Vestibular hypersensitivity to clicks is characteristic of the Tullio phenomenon

A Review of Neural Data and Modelling to Explain How a Semicircular Canal Dehiscence (SCD) Causes Enhanced VEMPs, Skull Vibration Induced Nystagmus (SVIN), and the Tullio Phenomenon

Angular acceleration stimulation of a semicircular canal causes an increased firing rate in primary canal afferent neurons that result in nystagmus in healthy adult animals. However, increased firing rate in canal afferent neurons can also be caused by sound or vibration in patients after a semicircular canal dehiscence, and so these unusual stimuli will also cause nystagmus. The recent data and model by Iversen and Rabbitt show that sound or vibration may increase firing rate either by neural activation locked to the individual cycles of the stimulus or by slow changes in firing rate due to fluid pumping ("acoustic streaming"), which causes cupula deflection. Both mechanisms will act to increase the primary afferent firing rate and so trigger nystagmus. The primary afferent data in guinea pigs indicate that in some situations, these two mechanisms may oppose each other. This review has shown how these three clinical phenomena-skull vibration-induced nystagmus, enhanced vestibular evoked myogenic potentials, and the Tullio phenomenon-have a common tie: they are caused by the new response of semicircular canal afferent neurons to sound and vibration after a semicircular canal dehiscence.

Vestibular Hypersensitivity in Patients with Chronic Noise Exposure

It has been demonstrated that high-intensity noise exposure adversely affects the human balance function. The Tullio phenomenon (TP) refers to sound-induced imbalance which is resulted from hypersensitivity of vestibular end organs to normal acoustic stimuli. Although different etiologies have been attributed to TP, evidence on the role of excessive noise exposure in the development of this symptom is limited. The present study aims to assess the vestibular functions in patients manifesting TP symptom who were exposed to long-term excessive noise levels. This was an analytic cross-sectional study conducted on 17 males diagnosed with TP with a history of chronic noise-induced hearing loss (TP group) and 17 healthy individuals. All subjects in both groups underwent complete otological, videonystagmography (VNG), and cervical vestibular myogenic potential (cVEMP) assessments. The most common complaint in TP subjects was vertigo and imbalance. During the VNG assessment, we found abnormal positional nystagmus and caloric irrigation (vestibular hyperfunction) results in 4 (23.53%) and 9 (52.94%) patients, respectively. Seven (41.17%) patients indicated cVEMP thresholds which were abnormally lower than the normal values ( ≤ 70 dB HL). However, when both VNG and cVEMP results were considered together, the abnormal rate reached 70.58% (12 of 17 cases). Our findings showed that both the semicircular canal as well as otolith stuctures could be affected in TP patients with a history of chronic noise exposure.

Similarities and Differences Between Vestibular and Cochlear Systems - A Review of Clinical and Physiological Evidence

The evoked response to repeated brief stimuli, such as clicks or short tone bursts, is used for clinical evaluation of the function of both the auditory and vestibular systems. One auditory response is a neural potential - the Auditory Brainstem Response (ABR) - recorded by surface electrodes on the head. The clinical analogue for testing the otolithic response to abrupt sounds and vibration is the myogenic potential recorded from tensed muscles - the vestibular evoked myogenic potential (VEMP). VEMPs have provided clinicians with a long sought-after tool - a simple, clinically realistic indicator of the function of each of the 4 otolithic sensory regions. We review the basic neural evidence for VEMPs and discuss the similarities and differences between otolithic and cochlear receptors and afferents. VEMPs are probably initiated by sound or vibration selectively activating afferent neurons with irregular resting discharge originating from the unique type I receptors at a specialized region of the otolithic maculae (the striola). We review how changes in VEMP responses indicate the functional state of peripheral vestibular function and the likely transduction mechanisms allowing otolithic receptors and afferents to trigger such very short latency responses. In section "ELECTROPHYSIOLOGY" we show how cochlear and vestibular receptors and afferents have many similar electrophysiological characteristics [e.g., both generate microphonics, summating potentials, and compound action potentials (the vestibular evoked potential, VsEP)]. Recent electrophysiological evidence shows that the hydrodynamic changes in the labyrinth caused by increased fluid volume (endolymphatic hydrops), change the responses of utricular receptors and afferents in a way which mimics the changes in vestibular function attributed to endolymphatic hydrops in human patients. In section "MECHANICS OF OTOLITHS IN VEMPS TESTING" we show how the major VEMP results (latency and frequency response) follow from modeling the physical characteristics of the macula (dimensions, stiffness etc.). In particular, the structure and mechanical operation of the utricular macula explains the very fast response of the type I receptors and irregular afferents which is the very basis of VEMPs and these structural changes of the macula in Menière's Disease (MD) predict the upward shift of VEMP tuning in these patients.

Response characteristics of vestibular evoked myogenic potentials recorded over splenius capitis in young adults and adolescents

BACKGROUND AND OBJECTIVES

Examine vestibular evoked myogenic potential (VEMP) responses recorded from surface electrodes over Splenius Capitis (SPC) in a seated position.

SPECIFIC AIMS

(1) validate response characteristics of VEMP recordings from surface electrodes over Sternocleidomastoid (SCM) and over SCP and (2) assess age effects on responses in adolescents and young adults.

MATERIALS AND METHODS

Simultaneous surface VEMP was recorded bilaterally from electrodes placed over the dorsal neck musculature at a location known from previous work to record from SPC in 15 healthy participants during trials with head rotation toward and away from the stimulated ear. VEMP was also recorded from electrodes over SCM, ipsilateral to the stimulus ear, in the same participants in a supine, head lift/turn position.

RESULTS

Response amplitudes significantly increased with contraction strength and decreased with age. Participants were able to maintain sufficient contraction strength (amplitude) with head rotation to reliably measure over SPC. Normalized response amplitudes measured from electrodes over contralateral SPC were largest with head rotation contralateral to the stimulus ear. Normalized amplitudes and peak latencies were comparable to the same measures from SCM obtained in supine, head lift/turn position.

