Utricular sensitivity and preponderance assessed by the unilateral centrifugation test

Utricular sensitivity and preponderance of the right or left utricle can be assessed by means of the unilateral centrifugation test. In this test, subjects are rotated about an earth vertical axis at a velocity of 400 degrees per second. During the ongoing rotation, the subject is gradually translated 4 cm first to the right, and then to the left, along an interaural axis, to a position at which one utricle becomes aligned with the axis of rotation, and at this point is subjected only to gravitational forces. At this eccentric position, the contralateral utricle is exposed to the combination of gravity and a centrifugal acceleration of 0.4g, corresponding to an apparent roll-tilt of 21.7 degrees. This stimulus induces ocular counterrolling (OCR), which is measured on-line using three-dimensional video-oculography (VOG). We observed that ocular counterrolling appears as a linear function of the gravito-inertial acceleration tilt of the head centre (GIA(HC)) during the lateral translation. We present a theoretical model for this linear relationship that contains two parameters: 1) the slope of the linear regression is a measure for the utricular sensitivity and 2) the intercept of the linear regression is a measure of the preponderance of the right or left utricle. The strength of the model is supported by data obtained from 28 healthy subjects and 14 patients with unilateral vestibular deafferentiation (UVD) due to acoustic neuroma surgery.

Head and body center of gravity control strategies: adaptations following vestibular rehabilitation

OBJECTIVE

We present for the first time evidence that vestibulopathy impairs coordination of the head with the body center of gravity (CG) during free speed gait over ground. Vestibulopathic individuals demonstrate uncoordinated movement and gait due, at least in part, to impaired head stability and visual fixation. Vestibular rehabilitation increases speed and stability during gait and stair climbing, although the underlying mechanisms are poorly understood.

MATERIAL AND METHODS

To determine whether these locomotor improvements are due to reorganized coordination of the head with whole body CG, three-dimensional kinematics were obtained from 10 vestibulopathic individuals before and after vestibular rehabilitation and from 10 matched healthy control subjects during unconstrained, paced and in-place gait. Head control patterns were characterized using both qualitative pattern analysis and quantification of coherence between head and body CG displacements.

RESULTS

Patterns of head-CG coordination differ between normal and vestibulopathic individuals in all three directions of head rotation--pitch, roll and yaw--before rehabilitation. Following vestibular rehabilitation, subjects with vestibulopathy demonstrate more normal patterns in pitch and improvements toward normal in roll and yaw.

CONCLUSION

These data strongly suggest that compensatory mechanisms, obtained during vestibular rehabilitation, mediate head-CG coordination.

Eye movement responses to active, high-frequency pitch and yaw head rotations in subjects with unilateral vestibular loss or posterior semicircular canal occlusion

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.

Otolith-ocular responses in patients with surgically confirmed unilateral peripheral vestibular loss

The chronic effects of unilateral peripheral vestibular loss (UPVL) are influenced by vestibular compensation. This study documents the balance-related symptoms and quantitative vestibular laboratory testing of 20 patients with surgically confirmed UPVL. Included are measures of the semicircular canal-ocular reflex, the otolith-ocular reflex, and both static and dynamic semicircular canal-otolith-interaction. This study differs from previous studies of patients with UPVL in that a large number of patients with surgically confirmed lesions were tested with three types of off-vertical axis rotation, several of the patients had anatomically preserved superior vestibular nerves, and self-perceived level of disability related to dizziness and imbalance were available. Results confirmed previously reported changes in the vestibulo-ocular reflex of patients with UPVL. Also, there was no apparent effect of anatomically preserving the superior vestibular nerve during surgical resection of vestibular schwannomas based on either subjective or objective measures of vestibular dysfunction. Further, there were no apparent correlations between subjective measures of dizziness and imbalance and objective measures of vestibulo-ocular function. These results have clinical implications for the management of patients with unilateral vestibular loss and provide insights into the process of vestibular compensation especially with respect to the otolith-ocular reflex.

