.5 %) patients showed abnormal canal paresis and direction preference in caloric test.  The authors concluded that VAT can indicate information of vestibular function in both vertical as well as horizontal semicircular canal; and phase of VAT is constantly enhanced in BPPV, especially in 2 to 3 Hz.  They noted that as the supplement of caloric test, VAT may prove helpful in the assessment of semicircular canal function.

Correlational Vestibular Autorotation Test:

Hsieh et al (2014) stated that imbalance from degeneration of vestibular end organs is a common problem in the elderly.  However, the decline of vestibular function with aging was revealed in few vestibular function tests such as VAT.  In the current VAT, there are drawbacks of poor test-retest reliability, slippage of the sensor at high-speed rotations, and limited data about the effect of aging.  These researchers developed a correlational-VAT (cVAT) system that included a small, light sensor (less than 20 g) with wireless data transmission technique to evaluate the aging of vestibular function.  They enrolled 53 healthy participants aged between 25 and 75 years and divided them into 5 age groups.  The test conditions were vertical and horizontal head auto-rotations of frequencies from 0 to 3 Hz with closed eyes or open eyes.  The cross-correlation coefficient (CCC) between eye velocity and head velocity was obtained for the head auto-rotations between 1 Hz and 3 Hz.  The mean of the CCCs was used to represent the vestibular function.  Age was significantly and negatively correlated with the mean CCC for all test conditions, including horizontal or vertical auto-rotations with open eyes or closed eyes (p < 0.05).  The mean CCC with open eyes declined significantly at 55 to 65 years old and the mean CCC with closed eyes declined significantly at 65 to 75 years old.  The authors concluded that vestibular function evaluated using mean CCC revealed a decline with age, and the function of visual-VOR declined 10 years earlier than the function of VOR.  The clinical value of cVAT needs to be ascertained by well-designed studies.

Hsieh et al (2015) developed a cVAT system and evaluated the reliability and applicability of this system.  A total of 20 healthy participants and 10 vertiginous patients were enrolled in this study.  Vertical and horizontal auto-rotations from 0 to 3 Hz with either closed or open eyes were performed.  A small sensor and a wireless transmission technique were used to acquire the electro-ocular graph and head velocity signals.  The 2 signals were analyzed using CCCs to assess the functioning of the VOR.  The results showed a significantly greater CCC for open-eye versus closed-eye of head auto-rotations.  The CCCs also increased significantly with head rotational frequencies.  Moreover, the CCCs significantly correlated with the VOR gains at autorotation frequencies greater than or equal to 1.0 Hz.  The test-retest reliability was good (intra-class correlation coefficients greater than or equal to 0.85).  The vertiginous participants had significantly lower individual CCCs and overall average CCC than age- and-gender matched controls.  These preliminary findings need to be validated in well-designed studies.

Vestibular Migraine:

Barbosa and Villa (2016) noted that approximately 1 % of the general population suffers from vestibular migraine (VM).  Despite the recently published diagnostic criteria, it is still under-diagnosed condition.  The exact neural mechanisms of VM are still unclear, but the variability of symptoms and clinical findings both during and between attacks suggested an important interaction between trigeminal and vestibular systems.  Vestibular migraine often begins several years after typical migraine and has a variable clinical presentation.  In patients with VM, the neurological and neurotological examination is mostly normal and the diagnosis will be based in the patient clinical history.  Treatment trials that specialize on VM are scarce and therapeutic recommendations are based on migraine guidelines.  The authors concluded that controlled studies on the efficacy of pharmacologic interventions in the treatment of VM should be performed.

Thungavelu and colleagues (2017) examined the characteristics and clinical utility of VAT in patients with VM.  This study included 2 groups, an experimental group (441 patients) and a control group (65 healthy subjects).  Both groups undertook VAT; the parameters evaluated were horizontal gain/phase, vertical gain/phase and asymmetry.  The differences in VAT results between the 2 groups were investigated.  There were no statistical differences between the VAT data of the control group when compared to the reference value from the manufacturer (p > 0.05).  There were statistically significant differences in VAT results between the experimental and control group, namely elevated horizontal gain at frequency 2-, 3-, 4- and 5-Hz, horizontal phase delay at frequency 2-, 4-, 5- and 6-Hz, elevated vertical gain at frequency 2 6-Hz and vertical phase delay at frequency 4 6-Hz.  The authors concluded that the findings of this study using VAT in VM patients demonstrated elevated horizontal gain, vertical gain and delay in horizontal phase, vertical phase.  They suggested the application of VAT as a diagnostic tool that may provide objective evidence that can contribute to the diagnosis of VM and also in differential diagnosis.

Furthermore, an UpToDate review on “Vestibular migraine” (Robertson, 2018) does not mention vestibular autorotation test as a diagnostic tool.

The above policy is based on the following references: