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We investigate the role of vestibular information in judging the gravity-referenced eye level (i.e., earth-referenced horizon or GREL) during sagittal body tilt whilst seated. Ten bilateral labyrinthine-defective subjects (LDS) and 10 age-matched controls set a luminous dot to their perception of GREL in darkness, with and without arm pointing. Although judgements were linearly influenced by the magnitude of whole-body tilt, results showed no significant difference between LDS and age-matched controls in the subjective GREL accuracy or in the intra-subject variability of judgement. However, LDS performance without arm pointing was related to the degree of vestibular compensation inferred from another postural study performed with the same patients. LDS did not utilize upper limb input during arm pointing movements as a source of graviceptive information to compensate for the vestibular loss. The data suggest that vestibular cues are not of prime importance in GREL estimates in static conditions. The absence of difference between controls and LDS GREL performance, and the correlation between the postural task and GREL accuracy, indicate that somatosensory input may convey as much graviceptive information required for GREL judgements as the vestibular system.

Background: Sudden sensorineural hearing loss is infrequent, with an estimated incidence of 5 to 20 cases yearly per 100,000 people. Although multiple etiologies have been identified, infection and idiopathic SNHL are most common. Sudden sensorineural hearing loss after nonotologic noncardiac surgery is highly unusual, particularly after spinal surgery., Case Description: We report a case of unilateral sudden SNHL after lumbar spinal fusion with review of the literature. Potential etiologies, treatment, and prognosis are summarized., Conclusion: Multiple etiologies have been proposed for SNHL after nonotologic noncardiac surgery. Excessive positive upper airway pressure during induction of anesthesia or Valsalva maneuvers can result in SNHL from LMR. Aberrant NO accumulation in the middle ear cavity during general anesthesia with subsequent LMR is also a potential etiology, as is excessive leakage of CSF causing a form of endolymphatic hydrops. There is no definitive treatment of postoperative SNHL, although middle ear exploration may be beneficial for suspected overpressure injury to the middle ear, causing a perilymphatic fistula. Corticosteroids have been beneficial in certain cases of idiopathic SNHL; however, its effectiveness for postoperative SNHL is undocumented.

Objective: To evaluate the power of various parameters of the vestibulo-ocular reflex (VOR) in detecting unilateral peripheral vestibular dysfunction and in characterizing certain inner ear pathologies., Study Design: Prospective study of consecutive ambulatory patients presenting with acute onset of peripheral vertigo and spontaneous nystagmus., Setting: Tertiary referral center., Patients: Seventy-four patients (40 females, 34 males) and 22 normal subjects (11 females, 11 males) were included in the study. Patients were classified in three main diagnoses: vestibular neuritis: 40; viral labyrinthitis: 22; Meniere's disease: 12., Methods: The VOR function was evaluated by standard caloric and impulse rotary tests (velocity step). A mathematical model of vestibular function was used to characterize the VOR response to rotational stimulation. The diagnostic value of the different VOR parameters was assessed by uni- and multivariable logistic regression., Results: In univariable analysis, caloric asymmetry emerged as the most powerful VOR parameter in identifying unilateral vestibular deficit, with a boundary limit set at 20%. In multivariable analysis, the combination of caloric asymmetry and rotational time constant asymmetry significantly improved the discriminatory power over caloric alone (p<0.0001) and produced a detection score with a correct classification of 92.4%. In discriminating labyrinthine diseases, different combinations of the VOR parameters were obtained for each diagnosis (p<0.003) supporting that the VOR characteristics differ between the three inner ear disorders. However, the clinical usefulness of these characteristics in separating the pathologies was limited., Conclusion: We propose a powerful logistic model combining the indices of caloric and time constant asymmetries to detect a peripheral vestibular loss, with an accuracy of 92.4%. Based on vestibular data only, the discrimination between the different inner ear diseases is statistically possible, which supports different pathophysiologic changes in labyrinthine pathologies.

The recording of vestibular evoked myogenic potentials is a relatively new neuro-otologic method which gives specific information about the function of the sacculus and the inferior vestibular nerve on each side separately. The main indications for this method are vestibular schwannoma and fistula of the labyrinth, involvement of the sacculus or the inferior vestibular nerve in Menière's disease and vestibular neuritis, vertigo of unknown etiology, and forensic questions.

Introduction: Impaired glucose metabolism is characterized by conditions of hypo and hyperglycemia., Aim: The objective of the present study was to asses whether or not there is a relationship between impaired glucose metabolism and dizziness. In the clinical laboratory settings, patients were examined using vectoelectronystagmography in association with glycemic levels., Methods: 33 patients were divided in 3 groups: diabetics; patients with dizziness and a control group., Results: 65% of the patients with dizziness showed impaired glucose metabolism. 40% of the patients with dizziness had alterations in their vectoelectronystagmography results., Conclusion: Dizziness is a good indicator of glucose metabolism alterations and these may be a good indicator of alterations in vectoelectronystagmography responses. The study of glycemic levels after glucose overexposure is a good prognosis factor to evaluate dizziness and shows the same results as insulin level studies after glucose overexposure.

