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

In order to localize the site of lesion of peripheral vertigo, 3D analysis of nystagmus during peripheral vertiginous attacks was carried out. In comparison between the three components, the horizontal component had the largest ratio in each disease. Spontaneous nystagmus was directed toward the affected side in 3 cases and to the opposite side in 15. In patients with Menière's disease (MD), all subjects had horizontal and torsional components and had almost the same slow phase velocity in these two components. In patients with vestibular neuritis (VN) and Hunt's syndrome (HS), nystagmus was directed toward the opposite side. Furthermore, in VN, all subjects had an upward component, in addition to horizontal and torsional components. Inferring the focus from the character of nystagmus, it is speculated that the pathological changes are located in the entire inner ear in MD, whereas in VN the lesion is located in the horizontal and anterior semicircular canal or the superior vestibular nerve.

Immune inner ear disease is a somewhat controversial entity which describes cochleovestibular dysfunction that is related to immune-mediated mechanisms. The diagnosis of this disease is based on clinical presentation and response to various treatment protocols. Unfortunately, the presentation is variable and the treatment empirical, and this has caused much confusion in the diagnosis and management of the condition. To elucidate the variable nature of the disease, it is important to understand that more than one mechanism of immune injury may be involved. This paper attempts to classify clinical and experimental cases of immune inner ear disease with regard to the Gell and Coombs classification scheme of immune-mediated injury. By understanding the different pathophysiological mechanisms involved, the clinician should be better able to diagnose and manage this difficult problem in a directed fashion. The ramifications of the proposed classification system on the diagnosis, treatment and future research of immune inner ear disease are discussed.

Thresholds for detection of direction of whole-body lateral linear acceleration were determined for normal (N) and labyrinthine defective (LD) subjects. Thresholds for 67% correct detection of direction of acceleration steps for 5 LDs (mean 5.65 cm/s2, peak gradient = 25 cm/s3) were not significantly different from 8 Ns (mean 4.84 cm/s2, peak gradient = 22 cm/s3). High inter-subject variability was found both among the 7 Ns and 3 LDs for detection of parabolic accelerations with some individuals being unable to detect their motion direction. Mean Ns thresholds were 15.2 cm/s2 for a ramp with gradient of acceleration = 2.8 cm/s3, 26.4 cm/s2 for a ramp with gradient = 7.9 cm/s3 and 20.2 cm/s2 for a parabola with second derivative = 1.52 cm/s4. Thresholds for LDs were respectively 19.1 cm/s2, 32 cm/s2 and 26.7 cm/s2. The lower thresholds for acceleration steps demonstrate the important effect of acceleration gradient on motion detection. For all stimuli, thresholds for some LDs could be in the range of Ns showing that somatosensory signals can play a significant role in detecting lateral acceleration.

Vestibular function of a population including labyrinthine-defective patients and a control group of age-matched normal healthy volunteers was evaluated using videonystagmoscopy. This device is made of one or two CCD infra-red cameras mounted on diving glasses and allows observation of ocular movements on a video monitor and/or recording on a videotape. Eye movements are observed after rotations in a Bárány chair and during passive head tilts. With this simple and non-invasive test, a screening of vestibular function at bedside or during ENT clinical investigations can be performed. A further study with videonystagmography to quantify these results being prepared.

A sensitive method of demonstrating latent imbalance of labyrinthine function was devised. The subject was asked to walk at his or her usual speed with eyes closed in a circle 2 m in diameter. This test was done by 22 patients whose vestibular function as tested by the Romberg, Mann, Fukuda and Babinski-Weil's methods had become normal after an attack of vertigo due to unilateral vestibular disorder. Eighteen patients complained of difficulty in walking while turning toward the affected side, and 11 tended to fall to the inside of the circle. Turning in the opposite direction, however, was performed without any difficulty. It was thought that disorders of the cristospinal reflex became manifest during circular walking toward the affected side. The body is inclined to the inner side of circular walking. Endolymph flows toward the ampulla of the lateral semicircular canal on the same side as turning. This would exert a facilitatory action on extensor neurons and give the ipsilateral leg assistance for supporting the body's weight which shifts to the centre of the circle. Disorders of the cristospinal reflex would cause difficulty in circular walking toward the affected side.

