RESUMEN

The insertion of reliable extracochlear single-canal cochlear implants in cophotic and subcophotic patients allows the electrical stimulation of the acoustic nerve for rehabilitation, as well as audiovestibular explorations that are no longer possible in the acoustic mode. The authors therefore aim at replacing all these examinations with their Electrical equivalent: --early evoked potentials (E-BERA), --medium-latency evoked potentials (E-MLR), --Event-related evoked potentials (E-P300), for which, to our knowledge, theses are the first recordings, --electrical stapedial reflex, --vestibular stimulations. The method, results and clinical and physiological applications of each method are given, as well as its prospects.

Asunto(s)

Asunto(s)

RESUMEN

Numerous factors can influence evoked or spontaneous nystagmus. In this study, the influence of reducing the visual field to a peripheral field of 18 degrees 40' was investigated in 15 subjects with normal vision. In order to reproduce the conditions of photoelectric recording with Torok's glasses, a tube was placed in front of one eye while the other eye was covered. This resulted in the enhancement of the evoked vestibular and optovestibular responses and the reduction of the subjective sensations of the subject, suggesting that the tubular vision might be helpful for the study of cinetosis. Our study also showed two culminating points and two critical phases in caloric nystagmus.

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

RESUMEN

In a population of 241 head injuries, some of which dated prior to 3 months and others after, the modalities of graphic responses to an oblique stimulation are described (optokinetic test and ocular calibration). In fact, the distribution of the various types of graphic responses differ statistically depending on the age of the injury. In injuries less than 3 months old a majority of oblique ocular responses were found to be of the intermediate type, while in those with injuries of more than 3 months ago, the oblique ocular responses of a rotary type predominated. However, above all the results of the video recording used to visualize the ocular responses, which until now have been presented graphically, will be discussed.

Asunto(s)

RESUMEN

Electronystagmographic (ENG) recordings were compared in patients with multiple sclerosis (30 cases) or with an allergic diathesis (100 cases) presenting, in addition to other symptoms, disturbances in balance and vertigo. The ENG examination included: study of voluntary 10 degrees ocular movements and spontaneous ocular signs, the blinking test and pendulum tracking test, the optokinetic reactivity test, the damped pendulum giration test, and thermal tests. Absence or desynchronization of the subjective sensation of giration in relation to the true movement of the armchair was noted during the damped pendulum giration test. Optokinetic reactivity was indicative of possible optokinetic recruitment. Multiple sclerosis patients showed a higher frequency of bilateral vestibular hyperreflectivity in the thermal test whereas peripheral hypovalence was more common in allergic patients. Overall alterations were generally more marked and more stable in multiple sclerosis, more labile forms being observed in neuro-allergies. It is suggested that the mechanism of the inflammatory edematous reaction in the plaques could be similar to that of the angioneurotic edema observed in the neuro-allergic affection.

Asunto(s)

RESUMEN

Ocular incongruity is not always symptomatic of pathology: it is sometimes simply found among the many physiological characteristics of man. The various situations which can bring about a physiological ocular incongruity are found successively during instrumental vestibular trials: incongruities in amplitude are recorded during the rapid phase of the provided nystagmus and incongruities in speed during the slow phase. These incongruities appear during the caloric responses for the homolateral eye to the irrigation and in the rotary, sinusoidal pendular test for the eye homolateral to the direction of the rapid phase of the provoked nystagmus. During a voluntary blink an ocular incongruity of direction appears as an intorsion of the two eyes. Incongruous ocular movements increase during sleep. They appear equally often during onset of sleep and during the stages comprising slow waves or paradoxical sleep. In children engaged in reading or submitted to an optokinetic test, congruity is not present at first but only occurs once the child has acquired the oculocephalic dissociation.