Background: An enlarged, low-threshold click-evoked vestibulo-ocular reflex (VOR) can be averaged from the vertical electro-oculogram in a superior canal dehiscence (SCD), a temporal bone defect between the superior semicircular canal and middle cranial fossa., Objective: To determine the origin and quantitative stimulus-response properties of the click-evoked VOR., Methods: Three-dimensional, binocular eye movements evoked by air-conducted 100-microsecond clicks (110 dB normal hearing level, 145 dB sound pressure level, 2 Hz) were measured with dual-search coils in 11 healthy subjects and 19 patients with SCD confirmed by CT imaging. Thresholds were established by decrementing loudness from 110 dB to 70 dB in 10-dB steps. Eye rotation axis of click-evoked VOR computed by vector analysis was referenced to known semicircular canal planes. Response characteristics were investigated with regard to enhancement using trains of three to seven clicks with 1-millisecond interclick intervals, visual fixation, head orientation, click polarity, and stimulation frequency (2 to 15 Hz)., Results: In subjects and SCD patients, click-evoked VOR comprised upward, contraversive-torsional eye rotations with onset latency of approximately 9 milliseconds. Its eye rotation axis aligned with the superior canal axis, suggesting activation of superior canal receptors. In subjects, the amplitude was less than 0.01 degrees, and the magnitude was less than 3 degrees/second; in SCD, the amplitude was up to 60 times larger at 0.66 degrees, and its magnitude was between 5 and 92 degrees/second, with a threshold 10 to 40 dB below normal (110 dB). The click-evoked VOR magnitude was enhanced approximately 2.5 times with trains of five clicks but was unaffected by head orientation, visual fixation, click polarity, and stimulation frequency up to 10 Hz; it was also present on the surface electro-oculogram., Conclusion: In superior canal dehiscence, clicks evoked a high-magnitude, low-threshold, 9-millisecond-latency vestibulo-ocular reflex that aligns with the superior canal, suggesting superior canal receptor hypersensitivity to sound.

Background: Horizontal canal benign paroxysmal positional vertigo is characterized by horizontal direction-changing nystagmus induced by lateral head turning in supine position. According to Ewald's second law, the direction of head turning that creates a stronger response represents the affected side in geotropic nystagmus and the healthy side in apogeotropic nystagmus. However, it may not always be possible to lateralize the involved ear only by comparing the intensity of the nystagmus. We studied the values of nystagmus induced by position change from sitting to supine in the lateralization of horizontal canal benign paroxysmal positional vertigo., Methods: A retrospective study of 54 patients who had been diagnosed as having horizontal canal benign paroxysmal positional vertigo at the Dizziness Clinic of Seoul National University Bundang Hospital from May 2003 to February 2004 was performed. The directions of the nystagmus induced by lying down were compared with those determined by Ewald's second law., Results: Of the 54 patients, 32 (20 apogeotropic and 12 geotropic) showed horizontal nystagmus induced by lying down. The nystagmus tended to be ipsilesional in apogeotropic patients (80%) and contralesional in their geotropic counterparts (75%)., Conclusion: In horizontal canal benign paroxysmal positional vertigo, lying-down nystagmus mostly beats toward the involved ear in the apogeotropic type and directs to the healthy ear in the geotropic type. The direction of lying-down nystagmus may help lateralizing the involved ear in horizontal canal benign paroxysmal positional vertigo.

Objective: To observe the changes of auditory steady-state response (ASSR) threshold in guinea pigs with posterior semicircular canal fistula., Methods: In 10 guinea pigs, a window was opened in the posterior semicircular canal of the left ear with the right ear serving as the control for testing the ASSR under anesthesia with pentobarbital sodium., Results: The mean and standard deviation of ASSR threshold (dB SPL) at 0.5, 1, 2, and 4 kHz in the left ear was 35.00+/-14.33, 25.50+/-12.37, 20.00+/-9.37 and 20.00+/-9.18, respectively, and was 31.00+/-16.19, 25.50+/-12.34, 18.00+/-6.96 and 18.50+/-6.71 in the right ear, respectively. Paired-sample t test showed no significant difference in the ASSR at the same frequency between the two ears., Conclusion: Small fistula by surgery causes no significant hearing loss in guinea pigs.

From April 2001 to November 2003, we investigated 8 patients with benign paroxysmal positional vertigo (BPPV) that was suspected to simultaneously affect both the horizontal and posterior semicircular canals (HSCC and PSCC). These cases showed typical vertical-torsional nystagmus induced by the Dix-Hallpike maneuver, followed by a horizontal nystagmus. They also showed a direction-changing geotropic or apogeotropic positional nystagmus triggered by lateral head rotations in the supine position. Using the three-dimensional analysis of the positional nystagmus, the rotation axis of the positional nystagmus had a component perpendicular to the plane of PSCC and another component perpendicular to the plane of HSCC. All these findings suggest that BPPV in these patients was a combination of posterior and horizontal canal BPPV. The observation of a vertical-torsional positional nystagmus should prompt the specialist to perform not only the canalith repositioning procedure, but also to execute lateral head turns in the supine position., (Copyright (c) 2006 S. Karger AG, Basel.)

We present a case study of a 49-year-old patient with an 8-year history of hypersensitivity to sound produced by intrinsic but not extrinsic sources. Findings that indicated an organic problem were: a supranormal bone conduction threshold of -25 to -15 dB HL from 0.25 to 1 kHz with an air-bone gap of 15 to 45 dB HL, a lower threshold and larger amplitude for vestibular-evoked myogenic potentials, eye movement reactions to sound and trunk pitch sway in response to sound. Results of immitance audiometry and otoacoustic emission testing were within normal limits and indicative of intact middle ear conductance. A high-resolution CT scan of the temporal bone demonstrated a dehiscence of bone overlying the superior semicircular canal. These findings support previous research indicating that auditory energy reaches the cochleo-vestibular receptor systems more easily via transmission through cerebrospinal fluid than through bone. Therefore, a dehiscence of the bone overlying the superior semicircular canal may lead to hypersensitivity to intrinsic sound. We recommend that similar findings in other patients be followed up with an evaluation of middle ear function and the temporal bone with high-resolution CT scan.

