Skull Vibration-induced Nystagmus Test Research Articles

Determination of Recovery by Total Restitution or Compensation Using Multifrequency Vestibular Tests and Subjective Functional Scales in a Human Model of Vestibular Neuritis

Background: Vestibular Neuritis (VN) can induce unilateral acute vestibular syndrome (AVS). This study aimed to identify predictive factors of recovery from vestibular neuritis considering total restitution and/or compensation. Methods: In this longitudinal study, 40 patients were included. The initial assessment, performed within 36 to 72 h from the onset (T0), included medical history taking (general and specific), including screening for cardiovascular risk factors (CVRFs), and a battery of diagnostic vestibular tests, comprising the bithermal caloric test (BCT), video head impulse test (VHIT), and skull vibration-induced nystagmus (SVIN) test. All patients also completed a Dizziness Handicap Inventory (DHI). All assessments were repeated 90 ± 15 days later (T3). Subjective compensation criteria were based on the DHI total score, and objective compensation criteria were based on laboratory test results. Four groups of patients (A, B, C, D) were delineated by combining patients with normal vs. abnormal vestibular tests and patients with normal vs. abnormal DHI. Results: CVRFs (but not age or body mass index (BMI)) were associated with a poorer recovery of symptoms. The BCT (lateral semicircular canal paresis %), VHIT (lateral semicircular canal gain), and SVINT (nystagmus slow phase velocity) recovered to normal values in 20%, 20%, and 27% of patients, respectively, at T3. Conclusions: Vascular risk factors (hypercholesterolemia) are correlated with patients who do not recover their symptoms via either total restitution or compensation. There was no significant difference between high- and low-frequency vestibular tests in patients recovering from their symptoms. Some patients with objective recovery may continue to have persistent subjective symptoms.

Vestibular Assessment with the vHIT and Skull Vibration-Induced Nystagmus Test in Patients with Nonprogressive Vestibular Schwannoma.

Background: Our primary objective was to monitor nonprogressive unilateral vestibular schwannomas (VSs) to assess the efficiency of rapid bedside examinations, such as the video head impulse test (vHIT) and skull vibration-induced nystagmus test (SVINT), in identifying vestibular damage. Methods: An observational study was conducted from March 2021 to March 2022 on all adult patients (>18 years old) with a confirmed nonprogressive VS (no active treatment). The SVINT (using a 100 Hz vibrator with two (SVINT2) or three (SVINT3) stimulation locations) and vHIT (for the six semicircular canals (SCCs)) were performed on all patients. The asymmetry of function between the vestibules was considered significant when the gain asymmetry was greater than 0.1. Rapid and repeatable assessment of VSs using two- and three-stimulation SVINT plus vHIT was performed to quantify intervestibular asymmetry. Results: SVINT3 and SVINT2 triggered VIN in 40% (24/60) and 65% (39/60) of patients, respectively. There was significant asymmetry in the vestibulo-ocular reflex (VOR), as shown by a VS-side gain < healthy-side gain in 58% (35/60) of the patients. Among the patients with significant gain asymmetry between the two vestibules according to the vHIT (VS-side gain < healthy-side gain), the proportion of patients expressing vestibular symptomatology was significantly greater than that of patients without any symptoms [67% (29/43) vs. 35% (6/17), respectively; p = 0.047]. Conclusions: The SVINT2 can be combined with the vHIT to form an interesting screening tool for revealing vestibular asymmetry. This work revealed the superiority of mastoid stimulation over vertex stimulation for SVINT in patients with unilateral vestibular loss.

Skull-vibration-induced nystagmus test in patients who are candidates for intratympanic gentamicin injection

This study aims to evaluate the utility of the skull-vibration-induced nystagmus test (SVINT) in the selection of patients with Ménière's disease (MD) for intratympanic injection of gentamicin. To date the indications for this treatment have been based only on subjective elements. A retrospective study was performed in 20 patients diagnosed with unilateral MD. SVINT were performed monthly and the evoked responses were evaluated. After 6 months, the results from patients who were candidates for gentamicin treatment (G group) were compared with those who did not need it (nG group). Correlation with Dizziness Handicap Inventory (DHI) score was evaluated. 120 tests were performed. Positive SVINTs were identified in 52 cases (43.3%) and included excitatory nystagmus in 18 (34.7%), inhibitory nystagmus in 28 (53.8%), and atypical pattern in 6 cases (11.5%). A significant increase excitatory nystagmus was recorded in group G (p = 0.00001). Moreover, there was a significant increase in the DHI score in group G compared with the nG group (p < 0.0001) and in patients with evoked excitatory nystagmus. The finding of excitatory nystagmus during SVINTs performed on several occasions in the follow-up prior to intratympanic injection of gentamicin strengthens this therapeutic choice.

