Vestibular evoked myogenic potential (VEMP) testing, also known as click evoked neurogenic vestibular potential testing, is a noninvasive, neurophysiological test used to determine the function of vestibular organs in the inner ear, specifically the utricle and saccule. VEMP testing has been investigated in the diagnosis and management of several disorders, including superior canal dehiscence, benign paroxysmal positional vertigo, Ménière's disease, vestibular schwannoma, vestibular neuritis, otosclerosis, and multiple sclerosis.
The test measures a muscle reflex evoked by stimulation of the vestibular organs and recorded from electrodes placed on the skin over tensed sternocleidomastoid muscles in the neck (cervical VEMP) or over extraocular muscles beneath the eyes (ocular VEMP). Vestibular stimulation is performed using a loud sound or vibration. Variations in the response of the muscle to the vestibular stimulation, such as absent or decreased electrical activity in the muscle, have been associated with certain disorders.
The U.S. Food and Drug Adminstration (FDA) has not approved specific devices for VEMP testing. Commercially available auditory brainstem response (ABR) equipment can be adapted to perform VEMP testing.
Vestibular evoked myogenic potential (VEMP) testing is considered EXPERIMENTAL/INVESTIGATIVE for all indications due to the lack of clinical evidence demonstrating an impact on improved health outcomes.
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Summary of Evidence
Vestibular evoked myogenic potential (VEMP) testing is a noninvasive, neurophysiological test used to determine the function of vestibular organs in the inner ear, specifically the utricle and saccule. This testing has been investigated in the diagnosis and management of several disorders, including superior canal dehiscence and Meniere’s disease. Clinical literature on VEMP testing is limited to case series and case reports that describe results of VEMP testing in patients previously diagnosed with a central or peripheral vestibular disorder. Clinical studies on VEMP testing that demonstrate its impact on diagnosis or monitoring of vestibular disorders or its impact on improved health outcomes are unavailable.
Rationale
No clinical studies on VEMP testing were identified that demonstrate its impact on diagnosis or monitoring of vestibular disorders (i.e., its clinical utility). In addition, no studies were identified that demonstrate its impact on improved health outcomes. The majority of the published clinical literature on VEMP testing is comprised of uncontrolled, observational studies. Numerous case series and case reports are published that describe results of VEMP testing in patients previously diagnosed with a central or peripheral vestibular disorder. Reviews and clinical studies with a higher level of evidence are summarized below. Overall, the evidence is insufficient to determine whether adding VEMP testing to the standard battery of inner ear tests has clinical benefit.
A review by Rauch et al (2006) states that there has been increased interest in VEMP testing in recent years due to its potential utility in diagnosing third-window disorders (i.e., superior canal dehiscence) and in diagnosing and monitoring Ménière's disease. The review identified many review articles, method articles, case reports, and uncontrolled case series seeking new applications for VEMP testing in diagnosis and monitoring of neurotologic diseases, though many aspects of the testing had not yet been adequately studied or described. The author concluded that the methods, equipment, and applications for VEMP testing are not yet standardized.
Superior canal dehiscence (SCD) is a vestibular disorder characterized by vertigo and oscillopsia in response to loud sounds or pressure secondary to a dehiscent superior semicircular canal. The dehiscence is thought to create a “third-window,” resulting in enhanced vestibular sensitivity. This vestibular hypersensitivity to sounds is referred to as the Tullio phenomenon. A diagnosis of SCD is made on the basis of high-resolution CT scans demonstrating the dehiscence and on sound- or pressure-evoked eye movements. Several studies have demonstrated that patients with SCD also have a large VEMP amplitude and a low VEMP threshold.
A review by Brantberg (2009) identifies limitations to using VEMP testing for diagnosing SCD, including the time needed to do VEMP threshold testing and the low signal-to-noise ratio close to threshold. Large VEMP amplitudes in response to high-intensity stimulation have also been reported in patients without symptoms of vestibular hypersensitivity to sounds. The author states that VEMP testing is not needed to confirm the diagnosis in patients with typical SCD presentation; however, VEMP testing may be useful for patients with suspected SCD who do not display sound- or pressure-induced eye movements. VEMP testing has also been proposed for use in postsurgical follow-up of patients with SCD who undergo corrective surgery.
