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Results for “VESTIBULAR FUNCTION TESTS”

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At least 433 records · Page 24Linked to original sources
PubMed1995

Peripheral generators of the vestibular evoked potentials in the cat.

OBJECTIVES: The contributions of each of the vertical semicircular canals (SCCs) and otoliths to the short-latency vestibular evoked potentials in response to angular acceleration impulses were studied in the cat. DESIGN: The experiments were conducted on unilateral labyrinthectomized cats. Vestibular activation was achieved by delivering angular acceleration impulses to the animal's head, held in the position presumed to be optimal for maximal stimulation of either the anterior or the posterior SCCs before and after obliteration of the SCC studied, and before and after obliteration of the other SCCs and ablation of the maculae. INTERVENTIONS: Unilateral labyrinthectomy, obliteration of the SCCs, and ablation of the otoliths and section of the commissural vestibular fibers in the brain stem with histologic confirmation were carried out in the experiments. RESULTS: Following selective obliteration of either the anterior or the posterior SCC of the remaining ear and stimulation in the presumed optimal plane of the obliterated canal, the early prominent waves (P1 and P2) disappeared, leaving only much smaller-amplitude waves. These were severely depressed after ablation of the maculae. On the other hand, the vestibular evoked potentials in response to excitatory stimuli were not affected by obliteration of the other two SCCs and ablation of the maculae. CONCLUSION: These results indicate that when the head is stimulated in the optimal plane of each of the SCCs, the vestibular evoked potentials are generated mainly by the cristae ampullaris being stimulated, while the otoliths contribute smaller responses.

Animals↗
PubMed1985

Brain-stem dysfunction in autism. Results of vestibular stimulation.

Responses to vestibular stimulation can, under well-controlled experimental conditions, provide a measure of brain-stem function. Autistic children had significantly longer time constants during the primary nystagmus response and significantly fewer beats during the secondary response than normal children when stimulated with constant angular acceleration in complete darkness. These findings could not be attributed to gross differences in arousal, to developmental retardation, to associated clinical conditions, or to either the influence of vision or habituation. Rather, they are suggestive of a neurophysiologic dysfunction, perhaps involving the brain stem, and may be an expression of the process that underlies those autistic behaviors that suggest faulty modulation of sensory input and motor output. Brain-stem centers modulate both general sensory input and motor excitation and may play a role in the elaboration of the more complex adaptive and motivated behaviors that are also disturbed in autism.

Arousal↗
PubMed1980

Optokinetic nystagmus and parietal lobe lesions.

In an attempt to define better the mechanism of impaired optokinetic nystagmus (OKN) caused by parietal lobe lesions, we recorded the eye movements of two patients. One had a slowly enlarging parietal glioma, and the other, an infarction involving the parietal and occipital lobes. In both patients, ipsilateral foveal pursuit and full-field pursuit of a surrounding optokinetic drum were impaired while voluntary and involuntary saccades (fast components) were normal. Foveal pursuit was impaired more than full-field pursuit, suggesting the existence of two separate pathways by which visual signals for OKN slow phases reach the oculomotor centers in the brainstem. We conclude that the ipsilateral slow phase OKN deficit seen in our patients resulted from damage to the foveal pursuit pathway that runs from the occipitoparietal association area to the ipsilateral brainstem horizontal gaze center.

Adult↗
PubMed2004

Impaired modulation of the vestibulo-ocular reflex in Huntington's disease.

The vestibulo-ocular reflex (VOR) stabilizes gaze during movement, in conjunction with other afferent information: visual, proprioceptive, and somaesthetic. The reflex can either be augmented or suppressed, depending on visual requirements, and undergoes long-term adaptation to compensate for physical changes in the subject. Importantly, over relatively short periods of time, the VOR should function consistently under the same circumstances. This study examines VOR function in patients with Huntington's disease (HD), with a view to investigating cortical influences on the reflex. Horizontal eye movements were recorded in 9 patients with HD and 7 normal subjects, using the scleral search coil technique, in response to high frequency, unpredictable head rotations imposed manually. To establish base VOR function, recordings were made in darkness, without instruction, before and after wearing x2 magnifying lenses for a period of 2 hours to adapt the reflex. Recordings were also made before adaptation, while fixating a stationary visual target (VOR augmentation), and while fixating a target moving with the head (VOR suppression). Although results suggest that the VOR is preserved in HD, with relatively normal gain values and appropriate augmentation and suppression of the reflex with visual input, patients were unable to adapt the VOR to altered visual conditions. This represents a novel finding in HD and suggests that cortical structures compromised in HD exert influences on the long-term adaptation of the VOR.

