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Biomedical subjects

M M Levashov

Publications and source records attributed to M M Levashov.

At least 19 recordsLinked to original sources
PubMed1998

[The phenomenon of the fixation suppression of caloric nystagmus in the diagnosis of vestibular disorders].

Fixation nystagmus suppression in caloric tests was used in examination of 56 patients suffering from chronic remittent labyrinthopathy, acute labyrinthopathy, vestibular neuronitis, otosclerosis, adhesive otitis media, vertebrobasilar insufficiency, motor disease, chronic remittent vestibulopathy and neurinoma of the VIII nerve. The bithermal test (BT) with electronystagmography was made to calculate the fixation suppression index (FSI). Complete suppression of the caloric nystagmus in at least one BT test appeared to be the most frequent variant of the response (24 cases). This was not dependent on the severity of the vestibular analyzer lesion. In 3 cases FSI of the caloric nystagmus was rather high (> 0.50). Introduction of the period of glance fixation in performance of all the 4 BT tests may serve an additional method in differential diagnosis of the vestibular disorders. The fixation test results should be compared to findings obtained in the other vestibulometric tests.

Acute Disease↗
PubMed1998

[Possibilities for computer-assisted analysis of nystagmography with optokinetic and caloric stimulation].

Examination of patients with dizziness has been performed with an original computer nystagmus analyzer which consists of an alternating current amplifier, analog-digital transformer, personal computer with special software. The technique of electronystagmography in optokinetic and bithermal tests was applied. The programs provide good quality of recording nystagmic reactions and protect from artefacts of different origin. All the nystagmic responses are measured with identification of the extremums indicating the beginning and end of each nystagmic cycle. The amplitude, duration and speed of the slow and fast nystagmic components are calculated both for the overall nystagmogram and its fragments. The computer analysis of nystagmograms provides rapid and accurate differential diagnosis of various types of vestibular dysfunction.

Caloric Tests↗
PubMed1977

[Participation of vertical semicircular canals in the vestibulo-oculomotor response to the horizontal rotation test].

The horizontal rotatory test was shown to elicit in rabbits a complex three-plane vestibular oculomotor response with rotatory nystagmus (RN) in sagittal plane. The leftward accelerating rotation caused the clockwise RN of the right eye; during decelerating rotation the RN was directed counterclockwise. Its frequency may differ from that of the horizontal nystagmus. The cupulo-endolymphatic displacements seem to occur not only in the horizontal canal, i.e. in the plane of rotation, but also in the vertical canals as a result of a hypothetical hydrodynamic interaction between the canals. The displacements in the anterior and the horizontal canals of the labyrinth were analogous, whereas that in the posterior canal was of the opposite direction. That suggests that the utriculofugal displacements in the horizontal and the anterior canals are accompanied by an utriculofugal displacement in the posterior canal, and vice versa.

Animals↗
PubMed1975

[The vertical and rotatory components of ocular nystagmus induced by rotation in a horizontal plane].

During rotation of the rabbit around a vertical axis, movements of the eye were recorded on film. The rotation test involved positive angular accelaration (10 grade. sec(-2)), two-minute rotation with constant angular speed (166 grade. sec(-1)), and negative angular acceleration (10 grade. sec(-2)). Two variants of rotation were used: in one of them the rotation axis passed between labyrinths, in another - an excentricitet providing centrifugal force of 0.5 g was present. The successive processing of the film revealed simultaneous movements of the eye in three planes: horizontal, frontal, and sagittal. The movements in all the planes consisted of rhythmic (hystagmal proper) and tonic components. The movements in sagittal and frontal planes were comparable with those in horizontal planes. A tonic otolith reflex occurred additionally at the excentric rotation. The complex form of the nystagmus is regarded as a result of hydromechanical interaction between semicircular canals.

Animals↗
PubMedDate not supplied

[Significance of comparing the results of caloric and vestibulometric rotation tests].

The use of modified, less laborious, easier endured vestibulometric tests made it possible to facilitate diagnosing Menière's disease and neurinomas of the vestibular nerve. Comparison of nystagmometric findings recorded in the same patient during caloric and rotation tests using the diagnostic model of a bithermal test permitted some assumptions to be made in relation to the mechanisms for nystagmogenesis associated with pathologic states in ear labyrinth and vestibular portion craniocerebral (VIII) nerve. It is found that in the majority of Meniere's disease cases (61%) there is a decrease in an intensity of caloric nystagmus induced by Lasix dehydration effect. This phenomenon can be explained by a reduced difference in energy levels of two complexes of vestibular nuclei and, therefore, by an attenuated afferents to peripheral compartment of vestibular system. In neurinoma of aural nerve, the phenomenon of vestibular recruitment (20%) was noted. The diagnostic model of a bithermal test makes it possible to explain an effect of smoothing out the nystagmic responses induced by an intensive stimulus when used a sinusoidal stepwise test. The observed vestibular recruitment results from the severe disorder of one of the afferent inputs due to destruction of induced by tumor pressure.

Adult↗