CONCLUSIONS

Otolith generated myogenic responses can be recorded seated from electrodes over the dorsal neck with head rotation contralateral to the stimulus ear. In this position, contralateral recordings are consistent with responses known from previous work to arise from SPC; ipsilateral recordings may include crosstalk from activated muscles nearby, including ipsilateral SCM. Overall, techniques targeting contralateral SPC during contralateral head turn may provide additional methods of recording VEMPs.

Vestibular-evoked myogenic potentials in patients with severe obstructive sleep apnea

Objective

Previous studies have shown that patients with obstructive sleep apnea syndrome (OSAS) may have various vestibular abnormalities, and these mainly present as subclinical lesions. In this study, we attempted to combine ocular vestibular-evoked myogenic potentials (VEMPs) and cervical (VEMPs) to investigate vestibular dysfunction in patients with OSAS.

Methods

Thirty-eight patients with severe OSAS and 42 healthy controls were enrolled and divided into two groups according to results of polysomnography. All parameters of VEMP graphs were analyzed.

Results

The response rate of ocular VEMPs was significantly lower in patients with severe OSAS (85.5%) than in controls (96.4%). The mean n1 latency of patients with severe OSAS (10.6 ± 1.0 months) was significantly longer than that of controls (10.2 ± 1.1 months). With regard to cervical VEMP, p1-n1 amplitudes were significantly different between the groups. Other VEMP parameters were not significantly different between the groups.

Conclusions

VEMPs can potentially be used to evaluate vestibular system lesions at the early stage of OSAS, including not only the vestibular nerve, but also the otolith organs involved.

Investigating short latency subcortical vestibular projections in humans: what have we learned?

Vestibular evoked myogenic potentials (VEMPs) are now widely used for the noninvasive assessment of vestibular function and diagnosis in humans. This review focuses on the origin, properties, and mechanisms of cervical VEMPs and ocular VEMPs; how these reflexes relate to reports of vestibular projections to brain stem and cervical targets; and the physiological role of (otolithic) cervical and ocular reflexes. The evidence suggests that both VEMPs are likely to represent the effects of excitation of irregularly firing otolith afferents. While the air-conducted cervical VEMP appears to mainly arise from excitation of saccular receptors, the ocular VEMP evoked by bone-conducted stimulation, including impulsive bone-conducted stimuli, mainly arises from utricular afferents. The surface responses are generated by brief changes in motor unit firing. The effects that have been demonstrated are likely to represent otolith-dependent vestibulocollic and vestibulo-ocular reflexes, both linear and torsional. These observations add to previous reports of short latency otolith projections to the target muscles in the neck (sternocleidomastoid and splenius) and extraocular muscles (the inferior oblique). New insights have been provided by the investigation and application of these techniques.

Approach to Ménière disease management

OBJECTIVE

To provide family physicians with an updated approach to the diagnosis and management of Ménière disease (MD), detailing the natural course of MD and describing how to initiate medical therapy while awaiting consultation with otolaryngology-head and neck surgery.

SOURCES OF INFORMATION

The approach is based on the authors' clinical practices and review articles from 1989 to 2018. Most of the cited studies provided level II or III evidence.

MAIN MESSAGE

Ménière disease is an uncommon disorder of the inner ear causing vertigo attacks with associated unilateral hearing loss, tinnitus, and aural fullness. It has a degenerative course that often results in permanent sensorineural hearing loss. On average, MD stabilizes with no further vestibular attacks by about 8 years after the onset of symptoms; however, this is highly variable. Vertigo symptoms can be controlled through a combination of dietary salt restriction, stress reduction, and medical therapy (betahistine, diuretics, or both). These can be initiated by family physicians before consultation with otolaryngology-head and neck surgery. Symptoms refractory to such strategies can be treated using nonablative, and occasionally ablative, therapies.

CONCLUSION

A thorough history is key to the approach to and management of MD and permits differentiating MD from other vestibular and nonvestibular conditions.

[Not Available]

Objectif

Fournir aux médecins de famille une approche actualisée pour le diagnostic et la prise en charge de la maladie de Ménière, décrivant en détail l’évolution naturelle de la maladie de Ménière et la façon d’instaurer un traitement médical en attendant une consultation en otorhinolaryngologie–chirurgie cervico-faciale.

Sources de l’information

L’approche se base sur les pratiques cliniques des auteurs et sur des articles de synthèse publiés entre 1989 et 2018. La plupart des études citées ont fourni des données probantes de niveau II ou III.

Message principal

La maladie de Ménière est une affection peu fréquente de l’oreille interne, qui cause des crises de vertige et qui est associée à une perte auditive unilatérale, un acouphène et une sensation de plénitude auditive. La maladie est dégénérative et entraîne souvent une perte auditive neurosensorielle permanente. En moyenne, la maladie de Ménière se stabilise sans autre crise vestibulaire environ 8 ans après l’apparition des symptômes; cela est cependant très variable. Les symptômes de vertige peuvent être maîtrisés en combinant une alimentation hyposodée, une réduction du stress et un traitement médical (bétahistine, diurétiques ou les 2). Ces interventions peuvent être instaurées par le médecin de famille avant la consultation en otorhinolaryngologie–chirurgie cervico-faciale. Les symptômes réfractaires à ces interventions sont traités par l’entremise de traitements non ablatifs et, occasionnellement, ablatifs.

Conclusion

Une anamnèse détaillée est la clé de l’approche à adopter pour la prise en charge de la maladie de Ménière et permet de différencier la maladie de Ménière des autres affections vestibulaires et non vestibulaires.