A superior semicircular canal dehiscence (SCD) is a break or hole in the bony wall of the superior semicircular canal. Patients with SCD syndrome present with a variety of symptoms: some with vestibular symptoms, others with auditory symptoms (including low-frequency conductive hearing loss) and yet others with both. We are interested in whether or not mechanically altering the superior canal by introducing a dehiscence is sufficient to cause the low-frequency conductive hearing loss associated with SCD syndrome. We evaluated the effect of a surgically introduced dehiscence on auditory responses to air-conducted (AC) stimuli in 11 chinchilla ears. Cochlear potential (CP) was recorded at the round-window before and after a dehiscence was introduced. In each ear, a decrease in CP in response to low frequency (<2 kHz) sound stimuli was observed after the introduction of the dehiscence. The dehiscence was then patched with cyanoacrylate glue leading to a reversal of the dehiscence-induced changes in CP. The reversible decrease in auditory sensitivity observed in chinchilla is consistent with the elevated AC thresholds observed in patients with SCD. According to the 'third-window' hypothesis the SCD shunts sound-induced stapes velocity away from the cochlea, resulting in decreased auditory sensitivity to AC sounds. The data collected in this study are consistent with predictions of this hypothesis.

Objective: Immune-mediated cochleovestibular disorders (IMCVDs) continue to present a diagnostic and therapeutic challenge. Antirheumatic agents, commonly employed for IMCVDs, are associated with variable efficacy and sometimes with serious side effects. The objective of the current study was to preliminarily evaluate the efficacy of etanercept therapy for IMCVD., Methods: In this open-label prospective pilot study, 23 patients with bilateral IMCVDs or symptoms of bilateral Meniere's disease were treated with etanercept (25 mg twice weekly, by subcutaneous injection) for 24 weeks. All participants showed progressive hearing loss within 3 months prior to the study and responded to prednisone therapy. Hearing improvement was defined as an improvement of sensorineural hearing from baseline, in at least one ear, of 15 dB or more in the pure-tone air conduction thresholds, or an increase of more than 12% in word identification score. When present, vertigo and tinnitus were assessed by frequency and severity of attack and a functional level scale. Limited serial positron emission tomography (PET) of the inner ear region was performed in 5 patients to assess disease activity., Results: There were 12 female (52%) and 11 male patients with a mean age of 48 years. Hearing improved in 7 (30%) patients, was unchanged in 13 (57%), and worsened in 3 (13%). Of 21 patients with tinnitus, this symptom improved in 7 (33%), was unchanged in 10 (48%), and worsened in 3 (13%). Of 16 patients with vertigo, 8 (50%) were improved, 7 (47%) unchanged, and 1 (3%) worse at the end of the study. Etanercept was generally well tolerated. PET was positive on one ear of 2 of 5 patients, remained positive with treatment on 1 of these, and was initially positive in 1 deaf ear, becoming negative at followup., Conclusion: These prospective pilot data suggest that etanercept therapy is safe among patients with IMCVDs. However, these data do not suggest substantial efficacy of etanercept among patients with IMCVDs in improving hearing loss. There appeared to be stabilization or improvement of hearing in 87% in this group of patients with pretreatment intractable progressive hearing loss. However, the study endpoint of improvement in 70% of patients was not attained. This short-term effect of possible stabilization requires further study. PET scanning was not useful as a tool to evaluate hearing loss in a limited subset of patients.

The Cervico-ocular reflex (COR), which depends on proprioceptive afferents from neck muscles to the vestibular nucleus, makes little contribution to the stabilization of gaze in humans. If labyrinthine function is lost because of disease, however, the COR may increase in gain and assume greater importance in generating compensatory eye rotations during natural head movements. We tested the COR, i.e., eye movement responses to rotation of the trunk about the earth fixed head (swinging test with fixed head STFH). If the vestibular function is intact, normally there should be no nystagmus. A total of 88 labyrinthine defective patients and 78 controls were studied. Of the 166 subjects evaluated, 88 presented some kind of alteration (either central or peripheral) and had STFH results showing "no inhibition" in 85 patients. Therefore, the STFH's sensibility is 96.6%. The remaining 3.4% were false negatives (i.e., pathology that could not be detected by the test). Of the 166 subjects evaluated, 78 had normal results and normal STFH. Therefore, STFH's specificity was 100%. We conclude that the study of the COR through STFH is a simple, useful, and clinically reliable test which should improve our knowledge of the interesting relationship between VOR and COR.

We report horizontal canal BPPV (HC-BPPV) targeting its pathophysiology, the affected side, and the function of the horizontal semicircular canal, together with a review of the literature. Subjects were 13 patients with HC-BPPV visiting our vertigo outpatient clinic at Nara medical university hospital and a related hospital in the 2.5 years from January 2000 to June 2002. Subjects were classified into 7 with canalolithiasis and 6 patients of cupulolithiasis after a neurotological examination. CP was positive in 54% of all patients, 71% of those with canalolithiasis, and 33% of those with cupulolithiasis. To determine the affected side in HC-BPPV, we used the affected side by using the law of Ewald in canalolithaisis patients and the detection of a neutral diminishing nystagmus in cupulolithiasis patients. CP positive in caloric testing indicated insignificant dysfunction of the horizontal semicircular canal in canalolithiasis patients compared to that in cupulolithasis patients. The mechanism behind caloric nystagmus was thought to be a convection of endolymphatic fluid interrupted consequently by an otolith in the semicircular canal in canalolithiasis patients. In contrast, CP was positive in cupulolithiasis patients regarded as having no convection of endolymphatic fluid. The mechanism causing a difference in caloric test results between canalolithiasis and cupulolithiasis patients thus requires a larger patient population and further examination to be conclusive.

Degeneration of inner ear cells, especially sensory hair cells and associated neurons, results in hearing impairment and balance disorders. These disabilities are incurable because loss of hair cells and associated neurons is currently irreversible. Protection or regeneration of hair cells and associated neurons is an important area of research for developing an effective treatment for inner ear diseases. Cell therapy is a rapidly growing area of research and has potential applications in the treatment of inner ear disorders. The first attempts to examine the feasibility of cell therapy in the treatment of inner ear disorders have been performed using neural stem cells (NSCs). Grafted NSCs can survive in the inner ear and differentiate into neural, glial and/or hair cell-phenotypes, making NSC transplantation for the restoration of inner ear cells a potentially viable treatment. Further studies have suggested embryonic stem cells (ESCs), dorsal ganglion cells and cell lines derived from fetal inner ear cells could be used to restore damaged inner ear cells. Cell transplantation has also been suggested as a strategy for drug delivery into the inner ear, and the ability of NSC-derived cells to produce neurotrophins in the inner ear has been demonstrated. Results from studies using autologous bone marrow stromal cells (MSCs) indicate a high survival and migration potential suggesting that MSCs can be used as a drug delivery vehicle to the inner ear. These cell transplantation findings provide a sound foundation for the development of therapies to treat inner ear disorders.

