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Biomedical subjects

M Toupet

Publications and source records attributed to M Toupet.

At least 37 records · Page 2Linked to original sources
PubMed1982

[How spontaneous nystagmus modifies nystagmus induced by caloric vestibular stimulation, studied in 34 patients with vestibular neuritis].

Spontaneous nystagmus modifies the degree of rotatory pendular and caloric vestibular nystagmic responses, provoking directional preponderance towards the same side. Until now, no true correlation has been able to be established between directional preponderance intensity and that of spontaneous nystagmus, correlation between these two parameters depending, in fact, on a third factor; vestibular reflectivity. Spontaneous nystagmus can apparently be defined as a directional preponderance inversely proportional in degree to vestibular reflectivity (the reflectivity of a vestibule being the sum of the hot and cold stimulation response indices). This phenomenon produces a thermal preponderance during the caloric test, and "vestibular recrutment" during the rotatory pendulum test. These findings are the result of 56 measurements conducted in 34 patients with vestibular neuritis. There was also a significant increase in vestibular reflectivity on the healthy side in these patients, suggesting both central and peripheral lesions. Because of the difficulty sometimes encountered when attempting to relaste the different concepts of overall vestibular responses, a new clinical unit of measure is proposed: the number of nystagmic jerks in 30 s. Hinchcliffe has previously employed this unit for the vestibular response, but it is now proposed for more general application to measurement of reflectivity, mean directional preponderance, unilateral directional preponderance, and mean thermal preponderance.

Caloric Tests↗
PubMed1982

[The functional investigation of vestibular balance and oculomotor function in 17 children with apparently congenital unilateral deafness and normal contralateral hearing].

Thorough study of vestibular and oculomotor function as well as radiological investigations were undertaken in 17 subjects with an apparently congenital unilateral cophosis. In 5 cases there was vetsibular hypovalence on the same side as the cophosis and bilateral impairment in 2 cases. No central abnormality was found. In one case tomograms showed atresia of the internal auditory meatus. The aetiopathogenesis of this labyrinthine involvement remains mysterious.

Adolescent↗
PubMed1981

[The diagnostic value of vertical nystagmus in the simultaneous bilateral calibrated caloric vestibular test (author's transl)].

Vertical nystagmus provoked by simultaneous bilateral caloric stimulation has been known since 1907 (Bàràny). However, if a controlled and calibrated injection os water at 44 degrees C or 30 degrees C for 30 seconds at a flow rate of 250 ml/minute is given in normal subjects, this stimulus is insufficient to provoke a response, whilst in subjects with a central vestibular disorder there appear upward vertical movements with hot stimulation and downward movements with cold stimulation. The degree of this response is proportional to the degree of horizontal nystagmic responses to classical unilateral caloric tests. The authors feel that vertical nystagmic responses to simultaneous bilateral caloric stimulation reflect a loss of control of the vestibular reflex activity of the superior semicircular canals.

Adult↗
PubMed1981

[Pseudocaloric nystagmus (author's transl)].

The effect of bithermal caloric tests on the velocity of spontaneous nystagmus was retrospectively studied in 107 patients with unilateral vestibular areflexia. In 35 out of 107 patients, the velocity or pre-test nystagmus was not lower than 15 jerks in 30 seconds. In our series, spontaneous nystagmus before the caloric test was mostly seen in patients with neuritis or sudden deafness, and as a rule, the tests had little effect on the velocity of the nystagmus. In 7 out of 10 cases of areflexic Mènière's disease spontaneous nystagmus was revealed by caloric tests. Spontaneous pre-test nystagmus was present in 6 out of 29 cases of neurinoma; its velocity was always reduced during the caloric tests. In 14 out of 25 cases of head injury, areflexia was usually compensated. Vestibular compensation can now be defined as the absence of vertigo, of spontaneous nystagmus before and after caloric tests and directional predominance.

Adult↗
PubMed1981

[Comparative values of unilateral and bilateral caloric bithermal vestibular tests in the diagnosis of acoustic neurinoma (author's transl)].

Acoustic neurinomas must be diagnosed as early as possible for the tumour to be removed while it is still small and the facial and, sometimes, auditory functions to be preserved. Since 89% of neurinomas lie on the vestibular nerve, enhancing the sensitivity of test exploring this nerve is important. Bilateral bithermal caloric stimulation is more sensitive (85%) than unilateral stimulation (71%) in detecting functional impairment. By comparing the two examinations in a series of 28 patients the authors have demonstrated that the test is more sensitive and reliable when bilateral and unilateral stimulation are practised successively. A study of correlations between these tests and the volume of the neurinoma showed that while functional impairment generally increases with the size of the tumour, it may vary from nil to 100% in small neurinomas. However, the sensitivity of the caloric test remains inferior to that of more sophisticated audiometric techniques, such as BERA-recording of stapedial reflex.