Sound-evoked vestibular projections to the splenius capitis in humans: comparison with the sternocleidomastoid muscle

The short-latency vestibulo-collic reflex in humans is well defined for only the sternocleidomastoid (SCM) neck muscle. However, other neck muscles also receive input from the balance organs and participate in neck stabilization. We therefore investigated the sound-evoked vestibular projection to the splenius capitis (SC) muscles by comparing surface and single motor unit responses in the SC and SCM muscles in 10 normal volunteers. We also recorded surface responses in patients with unilateral vestibular loss but preserved hearing and hearing loss but preserved vestibular function. The single motor unit responses were predominantly inhibitory, and the strongest responses were recorded in the contralateral SC and ipsilateral SCM. In both cases there was a significant decrease or gap in single motor unit activity, in SC at 11.7 ms for 46/66 units and in SCM at 12.7 ms for 51/58 motor units. There were fewer significant responses in the ipsilateral SC and contralateral SCM muscles, and they consisted primarily of weak increases in activity. Surface responses recorded over the contralateral SC were positive-negative during neck rotation, similar to the ipsilateral cervical vestibular evoked myogenic potential in SCM. Responses in SC were present in the patients with hearing loss and absent in the patient with vestibular loss, confirming their vestibular origin. The results describe a pattern of inhibition consistent with the synergistic relationship between these muscles for axial head rotation, with the crossed vestibular projection to the contralateral SC being weaker than the ipsilateral projection to the SCM.

NEW & NOTEWORTHY We used acoustic vestibular stimulation to investigate the saccular projections to the splenius capitis (SC) and sternocleidomastoid (SCM) muscles in humans. Single motor unit recordings from within the muscles demonstrated strong inhibitory projections to the contralateral SC and ipsilateral SCM muscles and weak excitatory projections to the opposite muscle pair. This synergistic pattern of activation is consistent with a role for the reflex in axial rotation of the head.

Electrical Vestibular Stimuli Evoke Robust Muscle Activity in Deep and Superficial Neck Muscles in Humans

Neck muscle activity evoked by vestibular stimuli is a clinical measure for evaluating the function of the vestibular apparatus. Cervical vestibular-evoked myogenic potentials (cVEMP) are most commonly measured in the sternocleidomastoid muscle (and more recently the splenius capitis muscle) in response to air-conducted sound, bone-conducted vibration or electrical vestibular stimuli. It is currently unknown, however, whether and how other neck muscles respond to vestibular stimuli. Here we measured activity bilaterally in the sternocleidomastoid, splenius capitis, sternohyoid, semispinalis capitis, multifidus, rectus capitis posterior, and obliquus capitis inferior using indwelling electrodes in two subjects exposed to binaural bipolar electrical vestibular stimuli. All recorded neck muscles responded to the electrical vestibular stimuli (0–100 Hz) provided they were active. Furthermore, the evoked responses were inverted on either side of the neck, consistent with a coordinated contribution of all left-right muscle pairs acting as antagonists in response to the electrically-evoked vestibular error of head motion. Overall, our results suggest that, as previously observed in cat neck muscles, broad connections exist between the human vestibular system and neck motoneurons and highlight the need for future investigations to establish their neural connections.

The Contributions of Vestibular Evoked Myogenic Potentials and Acoustic Vestibular Stimulation to Our Understanding of the Vestibular System

Vestibular-evoked myogenic potentials (VEMPs) are short-latency muscle reflexes typically recorded from the neck or eye muscles with surface electrodes. They are used clinically to assess otolith function, but are also interesting as they can provide information about the vestibular system and its activation by sound and vibration. Since the introduction of VEMPs more than 25 years ago, VEMPs have inspired animal and human research on the effects of acoustic vestibular stimulation on the vestibular organs, their projections and the postural muscles involved in vestibular reflexes. Using a combination of recording techniques, including single motor unit recordings, VEMP studies have enhanced our understanding of the excitability changes underlying the sound-evoked vestibulo-collic and vestibulo-ocular reflexes. Studies in patients with diseases of the vestibular system, such as superior canal dehiscence and Meniere's disease, have shown how acoustic vestibular stimulation is affected by physical changes in the vestibule, and how sound-evoked reflexes can detect these changes and their resolution in clinical contexts. This review outlines the advances in our understanding of the vestibular system that have occurred following the renewed interest in sound and vibration as a result of the VEMP.

Vestibular evoked myogenic potentials in patients with ankylosing spondylitis

Ankylosing spondylitis (AS) is a chronic systemic inflammatory disease with unknown etiology. Although sacroiliac joint involvement is the classic sign along with the formed immune mediators, it may result in immune-mediated inner ear disease and may cause damage to the audiovestibular system. Vestibular evoked myogenic potentials (VEMP) is a clinical reflex test used in the diagnosis of vestibular diseases and is performed by recording and evaluating the muscle potentials resulting from the stimulation of the vestibular system with different stimuli. The aim of this study is to evaluate the cervical VEMP test results in AS patients without vestibular symptoms. Thirty-three patients with AS and a control group of 30 healthy volunteers with similar demographic characteristics were evaluated in the study. VEMP wave latency, P13-N23 wave amplitude, and VEMP asymmetry ratio (VAR) values were compared between the groups. The relationship between clinical and laboratory findings of the AS patients and VEMP data were also investigated. Compared with healthy people, this study shows the response rate of patients with ankylosing spondylitis was reduced in the VEMP test, and P13-N23 wave amplitude showed a decrease in AS patients who had VEMP response (p < 0.001). There was no correlation between the clinical and laboratory findings and VEMP findings in patients with ankylosing spondylitis. The data obtained from this study suggest that AS may lead to decreased sensitivity of the vestibular system.

Vestibular-evoked myogenic potentials

The vestibular-evoked myogenic potential (VEMP) is a short-latency potential evoked through activation of vestibular receptors using sound or vibration. It is generated by modulated electromyographic signals either from the sternocleidomastoid muscle for the cervical VEMP (cVEMP) or the inferior oblique muscle for the ocular VEMP (oVEMP). These reflexes appear to originate from the otolith organs and thus complement existing methods of vestibular assessment, which are mainly based upon canal function. This review considers the basis, methodology, and current applications of the cVEMP and oVEMP in the assessment and diagnosis of vestibular disorders, both peripheral and central.

Effectiveness of different click stimuli in diagnosing superior canal dehiscence using cervical vestibular evoked myogenic potentials

CONCLUSION

Testing cervical vestibular evoked myogenic potential (cVEMP) in response to 90 dB nHL clicks can, in contrast to high-intensity 500 Hz tone bursts, be used as a screening test for superior canal dehiscence (SCD) syndrome.