Increasingly more detailed imaging techniques have recently highlighted the frequent occurrence of bony labyrinthine dehiscence. Among them, superior canal dehiscence (SCD) has been described in a number of cases presenting different features. Here, we report a series of 13 cases, in which the detection of vestibular evoked myogenic potentials (VEMPs) in response to stimuli of abnormally low intensity as compared to normal responses led us to suspect the presence of a 'third window effect'. An accurate HRCT investigation allowed the diagnosis of SCD. Anamnestic and symptomatologic differences seem difficult to explain, although in our opinion a dural rupture could be at the basis of the onset of pathologic manifestations after many years of silence of a probably malformative condition.

Certain peripheral vertigos undoubtedly do not raise from neuro-sensorial structures but rather of the secretory structures and can be called "endolymphatic". They deserve to be individualized because concerning different pathogenic mechanisms and certainly are relevant for a specific treatment. We hope that in the next years new investigation tools will allow to explore in a noninvasive way the endolymphatic contents and dysfunctions of these structures.

The evaluation of cochleovestibular dysfunction in psychiatric patients often causes a difficult problem in neurootological experience. The authors discuss here the neurobiological basis of panic disorders and cochleovestibular dysfunction. In this multicenter study, we examined 63 patients with vertigo and panic disease. Twenty patients with primary panic disease and consecutive vertigo composed group 1, whereas group 2 comprised 43 vertiginous patients with secondary panic disease. The most interesting question is whether the patients have an organic vestibular lesion, which would explain why vertigo alone is the problematic symptom in these panic patients, whereas in other patients, panic disease can cause other severe symptoms that resemble heart attack, dyspnea, or abdominal crisis. Vertigo has a bidirectional connection with psychiatric disorders. The panic disorder can be superimposed on chronic vertigo, and psychiatric patients with a cochleovestibular lesion have diminished chances for complete recovery. The examination of psychiatric patients with vertigo is very time consuming and requires much more empathy than does examination of vertiginous patients with a normal mental state. Anxiety provokes somatic and behavioral symptoms in most such patients. The treatment of vertigo in panic patients and of the panic disorder in vertiginous patients requires cooperation between neurootologist and psychiatrist.

Inner ear physiology is reviewed with emphasis on features common to renal physiology. Genetic disorders in transporters/channels for chloride (ClC-K), bicarbonate (Cl(-)/HCO(3)(-) exchanger), protons (H(+)-ATPase), sodium (ENaC, NKKC1, NBC3, NHE3), potassium (KCNQ1/KCNE1, Kcc4), and water (AQP4) in the inner ear and their relation to the kidney are discussed. Based on data from human disorders (with or without mouse counterparts) and mouse models (without human counterparts) this article focuses on the involvement of these transporters/channels in hearing loss.

Histamine is thought to be involved in the recovery of vestibular function after damage to the vestibular receptors of the inner ear. This study evaluated the effects of post-operative treatment using Chlorpheniramine (H1 histamine antagonist) and L-histidine, (a histaminergic precursor), after hemilabyrinthectomy in goldfish. In this lesion model, the unilateral removal of the labyrinth induces a transient postural imbalance in response to light. After the lesion, the animals were injected intraperitoneally, during 12 consecutive days, with Chlorpheniramine, L-histidine and saline. All the substances were administered in a volume of 1 ml/kg body weight. Another group, which served as a non-lesion control, did not receive hemilabyrinthectomy or systemic injections. Chlorpheniramine accelerated the functional recovery when compared with that of the saline group. These data suggest that the inhibition of the histaminergic system facilitates the functional recovery in goldfish.

It has been reported that patients with vestibular disorders experience a wide range of cognitive disorders, including memory loss. However, to our knowledge, no study has investigated the contribution of vestibular information to episodic memory in experimental animals using vestibular deafferentation. In the present study, the effects of a complete unilateral or bilateral surgical lesion of the vestibular labyrinths in a spontaneous object recognition task were evaluated in Wistar rats 3 and 6 months following the surgery. We found that rats with bilateral vestibular deafferentation, but not those with unilateral vestibular deafferentation were impaired on the task at both time points. These results suggest for the first time that vestibular information may contribute to non-spatial memory to some extent.

Objective: To report our experience on a multicentre series of 32 patients with either typical or atypical Cogan's syndrome, to combine our results with a detailed review of the literature, and to compare the clinical manifestations of typical and atypical Cogan's syndrome., Methods: Patients were identified from a survey conducted with physicians affiliated to the French National Society for Internal Medicine, and were classified into typical or atypical Cogan's syndrome according to the Haynes criteria. Clinical data were collected in a standardized manner. A comprehensive literature review using the Medline database and the reference lists of identified articles was performed., Results: Seventeen patients had typical Cogan's syndrome and 15 had atypical Cogan's syndrome. Apart from non-syphilitic interstitial keratitis, the ocular manifestations of patients with atypical Cogan's syndrome were mainly uveitis and episcleritis. All but one patient presented with Ménière-like syndrome, and at the end of follow-up 11 were deaf and 19 additional patients had developed a significant decrease in auditory acuity. Twenty-five patients (78%) developed systemic manifestations, including aortitis in four. Comparison of typical and atypical Cogan's syndrome showed that some systemic manifestations were more common in atypical Cogan's syndrome, but these differences may be explained by reporting bias in the literature., Conclusion: Differences regarding the associated systemic manifestations of typical and atypical Cogan's syndrome may reflect reporting bias in the literature. However, the diversity of the ocular and audiovestibular manifestations and the acceptable lengthy delay between the two types of involvement in atypical Cogan's syndrome should make one cautious before accepting this diagnosis as the diagnosis may mimic various other systemic diseases.