Correlation of SVINT and Sensory Organization Test in Children with Hearing Loss.

Objective: The skull vibration-induced-nystagmus test (SVINT) is a noninvasive and effective screening tool for the function of the otolith and canal structures in children. It can instantaneously assess vestibular asymmetry. This study aimed to analyze the SVINT results of healthy children vs. children with hearing loss (HL) and to correlate it with sensory organization test (SOT) results as a functional balance evaluation tool. Design: This case-controlled study compared the results of SVINT to the results of the SOT of the computerized dynamic posturography (CDP) in a control group of 120 healthy normal-hearing children (i.e., NH group) vs. hearing loss (HL) group of 60 children, including 30 children with hearing aids (HAs) and 30 children with a unilateral cochlear implant (CI). The SVINT results were compared to the caloric test (CaT) and video head impulse test (vHIT) and associated with SOT scores. Results: Thirty-one children in the HL group had normal SVINT and normal SOT results. A total of 21 children in the HL group had SVINT-negative and abnormal results in the SOT (possibly due to bilateral vestibular loss (BVL)). Eight children in the HL group had positive SVINT and abnormal SOT results. However, none of the children had only positive SVINT with normal SOT findings. Moreover, 52% of children had a normal result on both the SOT and CaT, whereas 27% had abnormal results on both tests (17% bilateral weakness and 10% unilateral), and 22% had the only result of the SOT suggesting a functional abnormality. Similarly, when associating the result to vHIT, 51% had normal results on both tests, and 25% had abnormal results (13% bilateral and 12% unilateral weakness). Conclusions: SVINT findings can be correlated with SOT findings in the case of the unilateral vestibular lesion (UVL), which adds a diagnostic value in these pediatric cases but may differ in the case of the bilateral vestibular lesion (BVL). However, SVINT findings need to be cautiously interpreted in light of other test findings such as the SOT, CaT, and vHIT.

Fifty Years of Development of the Skull Vibration-Induced Nystagmus Test.

This review enumerates most of the studies on the Skull Vibration-Induced Nystagmus Test (SVINT) in the past 50 years from different research groups around the world. It is an attempt to demonstrate the evolution of this test and its increased interest around the globe. It explores clinical studies and animal studies, both permitting a better understanding of the importance of SVINT and its pathophysiology.

Skull Vibration Induced Nystagmus Test: Correlations with Semicircular Canal and Otolith Asymmetries.

Background: To establish in patients with peripheral vestibular disorders relations between skull vibration-induced nystagmus (SVIN) different components (horizontal, vertical, torsional) and the results of different structurally related vestibular tests. Methods: SVIN test, canal vestibular test (CVT: caloric test + video head impulse test: VHIT), otolithic vestibular test (OVT: ocular vestibular evoked myogenic potential oVEMP + cervical vestibular evoked myogenic potential cVEMP) performed on the same day in 52 patients with peripheral vestibular diseases (age < 65 years), and 11 control patients were analyzed. Mixed effects logistic regression analysis was performed to assert whether the presence of nystagmus in SVIN (3D analysis) have an association with the presence of peripheral vestibular dysfunction measured by vestibular explorations (CVT or OVT). Results: We obtained different groups: Group-Co (control group), Group-VNT (dizzy patients with no vestibular tests alterations), Group-O (OVT alterations only), Group-C (CVT alterations only), Group-M (mixed alterations). SVIN-SPV horizontal component was significantly higher in Group-M than in the other groups (p = 0.005) and correlated with alterations of lateral-VHIT (p < 0.001), caloric test (p = 0.002) and oVEMP (p = 0.006). SVIN-SPV vertical component was correlated with the anterior-VHIT and oVEMP alterations (p = 0.007; p = 0.017, respectively). SVIN-SPV torsional component was correlated with the anterior-VHIT positivity (p = 0.017). SVIN was the only positive test for 10% of patients (83% of Group-VNT). Conclusion: SVIN-SPV analysis in dizzy patients shows significant correlation to both CVT and OVT. SVIN horizontal component is mainly relevant to both vestibular tests exploring lateral canal and utricle responses. SVIN-SPV is significantly higher in patients with combined canal and otolith lesions. In some patients with dizziness, SVIN may be the only positive test.