A new technique was developed to test the VOR in humans. A tightly but comfortably fitting helmet was provided with an electronically controlled torque motor that rotated a mass around a vertical axis. Acceleration of the motor caused reactive torque of the helmet in the opposite direction which was transmitted to the (freely movable) head. Sinusoidal head oscillations in the frequency range 2-20 Hz (peak-to-peak amplitudes about 10 degrees and 0.1 degrees respectively) were easily achieved, as well as step displacements of the head with accelerations on the order of 1000 degrees/s2. Limitation of the maximum torque and lack of any rigid attachment of the head to a fixed structure made the technique safe and comfortable. Eye and head rotations were recorded, independently of head translations, with eye and head search coils in a homogeneous a.c. magnetic field. In normal subjects, gain was near unity at 2 Hz: above 8 Hz, gain increased progressively toward 1.1-1.3 at 20 Hz. Phase lag increased from a few degrees at 2 Hz to about 45 degrees at 20 Hz. Above 2 Hz, these results were unaffected by visual conditions; lower gains and increased phase lags were found in subjects with bilateral or unilateral vestibular loss. For step displacements, gain (measured in the first 100 ms) was near unity for normals, near zero after bilateral vestibular loss and strongly asymmetrical after unilateral vestibular loss. Thus, the technique seems highly effective in testing vestibular function with minimal contamination by other systems.

We have measured a spatial visual response and visual velocity discrimination in 4 patients with long standing vestibular loss and 6 controls. The spatial response was measured during; i) body and visual display stationary conditions, ii) whole-body oscillation (1 Hz +/- 50 degrees/s) and iii) visual stimulus oscillation (1 Hz +/- 50 degrees/s). Velocity discrimination was assessed during conditions i) and ii). The visual tests applied were selected on the basis that the spatial response is known to reflect peripheral processes of the retina, whereas velocity processing is more central in origin. Patients had normal spatial responses under static conditions and they suffered a degradation in their spatial responses during whole-body oscillation, whereas, normals' responses remained unaltered. During oscillation of the visual display both patients and normals suffered a degradation in their spatial responses, and for patients the change was very similar to that observed during whole-body oscillation. The changes in the spatial responses were dependent on the gain of the eye movements which compensated for the whole-body or visual display oscillation. In 3 patients and all controls whole-body oscillation did not alter the discrimination of velocity of a vertically moving horizontally orientated grating compared with when the subjects were stationary. One patient suffered a severe reduction in the ability to discriminate velocity under whole-body oscillation, which suggests that central suppression of motion perception reduces oscillopsia.

This paper reviews the physiopathological basis of some labyrinthine or vestibular nerve disorders illustrating a particular mode of vestibular dysfunction. The discovery of the physiopathology of these disorders has relied on neuroanatomical data, histopathological observations of human temporal bones, historical principles of vestibular physiology, surgical exploration, blood testing which provides indirect evidence of immune or metabolic disorders, and results from animal experiments. While all data are valid, advances in sensory cell physiology, development of new vestibular tests, and progress in imaging techniques are necessary in order for a better understanding of the mechanisms involved in vestibular end organ dysfunction to be obtained.

Hearing impairment caused by sequential rupture of Reissner's membrane and the round window was investigated in guinea pigs to determine if the double-membrane break can cause acute profound sensorineural hearing loss. Reissner's membrane was lacerated through the stria vascularis at one of the turns of the cochlea, followed by rupture of the round window to create leakage of the perilymph. Action potentials (APs) to tone pip stimuli were recorded from the Fallopian canal electrode before and 90 min after these procedures. The results showed that the ears with the double-membrane break at the second turn showed a larger increase in AP threshold than did the control ears with only round window rupture. However, this was not seen when Reissner's membrane had been ruptured at the other turns.

The effect of blood pressure (BP) changes on per-rotational nystagmus (PRN) was compared between normal guinea pigs and guinea pigs with unilaterally obliterated endolymphatic sac. Eye movements were recorded 3 months postoperatively. When the animal was rotated sinusoidally, asymmetry of PRN was minimal in the control animals. In the operated guinea pigs, however, nystagmus oscillating toward the operated side was largely suppressed when BP was decreased (30-40 mmHg). Thus, directional preponderance of PRN toward the nonoperated side was established. Oxygen tension (pO2) was measured in the perilymphatic space of the lateral semicircular canal to investigate the mechanisms underlying the PRN asymmetry. When BP was reduced below normal, pO2 on the operated side decreased much more than that on the intact side. It is suggested that obliteration of the endolymphatic sac results in an autoregulatory dysfunction in the semicircular canal. Asymmetry of the vestibulo-oculomotor reflex at low BP may be the result of decreased blood flow to the semicircular canal.