OBJECTIVES

cVEMP testing has its key clinical significance for evaluating saccular and inferior vestibular nerve function, but also for assessment of vestibular hypersensitivity to sounds in patients with SCD syndrome. The routine stimulus used in cVEMP testing is high-intensity 500 Hz tone bursts. The aim of the present study was to compare the high-intensity tone burst stimulation with less intense click stimulations for the diagnosis of SCD syndrome.

METHODS

cVEMP amplitudes in response to 500 Hz tone bursts and clicks were studied in 38 patients with SCD syndrome unilaterally.

RESULTS

cVEMP testing using high-intensity 500 Hz tone bursts did not consistently distinguish SCD patients. This nonfunctioning of high-intensity 500 Hz stimulation is most likely due to saturation. With 90 and 80 dB nHL clicks there is low risk for saturation and both these click stimulations were effective. Testing with both 80 and 90 dB nHL clicks did not have any significant advantage over just using 90 nHL dB clicks.

Perilymph fistula: fifty years of controversy

Perilymph fistula (PLF) is defined as a leak of perilymph at the oval or round window. It excludes other conditions with "fistula" tests due to a dehiscent semi circular canal from cholesteatoma and the superior canal dehiscence syndrome. It was first recognized in the early days of stapedectomy as causing disequilibrium and balance problems before sealing of the stapedectomy with natural tissue became routine. It then became apparent that head trauma and barotraumatic trauma from flying or diving could be a cause of PLF. Descriptions of "spontaneous" PLF with no trauma history followed. A large literature on PLF from all causes accumulated. It became an almost emotional issue in Otolaryngology with "believers" and "nonbelievers." The main criticisms are a lack of reliable symptoms and diagnostic tests and operative traps in reliably distinguishing a perilymph leak from local anaesthetic. There are extensive reviews on the whole topic, invariably conveying the authors' own experiences and their confirmed views on various aspects. However, a close examination reveals a disparity of definitions and assumptions on symptoms, particularly, vestibular. This is an intentionally provocative paper with suggestions on where some progress might be made.

Ménière's disease in children aged 4-7 years

This is a retrospective review of clinical data and audiovestibular test results from four children in whom symptoms suggesting Ménière's disease started at 4-7 years of age. The four patients all had spontaneous recurrent attacks of (spinning) vertigo and fluctuating low frequency sensorineural hearing loss from an early age, suggesting a diagnosis of definite Ménière's disease. Presumably, due to age-related inability to communicate auditory symptoms, the children did not initially meet requirements for a diagnosis of Ménière's disease. However, by 8 years of age, all four children reported tinnitus and/or fullness in the affected ear and, thus, met the AAO criteria for Ménière's disease. Even if information on subjective auditory symptoms is missing, it is reasonable to consider young children with idiopathic spontaneous recurrent attacks of vertigo in whom audiograms reveals fluctuating low frequency hearing loss to have Ménière's disease. This report is a reminder that Ménière's disease may also occur in young children.

[Recording cervical and ocular vestibular evoked myogenic potentials. Part 2: influencing factors, evaluation of findings and clinical significance]

VEMP measurements are subject to various influencing factors: patient age, threshold, sound intensity and frequency. Using air (AC) and bone conduction (BC) the vestibular receptors and afferents of the otolith organs can be activated to varying degrees. Recordings of cervical (cVEMP) and ocular VEMP (oVEMP) are clinically possible. AC-cVEMP are primarily an indicator of the sacculocollic reflex pathway. Together with findings on the vestibuloocular reflex (VOR) and complimentary otolith tests, VEMP enable otolith function analysis of each side separately. In addition, the distinction between combined or isolated canal and otolith dysfunction in terms of subtyping and patterns of damage in mono- and bilateral disorders, such as vestibular neuritis or bilateral vestibulopathy, is possible. Moreover, VEMP is relevant in terms of prognostic and therapeutic considerations as well as expert assessments.

Vestibular-evoked myogenic potentials eliciting: an overview

Recently, the favoured approach for unilateral testing of saccular function is the recently developed method of vestibular-evoked myogenic potentials (VEMPs). VEMP testing is a reliable technique, since it selectively stimulates and investigates each lateral canal in isolation from the other, providing information for the assessment of otolith function and inferior vestibular nerve integrity. The aim of this study was to provide a current review of the different methods used to record VEMPs. We noticed discrepancies in relation to the ways used to record the VEMPs in relation to the following factors: types of stimuli used (clicks or tone bursts) and body muscles tested, patient position at the time of recording, response, type of phone used and way of stimulus presentation (mono or binaural, ipsi or contralateral) and others. As a conclusion, despite the numerous studies in the field, there is no consensus in the literature as to the best recording method for VEMPs. However, the new ocular VEMPs in response to bone conducted vibration seem to be of clinical importance for the evaluation of utricular function. Further research is needed to support its clinical usefulness.

Vestibular evoked myogenic potentials: review

Background:

Disorders of balance often pose a diagnostic conundrum for clinicians, and a multitude of investigations have emerged over the years. Vestibular evoked myogenic potential testing is a diagnostic tool which can be used to assess vestibular function. Over recent years, extensive study has begun to establish a broader clinical role for vestibular evoked myogenic potential testing.

Objectives:

To provide an overview of vestibular evoked myogenic potential testing, and to present the evidence for its clinical application.

Review type:

Structured literature search according to evidence-based medicine guidelines, performed between November 2008 and April 2009. No restrictions were applied to the dates searched.

Conclusion:

The benefits of vestibular evoked myogenic potential testing have already been established as regards the diagnosis and monitoring of several clinical conditions. Researchers continue to delve deeper into potential new clinical applications, with early results suggesting promising future developments.