The expression of phosphorylated extracellular signal-regulated kinase 1/2 (pERK 1/2) was evaluated in the vestibular nuclei (VN) of rats following unilateral labyrinthectomy (UL). Immunohistochemistry revealed a significant asymmetrical increase in pERK 1/2 expression in the VN, 5 min after UL, after which pERK 1/2 immunoreactivity decreased rapidly and was undetectable by 90 min after UL. These results suggest that unilateral deafferentation of the vestibular system triggers intracellular signal pathways that activate ERK 1/2 in the VN., (Copyright 2004 Elsevier B.V.)

Posture has traditionally been examined by isolating individual control pathways to determine their specific contributions. However, if these pathways are responsive to functional contexts, then their responses may differ when the system is receiving simultaneous inputs from multiple pathways. Thus, we may never fully understand how the central nervous system (CNS) organizes behaviors in the real world from studies conducted in the minimized environment of the laboratory. The consequence of this is that when findings from the laboratory are applied to therapeutic intervention, the intervention may not be appropriate for all circumstances and will not fully meet the needs of the patient. We have united an immersive dynamic virtual environment with motion of a posture platform to record the biomechanical and physiological responses to combined visual, vestibular, and proprioceptive inputs. The virtual environment possesses content, contrast, and texture so that we can examine postural responses as they might occur in a complex, real-world environment. In this paper we specifically describe the factors guiding our choices of virtual technology and present data from young adults, elderly adults, and an individual with bilateral labyrinthine loss to demonstrate how multimodal inputs influence their postural response organization. Significant implications for future experimental and rehabilitation protocols are also discussed.

Hypothesis: Afferents innervating the superior semicircular canal are rendered especially sensitive to acoustic stimulation when there is a dehiscence of the superior canal. Other vestibular end organs are also more sensitive to acoustic stimulation., Background: Dehiscence of the superior semicircular canal is associated with vertigo and nystagmus caused by loud sounds (Tullio phenomenon) or changes in middle ear or intracranial pressures. The mechanisms by which acoustic stimuli act on the vestibular end organs are unclear. The nystagmus caused by acoustic stimuli generally aligns with the affected superior canal., Methods: Responses to acoustic stimuli in the superior vestibular nerves of anesthetized chinchillas were recorded before and after fenestration of the superior canal., Results: Two acoustic response patterns were seen: rapid phase locking and slow tonic changes in firing rate. Phasic responses principally occurred in irregular afferents and tonic responses in regular afferents. Afferents from all of the vestibular end organs encountered could respond to acoustic stimuli, even before fenestration. However, fenestration lowered the thresholds for acoustic stimulation in superior canal afferents with phasic responses and increased the magnitude of tonic responses., Conclusions: Superior canal dehiscence may render the irregular afferents innervating the superior canal particularly sensitive to loud sounds. Rapid phase-locking responses may explain the short latency of nystagmus seen in patients with superior canal dehiscence syndrome. The mechanisms by which acoustic stimuli activate the vestibular end organs may differ from the damped endolymph motion associated with head acceleration.

Dehiscence of the superior semicircular canal is a 'new' vestibular entity. Among these patients, the vestibular evoked myogenic potentials (VEMP) in response to air-conducted sounds are large. In the present study, VEMP in response to bone-conducted sounds were studied in 5 normal subjects, in 3 patients after (unilateral) labyrinthectomy and in 4 patients with (unilateral) superior canal dehiscence syndrome. The bone-conducted sound stimulus was a 250- and a 500- tone burst delivered monaurally on the mastoid using standard bone conductors. Among the normals, bone-conducted sounds delivered monaurally caused VEMP bilaterally. There was, however, a transcranial attenuation for the 500-Hz stimulus, but less so for the 250-Hz stimulus. Among the patients with labyrinthectomy there were VEMP on the healthy side, but not on the lesioned side, irrespective of whether the bone-conducted sounds were presented behind the healthy or the operated ear. Among the patients with superior canal dehiscence syndrome, the VEMP on the affected side were larger than on the healthy side. This suggests that there is also vestibular hypersensitivity for bone-conducted sounds in these patients., (Copyright 2004 S. Karger AG, Basel)

A patient sought treatment for vertical oscillopsia and impaired vision during locomotion, and unsteadiness of gait. Positive fistula tests and CT of the temporal bones confirmed a diagnosis of bilateral superior canal dehiscence. An impairment of the superior canal vestibulo-ocular reflex, documented by three-dimensional search coil eye movement recordings for oblique (single) and downward pitch head motion (bilateral canal testing), is proposed to induce vertical rather than torsional-vertical oscillopsia during locomotion.

Perilymphatic fistula (PLF) is often difficult to diagnose because of the similar symptomatology, such as vertigo, tinnitus and hearing loss, which is found in several inner ear diseases. We attempted to correlate a positive result of low frequency sound (LFS) stimulation tests in posturography with the presence or absence of a PLF confirmed by transtympanic endoscopy in 209 patients with various inner ear diseases (Meniere's disease ( n=128), vestibulopathy ( n=41), cochleopathy ( n=28) and sudden deafness ( n=12). LFS provoked unsteadiness in posturography without PLF in 24 patients with Meniere's disease, in 5 patients with vestibulopathy, in 3 patients with cochleopathy and in 2 patients with sudden deafness. In one patient, tympanoscopy revealed fistula in the round window membrane that was covered with a fibrinous layer. In four cases there was abnormal light reflex in the round window but without PLF. In eight cases, Hennebert's sign was present with nystagmus, without PLF. We conclude that pathological responses to the LFS test in posturography can also be encountered in other inner ear diseases without PLF.

