VEMP Responses Research Articles

Clinical Usefulness of the VEMP Test in Vestibular Diagnosis

Objective 1) Assess the clinical usefulness of the VEMP test in identifying vestibular disease. 2) Evaluate the criteria used for a positive VEMP test. Methods We prospectively evaluated 166 consecutive patients complaining of dizziness with a neurotologic examination including spontaneous nystagmus, head-shake testing, gaze testing, and Hallpike maneuver. ENG testing and MRI scanning were done when indicated. All underwent VEMP testing. We considered 30% and 40% amplitude asymmetry criteria as abnormal for peripheral, and 17 msec latency abnormal for central disease and compared these with the complete clinical evaluation. Results 44 patients had no VEMP response and were excluded. Analysis of the remaining 122 patients showed that 47% of patients with a peripheral vestibular disorder had an abnormal VEMP, using the 30% amplitude asymmetry criterion (p<0.001) (Fisher Exact Test), and 29% had an abnormal VEMP using the 40% criterion (p<0.001). The likelihood of a false positive was very low (3%, p<0.001). 42% of patients diagnosed with central vestibular dysfunction had delayed latency responses and the false positive rate was 2% (p<0.001). Conclusions The very low false positive rate (high specificity) indicates that an abnormal VEMP test is a good predictor of the presence of vestibular dysfunction, but a normal VEMP test does not exclude it. More patients with vestibular disease are identified (47% vs. 29%) just as accurately using a 30% rather than 40% criterion for a positive test. VEMP testing appears to be a valuable addition to the vestibular test battery and should be considered in the evaluation of dizzy patients.

The Recordability of Two Sonomotor Responses in Young Normal Subjects

It has been reported that up to 40% of patients over age 60 fail to generate a vestibular evoked myogenic potential (VEMP; Su et al, 2004). When this occurs it is difficult to determine whether the absent VEMP represents evidence of bilateral impairment of the vestibulocollic reflex pathway or a normal age-related variant (i.e., idiopathic absence). The purpose of the present investigation was to determine whether both VEMPs and PAMs could be recorded reliably in a sample of neurologically and otologically intact young adults. If both could be obtained with high reliability in normal subjects, then the bilateral presence of PAM in the bilateral absence of VEMP, at least in younger patients, could be used to support the contention that the absent VEMP represented evidence of bilateral impairment. A descriptive study. Attempts were made to record both the VEMP and a second sonomotor response, the postauricular muscle potential (PAM) from 20 young adults. Results showed both the VEMP and the PAM were present in 90% of the ears. Both the VEMP and PAM responses were bilaterally absent for one subject. Also, the VEMP and PAM were unilaterally absent for two subjects. Subjects who generated VEMPs also generated a PAM in at least one ear. The present investigation represents an initial step in the determination of whether the presence of PAMs in the absence of VEMPs can be used as a method of validating the presence of an impairment affecting the vestibulocollic reflex pathway.

Vestibular hypersensitivity to sound in superior canal dehiscence: Large evoked responses in the legs produce little postural sway

Objective Patients with superior canal dehiscence (SCD) typically have enhanced sound-evoked vestibular reflexes, such as vestibulo-collic and vestibulo-ocular reflexes. We wished to investigate whether sound-evoked lower limb EMG responses and postural sway are also enhanced in this condition. Methods Eight patients with CT confirmed SCD (11 affected ears) and 8 age-matched normal controls participated. Three sound-evoked responses were measured; vestibulo-collic reflexes (i.e. vestibular-evoked myogenic potentials, VEMPs), lower limb vestibulo-spinal reflexes and body sway (centre of pressure in mm). Sound stimuli were 500 Hz air-conducted tone bursts of varying lengths (VEMPs: 2 ms; vestibulo-spinal: 20 ms; sway: 1 s and 200 ms) set at fixed levels above each subject’s VEMP threshold. Results SCD patients had very large VEMP and vestibulo-spinal responses following high intensity stimulation, but at the matched intensity of 15 dB above threshold amplitudes were similar in both SCD patients and controls. The amplitude of both responses increased linearly with increasing stimulus intensity in both groups. Large (∼20 mm), stereotyped sway responses were present in only one (atypical) patient with high intensity stimulation. Small (∼2 mm) sway responses were present in the remaining patients, and began immediately following the vestibulo-spinal responses. Conclusions Despite the presence of large vestibular reflexes, there is usually very little body sway in response to loud sounds in SCD patients. Significance Large short-latency vestibulo-spinal reflexes in SCD do not necessarily evoke large sway responses.