Adult↗
PubMed1998

Test-retest reliability of the Fukuda Stepping Test.

BACKGROUND AND PURPOSE: Although the Fukuda Stepping Test (FST) is commonly used to assess individuals with peripheral vestibular dysfunction or balance instability, test-retest reliability has not been examined. METHODS: Sixteen males and 14 females, ranging in age from 23 to 56 years (mean 32.8 years), with no known vestibular dysfunction were tested. The subjects stood in the center of two concentric circles with eyes blindfolded. They stepped in place with outstretched arms for the prescribed number of steps. Subjects were tested on two consecutive days. Their angle of rotation, angle of displacement and distance of displacement were measured. RESULTS: Inter-class correlation coefficients were moderate for the 50-step protocol but lower for the 100-step protocol. CONCLUSIONS: If practitioners use the FST they should use the 50-step protocol. In addition, practitioners should interpret the results of the FST with caution if it is used as a screening tool. The test should be used in conjunction with other tests for vestibular function.

Adult↗
PubMed1979

A model of Alexander's law of vestibular nystagmus.

The observation that the amplitude of vestibular nystagmus grows as gaze is increased in the direction of the nystagmus fast phase and diminished with gaze in the opposite direction is known as "Alexander's law". We have developed an analog computer model to simulate Alexander's law in nystagmus secondary to dysfunction of a semicircular canal. The model utilizes relevant brainstem anatomy and physiology and includes gaze modulation of vestibular signals and push-pull integration to create eye position commands. When simulating normally functioning semicircular canals, the model produced no nystagmus. When simulating total impairment of the canal on one side with gaze directed maximally in the opposite direction, the model produced a large amplitude nystagmus with linear slow phases directed toward the affected side. As gaze was changed from far contralateral to ipsilateral, the nystagmus gradually diminished to zero. When simulating partial impairment of one canal, the nystagmus was smaller in amplitude and absent in ipsilateral gaze.

Brain Stem↗
PubMed1976

[The activity of motor units of the musculus splenius capitis in pheripheral vestibular lesions (author's transl)].

The activity of single motor units of the splenius-capitis muscle of healthy human subjects and patients with unilateral vestibular lesions was recorded by means of microelectrodes. The major part of these units reacted to vestibular stimulation in the same way as primary and secondary vestibular neurones of other vertebrates. The reactions of these units to trapezoidale stimuli is identical to that of vestibular neurones. An angular acceleration of more than 0.6 degrees/s2 is for these units a stimulus which is above threshold, this too corresponds to findings in the vestibular nerve. In patients with unilateral vestibular lesions the threshold for rotatory stimuli is markedly increased on the side of the lesion, whereas the threshold on the other side remains constant. This method is very sensitive and vestibular lesions can be detected which cannot be seen using the common technics for vestibular examination.

Action Potentials↗
PubMed1987

A scanning electron microscopic study of vestibular organ malformation following prenatal gamma irradiation.

Pregnant CBA/CBA mice were exposed to 1 and 2 Gy whole-body gamma irradiation on the 13th and 16th gestational days, respectively. The litters were born on the 21st day of gestation and were tested for vestibular function at the age of 1 month. The animals were then sacrificed and their inner ears were analyzed by scanning electron microscopy. No disturbances of vestibular function were noted in the animals studied. However, the cristae ampullares showed severe malformations as regards their gross shape, with irregularities of their outer contours. Type I hair cells seemed to be more severely changed than Type II hair cells, with fusion of sensory hairs, giant hair formation and bulging of the cuticular plate. In certain sites the hair cells were totally missing. These derangements were usually located in the central areas of the cristae ampullares and in the striolar portion of the maculae utriculi. The morphological damage found showed a dose-dependent, time-related pattern.

Abnormalities, Radiation-Induced↗
PubMed1979

[Function returning without and with recovery nystagmus after sudden unilateral isolated vestibular loss (author's transl)].

The restoration of peripher labyrinthine excitability after sudden unilateral isolated vestibular loss shows a different behaviour: It can happen with or without recovery nystagmus with a numerical nearly equal frequency. In a follow-up of 44 patients with unilateral vestibular loss of vascular genetics the objective and subjective characteristics of both states are described. In explanation of it a lesion of variable etiology in the region of the vestibular artery and a supposition of a not yet or already occured compensation of the disturbed tonus balance in the nuclear area are not sufficient. Rather the origin of the different clinical states of recovery phenomenon must be presumed in all probability as the result of a primary and secondary retrograde degeneration of the vestibular neurons. Thereby the distance of the lesion from the Scarpa ganglion is presumably of decisive importance.