Effects of occupational exposure to a mixture of solvents on the inner ear: a field study

Some clinical and laboratory studies indicate that industrial solvents such as toluene, styrene, xylene, trichloroethylene and carbon disulfide or their mixtures may affect the inner ear, although the mechanism of this process is still not well understood. The aim of this investigation was to assess the incidence of hearing and vestibular disorders (using modem audiological and vestibular tests) in 61 workers exposed to a mixture of organic solvents at the production of paints and varnishes; the control group included 40 age-matched non-exposed subjects. Environmental and biological monitoring revealed that the most significant exposure can be attributed to the following mixture constituents: ethylbenzene, xylene and trimethylbenzene isomers such as pseudocumene, mesitylene and hemimellitene. Electronystagmographic examinations showed the symptoms of vestibular dysfunction, as well as the decreased duration, amplitude and slow phase angular velocity of induced nystagmus in 47.5% of the subjects exposed versus 5% of controls. This was accompanied by sensorineural high frequency hearing loss, identified by means of pure tone audiometry in 42% of those exposed versus 5% controls, and reduced amplitudes of transiently evoked and distortion-product otoacoustic emissions. The findings closely correspond with the rate of the total exposure to the solvent mixture. A possible mechanism responsible for ototoxicity of solvents is discussed.

[The influence of metabolic disturbances present in diabetes mellitus type I on vestibulo-spinal reflexes in children and young adults]

Diabetic neuropathy encompasses various disturbances concerning somatic and autonomic nervous system and has significant impact on prognosis and course of diabetes mellitus. The aim of the work is an evaluation of vestibulo-spinal reflexes in children and young adults suffering from diabetes mellitus type 1. Material--95 children and young adults aged from 6 to 28 years with diabetes mellitus type 1 diagnosed. The control group consisted of 44 otoneurologically healthy subjects aged from 6 to 28 years. After detailed medical history collection and physical ENT examination stato-posturography was performed in each case. Posturographer PE 62 Model 04 was applied in the studies. Static posturography as well as dynamic one (one leg standing test) was performed in each case. 6 patients belonging to diabetic group complained about vertigo or dizziness. There were worse stabilograms parameters in diabetic group in comparison to control one, statistically significant in younger children. There were better stabilogram parameters in diabetic patients with longer history of the disease. The parameters analysed were significantly worse in the subgroup with not compensated diabetes. The parameters were slightly better in relation to the presence of hypoglycaemic incidents. No apparent differences in stabilograms parameters were present in relation to the presence of diabetic complications. Diabetes mellitus type 1 with slight or without complications does not have significant influence on vestibulo-spinal reflexes and posture stability of the patients. Balance organ disturbances in diabetes mellitus type 1 in children and young adults despite their presence have subclinical course. Perhaps one should consider monitoring of those disturbances in the course of the disease.

Podokinetic after-rotation in patients with compensated unilateral vestibular ablation

Previous studies showed that after stepping-in-place on a rotating turntable, blindfolded subjects cannot step-in-place on firm ground. Instead they involuntarily turn themselves relative to space in the same direction as they were turning relative to the rotating turntable. This phenomenon has been termed podokinetic after-rotation (PKAR). PKAR comprises a brief exponentially rising phase of response during the first 2 min followed by a prolonged second phase of slow exponential decline during the next 28 min. Here we ask whether PKAR is modified in patients with compensated unilateral vestibular loss. Eleven patients who had previous vestibular ablation underwent (1) a Fukuda-like control stepping test, (2) podokinetic adaptation to 30 min of stepping in place on the centre of a turntable rotating at 45 deg/s and (3) PKAR. Control tests showed that the blindfolded patients had no significant rotational bias while stepping-in-place on the ground for 1 min. After 30 min of adaptation, the 2-min rising phase of PKAR was indistinguishable from normal. In contrast, the subsequent 28-min phase of exponential decline showed a lesion-dependent asymmetry. PKAR had significantly higher mean velocities toward the side of the lesion than away from the lesion. The observed PKAR asymmetry may signify occult residual static vestibular imbalance.

Motion sickness and vestibular hypersensitivity

OBJECTIVE

Motion sickness is poorly understood, although it has been recognized for years as debilitating. Vestibular function is required for motion sickness to occur, but motion sickness can also be brought on without body motion. The aim of this study was to see if there was a correlation between caloric response and motion sickness susceptibility.