A 54-year-old woman complained of positional vertigo. During 3 months' observation, the patient showed mostly geotropic or apogeotropic nystagmus due to right canalolithiasis or cupulolithiasis, however, she sometimes showed nystagmus which suggested left horizontal canalolithiasis. We suspected that she suffered from bilateral horizontal canal type benign paroxysmal positional vertigo (BPPV) and performed Lempert's maneuver for both directions, however, they were ineffective. She underwent canal plugging for right horizontal canal. After surgery she showed no positional nystagmus of right horizontal canal origin. However, apogeotropic nystagmus of the left horizontal canal origin was still observed. This nystagmus changed to geotropic nystagmus and finally disappeared following Lempert's maneuver for the left side. Bilateral horizontal canal BPPV is difficult to be resolved, probably because physical treatment for one side would move debris to the cupula in the other canal. Canal plugging combined with Lempert's maneuver to the other side is one treatment option for intractable bilateral horizontal canal BPPV., (Copyright 2003 S. Karger AG, Basel)

Purpose of Review: This article reviews literature on three manifestations of these pathologic mechanisms: leakage of perilymph from the inner ear into the middle ear, disruption of the bone of the labyrinth caused by cholesteatoma or other manifestations of chronic otitis media, and superior semicircular canal dehiscence syndrome., Recent Findings: Labyrinthine fistulae are caused by abnormal communications between the inner ear and surrounding structures. Under normal circumstances, the fluid-filled spaces of the membranous labyrinth are encased in the dense bone of the otic capsule with only two places of increased compliance: the oval window and the round window. Disruption of the labyrinthine bone can lead to areas of increased compliance, with symptoms and signs that can be understood based upon abnormal pressure transmission in the system. Communication between the endolymphatic and perilymphatic spaces of the labyrinth or passage of perilymph from the labyrinth into the middle ear or mastoid can lead to hearing loss and/or vestibular disturbances., Summary: Findings on clinical examination as well as CT imaging of the temporal bone can be useful in making the diagnosis. Management is based upon the specific pathological factors and the impact of the symptoms and signs on the patient.

Objectives/hypothesis: Inner ear decompression illness is thought to be a rare phenomenon in recreational divers, isolated signs and symptoms of inner ear dysfunction usually being attributed to inner ear barotrauma., Study Design: We present 11 cases of inner ear dysfunction in nine divers with inner ear decompression illness., Results: All nine divers had significant right-to-left shunt as diagnosed by transcranial Doppler sonography., Conclusions: The authors thought that mechanism of causation in these cases may have been intravascular bubble emboli and that inner ear decompression illness may be more common among recreational divers than currently recognized. Failure to treat inner ear decompression illness with recompression therapy can result in permanent disability. Because the differential diagnosis between inner ear barotrauma and inner ear decompression illness can be impossible, the authors suggested that divers who present with inner ear symptoms following a dive should have recompression immediately after having undergone bilateral paracentesis.

Objective: One of the clinical characteristics of benign paroxysmal positional vertigo (BPPV) is that the more quickly the head position changes, the more severe the vertigo. This suggests that the velocity of the head change is critical in determining the occurrence and severity of vertigo. The aim of this study was to examine factors determining the symptoms of BPPV using models of canalolithiasis and cupulolithiasis., Material and Methods: Canalolithiasis and cupulolithiasis models were prepared using the bullfrog posterior semicircular canal (PSC). The ampullary nerve discharges were compared between quick and slow positional changes to examine factors determining the symptoms of BPPV., Results: In the canalolithiasis model, the acceleration of the otoconia was greater for the quick positional change. This resulted in a greater discharge with a longer duration. With the slow positional change, the discharges were smaller and shorter. In the cupulolithiasis model, the discharges were sustained and their magnitude did not differ between the quick and slow positional changes. The canalolithiasis model influenced the magnitude of discharge of the PSC depending on the speed of the positional change., Conclusion: Canalolithiasis is the more likely mechanism of BPPV, which is characterized by various degrees of vertigo upon kinetic positional change.

This is a report of a patient with an air-bone gap, thought 10 years ago to be a conductive hearing loss due to otosclerosis and treated with a stapedectomy. It now transpires that the patient actually had a conductive hearing gain due to superior semicircular canal dehiscence. In retrospect for as long as he could remember the patient had experienced cochlear hypersensitivity to bone-conducted sounds so that he could hear his own heart beat and joints move, as well as a tuning fork placed at his ankle. He also had vestibular hypersensitivity to air-conducted sounds with sound-induced eye movements (Tullio phenomenon), pressure-induced nystagmus and low-threshold, high-amplitude vestibular-evoked myogenic potentials. Furthermore some of his acoustic reflexes were preserved even after stapedectomy and two revisions. This case shows that if acoustic reflexes are preserved in a patient with an air-bone gap then the patient needs to be checked for sound- and pressure-induced nystagmus and needs to have vestibular-evoked myogenic potential testing. If there is sound- or pressure-induced nystagmus and if the vestibular-evoked myogenic potentials are also preserved, the problem is most likely in the floor of the middle fossa and not in the middle ear, and the patient needs a high-resolution spiral computed tomography (CT) of the temporal bones to show this.

Isolated inner ear decompression sickness (DCS) is recognized in deep diving involving breathing of helium-oxygen mixtures, particularly when breathing gas is switched to a nitrogen-rich mixture during decompression. The biophysical basis for this selective vulnerability of the inner ear to DCS has not been established. A compartmental model of inert gas kinetics in the human inner ear was constructed from anatomical and physiological parameters described in the literature and used to simulate inert gas tensions in the inner ear during deep dives and breathing-gas substitutions that have been reported to cause inner ear DCS. The model predicts considerable supersaturation, and therefore possible bubble formation, during the initial phase of a conventional decompression. Counterdiffusion of helium and nitrogen from the perilymph may produce supersaturation in the membranous labyrinth and endolymph after switching to a nitrogen-rich breathing mixture even without decompression. Conventional decompression algorithms may result in inadequate decompression for the inner ear for deep dives. Breathing-gas switches should be scheduled deep or shallow to avoid the period of maximum supersaturation resulting from decompression.