Jumbling consists of loss of vestibular eye movement reflexes and resultant oscillopsia during movement of the head. This results in a failure of clear vision during head movement. The head-shaking test for evaluation of the jumbling phenomenon was initially suggested by Meyer zum Gottesberge in 1952. In this test, binocular visual acuity is measured while the patient shakes his head at a rate of 2 or 3 movements per second, 10 to 20 degrees horizontally or vertically, and compared head still position. In normal subjects, only a slight decrease in visual acuity is noted due to this head-shaking. A diagnosis of jumbling is made when the visual acuity during head-shaking is less than half the visual acuity when the head is held motionless. When the visual acuity during head movement is expressed as a percentage of the value obtained while the head is motionless, a quantitative evaluation of jumbling is possible. This test should be done at regular intervals especially on patients who receive parenteral administration of ototoxic aminoglycosides for an early detection of jumbling and an appropriate discontinuation of the drugs, along with repeated auditory testing. The test is also useful in monitoring recovery from jumbling.

Vascular permeability of the stria vascularis was morphologically examined in hydrops animals, using the tracer method of horseradish peroxidase (HRP). The reaction product of HRP was observed in the capillary of the stria vascularis, not outside of it. The finding suggests that the vascular permeability of the stria vascularis is unchanged in Kimura's hydrops model.

Abnormal vestibular function disrupts a subject's reference to gravity (earth) vertical, and prevents resolution of conflicting or inaccurate visual and somatosensory spatial references. However, errors which patients make when attempting to resolve conflicting visual and somatosensory orientation inputs during upright stance differed markedly in patients with (1) symmetric or asymmetric reduced vestibular function, (2) benign paroxysmal positional nystagmus and vertigo, and (3) a combination of distorted and reduced function. Objective characterization of spatial orientation systems and compensatory strategies under altered sensory conditions is an essential first step toward identifying optimal treatment methods for each of these three types of vestibular deficient patients.

In order to investigate otolith function, horizontal eye displacement in total darkness during tilting laterally about body axis was examined in 23 normal subjects and 29 patients with vestibular lesions. The mean and standard deviation of this eye displacement in normal subjects were 18.9 + 6.1 degrees at 15 degrees of body-tilt. Thus, eye displacement below the lower tolerance limit of normal eye displacement at 15 degrees of body-tilt, that is, 8.8 degrees, was judged to be abnormal. Meanwhile, 12 cases or 41.4% of 29 patients with vestibular lesions showed abnormal eye displacement in this test. Especially in cases with positional vertigo and/or dizziness, the occurrence of abnormal results in this test (69%) was far higher compared with that of cases where vertigo and/or dizziness was not associated with postural changing (19%). Therefore, these abnormal results seem to be closely related to the disorder of otolith system.

We found a consistent pattern of response to low and high frequency sinusoidal rotational testing in patients with chronic compensated unilateral and bilateral peripheral vestibular lesions. Gain (peak slow phase eye velocity/peak chair velocity) was decreased and phase lead increased at low frequencies but both measurements approached normal at high frequencies. Asymmetries in gain, when present, were approximately the same in the low and high frequency range. These changes can be explained by a simple first order linear model of the vestibulo-ocular reflex if one assumes that the goal of the compensation process is to maintain gain in the high frequency range.

Based upon the results of a double-blind study carried out in a series of 120 patients suffering from vertigo and objective vestibular symptoms, we made the following observations during the treatment of vestibular disorders by means of calcium-entry blockers: Subjective symptoms regress fairly well during treatment, but no better than after betahistine-dihydrochloride (BHC) or thietylperazine therapy (TP). Objective assessment of the therapeutic action of calcium antagonists on vestibular dysfunction is based on the results of the Harmonic Acceleration test, which was carried out by using a computerized rotatory chair. The most reliable parameter with respect to the objective assessment of the experimentally induced vestibular responses (VOR) is the gain. Our test results show a progressive decrease in GAIN, indicating a depressive or inhibitory effect of the calcium antagonist flunarizine upon the VOR. If we compare these results with those obtained in the betahistidine- and thiethylperazine groups, we cannot confirm the same decline in GAIN within the latter two groups. A statistical analysis demonstrates a significant difference between the F-gain on the one hand, and the BHC gain and TP gain on the other hand.

