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PubMed1978

Criteria for the evaluation of nystagmus.

Suitable criteria are reported for the analysis and evaluation of the caloric nystagmus as well as for the differentiation of the pathological from the physiological spontaneous nystagmus. Relative values for the difference and the directional preponderance, related to the intensity of the total reaction, seem to be the most appropriate criteria for the evaluation of the caloric test. The values obtained in patients should be compared with interquantile areas of healthy subjects. The parameters 'maximum slow phase velocity' and 'maximum frequency' seem most suitable for the assessment of the reaction intensity in the ENG. At present, the examination with Frenzel's glasses represents the best possibility for differentiation between physiological and pathological spontaneous nystagmus.

Adolescent↗
PubMed1975

Vestibulo-ocular function in patients with cerebellar atrophy.

Eye movement abnormalities were quantiatively assessed in four patients with clinically pure cerebellar atrophy (group A), six patients with brainstem plus cerebellar atrophy (group B), and five patients with Friedreich's ataxia (group C). Twelve patients had one or more types of spontaneous nystagmus; eight gaze nystagmus, three rebound nystagmus, wo positional nystagmus, and one vestibular nystagmus. Catoric-induced and rotatory-induced nystagmus was hyperactive in group A and diminished in group C. Group B had mixed responses. All patients demonstrated significant fixation instability and impaired smooth pursuit. There was dysmetria of voluntary saccades, with flutter and "rebound" saccades. Nine of 15 patients had significant slowing of induced saccades, including two patients in group A. It is concluded that quantitative vestibulocular tests can be useful in classifying the cerebellar atrophy syndromes.

Cerebellar Ataxia↗
PubMed1975

Superior vestibular nerve sectioning. Experimental studies in squirrel monkeys.

Spontaneous, positional, and paroxysmal positional nystagmus were studied before and after sectioning the superior division of the vestibular nerve and the anterior vestibular artery in squirrel monkeys. Histopathologic study of the temporal bones confirmed the degeneration of the macula utriculi with release of statoconia, but failed to identify the released utricular statoconia within the vestibular endolymphatic space in any animal. Postoperatively the animals consistently demonstrated direction-fixed spontaneous nystagmus until the end of the experiment (five months). Positional tests and Dix-Hallpike maneuver occasionally changed the intensity of the spontaneous nystagmus, but never elicited paroxysmal positional nystagmus. Possible reasons for not demonstrating paroxysmal positional nystagmus in the squirrel monkey are as follows: a resorption of statoconia; slight morphological alteration of the sensory epithelia of the posterior cristae; interference of the posterior crista function due to partial collapse of the membranous ampulla; the existence of interspecies difference; or possibly a faulty hypothesis regarding the etiologic mechanism of benign paroxysmal positional vertigo.

Animals↗
PubMed1976

Clinically relevant physiology of the vestibulo-ocular reflex.

This review attempts to explain those aspects of the physiology of the vestibulo-ocular reflex (VOR) which could be of future clinical value. The literature cited has been selected for its didactic worth to readers with limited time, preferring concise reviews to detailed reports wherever possible. Physiological data provide the background for the following possible improvements in clinical diagnosis: 1) In gaze analysis, coordination of the VOR with other motor patterns can be analyzed. 2) Precision of vestibular tests can be improved by selecting stimuli within the range of natural movements.3) Resolution of the caloric test can be imporved when the change of temperature at the semicircular canal mimics endolymph pressure changes during natural movements. 4) A direct test of the three neuron VOR pathways is possible, but not practicable. 5) Integration of the input signal (transformation from head acceleration to eye position information) can be directly tested. 6) Plasticity (the adaptation to visual requirements) of the VOR can be examined. 7) It is possible to quantify vestibular damage and detect the side of lesion in one test analyzing gain and binocular symmetry of the vertical VOR.

Cerebellum↗
PubMedDate not supplied

[Study on the nature of tonic ocular movement produced during pendular vestibular stimulation (author's transl)].

During vestibular function tests using the pendulum chair, electronystagmography has repeatedly shown that a tonic ocular deviation precedes the change in nystagmus. This tonic movement may be anticipated in respect to the change in the sinusoidal movement of the chair. Greiner, Conraux, Collard and more recently J.B. Causse, have proposed a hypothesis based on the own periodicity of the vestibular system. J. Max explained this phenomenon in terms of a difference in phase with the electronic system. Our investigation suggests another explanation of this phenomenon. Each half-period consists of a acceleration phase and a decelaration phase. Thus within half-period alone there are two successive forms of nystagmus induced. The succession of half-periods gives the usual systagmus response. We consider that the tonic response of the eyes is not an anticipated one in respect to the change in sinusoidal movement of the chair, but rather a delayed one in respect to the reversal in the direction of acceleration.