Skull Vibration-Induced Nystagmus Test in a Human Model of Horizontal Canal Plugging.

Background/Aim: the aim of this study was to assess the skull vibration-induced nystagmus test (SVINT) results and vestibular residual function after horizontal semicircular canal (HSCC) plugging. Methods: In this retrospective chart review performed in a tertiary referral center, 11 patients who underwent unilateral horizontal semicircular canal plugging (uHSCCP) for disabling Menière’s disease (MD) were included. The skull vibration-induced nystagmus (SVIN) slow-phase velocity (SPV) was compared with the results of the caloric test (CaT), video head impulse test (VHIT), and cervical vestibular-evoked myogenic potentials (cVEMP) performed on the same day. Results: Overall, 10 patients had a strong SVIN beating toward the intact side (Horizontal SVIN-SPV: 8.8°/s ± 5.6°/s), 10 had a significant or severe ipsilateral CaT hypofunction, 10 had an ipsilateral horizontal VHIT gain impairment, and 3 had altered cVEMP on the operated side. Five had sensorineural hearing worsening. SVIN-positive results were correlated with CaT and horizontal VHIT (HVHIT) results (p < 0.05) but not with cVEMP. SVIN-SPV was correlated with CaT hypofunction in % (p < 0.05). Comparison of pre- and postoperative CaT % hypofunction showed a significant worsening (p = 0.028). Conclusion: SVINT results in a human model of horizontal canal plugging are well correlated with vestibular tests exploring horizontal canal function, but not with cVEMP. SVINT always showed a strong lesional nystagmus beating away from the lesion side. SVIN acts as a good marker of HSCC function. This surgical technique showed invasiveness regarding horizontal canal vestibular function.

Agreement between the Skull Vibration-Induced Nystagmus Test and Semicircular Canal and Otolith Asymmetry.

How significant asymmetries in otolith organ function in the presence of symmetrical and asymmetrical semicircular canal function influence skull vibration-induced nystagmus testing (SVINT) has not been well described. The aim of the study is to examine the agreement between SVINT and caloric testing, ocular vestibular-evoked myogenic potentials (oVEMP), and cervical vestibular-evoked myogenic potentials (cVEMP) for detecting asymmetric vestibular function. This is a retrospective study of patients presenting with the chief complaint of vertigo, dizziness, or imbalance. A total of 812 patients were studied with a median age at testing of 59 years (interquartile range 46-70; range 18-93) and included 475 (59%) women. Either the monothermal warm caloric test or alternate binaural bithermal caloric test, oVEMP, and cVEMP tests were administered to all patients. All patients underwent the SVINT prior to vestibular laboratory testing. Agreement between tests categorized as normal versus abnormal was summarized using percent concordance (PC). Sensitivity and specificity values were calculated for SVINT compared with other tests of vestibular function. There was higher agreement between ipsilateral and contralateral SVINT with the caloric test (PC = 80% and 81%, respectively) compared with oVEMP (PC = 63% and 64%, respectively) and cVEMP (PC = 76% and 78%, respectively). Ipsilateral and contralateral SVINT showed higher sensitivity for the caloric test (sensitivity = 47% and 36%, respectively) compared with oVEMP (sensitivity = 26% and 21%, respectively), or cVEMP (sensitivity = 33% vs. 27%, respectively). Specificity of SVINT was high (>80%) for all assessments of vestibular function. The presence of SVIN is a useful indicator of the asymmetry of vestibular function between the two ears when making judgments about semicircular canal asymmetry but is less sensitive to asymmetries in otolith organ function.

The Skull Vibration-induced Nystagmus Test (SVINT) for Vestibular Disorders: A Systematic Review.