A review by Rosengren (2013) states that VEMP testing has its clearest role in diagnosis of SCD and other third-window disorders, as multiple studies have reported the sound-evoked cVEMP has a characteristically low threshold in these patients. While the sound-evoked cVEMP amplitude is often large in SCD patients, there is significant overlap with the normal range. According to the author, more recent evaluation of the ocular VEMP (oVEMP) test has shown a low threshold and a reliably high amplitude in these patients. The author notes that abnormal VEMP testing does not rule out concomitant dysfunction of the superior canal.
Akkuzu et al (2006) conducted a prospective study to evaluate whether VEMP testing is valuable for assessing the vestibular system in patients with benign paroxysmal positional vertigo (BPPV) and Ménière's disease. A total of 62 patients who received care at a tertiary referral center were involved, including 17 healthy controls, 25 patients diagnosed with BPPV, and 20 patients diagnosed with Ménière's disease. All patients diagnosed with BPPV or Ménière's disease presented with vertigo. Among the 25 patients with BPPV (30 affected ears), VEMP testing revealed 8 ears with prolonged latencies and 1 ear with decreased amplitude, for a total of 9 (30%) abnormal ears. Among the 20 patients with Ménière's disease (20 affected ears), VEMP testing revealed 6 ears with prolonged latencies and 4 ears with no response, for a total of 10 (50%) abnormal ears. Control patients demonstrated an abnormal VEMP response in 2 (6%) ears. The rate of VEMP abnormalities was reported to be significantly lower in control ears compared with BPPV ears and Ménière's disease ears (p=0.012 and p<0.001, respectively). The authors concluded that VEMP testing is a promising method for diagnosing and following patients with BPPV and Ménière's disease.
The 2009 review by Brantberg states that there have been reports of VEMP testing on more than 400 patients with Ménière's disease. Multiple studies have reported that approximately 50% of patients with Ménière's disease have decreased or absent VEMP amplitudes. Studies have also shown that VEMP testing can be used to monitor the results of intratympanic gentamicin therapy in these patients by measuring the degree of peripheral vestibular damage due to the vestibulotoxic substance. The author states that VEMP testing in Ménière's disease seems to be helpful for estimating the severity of vestibular damage due to the pathophysiologic process and/or treatment.
Zuniga et al (2012) conducted a prospective cohort study to evaluate whether cVEMP or oVEMP testing could differentiate Ménière's disease from vestibular migraine. A total of 69 patients who received care at a tertiary referral center were involved, including 20 patients with unilateral definite Ménière's disease, 21 patients with probable or definite vestibular migraine, and 28 age-matched healthy controls. Compared with controls, both Ménière's disease and vestibular migraine groups showed reduced click-evoked cVEMP (p<0.001) and oVEMP amplitudes (p<0.001). Only the Ménière's disease group showed reduction in tone-evoked oVEMP amplitudes, which differentiated the Ménière's disease group from controls (p=0.001) and the vestibular migraine group (p=0.007). The authors note that, while oVEMP responses to a 500-Hz tone burst may separate Ménière's disease from vestibular migraine as groups, no VEMP test investigated in the study could differentiate individuals with Ménière's disease from those with vestibular migraine. The authors concluded that Ménière's disease and vestibular migraine behave similarly on most VEMP tests.
A review by Le et al (2013) states that the inconclusive findings reported by Zuniga et al. demonstrate the lack of sensitivity and specificity to Ménière's disease in both cVEMP and oVEMP testing, and calls into question the absolute utility of the VEMP phenomenon in diagnostic algorithms for Ménière's disease. In their key points, they note that cVEMP and oVEMP are new diagnostic techniques that measure saccular and utricular function, but whose utility in the diagnosis of Ménière's disease is limited by poor sensitivity. The authors conclude that, for now, Ménière's disease remains best diagnosed through the standard AAO-HNS clinical inclusionary and exclusionary criteria.