Vestibular evoked myogenic potentials: past, present and future

Since the first description of sound-evoked short-latency myogenic reflexes recorded from neck muscles, vestibular evoked myogenic potentials (VEMPs) have become an important part of the neuro-otological test battery. VEMPs provide a means of assessing otolith function: stimulation of the vestibular system with air-conducted sound activates predominantly saccular afferents, while bone-conducted vibration activates a combination of saccular and utricular afferents. The conventional method for recording the VEMP involves measuring electromyographic (EMG) activity from surface electrodes placed over the tonically-activated sternocleidomastoid (SCM) muscles. The "cervical VEMP" (cVEMP) is thus a manifestation of the vestibulo-collic reflex. However, recent research has shown that VEMPs can also be recorded from the extraocular muscles using surface electrodes placed near the eyes. These "ocular VEMPs" (oVEMPs) are a manifestation of the vestibulo-ocular reflex. Here we describe the historical development and neurophysiological properties of the cVEMP and oVEMP and provide recommendations for recording both reflexes. While the cVEMP has documented diagnostic utility in many disorders affecting vestibular function, relatively little is known as yet about the clinical value of the oVEMP. We therefore outline the known cVEMP and oVEMP characteristics in common central and peripheral disorders encountered in neuro-otology clinics.

Tone burst vestibular evoked myogenic potentials: diagnostic criteria in patients with Ménière's disease

CONCLUSION

We suggest that 1/0.5 kHz FPA would be clinically useful in the diagnosis of Ménière's disease.

OBJECTIVE

To determine whether clinically useful VEMP parameters could be identified using different tone burst stimuli for the diagnosis of Ménière's disease.

SUBJECTS AND METHODS

The Ménière's group included 24 affected ears from definite Ménière's disease and 26 affected ears from probable Ménière's disease. The control group included 20 normal ears. Using tone bursts of 0.5 and 1 kHz, two parameters were examined: 1) the frequency peak amplitude ratio (1/0.5 kHz FPA), where the peak amplitude was determined by the difference in amplitude between peak p13 and peak n23 ipsilaterally; and 2) the interaural amplitude difference (IAD) ratio, defined as the difference in amplitude between peaks p13 and n23 (p13-n23) in the right and left ears divided by the sum of p13-p23 in both ears.

RESULTS

Data showed that the 1/0.5 kHz FPA ratios in the Ménière's group were significantly elevated compared with those of the control group (p < 0.001) and the recommendable cut-off value for the diagnosis of Ménière's symptoms using 1/0.5 kHz FPA was > 0.7. However, the IAD ratio did not show significant differences in either the 0.5 or 1 kHz stimulus conditions.

SUPERIOR SEMICIRCULAR CANAL DEHISCENCE SYNDROME: SUCCESSFUL TREATMENT WITH REPAIR OF THE MIDDLE FOSSA FLOOR

OBJECTIVE

Superior semicircular canal dehiscence syndrome has recently been reported as a cause of pressure- or sound-induced oscillopsia (Tullio phenomenon). We report the presentation and successful treatment of 3 patients with superior semicircular dehiscence syndrome by a joint neurosurgical/neuro-otology team.

CLINICAL PRESENTATION

Patient 1 is a 37-year-old man who presented with complaints of disequilibrium, fullness in the left ear, hearing loss, and oscillopsia when pressure was applied to the left external auditory canal. Patient 2 is a 46-year-old man who presented with complaints of disequilibrium, fullness in the left ear, and blurred vision associated with heavy lifting or straining. On examination, pneumatic otoscopy produced a sense of motion. Patient 3 is a 29-year-old woman who presented with chronic disequilibrium that resulted in frequent falls. She had a positive fistula test on the left, and vertical nystagmus was elicited when pressure was applied to the left ear. In each patient, high-resolution computed tomographic scanning through the temporal bone revealed dehiscence of the superior semicircular canal on the symptomatic side.

INTERVENTION

In all 3 cases, a subtemporal, extradural approach was performed with repair of the middle fossa floor using calcium phosphate BoneSource (Howmedica Leibinger, Inc., Dallas, TX). All patients recovered well, with resolution of their symptoms.

CONCLUSION

Superior semicircular canal dehiscence syndrome is a cause of disequilibrium associated with sound or pressure stimuli. The workup includes a detailed history, electronystagmography including Valsalva maneuvers, and a high-resolution computed tomographic scan though the temporal bone. An extradural repair of the middle fossa floor with BoneSource can successfully treat this condition.

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: 1s 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 ( approximately 20mm), stereotyped sway responses were present in only one (atypical) patient with high intensity stimulation. Small ( approximately 2mm) 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.

Age-Related Changes in Vestibular Evoked Myogenic Potentials

Vestibular evoked myogenic potentials (VEMP) in response to sound stimulation (500 Hz tone burst, 129 dB SPL) were studied in 1000 consecutive patients. VEMP from the ear with the larger amplitude were evaluated based on the assumption that the majority of the tested patients probably had normal vestibular function in that ear. Patients with known bilateral conductive hearing loss, with known bilateral vestibular disease and those with Tullio phenomenon were not included in the evaluation. It was found that there was an age-related decrease in VEMP amplitude and an increase in VEMP latency that appeared to be rather constant throughout the whole age span. The VEMP data were also compared to an additional group of 10 patients with Tullio phenomenon. Although these 10 patients did have rather large VEMP, equally large VEMP amplitudes were observed in a proportion of unaffected subjects of a similar age group. Thus, the finding of a large VEMP amplitude in response to a high-intensity sound stimulation is not, per se, distinctive for a significant vestibular hypersensitivity to sounds.