Validity of a new feedback method for the VEMP test

Conclusions. We used a feedback method, based on a blood pressure manometer with inflatable cuff, to control the sternocleidomastoid muscle (SCM) contraction. To obtain comparable left-right VEMP responses, it is necessary (1) to determine which cuff pressures on both sides yield identical mean rectified voltage (MRV) values of the SCM contraction and (2) to apply these cuff pressures during the VEMP test. Objective. To investigate the ffect of the SCM muscle contraction variability on the VEMP variables when applying the feedback method. Materials and methods. Subjects pushed with their jaw against the hand-held inflated cuff to generate cuff pressures of subsequently 30, 40 and 50 mmHg during a MRV and VEMP measurement. Results. When analyzing the relationship between the applied cuff pressures and the MRV values/VEMP amplitudes, we showed that (1) there was a linear relationship, (2) there was no side effect and (3) there was an interaction effect between ‘side’ and ‘subject’. There was neither a side effect, nor an effect of the applied cuff pressure when considering the p13 latencies. As for the n23 values, there was no side effect but there was a significant difference when comparing the n23 latencies at cuff pressures of 30 vs 40 mmHg/50 mmHg.

Vestibular-evoked myogenic potentials in three patients with large vestibular aqueduct

An enlarged vestibular aqueduct (LVA) is a common congenital inner ear anomaly responsible for some unusual vestibular and audiological symptoms. Most of the cases show bilateral early onset and progressive hearing loss in children. The gross appearance on CT scan of the inner ear is generally normal. However, precise measurements of the inner ear components reveal abnormal dimensions, which may account for the accompanying auditory and vestibular dysfunction. Despite extensive studies on hearing and the vestibular apparatus, saccular function is not studied. To our knowledge this is the first report of saccular malfunction in three patients with LVA by means of vestibular evoked myogenic potentials. Conventional audiograms revealed bilateral severe sensorineural hearing loss in two patients and mixed type hearing loss in one patient. Two of the patients complained about vertigo and dizziness but vestibular assessments of the patients showed normal results. The diagnosis had been made by high-resolution CT scans and MR images of the skull that showed LVA in the absence of other anomalies. The VEMP threshold measured from the ear with LVA in two patients with unilateral enlargement of the vestibular aqueduct was 75–80 dB nHL whereas the threshold from normal ears was 95 dB nHL. The third patient with mixed type hearing loss and bilateral LVA had VEMP responses despite a big air–bone gap in the low frequency range. The VEMP in this patient was greater in amplitude and lower in threshold in the operated ear (the patient had a tympanoplasty which did not improve her hearing). These findings and results of other patients with Tullio phenomenon and superior semicircular canal dehiscence, who also showed lower VEMP threshold, confirmed the theory of a ‘third window’ that allows volume and pressure displacements, and thus larger deflection of the vestibular sensors, which would cause the vestibular organ to be more responsive to sound and pressure changes.

Vestibular-Evoked Myogenic Potentials in the Diagnosis of Superior Canal Dehiscence Syndrome

Patients with superior canal dehiscence (SCD) syndrome have vertigo and oscillopsia induced by loud noises and by stimuli that result in changes in middle ear or intracranial pressure. We recorded vestibular-evoked myogenic potentials (VEMP responses) in 10 patients with SCD syndrome. The diagnosis had been confirmed in each case by evoked eye movements and by high-resolution CT scans of the temporal bones that showed a dehiscence overlying the affected superior canal. For the 8 patients without prior middle ear disease, the VEMP threshold from the dehiscent ears measured 72 - 8 dB NHL (normal hearing level) whereas the threshold from normal control subjects was 96 - 5 dB NHL ( p < 0.0001). The VEMP threshold measured from the contralateral ear in patients with unilateral dehiscence was 98 - 4 dB NHL ( p > 0.9 with respect to normal controls). Two patients with apparent conductive hearing loss from middle ear disease, and SCD, had VEMP responses from the affected ears. In the absence of dehiscence, VEMP responses would not have been expected in the setting of conductive hearing loss. These findings confirm earlier studies demonstrating that patients with SCD syndrome have lowered VEMP thresholds. Conditions other than SCD syndrome may also lead to lowered VEMP thresholds. Rather than being based upon a single test, the diagnosis of SCD syndrome is best established when the characteristic symptoms, signs, VEMP response, and CT imaging all indicate SCD.

前庭誘発筋電位

Intense clicks evoke short-latency myogenic potentials on the sternocleidomastoid (SCM) muscle ipsilaterally. These potentials are namedvestibular evoked myogenic potentials (VEMP) because they are lost after vestibular deafferentation, but independent of the cochlear function. To induce VEMP, the subjects need to contract their SCM muscle during the test. The characteristics of the tuning curve of VEMP are a high threshold and low best frequency. They are similar in animal studies, suggesting that the saccule is the most promising candidate for the origin. Some diagnostic merit has been reported in previous papers. First, there is a discrepancy between VEMP and caloric response in patients with both inner ear and retrolabyrinthine disorders. Therefore, the test battery of these two tests is very useful for diagnosing vertiginous patients. Second, the Tullio phenomenon, the phenomenon of vertigo or loss of balance due to intense sound, is also evaluated by using VEMP. The Tullio phenomenon has been found in patients with various disorders, including congenital syphilis, Meniere's disease and perilymphatic fistula. VEMP are expected to be used in a new vestibular function test to evaluate the neural pathway from the saccule to the SCM muscle.