To determine the specificity and sensitivity of the skull vibration-induced nystagmus test (SVINT) for detecting vestibular hypofunction. The Cochrane Library, MEDLINE, PubMed, EMBASE, and SciELO. A systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Databases were searched using a comprehensive search strategy including the terms "Vibration-induced nystagmus" or "SVINT" or "skull vibration-induced nystagmus test" or "skull vibration-induced nystagmus" from inception to May 2020. A total of 79 articles were identified, and 16 studies met the inclusion criteria. The methodology for performing the SVINT and determining positivity is varied. Most authors refer to reproducibility, sustained response, ending with withdrawal of stimulus, nondirection changing, and response in more than one point of stimulation, as necessary for a positive test. Only seven studies included a slow phase velocity of 2 degrees/s or 2.5 degrees/s as a criterion. Most studies employed 100 Hz stimulus for 10 seconds, while longer duration is suggested for pediatric patients. For partial and total unilateral vestibular loss, positivity varied from 58 to 60%, and 93 to 100%, respectively. Sensitivity ranged from 50 to 100%, and specificity from 62 to 100%. Importantly, the SVINT may decrease with time but does not usually disappear, hence, can provide information of past/compensated vestibular events. The SVINT can be used in pediatric and adult patients. It provides information regarding unilateral vestibular loss, acute, or compensated. It is a quick, safe, and noninvasive test, and is complementary to the dynamic vestibular and positional tests.

Skull vibration induced nystagmus test in Ménière's disease

Skull vibration induced nystagmus test in Ménière's disease

How to do and why perform the skull vibration-induced nystagmus test

The skull vibration-induced nystagmus test (SVINT) is a global vestibular test stimulating otoliths and semicircular canals at a frequency of 100Hz, not modified by vestibular compensation, which may reveal vibration-induced nystagmus (VIN). Bone-conducted vibration applied to the mastoid processes and the vertex instantaneously induces predominantly low-velocity (∼10°/s) horizontal nystagmus, with rapid phases beating away from the affected side in patients with unilateral vestibular loss (UVL). VIN starts and stops immediately with stimulation, is continuous, reproducible, beats in the same direction irrespective of which mastoid process is stimulated, with no or little habituation. The SVINT acts like a vestibular Weber test. In peripheral UVL, the SVINT is a good marker of vestibular asymmetry and demonstrates pathological nystagmus beating towards the healthy side in 90% of cases of vestibular neuritis, 71% of cases of Menière's diseases and 44 to 78% of vestibular schwannomas. In superior semicircular canal dehiscence, VIN usually beats towards the affected side due to facilitation of bone conduction related to the presence of a third window. Stimulation of the vertex is more effective than in UVL patients, with sensitivity extending to higher frequencies, up to 700Hz. Observation of vibration-induced nystagmus then reveals equally represented vertical, torsional, and horizontal components beating towards the affected ear, suggesting dominant, but not exclusive, stimulation of the dehiscent superior semicircular canal.

The skull vibration-induced nystagmus test: A useful vestibular screening test in children with hearing loss

IntroductionSkull-Vibration-Induced-Nystagmus Test (SVINT), a non-invasive first line examination test, stimulates both otolith and canal structures and shows instantaneously a vestibular asymmetry. This study aimed to analyze the SVINT results observed in children with hearing loss (HL) amplified with hearing aids (HA) or unilateral cochlear implant (uCI) and healthy children. Material and methodsThis case-control study compared the results of SVINT, caloric test (CaT) and video head-impulse-test (VHIT) in 120 controls to 30 children with HA and 30 with uCI, aged 5-18 years old. SVINT was recorded with videonystagmography after very high frequency (VHF) stimulation of mastoids and vertex. ResultsSVINT results were non-pathological in 98% of the control group but modified in the HL group (P-value=0.04). In uCI participants, 13.3% had a bilateral weakness (BW) and 16.7% had a unilateral weakness (UW). In the HA group, 26.7% had BW, 10% had UW. SVINT was efficient to show a UW (6 out of 7 confirmed cases) but not efficient to show BW (1/12 confirmed cases). ConclusionSVINT can detect unilateral vestibular deficit in the VHF with a sensitivity of 86% and specificity of 96%. The positive predictive value is 75% and negative predictive value is 98%. In the case of bilateral deficit, the SVINT is inoperant. In amplified participants, a UW was equally detected whether using SVINT, CaT or VHIT. SVINT is a well-tolerated and useful test to screen vestibular asymmetry in children with HL when combined with other vestibular tests and shows its complementary at very high frequencies.