Origin of sound-evoked EMG responses in human masseter muscles

Sound is a natural stimulus for both cochlear and saccular receptors. At high intensities it evokes in active masseter muscles of healthy subjects two overlapping reflexes: p11/n15 and p16/n21 waves, whose origin has not yet been demonstrated. Our purpose was to test which receptor in the inner ear is responsible for these reflexes. We compared masseter EMG responses induced in normal subjects (n = 9) by loud clicks (70-100 dB normal hearing level (NHL), 0.1 ms, 3 Hz) to those evoked in subjects with a selective lesion of the cochlea (n = 5), of the vestibule (n = 1) or with mixed cochlear-vestibular failure (n = 5). In controls, 100 dB clicks induced bilaterally, in the unrectified mean EMG (unrEMG), a clear p11 wave followed by a less clear n15 wave and a subsequent n21 wave. Lowering the intensity to 70 dB clicks abolished the p11/n15 wave, while a p16 wave appeared. Rectified mean EMG (rectEMG) showed, at all intensities, an inhibitory deflection corresponding to the p16/n21 wave in the unrEMG. Compared to controls, all deaf subjects had a normal p11 wave, together with more prominent n15 wave; however, the p16/n21 waves, and their corresponding inhibition in the rectEMG, were absent. The vestibular patient had bilaterally clear p11 waves only when 100 dB clicks were delivered bilaterally or to the unaffected ear. Stimulation of the affected ear induced only p16/n21 waves. Data from mixed patients were consistent with those of deaf and vestibular patients. We conclude that click-induced masseter p11/n15 waves are vestibular dependent, while p16/n21 waves depend on cochlear integrity.

Interaction between acoustic startle and habituated neck postural responses in seated subjects

Postural and startle responses rapidly habituate with repeated exposures to the same stimulus, and the first exposure to a seated forward acceleration elicits a startle response in the neck muscles. Our goal was to examine how the acoustic startle response is integrated with the habituated neck postural response elicited by forward accelerations of seated subjects. In experiment 1, 14 subjects underwent 11 sequential forward accelerations followed by 5 additional sled accelerations combined with a startling tone (124-dB sound pressure level) initiated 18 ms after sled acceleration onset. During the acceleration-only trials, changes consistent with habituation occurred in the root-mean-square amplitude of the neck muscles and in the peak amplitude of five head and torso kinematic variables. The subsequent addition of the startling tone restored the amplitude of the neck muscles and four of the five kinematic variables but shortened onset of muscle activity by 9-12 ms. These shortened onset times were further explored in experiment 2, wherein 16 subjects underwent 11 acceleration-only trials followed by 15 combined acceleration-tone trials with interstimulus delays of 0, 13, 18, 23, and 28 ms. Onset times shortened further for the 0- and 13-ms delays but did not lengthen for the 23- and 28-ms delays. These temporal and spatial changes in EMG can be explained by a summation of the excitatory drive converging at or before the neck muscle motoneurons. The present observations suggest that habituation to repeated sled accelerations involves extinguishing the startle response and tuning the postural response to the whole body disturbance.

Startle responses elicited by whiplash perturbations

The human startle response produces muscle contractions throughout the body but the most brisk and synchronized contractions appear in the neck muscles. This response, which is greatest with the first exposure to a startling stimulus, could produce excessive and inappropriately directed muscle contractions that could explain the higher incidence of whiplash injuries in people who are unprepared for the collision. This study seeks neurophysiological evidence of startle responses in the neck muscles of 120 healthy subjects exposed to between 1 and 16 rear-end impacts or forward perturbations of different speeds. Startle responses were quantified by the synchronous electromyographic (EMG) activity between 10 and 20 Hz in bilaterally homologous sternocleidomastoid, scalene and cervical paraspinal neck muscles. Coherence analyses of EMGs from the left and right muscles were used to estimate synchrony for: (i) the first unexpected trial, (ii) subsequent habituated trials, and (iii) the superposition of habituated trials and a loud acoustic stimulus (40 ms, 124 dB sound). The peak in coherent EMG activity between contralateral muscle pairs in the 10-20 Hz bandwidth was related to startle. Synchrony in this bandwidth was observed between the left and right muscles during the first impact or whiplash-like perturbation. This synchrony decreased significantly in the habituated trials, but reappeared when the loud acoustic stimulus was introduced. Its presence in the first trial indicates that startle is part of the neuromuscular response to an unexpected rear-end impact. This startle component of the neuromuscular response could play a role in the aetiology of whiplash injuries.

Vestibular evoked myogenic potentials in benign paroxysmal positional vertigo and Meniere’s disease

The objective was to investigate vestibular evoked myogenic potentials (VEMP) in benign paroxysmal positional vertigo (BPPV) and Meniere's disease, and to determine if this type of testing is valuable for assessing the vestibular system. A prospective controlled clinical study was designed in a tertiary referral center setting. The 62 participants included 17 healthy controls and 45 other subjects selected from patients who presented with the complaint of vertigo (25 diagnosed with BPPV and 20 diagnosed with Meniere's disease). The main outcome measures of VEMP were recorded in all subjects and findings in each patient group were compared with control findings. The VEMP for the 30 affected ears in the 25 BPPV patients revealed prolonged latencies in eight ears and decreased amplitude in one ear (nine abnormal ears; 30% of total). The recordings for the 20 affected ears in the Meniere's disease patients revealed four ears with no response, six ears with prolonged latencies (ten abnormal ears; 50% of total). Only two (5.9%) of the 34 control ears had abnormal VEMP. The rate of VEMP abnormalities in the control ears was significantly lower than the corresponding rates in the affected BPPV ears and the affected Meniere's ears that were studied (P=0.012 and P<0.001, respectively). The results suggest that testing of VEMP is a promising method for diagnosing and following patients with BPPV paroxysmal positional vertigo and Meniere's disease. Further investigations with this method in other neurotologic pathologies might also be informative.

The Influence of Unilateral Versus Bilateral Clicks on the Vestibular-Evoked Myogenic Potentials

OBJECTIVE

Because a continuous muscular effort is required during recording of vestibular-evoked myogenic potentials, we assume vestibular-evoked myogenic potentials elicited by simultaneous bilateral clicks can be used as a more convenient mode compared with respective unilateral clicks. To investigate whether bilateral clicks provide the same information as unilateral clicks, we examined whether the responses are different between them in normal subjects and whether bilateral clicks have the same diagnostic value as vestibular-evoked myogenic potentials elicited by unilateral clicks in detecting retrolabyrinthine lesions.

STUDY DESIGN

Prospective study.

SETTING

Academic tertiary referral center.

SUBJECTS

Fourteen healthy volunteers and four patients with unilateral cerebellopontine angle tumors were enrolled in this study.