Asunto(s)

RESUMEN

An electronystagmographic study of optokinetic reactivity is conducted in 50 'normal' adult subjects and 200 patients suffering from various diseases, all of whom presented an abnormal electronystagmogram. Optokinetic reactivity is evoked by a sudden acceleration of the optokinetic stimulus. It is considered normal when this acceleration leads to an increase in amplitude. At the same time, the frequency of the optokinetic nystagmus decreases. This type of response can be modified by various disorders. Recent cranial trauma and tetany are associated with an incomplete or inadequate optokinetic response; brain vascular diseases and disorders of central origin induce an absence of that response, while some cases of multiple sclerosis and neuro-allergies give rise to an apparently momentary, unstable response. Optokinetic reactivity thus represents an extension of the classical optokinetic test and yields valuable diagnostic clues.

Asunto(s)

RESUMEN

Voluntary and reflex ocular scanning has been investigated in 55 dyslexic children, aged from 8 to 14 years 3 months, by means of potentiometric electrooculography with multiple monocular electrodes. Results are expressed in terms of amplitude, frequency, shape of movements and ocular congruence. A comparison between the oculomotor behaviour of dyslexic and normal children with no reading problem shows the same types of ocular movements as observed in normal schoolchildren, but they differ in their distribution according to age. Moreover, the evolution of oblique movements, described in normal children and correlated with the degree of schooling, is not the same in dyslexic children, where it instead seems to follow particular patterns. Finally, in stereotyped ocular scanning simulating reading movements, the dyslexics are characterized by the absence of two important stages leading to ocular congruence: scanning with random alternate monocular predominance and scanning with selected alternate monocular predominance.

Asunto(s)

Asunto(s)

RESUMEN

By measuring cerebral blood volume (CBV) and intracranial pressure (ICP) variations at the same running time during sleep, it has been demonstrated that the ICP wave which appears during the REM sleep in hydrocephalic infants is produced by intracerebral vaso-dilatation. Nine infants with stabilized hydrocephalus were investigated by non-invasive means: REM phases were distinguished with the usual polysomnographic electrodes. Intracranial pressure was measured with a fontanel palpation transducer and CBV variations were obtained by recording 99mTc activity at the head level after in vivo labelling of red cells with 99mTc--pertechnetate. The time-activity curves, obtained from regions of interest and selected on the sequential radioisotope images, show that an increased ICP wave, occurring during the REM period, is related to a simultaneous increase in the blood volume, limited to the cerebral sector and not to the area of the external carotid artery.

Asunto(s)

Asunto(s)

RESUMEN

This study was carried with the intention of explaining the causes of modifications in intracranial pressure (ICP) during paradoxical sleep (PS) in normal and hydrocephalic infants, and establishing relationships between these modifications and cerebral blood volume (CBV). All tests (conventional sleep polygraphy, ICP measured by a transducer on the fontanel, CBV measured by isotopic labelling of red blood cells in vivo) were carried out without use of surgical procedures. During paradoxical sleep there was a sustained wave of increased intracranial pressure lasting from 10 to 20 minutes, as well as phase-type variations lasting no longer than 1 minute. Increased ICP was also observed in the normal subjects. Recordings show that there is well-defined correlation between the sustained wave of high intracranial pressure and an increase in CBV.

Asunto(s)

Asunto(s)

Asunto(s)

RESUMEN

The authors describe a new method of optokinetic stimulation. The stimulus is applied during 3 successive sequences: the first and third include displacement of 1 to 2 black or white bands per second (apparent mean speed of 16 degrees/sec), while the second sequence comprises the sudden acceleration of 6 black or white bands per second (apparent mean speed of 59 degrees/sec.). Each sequence lasts 4 to 10 seconds. However many times the stimulus is repeated the optokinetic response becomes hyposynchronous at the frequency at which the bands are passing when the speed is increased, whereas the amplitude of the ocular responses is multiplied two to three times. The increase in the amplitude appears to be proportional to the reduction in frequency. In this way, optokinetic reactivity is tested when the subject looks in the three principal directions: horizontally, vertically, and obliquely. Particular types of reaction are observed in pathological conditions where they are either unadapted or incomplete, while absence of optokinetic reactivity can be found in all directions, several directions, or in one direction only.

Asunto(s)

Asunto(s)