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At least 1,009 records · Page 56Linked to original sources
PubMed1980

Isolated intralabyrinthine schwannoma.

Although most vestibular schwannomas arise in the internal auditory canal, a more peripheral site of origin is possible. We report a case of isolated schwannoma limited to the labyrinthine vestibule. Our description of the location of this tumor is further documentation that schwannomas can arise from the terminal vestibular nerve fibers to the cristae or maculae. Either the nerve roots of the superior vestibular nerve to the utricle and horizontal and superior semicircular canal cristae, or the nerve roots of the inferior vestibular nerve to the saccule and posterior semicircular canal crista may have been the locus of origin of this unusual tumor. Intralabyrinthine schwannoma should be included in the differential diagnosis in the face of progressive auditory and vestibular dysfunction. Because conventional roentgenographic studies usually fail to demonstrate the presence of schwannoma in this location surgical exploration of the labyrinthine vestibule in the presence of unserviceable hearing and incapacitating vertigo is indicated.

Diagnosis, Differential↗
PubMedDate not supplied

[Model of the formation of nystagmic reactions to a set of caloric tests].

The model can furnish additional information about the vestibulary system, when evaluating caloric tests. The model has been built with certain assumptions being made. The nystagmus intensity (the slow component rate during maximum intensity) is assumed to be proportional to the difference between energy levels (EL) of the right and left vestibular nuclear complexes (NC). El of each NC is equal to the afferent flow (AF) plus its inherent activity (IA). During caloric (two warm and two cold) tests IA remains constant. AF at rest is equal to spontaneous activity of receptors and during stimulation it increases or decreases in a linear fashion. Parameters of the model are: difference between intensities of reactions to warm and cold tests, difference between EL of two (right and left) unstimulated NC, and ratio of nystagmus intensity to the stimulus for each labyrinth. The behavior of the model during vestibular dysfunctions of various origin (changes in one of AF characteristics or changes in IA of one NC) is discussed. The diagnostic application of the model is illustrated by the discussion of nystagmometric data. The conclusion about vestibular dysfunction and its etiology can be made on the basis of statistic analysis of parameters of the model in the norm.

Caloric Tests↗
PubMed1981

Congenital labyrintho-tympanic fistula -- a recently recognized entity in children.

A case of congenital labyrintho-tympanic fistula is reported. The possible anatomical pathways and main clinical characteristics are discussed together with a review of the literature. Special emphasis is made for early recognition in children, of this entity without invasive forms of investigation, and the proper surgical approach via tympanotomy is described.

Child, Preschool↗
PubMed1985

[Dynamics of neurologic disorders in epileptics].

On the basis of the dynamic study of the neurological and otoneurological picture of epilepsy in 105 patients, the authors ascertained a definite complex of symptoms depending on the stage of the disease. Most frequently observed were symptoms of the involvement of the truncal-subcortical systems, which reflected the stage of the progression of the epileptic process associated with a sharp increase in the frequency (up to the daily pattern) and rhythm of attacks, as well as psychic disturbances, with the structure of paroxysms becoming more complicated and polymorphic. The pathological symptoms from the level of the brain stem, primarily vegetative and vestibular ones, regress considerably or are absent altogether against the background of a relatively favourable period of the disease (rare, single and homotypical attacks, mild psychic changes). The above neurological and otoneurological features are important not only for determining the localization of the pathological process but also for the clinical prognosis of epilepsy.

Adolescent↗
PubMed1987

Evaluation of optokinetic nystagmus in differentiating between peripheral vestibular and infratentorial lesions.

Optokinetic nystagmus (OKN) was studied in ten patients with vestibular neuritis, and in seventeen patients with unilateral and thirteen patients with bilateral infratentorial lesions and compared with OKN in fifty healthy subjects. Mean and maximum slow phase velocity of OKN was calculated as well as the asymmetry of responses. The efficiency of the different variables in OKN, in discriminating between different lesion sites, was tested in a linear discriminant function analysis. Slow phase velocity of OKN could satisfactorily separate patients with infratentorial lesions from healthy subjects or subjects with vestibular neuritis. Asymmetry of OKN did not contribute further to the correct diagnosis.