INTERVENTIONS

Recordings of vestibular-evoked myogenic potential responses.

MAIN OUTCOME MEASURES

The latency of each peak (p13, n23), the peak-to-peak interval, and amplitude (p13-n23).

RESULTS

Both unilateral and bilateral click stimulation of 28 ears (100%) produced vestibular-evoked myogenic potentials in normal subjects. The mean latencies of p13 and n23, peak-to-peak interval, and amplitude of vestibular-evoked myogenic potentials elicited with unilateral clicks were 11.62 +/- 0.99 ms, 19.74 +/- 1.30 ms, 8.12 +/- 1.66 ms, and 110.79 +/- 61.37 microV, respectively, whereas those elicited with bilateral clicks were 11.16 +/- 0.51 ms, 19.22 +/- 1.61 ms, 8.06 +/- 1.66 ms, and 111.77 +/- 40.98 microV, respectively. There was a significant difference (p < 0.05) in the latencies, but not for the interval and amplitude (p > 0.05). Four patients with unilateral cerebellopontine angle tumors and prolonged latencies of unilateral clicks vestibular-evoked myogenic potentials also showed latency prolongation in bilateral clicks vestibular-evoked myogenic potentials.

CONCLUSION

Although the use of bilateral acoustic stimulation shortens the vestibular-evoked myogenic potential latencies in normal subjects, it does not affect the bilateral clicks vestibular-evoked myogenic potential ability to detect retrolabyrinthine lesions. Bilateral clicks vestibular-evoked myogenic potentials are a more convenient mode with which to help diagnose both labyrinthine and retrolabyrinthine lesions than unilateral clicks vestibular-evoked myogenic potentials.

Modeling postural instability with Galvanic vestibular stimulation

In this study the effect of a pseudorandom binaural bipolar Galvanic stimulus generated by a sum of nonharmonically related sine waves on postural control was functionally assessed using computerized dynamic posturography (CDP), and the results compared to vestibulopathic patient populations and astronauts exposed to microgravity. The standardized CDP test battery comprised six sensory organization tests (SOTs) that combined three visual conditions (eyes open, eyes closed, and sway-referenced vision) with two proprioceptive conditions (fixed and sway-referenced support surfaces). Subjects (12) performed 18 randomized trials (three trials of each of the six SOTs) as a baseline, repeated the 18 trials with Galvanic vestibular stimulation (GVS), and then performed a post-GVS baseline. A 10 min rest period was inserted between each test battery. Anterioposterior postural sway increased significantly and was in the abnormal range (fifth percentile) during GVS for SOTs where visual input was compromised (sway-referenced surround) or absent. Postural stability returned to baseline when GVS was removed. An analysis of sensory input scores (somatosensory, visual, and vestibular) demonstrated the specificity of GVS in distorting vestibular input to postural control. The SOT scores observed in astronauts on landing day did not differ significantly to that generated by GVS in our normal subjects. GVS also induced a similar pattern of instability on CDP as profound bilateral vestibular loss, although not as severe. The results suggest that unpredictably varying GVS quantitatively and qualitatively models postural instability of vestibular origin.

Vestibular Responses to Sound

Research into vestibular responses to sound has evolved in four stages. The first, largely the work of Tullio in the 1920s, involved inspection of the eye, head, and postural responses to sound of alert animals with surgical fenestrae into various parts of the bony labyrinth. The second, begun in 1964 by Bickford and his group and continued by our group and then by others in the last 10 years, involves the measurement of evoked myogenic potentials to air-conducted and bone-conducted clicks and tones in normal humans. The third, begun by Mikaelian at about the same time as Bickford and continued by McCue, our group, and others, involves electrophysiological recordings of primary vestibular afferent neuron responses to sound in anesthetized animals. The fourth involves measurements of vestibulo-ocular responses to sound in humans with the Tullio phenomenon. It was begun by Minor and his group in 1998 with the observation that sound-induced nystagmus in humans, the Tullio phenomenon, aligned with the rotation axis of the superior semicircular canal. They then showed a defect in the temporal bone between the apex of the superior semicircular canal and the middle cranial fossa, which was the cause of most, if not all, cases of sound-induced nystagmus. Here some of the key observations made in each of these four stages are reviewed.

Clinical Manifestations of Superior Semicircular Canal Dehiscence

OBJECTIVES/HYPOTHESES

To determine the symptoms, signs, and findings on diagnostic tests in patients with clinical manifestations of superior canal dehiscence. To investigate hypotheses about the effects of superior canal dehiscence. To analyze the outcomes in patients who underwent surgical repair of the dehiscence.

STUDY DESIGN

Review and analysis of clinical data obtained as a part of the diagnosis and treatment of patients with superior canal dehiscence at a tertiary care referral center.

METHODS

Clinical manifestations of superior semicircular canal dehiscence were studied in patients identified with this abnormality over the time period of May 1995 to July 2004. Criteria for inclusion in this series were identification of the dehiscence of bone overlying the superior canal confirmed with a high-resolution temporal bone computed tomography and the presence of at least one sign on physiologic testing indicative of superior canal dehiscence. There were 65 patients who qualified for inclusion in this study on the basis of these criteria. Vestibular manifestations were present in 60 and exclusively auditory manifestations without vestibular symptoms or signs were noted in 5 patients.

RESULTS

For the 60 patients with vestibular manifestations, symptoms induced by loud sounds were noted in 54 patients and pressure-induced symptoms (coughing, sneezing, straining) were present in 44. An air-bone on audiometry in these patients with vestibular manifestations measured (mean +/- SD) 19 +/- 14 dB at 250 Hz; 15 +/- 11 dB at 500 Hz; 11 +/- 9 dB at 1,000 Hz; and 4 +/- 6 dB at 2,000 Hz. An air-bone gap 10 dB or greater was present in 70% of ears with superior canal dehiscence tested at 250 Hz, 68% at 500 Hz, 64% at 1,000 Hz, and 21% at 2,000 Hz. Similar audiometric findings were noted in the five patients with exclusively auditory manifestations of dehiscence. The threshold for eliciting vestibular-evoked myogenic potentials from affected ears was (mean +/- SD) 81 +/- 9 dB normal hearing level. The threshold for unaffected ears was 99 +/- 7 dB, and the threshold for control ears was 98 +/- 4 dB. The thresholds in the affected ear were significantly different from both the unaffected ear and normal control thresholds (P < .001 for both comparisons). There was no difference between thresholds in the unaffected ear and normal control (P = .2). There were 20 patients who were debilitated by their symptoms and underwent surgical repair of superior canal dehiscence through a middle cranial fossa approach. Canal plugging was performed in 9 and resurfacing of the canal without plugging of the lumen in 11 patients. Complete resolution of vestibular symptoms and signs was achieved in 8 of the 9 patients after canal plugging and in 7 of the 11 patients after resurfacing.