Horizontal eye displacement in total darkness during lateral tilting about the body axis was examined in 14 patients with unilateral loss of labyrinth function, including 8 cases of positional vertigo or dizziness and 6 symptom-free cases. The change in eye displacement following labyrinthectomy was also studied in 2 cases of labyrinthitis and one case of delayed hydrops. Seven out of 8 subjects suffering from positional vertigo or dizziness exhibited abnormal eye displacement on tilting to the affected side, while 5 out of 6 symptom-free subjects showed normal eye displacement. The correlation between anomalous eye displacement and the presence of subjective symptoms was statistically significant (p less than 0.05). Abnormal eye displacement following labyrinthectomy was readily noted within 2 weeks of surgery, but became almost undetectable 3 to 4 weeks postoperatively, in close accordance with a decrease in positional vertigo or dizziness. It was concluded that the measurement of eye displacement during lateral body tilt, although previously reported to be useful in the assessment of function, might also be employed to examine compensation for the loss of otolith function.

The cause of perilymph fistula, a subgroup of sudden deafness, has not been clearly understood. To study its etiology quantitatively, the inner ear pressure monitoring system with a computer controlled pressurizing device and three types of low-pressure monitoring sensors was constructed and utilized in ex vivo experiments using white guinea pigs. Hypothesizing that cerebrospinal pressure increases cause rupture of the round window membrane, direct and indirect pressurization to cerebrospinal region and simultaneous measurement of inner ear and cerebrospinal pressures were carried out. Ruptures of the round window membranes were seen in the experiments with direct saline infusion into the cochlea when the increment of inner ear pressure exceeded 500 mmH2O. There was no sign of rupture when squeezing abdomen was employed as an indirect pressurization, although cerebrospinal pressure increased.

We studied the dynamics of the horizontal vestibulo-ocular reflex using a broad range of sinusoidal rotational stimuli in 14 patients with acute unilateral peripheral vestibular lesions. From plots of slow phase velocity (SPV) versus stimulus velocity (phase shifts removed) we calculated the DC offset and gain to ampullopetal (AP) and ampullofugal (AF) stimulation of the remaining intact labyrinth. DC offset values were highly correlated with spontaneous nystagmus SPV values for all frequencies (0.0125-0.8 Hz) and amplitudes (30-120-deg/sec) of stimulation. Mean AP gain values were consistently higher than mean AF values with the greatest difference occurring at low frequencies of stimulation. Saturation nonlinearities were present with AF stimulation at high amplitudes. These findings can be explained by dynamic asymmetries at the level of the primary and secondary vestibular neurons.

Loss of auditory function was correlated with different pathological findings in the inner ear of the rabbit after 15 or 30 min exposure to high level broad band (2-7 kHz) noise. The ears from animals with post-exposure times ranging from 1 to 23 months were analysed by scanning electron microscopy (SEM). Complete cochleograms with quantification of loss of hair cells and damage to stereocilia were produced. Loss of function was defined by determining behavioural threshold, threshold of auditory brainstem response (ABR) to narrow-band stimuli and threshold of the middle ear muscle reflex (MER). A small scattered loss of OHCs and slight disarray of stereocilia were found in non-exposed ears of young animals, but fusion of IHC cilia was not observed. Normal auditory function was not found in any noise exposed animal with abnormal morphology. A loss of threshold sensitivity of up to about 30-40 dB was noted without loss of hair cells in the corresponding region of the cochlea. The mildest structural damage that correlated to a functional alteration consisted of damage to stereocilia of IHC. This correlated well to the MER threshold shift. In two animals a shift of MER threshold of about 20 dB was the only functional abnormality. In ears with more extensive IHC damage loss of OHCs was also found and these animals had primarily an increase in auditory threshold shift with only a small additional change in MER threshold. It is concluded that in the rabbit and with the methods used the IHC stereocilia are the structures most susceptible to damage by the noise used and that the degree of injury can be fairly well assessed by functional tests of a type that is used also routinely in the audiological clinic.