Electronystagmography↗
PubMed1975

[Reactions of human neck muscle-fibers to vestibular stimulation (author's transl)].

In healthy human subjects activity from single fibers of the splenius-capitis muscle was recorded by means of a microelectrode. Two types of muscle fibers could be distinguished according to their reaction on vestibular stimulation. The first type reacted only to stimuli (angular acceleration) exceeding 10 degrees per sec2. These units showed no resting activity. The second type had a resting activity between 20 to 40 impulses per second. Their reactions under vestibular stimulation resembled that of primary afferent neurones of the vestibular nerve of other vertebrates. The functional meaning of these findings is discussed.

Animals↗
PubMed1991

X-linked deafness, stapes gushers and a distinctive defect of the inner ear.

The association of X-linked mixed deafness with stapes gusher has been recognized for 20 years, and imaging studies by polytomography have shown dilatation of the lateral end of the internal auditory meatus (IAM) in some cases. We have made genetic linkage studies in 7 pedigrees in whom deafness was inherited in an X-linked manner. All patients had a full range of audiometric and vestibular function tests. Thin section high resolution CT in two planes was used to assess the state of the middle and inner ears. We found a distinctive inner ear deformity in some of the deaf males characterised not only by a wide bulbous IAM but more importantly, by deficient or absent bone between the lateral end of the IAM and the basal turn of the cochlea. We believe that this results in a communication between the subarachnoid space in the IAM and the perilymph in the cochlea, leading to perilymphatic hydrops and a "gusher" if the stapes is disturbed. Moreover, some of the obligate female carriers seem to have a milder form of the same anomaly associated with slight hearing loss. Genetic studies on some of the deaf males with apparently normal inner ear anatomy suggest a different locus on the X chromosome and hence a different pathogenesis for the deafness.

Audiometry↗
PubMed1997

Static and dynamic posturography in prevalent laterally directed whiplash injuries.

Static and dynamic posturography was used to study patients who had experienced a prevalent laterally directed whiplash in a car accident. Results of both static and dynamic examinations were recorded. Findings showed that the whiplash injury had provoked shifting of the pressor center of the body toward a side that was at least indicative of the kind of cervical twist experienced, even when not corresponding to the prevalent direction of the trauma incurred.

Adult↗
PubMed1988

Otosurgical aspects in diagnostics and therapy of acoustic neurinomas.

136 acoustic neurinomas were operated upon by otosurgical transtemporal or translabyrinthine interventions. The otosurgical approach was used when a suboccipital craniectomy with a certain retraction of the cerebellum seemed to be avoidable. The pure otosurgical tumour removal was restricted to a tumour extension up to 2.5 cm starting from the fundus of the internal auditory meatus. The transtemporal route was used when hearing was worth saving and the translabyrinthine when the pure tone auditogram showed an average loss of 50 dB or the speech audiogram a discrimination loss of 50% or more. In larger tumours the neurosurgeon removed the intracranial part of the acoustic neurinome preserving the facial nerve and, if possible, the cochlear nerve as well. If parts of the tumour had remained within the internal auditory meatus or if some uncertainty concerning complete tumour removal persisted, an otosurgical second intervention was considered indicated. In 41 patients the cochlear nerve could be preserved at operation. 12 of these patients showed a preservation of their hearing.

Audiometry, Pure-Tone↗
PubMed2003

[Bilateral vestibular loss. Diagnosis and follow-up].

BACKGROUND: Atypical symptom in patients with bilateral vestibular loss is head movement-induced oscillopsia. The paucity of precise complaints in many patients is surprising. Therefore, bilateral loss of vestibular function is often undiagnosed. PATIENTS: We report on the long-term follow-up in 29 patients. They were monitored for 2-7 years (mean: 4.5 years). RESULTS: Of the 29 patients 16 described oscillopsia. All symptomatic patients had acute bilateral vestibular loss.Patients described that their symptoms improved over a period of 1-2 years. Improvement was not age dependent. CONCLUSIONS: Otoneurologists should be aware of the particular clinical symptoms in bilateral vestibular loss. Regarding clinical features, compensation of bilateral vestibular loss seems to be unlikely only based on central compensatory eye movement reflexes. More likely perceptual adaptations and restriction of head movement are responsible for subjective improvement.

Adult↗