Adolescent↗
PubMed1981

[The perverted nystagmus (author's transl)].

The perverted nystagmus is a modification of the horizontal beating nystagmus (in classical caloric stimulation) by a vertical or rotatory mainly component. Experimentally, this disorder can be shown after an unilateral destroy of the superior or median vestibular nucleus. We show 32 cases of subjects with a perverted nystagmus. 75% of these subjects have a pure central disease and 20% a vestibular neuronitis. The perverted nystagmus had an upbeat component with the cold stimulation and downbeat component with the hot stimulation. It was accompanied by a spontaneous nystagmus in 66% (and 30% with vertical nystagmus). Some abnormal responses with the simultaneous bilateral vestibular caloric testing, were found in 95%. The analysis of the results of the unilateral caloric testing shown the frequent association: hyporeflectia (canal paresis) of one side and hyper-reflects of the other side. This fact would have evoked a mixed disease, peripheric and central (i.e. the vestibular neuronitis). Beside some pathogenic hypothesis, we prefer the fall of the inhibiting control of the superior semi-circular canal firing activity. Although, the perverted nystagmus is a simple and precious examination sign (it is directly shown with Frenzel glasses after caloric vestibular stimulation. It ought to do the brain stem topography diagnosis.

Adult↗
PubMed1979

[Rebound nystagmus: a new cerebellar sign (author's transl)].

Rebound nystagmus is a special type of nystagmus provoked by excentration of gaze of a sight (gaze nystagmus). Gaze nystagmus is absent when looking straight ahead, and is already clearly evident after excentration of gaze of less than 20 degrees. It beats in the direction of the excentration. The first special feature of rebound nystagmus is the fact that it disappears in 10 to 20 seconds. Its diagnostic significance could be based upon this feature alone, as was though up to now. However, its second original feature is fundamental. After excentration, gaze is brought back to the primary position (straight ahead). As confirmed by all the literature its value is of being pathognomic of a lesion of the cerebellar pathways. It is of the greatest simplicity, and it is sough by asking the subject to follow the finger of the examiner.

Adolescent↗
PubMed1978

The responses of frogs to vestibular and visual stimulation in weightlessness.

The authors, using rotatory visual and vestibular stimulators, propose to perform an experiment to study the effect of long periods of weightlessness on vestibular and visual interactions in frogs. The results will be analysed within the Framework of sensory conflict theory. Preliminary experiments are in progress in order to determine the best method for containments of long duration.

Animals↗
PubMedDate not supplied

Status of vestibular function after prolonged bedrest.

6 young, healthy, male volunteers were submitted to one week of head down (-4 degrees) bedrest. This position simulates the cerebral hemodynamic conditions in weightlessness. Measurements of vestibular equilibrium and of oculomotor system function were made before and after the prolonged bedrest. Analysis of the results indicates that vestibular responses, as measured by the maximal speed of the slow phase of the provoked nystagmus (caloric and sinusoidal rotatory stimulations), are decreased after prolonged bedrest. This statistically significant diminution requires confirmation with a greater number of cases. The reflex conflicting or interacting with the cervico-ocular and optokinetic reflexes on the one hand and the foveal vision on the other, is one of several possible explanations for the observed changes.

Adult↗
PubMedDate not supplied

Menière's disease in children.

Fourteen children (aged 14 years or younger) with typical Ménière's triad with cochlear sensorineural hearing loss, tinnitus, and intermittent vertigo attacks lasting from minutes to hours were investigated in four different neuro-otologic centers. Nine children, labeled as having "idiopathic Ménière's disease," developed the auditory and vestibular symptoms without any detectable causative factor. Five children, labeled as suffering from "secondary Ménière's syndrome," had histories of an initial hearing loss following mumps, hemophilus influenza meningitis, temporal bone fracture, or congenital or embryopathic complications in the ear that developed into the full Ménière's triad 5 to 11 years later. The 14 children represent 1% of all cases affected with idiopathic or secondary Ménière's disease (or syndrome) that have been detected during the past five years in the four collaborating centers.

Adolescent↗
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↗