Acceleration↗
PubMedDate not supplied

Implications of Ewald's second law for diagnosis of unilateral labyrinthine paralysis.

The feasibility of replacement of the caloric test with sinusoidal rotatory stimulations of differing frequencies was investigated in ten normal subjects and seven patients with unilateral labyrinthine paralysis. Testing was performed at frequencies ranging from 0.0125 to 0.2 Hz at 60 degrees/sec and at 0.05 Hz at peak velocities of 30 degrees/sec to 180 degrees/sec. Gain, phase, and asymmetry of the nystagmic responses were measured in these groups. Results indicated that the rotatory test was not reliable enough to be used as the sole measure for identifying patients with unilateral labyrinthine lesions.

Analog-Digital Conversion↗
PubMedDate not supplied

Computerized screening of the human vestibulospinal system.

The vestibular nerve projects rostrally via the ascending medial longitudinal fasiculus (MLF) to eventually supply the ocular muscles and also projects caudally via the descending MLF to eventually supply the spinal and limb musculature. Electronystagmographic techniques are designed to evaluate only portions of the vestibulo-ocular and oculomotor systems. Vestibular lesions affecting only the caudal vestibular nerve distributions or lesions affecting both neural distributions, therefore, cannot be objectively assessed except for the vestibulo-ocular component. A promising recording technique for the evaluation of the vestibulospinal system has been developed and tested in the Raymond E. Jordan Human Vestibular Systems Laboratory. A comparison of two data analysis techniques in normal subjects, unilateral vestibular lesion patients and patients with unilateral lesions of the cerebellar hemispheres have provided pilot data which indicate that the vestibulospinal stability test technique holds considerable promise for both research and clinical evaluation of the human vestibulospinal system.

Adult↗
PubMed1975

Studies on the integrative activity of the vestibular nuclei complex.

Central mechanisms currently used in clinical vestibular tests are far more complex than generally thought. The first synaptic station, the vestibular nuclei, represents a sensory-motor centre integrating vestibular impulses with proprioceptive afferents from muscles and joints. This convergence can be found on cells with long axons projecting to the oculo-motor system, to the spinal cord and to the thalamus as well as on cells without long projecting axons. There are also vestibulo-motor cells transmitting pure vestibular information.

Humans↗
PubMedDate not supplied

A new method for determining impulsive time constants and their application to clinical data.

We have developed an accurate, convenient method for determining unique values of vestibular time constants from impulsive tests. The method was used to determine the mean values and standard deviations of 36 normal subjects. A comparison between these normal values and data from patients with cerebellopontine (CP) angle tumors or unilateral peripheral vestibular lesions showed no significant difference in the values of the time constants. We conclude that shape-descriptive parameters such as time constants cannot differentiate between subjects and patients.

Adaptation, Physiological↗
PubMed1979

Vestibular unitary responses to visual stimulation in the rabbit.

Vestibular nucleus (VN) neurons, identified by sinusoidal rotation about the vertical axis, were tested for their response to moving visual field, and to electric stimulation on the optic chiasm (OX) and super colliculus (SC). Incremental responses during the rotation were inhibited by visual stimulus in cerebellectomized animals. Single-pulse stimulation applied to the OX was ineffective in producing a positive response in these neurons as well or in any other unit. Thus, such a visual pathway to VN must be located inside the brainstem and contains multi-synapses. Effects of repetitive stimulations (60 Hz) to OX and SC were more predominant in the cerebellectomized animal than in the intact animal. Cerebellar inhibitory control on visual-vestibular kinkage was suggested.

Animals↗
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↗
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↗
PubMed1975

Reversible hearing loss in tumours of the cerebello-pontine angle.

A survey of the literature concerning reversible hearing loss in tumours of the cerebello-pontine angle is presented together with two additional cases. After removal of one meningioma and one epidermoid tumour, respectively, the abolished acoustico-vestibular function returned in both cases. The pre-requisites for the restoration of hearing are discussed.

Adult↗
PubMed1975

Vestibular dysfunction in hereditary ataxia.

A kindred with a unique autosomal dominantly inherited ataxia of late onset is described. Manifestations of the condition include defective optokinetic nystagmus and absent or abnormal oculo-vestibular responses, in association with normal cochlear function. It is possible that these latter features may serve as "markers" to indicate the presence of the disease in presymptomatic young adults, thereby facilitating important genetic counseling.

Adolescent↗