Objective: Patients with superior canal dehiscence (SCD) syndrome experience vertigo and oscillopsia with loud sounds and/or stimuli that result in changes in middle ear or intracranial pressure. Findings on temporal bone CT were analyzed to determine if a developmental abnormality is associated with the syndrome., Material and Methods: Temporal bone CT scans [0.5 mm collimation and projections into the superior semicircular canal (SC) plane] were used to compare the bone overlying the SC in patients with SCD syndrome (20 unilateral, 7 bilateral) and in 88 patients without SCD syndrome who had undergone temporal bone CT for evaluation of other otologic disorders (controls)., Results: The thickness of bone overlying the SC in the controls measured 0.67 +/- 0.38 mm (mean +/- SD). For individual control subjects. the thickness of bone on one side was correlated with that on the other side (r = 0.43; p < 0.0001). The thickness of bone overlying the SC on the intact side in patients with unilateral dehiscence measured 0.31 +/- 0.23 mm, and was thinner than that noted in the controls (p < 0.0001)., Conclusion: These findings support the notion that there is a developmental abnormality underlying SCD syndrome. When dehiscence is found on one side, the contralateral side is likely to be thin.

The authors studied eye movement responses to loud (110dB) clicks in 4 patients with Tullio effect due to superior semicircular canal dehiscence and in 9 normal subjects, by averaging the electro-oculogram. All 4 patients had small (0.1-0.3 deg) but easily reproducible vertical vestibulo-ocular reflex eye movement responses to the clicks. Normal subjects had responses that were at least 10 times smaller. The click-evoked vestibulo-ocular reflex test is a simple, robust way to screen dizzy patients for symptomatic superior semicircular dehiscence.

Objectives: We investigated the results achieved in terms of hearing in 36 patients who had each undergone resection of a cholesteatoma and closure of a labyrinthine fistula., Patients and Methods: These patients included 28 who had a fistula of the semicircular canal, in 7 of them with an opened perilymphatic space. In 8 cases we found a fistula of the cochlea, with with a perilymphatic leak 7 in of them. We compared the sensorineural threshold before and after surgery and also the results in the two groups. Patients who were deaf preoperatively were excluded from further analysis., Results: Hearing did not improve in any of the patients (n=5) who were deaf preoperatively. There was no significant difference in changes to the hearing threshold between patients with fistula of the cochlear and those with fistula of the semicircular canal with opened perilymphatic space; nor did patients with a fistula of the semicircular canal without perilymphatic leakage have a better outcome than patients with an open membranous labyrinth., Conclusions: The outcome of cholesteatoma resection and closure of the fistula in a single operation was good. Perilymphatic leakage seems to be predictive of a poorer result in terms of hearing.

The purpose of this study was to evaluate the relative contributions of inputs from the vestibular system and the trunk to head-trunk coordination. Twelve healthy adults and 6 adults with diminished bilateral labyrinthine input (LD) were seated with their trunk either fixed to the seat or free to move. Subjects received 10-cm, 445-cm/s(2) anterior-posterior ramps and 0.35- to 4.05-Hz sum-of-sines translations while performing a mental distraction task in the dark. Kinematics of the head and trunk were derived from an Optotrak motion analysis system and a linear accelerometer placed on the head. EMG signals were collected from neck and paraspinal muscles. Data were tested for significance with multivariate ANOVA (MANOVA) and Bonferroni post hoc analyses. Initial linear and angular head acceleration directions differed in healthy subjects when the trunk was fixed or free, but did not differ in LD subjects. Peak head angular accelerations were significantly greater with the trunk fixed than when free, and were greater in LD than in control subjects. EMG response latencies did not differ when the trunk was fixed or free. Low-frequency phase responses in the healthy subjects were close to 90 degrees and had a delayed descent as frequency increased, suggesting some neural compensation that was absent in the LD subjects. Results of this study revealed a strong initial reliance on system mechanics and on signals from segmental receptors. The vestibular system may act to damp later response components and to monitor the position of the head in space secondary to feedback from segmental proprioceptors rather than to generate the postural reactions.

The Kir4.1 gene (KCNJ10) encodes an inwardly rectifying K(+) channel subunit abundantly expressed in the CNS. Its expression in the mammalian inner ear has been suggested but its function in vivo in the inner ear is unknown. Because diverse human hereditary deafness syndromes are associated with mutations in K(+) channels, we examined auditory function and inner ear structure in mice with a genetically inactivated Kir4.1 K(+) channel subunit. Startle response experiments suggest that Kir4.1-/- mice are profoundly deaf, whereas Kir4.1+/- mice react like wild-type mice to acoustic stimuli. In Kir4.1-/- mice, the Reissner membrane is collapsed, the tectorial membrane is swollen, and type I hair cells and spiral ganglion neurons as well as their central processes degenerate over the first postnatal weeks. In the vestibular ganglia, neuronal cell death with apoptotic features is also observed. Immunostaining reveals that Kir4.1 is strongly expressed in stria vascularis of wild-type but not Kir4.1-/- mice. Within the spiral ganglion, Kir4.1 labeling was detected on satellite cells surrounding spiral ganglion neurons and axons. We conclude that Kir4.1 is crucial for normal development of the cochlea and hearing, via two distinct aspects of extracellular K(+) homeostasis: (1). in stria vascularis, Kir4.1 helps to generate the cochlear endolymph; and (2). in spiral and vestibular ganglia, Kir4.1 in surrounding glial cells helps to support the spiral and vestibular ganglion neurons and their projecting axons.