Brantberg identifies several studies that failed to show a clear correlation between vestibular schwannoma tumor size and VEMP testing response. Additional studies were identified that demonstrated no difference in the percentage of abnormal VEMP responses based on vestibular schwannoma location (inferior versus superior vestibular nerve). It is noted that, while VEMP testing does not seem to be of importance for vestibular schwannoma screening or for determining nerve of origin, it may still be useful in clinical neurotology for assessing remnant preoperative vestibular function and for monitoring function in some patients selected for observation. The 2009 review by Brantberg states that there have been reports of VEMP testing on more than 250 patients with vestibular neuritis. Studies have reported that approximately 30% of patients with vestibular neuritis have decreased or absent VEMP amplitudes. It has been proposed that VEMP testing in patients with vestibular neuritis may be useful for determining whether the inferior vestibular nerve is affected; however, in what way this affects patients’ symptoms requires further study.
A study by Trivelli et al (2010) found no statistically significant difference in VEMP responses before and after stapes surgery, indicating inner ear impairment in patients with otosclerosis even when hearing is restored. In another study, Zhou et al. (2012) retrospectively reviewed case files for 50 patients with middle ear pathologies, including otosclerosis, and all had absent VEMP responses elicited by air-conduction stimuli. The authors concluded that VEMP testing is useful during clinical evaluation of patients with air-bone gaps.
Gabelić et al (2015) conducted a prospective case-control study to evaluate a newly developed VEMP score as a possible marker of brainstem involvement in patients with MS. A total of 150 patients were involved, including 50 patients with MS but no clinical signs of brainstem involvement (group 1), 50 patients with MS and clinical signs of brainstem involvement (group 2), and 50 healthy controls. Both cVEMP and oVEMP testing were performed, and a VEMP score representing the sum of 4 4-graded scores derived from the evaluation of each VEMP was calculated for each patient. The VEMP score was found to be significantly higher in group 2 compared with group 1 (p=0.018) and correlated with disability and disease duration (p=0.011 and p=0.032, respectively). The authors concluded that the VEMP score enables better evaluation of brainstem involvement than either cVEMP or oVEMP testing alone and correlates well with disability. They noted that additional studies are needed to determine the predictive value of the VEMP score on future disability.
In a 2012 statement on vestibular testing, the American Hearing Research Foundation identifies VEMP testing as an emerging, investigational test. The statement notes that VEMP testing has been described as useful in diagnosing Tullio’s phenomenon from SCD. They add that it may be difficult to locate a laboratory that performs it.
In 2014, the AAO-HNS issued a position statement specifically on VEMP testing. The AAO-HNS states that VEMP testing is a useful neurophysiologic test and is medically indicated and appropriate in the evaluation of certain persons with suspected auditory and balance or dizziness disorders. No other information on VEMP testing is provided. Five references are provided in support of this statement; three are conference presentations (2 abstracts; 1 poster), and the other two are pre-2005 publications on small case series (1 SCD; 1 Ménière's).
In 2017, the AAO-HNS updated its guidelines on BPPV, retaining the recommendation for the diagnosis of BPPV if a Dix-Hallpike maneuver elicits vertigo associated with nystagmus. The panel recommended a canalith repositioning procedure as treatment for posterior canal BPPV, although subsequent post procedural postural restrictions were strongly warned against. Patients with symptoms similar to BPPV but for whom the Dix-Hallpike does not evoke nystagmus should be subjected to a supine roll test. Potential diagnoses of BPPV should be distinguished from confounding factors, and patients should have regular reassessment and follow-up. The panel did not recommend radiographic imaging, vestibular testing, or vestibular suppressant medications as treatment for BPPV, although disease management options for caregivers include vestibular rehabilitation and/or observation.
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