CONCLUSIONS

Superior canal dehiscence causes vestibular and auditory symptoms and signs as a consequence of the third mobile window in the inner ear created by the dehiscence. Surgical repair of the dehiscence can achieve control of the symptoms and signs. Canal plugging achieves long-term control more often than does resurfacing.

Vestibular-evoked extraocular potentials produced by stimulation with bone-conducted sound

OBJECTIVE

To investigate the origin, whether ocular or extraocular, of the short latency frontal potential (N15) reported by following vestibular stimulation.

METHODS

Fourteen subjects with low VEMP thresholds (V(T)) and 9 patients with vestibular or ocular disorders were stimulated at the mastoid with bone-conducted tone bursts (500 Hz, 8 ms) above vestibular threshold, using a B71 bone vibrator. Surface potentials were recorded from Fpz and around the eyes and referred to linked earlobes.

RESULTS

The N15 was present at Fpz, but was largest around the eyes (mean amplitude 2.6 microV, peak latency 13.4 ms, with stimulation at +18 dB above threshold) and was generally in phase above and below the eyes. The response was vestibular-dependent and modulated by alteration of gaze direction. The potentials were delayed in a patient with Miller Fisher syndrome and were larger in patients with superior canal dehiscence than in controls.

CONCLUSIONS

We report a new vestibular-evoked extraocular potential. Its properties are not consistent with an eye movement. It is likely to be produced, mainly or exclusively, by synchronous activity in extraocular muscles (i.e. a myogenic potential).

SIGNIFICANCE

Vestibular-evoked extraocular potentials extend the range of vestibular pathways that can be assessed electrophysiologically, and may be a useful additional test of vestibular function.

A Sound-Evoked Vestibulomasseteric Reflex in Healthy Humans

Averaged responses to loud clicks were recorded in the unrectified and rectified masseter electromyogram (EMG) of 18 healthy subjects. Unilateral clicks (0.1 ms, 3 Hz, 70–100 dB NHL), delivered during a steady masseter contraction, evoked bilateral responses that appeared to consist of 2 components on the basis of threshold, latency, and their appearance in rectified EMG. The lowest threshold response appeared as a p16 wave (onset 11–13 ms) in the unrectified EMG and corresponded with a 10- to 12-ms period of inhibition in the rectified EMG. Higher-intensity clicks recruited an earlier p11 response in the unrectified EMG (onset 7.0–9.2 ms) that sometimes appeared as an initial increase in the rectified EMG before suppression. The amplitude of the p11 wave scaled with background EMG level and was asymmetrically modulated by 30° tilt of the whole body. The threshold of the early p11/n15 wave in masseter was the same as the threshold for click-induced vestibulocollic reflexes. Single motor unit recordings demonstrated that responses in masseters corresponded to a silent period in unit firing that began earlier and lasted longer at 100 dB than at 80 dB. We propose that loud clicks induce 2 partially overlapping short-latency reflexes in masseter muscle EMG: a p11/n15 response, which we suggest is of vestibular origin, and a p16/n21 response, which we suggest is equivalent to the previously described jaw–acoustic reflex.

Episodic vertigo

PURPOSE OF REVIEW

This review focuses on three neuro-otological syndromes, which are all marked by rapid scientific progress on the one hand but under-recognition or undertreatment on the other: benign paroxysmal positional vertigo and its variants, superior semicircular canal dehiscence syndrome, and migrainous vertigo.

RECENT FINDINGS

The efficacy of Epley's maneuver for treatment of benign paroxysmal positional vertigo has been convincingly demonstrated by a meta-analysis of nine randomized controlled trials. Head vibration during Epley's procedure and keeping upright for 48 h after effective treatment do not improve the outcome. Superior canal dehiscence syndrome presents not only with sound and pressure-induced vertigo but also with conductive hearing loss at low frequencies. Migrainous vertigo may present not only with spontaneous attacks but also with positional vertigo or with chronic dizziness and imbalance. Vestibular rehabilitation has been proven to relieve chronic dizziness and visual vertigo.

SUMMARY

Recent studies have eliminated several white spots on the neuro-otological map. However, many areas are still unexplored, particularly with regard to treatment of specific vestibular syndromes where randomized controlled trials are just at their beginning.

Potencial vestibular miogénico evocado: un aporte al conocimiento de la fisiología y patología vestibular. Patrones cuantitativos en la población normal

INTRODUCTION

Vestibulocollic reflex is a muscular reflex which is activated by acoustic stimulation. It shows two components: the first one, the vestibular evoked myogenic potential (VMEP) related to the vestibular pathway and the second, to the auditive pathway. The VMEP potential could be useful for vestibular physiology and pathology knowledge.

OBJECTIVE

To determine the VMEP's parameters of normality and to evaluate influential factors such as age, sex or stimulation intensity.

MATERIAL AND METHODS

Prospective study of the VCR in 40 healthy individuals, distributed in 4 groups according to their age. Stimulation was carried out at 100db and 85db on each ear independently.

RESULTS

There are not differences between both ears and sexes. Normal latency levels must be separated between two groups of age: older and younger than 11 years old. Normal absolute values of amplitude response differ depending on muscular contraction, age and stimulation intensity. It is more representative to consider the difference between the values obtained in the two ears of the same individual than to consider the absolute values.