The records of all patients attending a neurosensory genetics clinic over an 11-year period were reviewed. Of the 450 patients seen, 31 presented with sensorineural hearing loss, hypotonia, and delay in the acquisition of motor milestones. Of these, 4 children were found who did not have an etiologic diagnosis such as Down syndrome or cerebral palsy. Vestibular testing revealed hypoactive labyrinthine function in all 4 of the cases, and careful imaging of the temporal bone showed anomalous development of the cochlea, vestibule, and semicircular canals in 3 of the 4 cases. None of the patients had ataxia, tremor, or significant nystagmus. Over time, the hypotonia improved in all, and none were felt to have cognitive deficits. These cases demonstrate that hypoactive labyrinthine function may be associated with hypotonia that is severe enough to result in delayed acquisition of motor milestones. The patients followed the typical remitting course of "benign congenital hypotonia." The distinguishing clinical feature is the presence of moderate to profound sensorineural hearing loss in all of the patients.

Purpose: To describe the computed tomographic (CT) findings at different collimation widths associated with superior semicircular canal (SSC) dehiscence syndrome and to determine the frequency of these findings in a control population., Materials and Methods: Temporal bone CT scans with 1.0-mm and/or 0.5-mm collimation were obtained in 50 patients with sound- and/or pressure-induced vestibular symptoms. The control population consisted of 50 patients undergoing CT at 1.0-mm collimation and 57 patients undergoing CT at 0.5-mm collimation for other reasons., Results: SSC dehiscence was documented on CT scans in all 36 patients with the clinical syndrome, with bilateral findings in six patients. Six other patients without specific clinical signs appeared to have dehiscence on 1.0-mm-collimated scans. Intact bone overlaying the SSC was subsequently identified with 0.5-mm-collimated CT in each case. On the 1.0-mm-collimated scans in 50 control patients, an area judged as possible or definite dehiscence was identified in 18 of 100 ears. The bone overlaying the SSC was intact in each of the 114 control ears evaluated with 0.5-mm-collimated CT. CT findings from the patients with vestibular symptoms combined with those in the control population indicated that the positive predictive value of an apparent dehiscence in the diagnosis of SSC dehiscence syndrome improved from 50% with 1.0-mm-collimated CT with transverse and coronal images to 93% with 0.5-mm-collimated CT with reformation in the plane of the SSC., Conclusion: The positive predictive value of CT in identification of SSC dehiscence syndrome improves with 0.5-mm-collimated helical CT and reformation in the SSC plane.

This study assessed the eye movement responses to active head rotation in six subjects with complete unilateral vestibular loss (UVL), five subjects with posterior canal plugging (PCP) and age- and sex-matched normal subjects. Subjects performed head rotations in the pitch and yaw planes at frequencies ranging from 2 to 6 Hz, while looking at an earth-fixed target. Vertical eye movement gains obtained in UVL, PCP and normal subjects were not significantly different. Vertical phases decreased with increasing head movement frequencies in both UVL and PCP subjects. Although this decrease produced significantly different vertical phases between UVL and normal subjects for head movements above 3.9 Hz, vertical phases in some normal subjects were similar to those obtained in UVL subjects. We conclude that active head oscillations in the pitch plane are not clinically useful for the detection of vertical canal impairment limited to one ear. As expected, UVL subjects showed reduced horizontal gains, and eye velocity asymmetries during active head rotation in the yaw plane. Results in some PCP subjects suggested possible minor impairments of horizontal vestibulo-ocular reflexes.

Radionuclide tracing employed to study arterial and venous blood supply to the brain in 100 patients with angiogenic cochleovestibulopathies and lipid distress syndrome has provided information on perfusion of the brain, arterial and venous hemodynamics with reference to the form of cochleovestibular disorders and atherosclerotic defects of extra- and intracranial cerebral arteries.

Dead reckoning is an on-line form of spatial navigation used by an animal to identify its present location and return directly to a starting location, even after circuitous outward trips. At present, it is not known which of several self-movement cues (efferent copy from movement commands, proprioceptive information, sensory flow, or vestibular information) are used to compute homeward trajectories. To determine whether vestibular information is important for dead reckoning, the impact of chemical labyrinthectomy was evaluated in a test that demanded on-line computation of a homeward trajectory. Rats were habituated to leave a refuge that was visible from all locations on a circular table to forage for large food pellets, which they carried back to the refuge to eat. Two different probe trials were given: (1) the rats foraged from the same spatial location from a hidden refuge in the light and so were able to use visual cues to navigate; (2) the same procedure took place in the dark, constraining the animals to dead reckon. Although control rats carried food directly and rapidly back to the refuge on both probes, the rats with vestibular lesions were able to do so on the hidden refuge but not on the dark probe. The scores of vestibular reflex tests predicted the dead reckoning deficit. The vestibular animals were also impaired in learning a new piloting task. This is the first unambiguous demonstration that vestibular information is used in dead reckoning and also contributes to piloting.

This is a report of three cases of mixed hearing loss that resulted from inner ear disorders. Two cases were unilateral and the third was bilateral. The diagnosis was based on the findings of normal middle and external ears in association with the absence of round window reflexes. The contralateral stapedial reflex was present in the two unilateral cases. This is the first documentation of conductive deafness due to inner ear abnormality. This diagnosis should be considered in cases of conductive hearing loss if the middle and external ears are normal. More studies are needed to establish the pathophysiology of this entity.

In the guinea pig, in the absence of any stimulation, all the neurons of the vestibular nuclei are tonically firing. After an ipsilateral labyrinthectomy, these neurons first cease to fire but recover their previous discharge in 7 days. Here, we tested whether a modification of the spike generator, the process transforming synaptic currents into spike patterns, could be a factor underlying this restoration. For this purpose, we studied the firing rate responses of neurons of the medial vestibular nucleus in brain stem slices to intracellularly injected currents. We conclude that although labyrinthectomy induces some plastic changes in the excitability of the neurons of the medial vestibular nucleus, these changes do not underlie the restoration of activity which occurs in these neurons when they are deprived of their labyrinthine input.