The Skull Vibration-Induced Nystagmus Test of Vestibular Function—A Review

A 100-Hz bone-conducted vibration applied to either mastoid induces instantaneously a predominantly horizontal nystagmus, with quick phases beating away from the affected side in patients with a unilateral vestibular loss (UVL). The same stimulus in healthy asymptomatic subjects has little or no effect. This is skull vibration-induced nystagmus (SVIN), and it is a useful, simple, non-invasive, robust indicator of asymmetry of vestibular function and the side of the vestibular loss. The nystagmus is precisely stimulus-locked: it starts with stimulation onset and stops at stimulation offset, with no post-stimulation reversal. It is sustained during long stimulus durations; it is reproducible; it beats in the same direction irrespective of which mastoid is stimulated; it shows little or no habituation; and it is permanent—even well-compensated UVL patients show SVIN. A SVIN is observed under Frenzel goggles or videonystagmoscopy and recorded under videonystagmography in absence of visual-fixation and strong sedative drugs. Stimulus frequency, location, and intensity modify the results, and a large variability in skull morphology between people can modify the stimulus. SVIN to 100 Hz mastoid stimulation is a robust response. We describe the optimum method of stimulation on the basis of the literature data and testing more than 18,500 patients. Recent neural evidence clarifies which vestibular receptors are stimulated, how they cause the nystagmus, and why the same vibration in patients with semicircular canal dehiscence (SCD) causes a nystagmus beating toward the affected ear. This review focuses not only on the optimal parameters of the stimulus and response of UVL and SCD patients but also shows how other vestibular dysfunctions affect SVIN. We conclude that the presence of SVIN is a useful indicator of the asymmetry of vestibular function between the two ears, but in order to identify which is the affected ear, other information and careful clinical judgment are needed.

How to perform the skull vibration-induced nystagmus test (SVINT)

The skull vibration-induced nystagmus test is a robust, nonintrusive and easy to perform test. This test acts as a vestibular Weber test and is performed as a bedside examination. It usually instantaneously reveals vibration-induced nystagmus (VIN) even in long standing or chronic compensated unilateral vestibular lesions. The test requires stimulation at 30, 60 or more efficiently at 100Hz. The vibrator is applied perpendicularly to the skin on a subject sitting up straight on the right and then the left mastoid (level with external acoustic meatus) and vertex. The VIN can be observed under videonystagmoscopy or Frenzel goggles. Either the direct tracing or the VIN slow phase velocity can be recorded on a 2D or 3D videonystagmograph. The patients should be relaxed and not treated by strong sedative medications. This rapid first-line test is not influenced by vestibular compensation and usefully complements other tests in the multifrequency evaluation of the vestibule. It acts as a global vestibular test by stimulating both canal and otolithic structures at 100Hz. It is useful in case of external acoustic meatus or middle ear disease as a substitute for the water caloric test and is preferable in elderly patients with vascular disease or arthritis of the neck to the head-shaking-test or head-impulse-test.

Topographic analysis of the skull vibration-induced nystagmus test with piezoelectric accelerometers and force sensors.

Vibration-induced nystagmus is elicited by skull or posterior cervical muscle stimulations in patients with vestibular diseases. Skull vibrations delivered by the skull vibration-induced nystagmus test are known to stimulate the inner ear structures directly. This study aimed to measure the vibration transfer at different cranium locations and posterior cervical regions to contribute toward stimulus topographic optimization (experiment 1) and to determine the force applied on the skull with a hand-held vibrator to study the test reproducibility and provide recommendations for good clinical practices (experiment 2). In experiment 1, a 100 Hz hand-held vibrator was applied on the skull (vertex, mastoids) and posterior cervical muscles in 11 healthy participants. Vibration transfer was measured by piezoelectric sensors. In experiment 2, the vibrator was applied 30 times by two experimenters with dominant and nondominant hands on a mannequin equipped to measure the force. Experiment 1 showed that after unilateral mastoid vibratory stimulation, the signal transfer was higher when recorded on the contralateral mastoid than on the vertex or posterior cervical muscles (P<0.001). No difference was observed between the different vibratory locations when vibration transfer was measured on vertex and posterior cervical muscles. Experiment 2 showed that the force applied to the mannequin varied according to the experimenters and the handedness, higher forces being observed with the most experienced experimenter and with the dominant hand (10.3 ± 1.0 and 7.8 ± 2.9 N, respectively). The variation ranged from 9.8 to 29.4% within the same experimenter. Bone transcranial vibration transfer is more efficient from one mastoid to the other mastoid than other anatomical sites. The mastoid is therefore the optimal site for skull vibration-induced nystagmus test in patients with unilateral vestibular lesions and enables a stronger stimulation of the healthy side. In clinical practice, the vibrator should be placed on the mastoid and should be held by the clinician's dominant hand.