DESIGN

One experiment was a prospective study carried out on 200 patients. A second prospective study was carried out on 121 patients.

SETTING

Patients referred to our tertiary/quaternary care dizziness clinic.

METHODS

In experiment 1, caloric scores in patients were correlated with symptoms of motion sickness as established by responses to a simple question. In experiment 2, caloric scores were correlated with symptomatic responses to caloric testing itself.

MAIN OUTCOME MEASURES

Caloric responses of the best ear were measured according to standardized caloric evaluation methods.

RESULTS

There was no correlation between motion sickness and caloric scores. There was a significant difference in caloric scores between patients made symptomatic by calorics and those who were not.

CONCLUSIONS

The autonomic response seen in some patients is not triggered by a specific level of semicircular canal response (as measured by caloric testing). We hypothesize that (similar to space motion sickness) the trigger is a signal differential that arises between semicircular canals and otoliths and that some patients are unable to suppress this response. These patients often suffer motion sickness on a long-term basis.

Both actual and imagined locomotion suppress spontaneous vestibular nystagmus

Acute unilateral vestibulopathy is characterized by a combination of signs and symptoms including spontaneous nystagmus, postural imbalance and gait disturbance. A functional link between these vestibulo-ocular and vestibulo-spinal motor responses has been demonstrated. These responses use common vestibular input and partially overlapping neuronal networks, but it is not known if and to what extent they are linked or operate separately. We found that slow phase velocity of spontaneous vestibular nystagmus in patients with acute vestibulopathy was suppressed by 26% during actual walking (ANOVA p< 0.02, = 6). It was also suppressed by imagined locomotion: by 26% during the imagination of walking and by 42% during the imagination of running ( p< 0.003, = 10). The suppression of vestibular nystagmus might be beneficial for patients, for it alleviates the disturbing impression of movement of the visual scene (oscillopsia) caused by involuntary eye movements.

Oculo-auricular phenomenon secondary to vestibular dysfunction

The oculo-auricular phenomenon consists of coactivation of the ocular rectus lateralis and the posterior muscles of both ears (transverse auriculae and obliquus auriculae muscles). This coactivation produces a bilateral curling of auricles during extreme lateral gaze that can be observed in as much as an 80% of the normal population. We herein describe a 26-year-old man who presented a transient oculo-auricular phenomenon in the course of a vestibular vertigo.

Base of support is not wider in chronic ataxic and unsteady patients

"Wide-based gait" is considered indicative of imbalance. No quantitative gait analyses, however, have related base of support to steadiness during gait. To determine whether patients with cerebellar or vestibular disorders had a wider base of support than matched healthy individuals, we analyzed 102 balance-impaired patients and healthy subjects during free and paced gait. Kinematic data were collected using a high-precision optoelectronic system. There were no significant differences in the base of support between unsteady and healthy subjects, nor between patients with vestibular and cerebellar diagnoses. The base of support correlated with the body mass index and waist circumference in all subject groups. These data suggest that base of support during gait fails to identify balance-impaired subjects and is related more to biomechanical than to neurological factors. Therefore, "wide-based gait" should no longer be considered the sine qua non of ataxic or unsteady gait. Clinicians should not focus on decreasing base of support as a therapeutic goal for chronic, unsteady patients.

Dynamic and static subjective visual vertical with aging

OBJECTIVE

Our vestibular function is gradually deteriorating during aging, although, its behavioral consequences are not easily recognized due to a substitution process by other sensory modalities as visual or proprioceptive inputs.

METHODS

To reveal such a hidden substitution process by visual signals, the measurement of the static as well as the dynamic subjective visual vertical (SVV) was performed among 63 healthy subjects of different age.

RESULTS

The static SVV was found to be stable among all subjects, whereas the shift of the dynamic SVV during rotation of a background scene gradually increased with age.

CONCLUSION

This result indicates that the substitution process identified as a function of age in a perceptual test may have its counterpart in postural stabilizing reflex.

The effect of age on vestibular rehabilitation outcomes

OBJECTIVE

The purpose of the retrospective chart review was to compare vestibular rehabilitation outcomes in young versus older adults.

STUDY DESIGN

Retrospective matched design.