This study was performed on a material of 70 patients, who fulfilled the criteria of definitive MS. All the patients were examined by an otologist, a neurologist and a neuro-ophthalmologist. A wide range of audiologic and otoneurologic tests were used to obtain a good understanding of the respective disorders in MS, to gain a better knowledge of the role of otology in MS, to correlate the results with the clinical findings in order to find the most useful tests to detect MS lesions and to describe pathophysiologic aspects of central lesions using MS as a model. The material consisted of MS cases representing mild or moderate stages of disability (Hyllested classification 1.-4); 32 belonged to Hyllested group 1., 19 to group 2., 7 to group 3. and 12 to group 4. The age and sex distribution were similar with materials described earlier, as were most of the clinical neurologic findings. The material can thus be considered representative. The neuro-ophthalmologic examination served to rule out causes other than MS for abnormalities observed in the tests. Besides the clinical neurologic and otoneurologic evaluation a number of additional tests were performed. The ENG tests consisted of registration for spontaneous and positional nystagmus, of smooth pursuit and saccadic eye movements, optokinetic nystagmus and caloric reactions. The audiologic evaluation was based on the following tests: pure tone audiograms, speech reception thresholds, discrimination scores, filtered speech test, stapedius reflex thresholds, stapedius reflex decay and auditory brainstem responses. The clinical otologic examination revealed little abnormalities, which is well in accordance with the pathophysiology of MS. In addition the clinical examination ruled out peripheral lesions as reasons for observed abnormalities. Numerous abnormalities were found during the otoneurologic examination of the cranial nerves. The amount of abnormal findings in the otoneurologic examination were surprisingly high: only one patient exhibited normal results in all the tests used. The abnormalities most often encountered were those of smooth pursuit (96%), followed by saccadic eye movements (76%), optokinetic nystagmus (53 %), and abnormalities in the caloric reactions such as dysrhythmia (40%) and defective visual suppression of the nystagmus (43%). When comparing the results obtained with ENG with those of clinical findings seen during the neuro-ophthalmologic examination, a good intercorrelation was found. Yet, in many ENG tests a number of cases with subclinical abnormalities only, were observed, which stresses the importance of exact and objective methods for the registration of eye movements.(ABSTRACT TRUNCATED AT 400 WORDS)

During recent decades, vestibular research has emphasized that it is important to consider vestibular reflexes a part of the integrated balance system function. Vestibular diagnosis must be based on a system approach to vestibular dysfunction. The development of new balance system examination methods is based on computerization of the analysis of transfer functions. Using these methods, system dysfunction is more easily understood and a new universe of vestibular diagnosis might develop in the years to come.

The forward-backward and right-left sways in the upright standing posture were examined using stabilometry and analysis with a 5-dimensional feedback model. The forward-backward sway was found to have a fast, hidden periodicity, composed of sways due to a loss of the labyrinthine righting reflex upon the head and interaction between the head and knee sways. Furthermore, on the basis of our previous investigation, the forward-backward sway was found to depend on the increased spinal reflexes caused by a loss of labyrinthine inhibitory control upon the antigravity muscles. The right-left sway is slow and irregular, being mainly produced by disturbance of the head righting reflex.

A broad frequency-band rotatory test has been used to quantify compensatory eye movements in 13 healthy subjects during light and darkness conditions. Eye movements were recorded by EOG. Head movements were recorded either by a potentiometer attached to the chair's axis of rotation or by an angular rate sensory attached to a bite-board. Gain and phase values between eye and head velocity were calculated. A systematic error in the higher frequency range is introduced in the results by assuming head movement equal to chair movement. Different instructions in the dark can alter the gain values at lower frequencies (up to 2 Hz) during sinusoidal stimulation. During pseudorandom stimulation no such differences can be obtained. During all test conditions with the rate sensor the gain values approach unity at about 3 Hz.

In order to clarify the peculiarities of gait disturbances appearing in patients with labyrinthine and cerebellar disturbances, the upward-downward (U-D), right-left (R-L) and forward-backward (F-B) movements of the head and activities of both soleus muscles were recorded by a polygraph and a data recorder with the aid of a five-channel telemeter. The power spectrum and correlation analyses were carried out with a PDP-11 computer. The following are results obtained from walking with the eyes closed. (1) On normal subjects, the power spectrum of U-D head movement indicated a rise at about 2 Hz. The autocorrelograms of U-D, R-L head movements and soleus muscle activities showed a chopping or sine wave process with an attenuation of amplitude. A cross correlogram revealed that when the head was inclined to the right side, the contralateral soleus muscle was active and when the head was inclined forward, one of the soleus muscles was active. (2) A patient with bilateral loss of labyrinthine function showed an increased R-L head sway and irregularly undulating F-B head movement, indicating disturbances of the labyrinthine righting and linear movement reflexes. (3) A patient with cerebellar atrophy indicated irregular U-D, R-L and F-B head movements. The soleus muscle activity changed irregularly.