Vestibular results after intratympanic gentamicin therapy in disabling Menière's disease.

Intratympanic injection of gentamicin is increasingly used in the treatment of unilateral disabling Menière's disease (MD). Several objective functional and subjective tests have been developed to assess the control of vertigo after gentamicin treatment. The aim of this study was to show that subjective results require a vestibular deafferentation as profound as possible, evidenced with multifrequency vestibular assessment. Sixty four patients with intractable MD in situation of medical treatment failure longer than 6 months were included between 1998 and 2013 in this case control study. A 2-year follow-up was performed after the last intratympanic gentamicin performed with the titration technique. A vestibular assessment was applied before and after 2years of treatment with a functional level score using the AAOHNS vertigo scale and multifrequency vestibular assessment: skull vibration-induced nystagmus test (SVINT), head-shaking test (HST) and caloric test (CaTe). The correlation between the results of the questionnaire and the level of the deafferentation as evaluated by the tests was analyzed with the Spearman test. Among the 64 included patients, 56 (87.5%) described vertigo control. There was a correlation (=-0.33 [-0.53; -0.09], p=0.008) between subjective improvement (AAO -HNS 1 or 2) and the degree of vestibular deafferentation as evidenced by a destructive nystagmus (beating toward the safe side) with the HST and the SVINT, as well as a caloric hypofunction>90% with the CaTe. The present study demonstrates that a profound vestibular deafferentation confirmed with multifrequency test evaluation is needed to have a subjective improvement in the treatment of unilateral disabling MD with intratympanic gentamicin.

Skull vibration-induced nystagmus test in unilateral superior canal dehiscence and otosclerosis: a vestibular Weber test

Conclusions: The skull vibration-induced nystagmus test (SVINT) acts as a vestibular Weber test and reveals a vibration-induced nystagmus (VIN), elicited mainly on the vertex location, with a horizontal or torsional component beating more often toward the side of the lesion in superior canal dehiscence (SCD) than in otosclerosis (OS). In SCD, the VIN vertical component is most often up-beating. These results suggest more a global vestibular contribution than the sole stimulation of the superior semicircular canal. Objectives: This study aimed to evaluate the possible occurrence of nystagmus during SVINT in unilateral conductive hearing loss related to SCD or OS. Methods: The slow-phase velocities (SPVs) of the VIN horizontal, torsional, and vertical components were recorded in patients with a unilateral otologic lesion (17 SCD, 38 OS) and 12 control subjects. Vibratory stimulations (60 Hz, 100 Hz) were applied on the vertex and on each mastoid. Results: In SCD, VIN was observed in 82% of patients with a primarily torsional, horizontal, and vertical (up-beating) component in 40%, 30%, and 30%, respectively. Horizontal and torsional components beat toward the side of the lesion more often than in OS. Higher SPVs were observed after vertex stimulation. In OS, VIN was sparse with low amplitude and was not systematically lateralized to a specific side.

High-Frequency Skull Vibration-Induced Nystagmus Test in Partial Vestibular Lesions

To establish the effectiveness of the skull vibration-induced nystagmus test (SVINT) as a rapid high-frequency stimulation test, in the evaluation of partial unilateral vestibular lesions (pUVL). SVINT (30, 60, and 100 Hz), caloric, and head-shaking tests were performed in 99 patients with pUVL. These results were compared with those in 9 patients with symmetrical partial bilateral labyrinthine malformations, 131 patients with total unilateral vestibular lesions (tUVL), and 95 control subjects. A skull vibratory nystagmus (SVN) was found in 75% of patients with pUVL and 98% with tUVL. In pUVL: SVINT revealed asymmetric responses in 20% of patients where other tests were normal; SVN direction at 100 Hz was opposite to the head-shaking nystagmus direction in 30% and opposite to SVN at 30 Hz in 10% of cases. At 100 Hz, SVN beat toward the safe side in 91% of cases; SVN values at 60 and 100 Hz were higher than those at 30 Hz (p < 0.005). SVN was found in unilateral superior canal dehiscences. Partial bilateral labyrinthine malformations revealed no nystagmus. SVINT complements head-shaking and caloric tests in multifrequency assessment of patients with pUVL, as a global vestibular test. In contrast with tUVL results, SVINT does not always indicate the side of partial lesions, neither does it locate their level on the vestibulo-ocular pathway. This test is useful to reveal a vestibular asymmetry as a bedside examination test and may be used as a "vestibular Weber."