METHODS

Twenty-three persons with vestibular disorders aged 20 to 40 years were matched by gender, vestibular diagnosis, and vestibular function test results to 23 older adults aged 60 to 80 years. The patients were treated with a custom-designed physical therapy exercise program. Patients completed the Dizziness Handicap Inventory, the Activities-Specific Balance Confidence (ABC) scale, and the Dynamic Gait Index; number of falls; and rated the severity of their dizziness. The two-sample test, the Mann-Whitney test, and McNemar's test for correlated proportions were used to determine whether there was a difference in scores between the two age groups at the beginning and end of physical therapy.

RESULTS

During the initial evaluation, older adults reported having statistically greater space and motion discomfort and more severe symptoms on a scale of 0 to 100. Younger adults had more impaired DGI scores and a higher proportion of caloric testing abnormalities. After rehabilitation, overall improvement was seen in both the younger and older populations. There were no statistical differences between the two groups on the DHI, the DGI, reported symptoms at discharge, or number of falls. When only the complete matched-pair data were analyzed, there were no statistically significant differences between the age groups in the proportion of patients demonstrating clinical improvement.

CONCLUSION

Age does not significantly influence the beneficial effects of vestibular rehabilitation for persons with vestibular disorders.

Migraine and isolated recurrent vertigo of unknown cause

Chronic recurrent attacks of vertigo, not associated with any auditory or neurological symptoms, are a common reason for referral to our neurotology clinic. Even after an extensive neurotological evaluation, some cases remain undiagnosed. We prospectively evaluated 72 consecutive patients who presented to the clinic with isolated recurrent vertigo of unknown cause. All patients underwent diagnostic evaluation to exclude identifiable causes of isolated recurrent vertigo. We compared the prevalence of migraine, according to the International Headache Society (IHS) criteria, in the isolated recurrent vertigo group, with a sex- and age-matched control group of orthopedic patients. The prevalence of migraine according to IHS criteria was higher in the isolated recurrent vertigo group (61.1%) than in the control group (10%; p < 0.01). Only 16.7% of patients had an abnormal vestibular function test. The most common abnormal finding was a unilateral vestibular weakness to caloric stimulation. Our results suggest that migraine should be considered in the differential diagnosis of isolated recurrent vertigo of unknown cause.

The test and treatment methods of benign paroxysmal positional vertigo and an addition to the management of vertigo due to the superior vestibular canal (BPPV-SC)

A review of the tests and treatment manoeuvres for benign paroxysmal positional vertigo of the posterior, horizontal and superior vestibular canals is presented. Additionally, a new way to test and treat positional vertigo of the superior vestibular canal is presented. In a prospective study, 57 out of 305 patients' visits are reported. They had residual symptoms and dizziness after the test and the treatment of benign paroxysmal positional vertigo of the horizontal canal (BPPV-HC) and posterior canal (PC). They were tested with a new test and treated with a new manoeuvre for superior canal benign paroxysmal positional vertigo (BPPV-SC). Results for vertigo in 53 patients were good; motion sickness and acrophobia disappeared. Reactive neck tension to BPPV was relieved. Older people were numerous among patients and their quality of life (QOL) improved.

[Bilateral vestibular areflexia: quantification is required]

Bilateral vestibular loss, that should be more precisely qualified as "horizontal semicircular canal bilateral loss", is a concept usually defined by the following characteristics: - no response to caloric tests, - no response to pendular test with a 20-second period, - increasing gain of the cervico-ocular reflex. We present five cases. We increased the stimulation frequency to a level higher than usually, employed and observed that: - at a given frequency threshold a certain amount of reactivity may be observed, - above that threshold the reactivity increases in proportion with stimulation frequency. The apparent vestibular loss is actually related to stimulation frequency. This phenomenon could be explained by considering the physiology of phasic and tonic cells.

[Central vestibular syndromes]

The aim of this topic is on one hand to pick out the semiological features which can quickly show the way of central nervous system lesions related to the vestibular system and on the other hand to describe these main central vestibular syndromes. A particular attention is carried to central otolithics syndromes which often remain undiagnosed. They induce imbalance, non rotatory vertigo, intolerance to linear acceleration and most often there is no nystagmus on examination. Neurophysiological diagram are restricted to a minimum useful to the clinician.