Adolescent↗
PubMed1976

Galvanic vesitbular test.

Galvanic stimulation of the vestibular system provokes a nystagmus as well as a tendency to fall. The direction of these phenomena depends on the localization of the anode. In this study the value of the minimal current strength (threshold), which is able to provoke nystagmus with a constant frequency during at least 30 sec was determined. Also the effects of the lesions in the vestibular system on these threshold values were measured. The method of bipolar-biaruricular stimulation showed to be the most sensitive one. A striking difference was found in the thresholds in rabbits with a vestibular organ with a lesion on that side. In that case the threshold for a nystagmus directed to the side with the intact ear was at its lowest. The conclusion is drawn that the galvanic vestibular test is suitable for the detection of the localization of a vestibular lesion in patients, especially when this lesion is located in the peripheral vestibular organ.

Animals↗
PubMed1980

Interaction of vestibular and optokinetic nystagmus in patients with peripheral vestibular and central nervous disorders.

In 66 patients showing different lesions of the vestibular and central nervous system, the influences of spontaneous and experimentally (rotation) induced vestibular nystagmus on optokinetic nystagmus were investigated. Considering the large interindividual differences in the results of vestibulo-visual interaction, the actual values of nystagmus slow phase velocity obtained by means of a combined vestibular and visual stimulation are only of limited diagnostic value in a single case. But by averaging the results obtained from various nosologic groups of patients very different but distinct patterns of vestibulo-visual interaction can be demonstrated. This observation allows some speculation on the mechanism of how nystagmus might be generated as a common output of the vestibular and the visual system.

Brain Diseases↗
PubMed1984

Alexander's law: its behavior and origin in the human vestibulo-ocular reflex.

Alexander's law refers to the phenomenon in which the spontaneous nystagmus of a patient with a vestibular lesion is more intense when the patient looks in the quick-phase than in the slow-phase direction. Alexander's law was investigated in normal subjects as well as patients with vestibular lesions. During sinusoidal rotations of normal subjects, there was no trace of this phenomenon when subjects looked 25 degrees left and right in the dark. The phenomenon of Alexander's law is therefore created centrally and is not due to any mechanical properties of the orbit. During rotation at constant velocity in the dark, normal subjects did weakly demonstrate Alexander's law because of a mild gaze-evoked nystagmus present in normal subjects in the dark. Gaze-evoked nystagmus from a cerebellar lesion involved a pronounced demonstration of Alexander's law during rotatory nystagmus. In patients with a vestibular lesion and a mild spontaneous nystagmus in the dark that obeyed Alexander's law, the nystagmus reversed upon far gaze in the slow-phase direction. We propose that in patients with a vestibular lesion, the phenomenon of Alexander's law is created by the sum of vestibular nystagmus and an abnormally large gaze-evoked nystagmus that is consequent to the vestibular lesion. This conclusion has a number of neurological implications concerning the ways in which the nervous system attempts to compensate for vestibular lesions.

Adult↗
PubMedDate not supplied

Clinical evaluation of dysrhythmia of postrotatory nystagmus.

Postrotatory responses of nystagmus were analysed in an exponential model by utilizing linear regression analysis. Four nystagmus qualities (velocity and duration of slow and fast phases) were studied in 10 patients with vestibular peripheral lesions, 10 patients with frontal lobe lesions and 10 patients with brain-stem lesions, together with 10 control subjects. In addition, pauses during the responses were quantified. Patients with frontal lobe lesions differed from other groups by scoring higher values of slow phase velocity and by exhibiting more pauses. The time constant was significantly shorter in patients with brain-stem lesion than in any other group. As regards other qualities, e.g. slow phase duration and fast phase velocity, or duration, no differences were observed. The pathological dysrhythmia may therefore be presented as changes in the gain and time constant of slow phase velocity as well as in pauses during nystagmus. Since all these changes may be encountered in normal subjects, one should be cautious in interpreting these changes as being pathological in each individual case.

Adult↗