Nystagmus induced by high frequency vibrations of the skull in total unilateral peripheral vestibular lesions

Conclusion. The skull vibration-induced nystagmus test (SVINT) is a useful complementary test to the caloric test, which evaluates very low frequencies, and the head shaking test (HST), which explores medium range frequencies. These three tests are fully correlated in total unilateral vestibular lesions (tUVL) with a sensitivity of 98% and a specificity of 94% for the SVINT. The results of the interference of the SVINT with the cold caloric test on the intact ear suggest that different vestibular sensory cells are involved in these two tests. The stimulus location optimization suggests that vibrations directly stimulate the inner ear on the intact side. Objectives. The aim of this study was to establish the effectiveness of a rapid, non-invasive test used to detect vestibular asymmetry at 30, 60 and 100 Hz stimulation in tUVL. Patients and methods. The high frequency vibration test applied to the skull using the SVINT was compared to the results of HST and caloric test in 134 patients and 95 normal subjects: 131 patients had a total unilateral vestibular dysfunction and 3 had a bilateral total lesion (tBVL). The effects of stimulus frequency, topography and head position were studied using a video-nystagmograph. Results. In tUVL, the SVINT always revealed a lesional nystagmus beating toward the healthy side at all frequencies. The mastoid site was more efficient than the cervical and vertex sites (p<0.005). The mean skull vibratory nystagmus (SVN) slow phase velocity (SPV) is 10.7°/s (SD =7.5; n=20). Mastoid stimulation efficiency was not correlated with the side of stimulation. SVN SPV was correlated with the total caloric efficiency on the healthy ear (p=0.03). The interference of the SVINT during the cold caloric test on the intact ear demonstrated a reversal of the caloric nystagmus at each application of the vibrator. In tBVL, SVINT revealed no nystagmus.

Le test vibratoire osseux vestibulaire

Objectives To establish during a consensus meeting the fundamental basis, the validity criteria, the main indications and results of the skull vibration induced nystagmus test (SVINT) which explores the vestibule high frequencies. Material and methods The SVINT is applied on the mastoid process (right and left sides) at 100 Hz during 10 seconds on a sitting upright subject. Total unilateral peripheral lesions (tUVL: operated vestibular shwannomas, vestibular neurectomies ) and partial unilateral peripheral lesions (pUVL: preoperative neuromas, Meniere's disease, vestibular neuritis, chemical labyrinthectomies) were studied. Thirty-six patients had brainstem lesions and 173 normal subjects were used as controls. Results The SVINT is considered positive when the application of the vibrator produces a reproducible sustained nystagmus always beating in the same direction following several trials in various stimulation topographies (on the right and left mastoid). The skull vibratory nystagmus (SVN) begins and ends with the stimulation; the direction of the nystagmus has no secondary reversal. The slow phase velocity (SPV) is > 2°/second. In tUVL the SVINT always reveals a lesional nystagmus beating toward the safe side at all frequencies. The mean SVN SPV is 10.8°/s ± 7.5 SD ( N = 45). The mastoid site was more efficient than the cervical or vertex sites. Mastoïd stimulation efficiency is not correlated with the side of stimulation. The SVN SPV is correlated with the total caloric efficiency on the healthy ear. In pUVL the SVINT is positive in 71 to 76% of cases; the mean SVN. SPV (6.7°/s ± 4.7 SD)( N = 30) is significantly lower than in tUVL ( P = 0.0004). SVINT is positive in 6 to 10% of the normal population, 31% of brain stem lesions and negative in total bilateral vestibular peripheral lesions. Conclusions SVINT is an effective, rapid and non invasive test used to detect vestibular asymmetry between 20 to 150 Hz stimulation. This test used in important cohorts of patients during the ten last years has demonstrated no observable adverse effect. SVINT complements other tests which evaluate lower frequencies (caloric test: 0,003 Hz) and the medium frequencies (Head-Shaking–Test (HST): 2 Hz; the head impulse test (HIT): 6 Hz). SVINT is useful in the diagnosis of labyrinthine hydrops or detection of acoustic neuromas. It is useful when the caloric test can not be practised because of middle ear problems. SVINT has its limits: in pUVL, the nystagmus direction is not always specific of the pathologic side and can change with the stimulus frequency. This test does not precisely point out the level of the lesion on the vestibular pathway.