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Biomedical subjects

G Forrez

Publications and source records attributed to G Forrez.

At least 19 recordsLinked to original sources
PubMed1993

The effect of sustained phonation at high and low pitch on vocal jitter and shimmer.

Looking for possible signs of vocal fatigue, acoustic waveform perturbation was measured in normal female subjects during sustained phonation at various fundamental frequencies (Fo). At none of the pitch levels a rise of the jitter or the shimmer was found after 25 min of vocalization. On the other hand, an effect of Fo was seen from the start: above the habitual speaking Fo of our subjects' voices there was a tendency for the jitter to be higher and for the shimmer to be lower.

Adult↗
PubMed1989

Vestibulospinal findings in two syndromes with spontaneous vertigo attacks.

The influence of vestibular dysfunction upon the vestibulospinal reflex (VSR) in two common peripheral syndromes was investigated by two types of posturographic examination: "static" posturography, recording and analyzing the postural sway in stance, and "kinetic" posturography, recording the stepping in place test. The influence of the dysfunction was examined outside the attacks, ie, between attacks and not during or immediately after an attack, in patients with Meniere's disease and in others with a sudden vestibular loss syndrome, "neuronitis." However, in both syndromes the influence of the dysfunction was obvious only in some patients; this indicates that central adaptation intervened in the other patients. In this way, central compensation related to the VSR was assessed and compared with compensation for the vestibulo-ocular reflex assessed by the rotation tests. Discordance was shown in a number of cases, ie, a number of cases showed compensation for one reflex, but not for the other. Comparison of the results of both posturographic methods also showed discordance. Normal performance in the walking test could not always be correlated with normal performance in the standing test and vice versa.

Humans↗
PubMed1989

Clinical application of vestibulospinal reflex tests in peripheral vestibular disorders.

The influence of peripheral vestibular disturbances upon postural behaviour can be measured by posturography (PG). The results show that both otolithic and canal dysfunction can have some influence, whereas central compensation tries to suppress it. In this way, central compensation can be assessed by PG, which adds complementary information sui generis to the data of the 'classical' evaluation of a dizzy patient.

Humans↗
PubMed1987

Benign paroxysmal positional vertigo. Clinical observations by vestibular habituation training and by posturography.

Vestibular Habituation Training (VHT) is the treatment of choice for paroxysmal positional vertigo (ppv). The origin of the disturbance is peripheral and the data observed in the cases treated confirm that it is not located in horizontal canal function. However, canal dysfunction can be present together with ppv. Usually a separate course is observed for the phenomena attributed to horizontal dysfunction and those to the ppv lesion. The specificity of the Dix-Hallpike manoeuvres linked to the typical ppv is also confirmed by the data obtained by testing for VHT (VHT-test-battery). Ppv can have a repercussion upon the vestibulospinal reflex. That the same ppv disturbance can coincide with normal as well as with abnormal posturographic data, pleads for the intervention of central adaptive mechanisms. The effect of VHT is due to stimulation of these central adaptive mechanisms and not to any impact upon the peripheral lesion.

Exercise Therapy↗
PubMed1987

Posturography measuring instability in vestibular dysfunction in the elderly.

Balance dysfunction may be a cause of falling in the elderly. Disturbance of the vestibular system may have a repercussion upon balance performance, causing instability. Unilateral vestibular hypofunction (UVH) and its disturbing influence upon the vestibulospinal reflex (VSR), measured by the postural sway, has been studied. This influence is dependent on the interfering action of central adaptive and compensatory mechanisms. This central compensation may be different for vestibulo-ocular reflex (VOR) and the VSR. This comparative study shows that the elaboration of compensation in elderly people is less efficacious at the VSR level than at the VOR level. The influence of visual fixation is also stressed by comparing the posturographic recordings made with eyes open and eyes closed.

Accidental Falls↗
PubMed1987

Vestibulospinal function in two syndromes with spontaneous attacks of vertigo: evaluation by posturography.

Two vestibular syndromes comprising attacks of spontaneous vertigo were studied and disturbance of the vestibulospinal reflex was evaluated. Patients with Menière's disease were examined between attacks and patients with a sudden unilateral vestibular loss syndrome at least 3-4 weeks after the initial attack. Posturography, (recording and analysing the postural sway) was used to evaluate the influence of these disorders upon the vestibulospinal reflex. In 50% of the patients, the postural sway was disturbed compared with the performance of a normal control group. Menière's disease had a more pronounced effect on the posturographic results, whereas for the unilateral vestibular loss syndrome the rotation tests showed more asymmetry. It is obvious that the effect upon the vestibulospinal reflex cannot be deduced from the rotational test results. Indeed in a large number of patients discordance between rotational test results and posturography was seen. The presence or absence of attacks during the previous year in patients with Menière's disease had no influence on the presence of abnormal posturographic results. If other complaints of dizziness were mentioned by the patient, posturography was nearly always abnormal. It is evident that a complete evaluation of such patients must include information obtained by posturography.

Adult↗
PubMed1987

Vestibular habituation training and posturography in benign paroxysmal positioning vertigo.

A number of cases with typical positioning vertigo (BPPV) show a unilateral vestibular hypofunction (UVH) by caloric testing. However, treatment by habituation exercises (VHT) improves vertigo independently of the presence of UVH. Moreover, VHT has no influence upon the results of caloric and rotation tests. These findings prove the independence of the pathogenetic mechanisms of the peripheral vestibular disturbances UVH and BPPV.

Caloric Tests↗
PubMed1987

Cervical vertigo diagnosed by posturography? Preliminary report.

Posturographic recording with the patient's head in retroflexion has been proposed as a reliable test for diagnosing cervical vertigo. The clinical experience suggests that a positive result in this test-condition could be accepted as suggestive for cervical involvement, when other data corroborate it, but that it is not per se pathognomonic. In fact, this test is negative in most cases with other cervical indications, whereas it has been found positive, in cases with no cervical indications. A positive test, however, is significantly more frequent in "cervical" cases. On the other hand, otolithic influence upon the test-performance has also to be taken into account.

Adult↗
PubMed1987

Posturographic findings in two common peripheral vestibular disorders.

Peripheral vestibular pathology disturbs the vestibulospinal reflex in a number of cases. The recording of postural sway furnishes an evaluation of this vestibulospinal influence. Two common peripheral vestibular syndromes were studied: Ménière's disease and peripheral unilateral vestibular hypofunction. It is evident that, by posturography, vestibulospinal disturbance is shown in these peripheral syndromes, whereas its occurrence cannot be predicted by other tests, e.g. caloric and rotation tests. Normalization of the vestibulospinal reflex depends on central adapting mechanisms, which were evidently still incomplete in a number of the cases examined. Whereas abnormal postural results were equally observed in both groups, rotation tests showed better vestibulo-ocular compensation in Ménière's disease, compared to the cases with unilateral vestibular hypofunction. It mattered not whether the Ménière patient was in an active or a stabilized phase. A striking difference was noted for those Ménière patients with atypical vertigo complaints, who showed a high frequency of posturographic disturbances.

Humans↗
PubMed1986

Posture testing (posturography) in the diagnosis of peripheral vestibular pathology.

In patients with peripheral vestibular deficiencies, the testing of posture or "posturography" can give specific information about any compensation obtained in the vestibulospinal reflex (VSR). We have used the statokinesimetric parameter of length in this study. Nearly 50% of the patients with unilateral vestibular hypofunction as well as those patients with paroxysmal positional vertigo (PPV) show abnormal results. These findings indicate deficient compensation at the vestibulospinal level, which is independent of any compensation already achieved at the vestibulo-ocular level. The tests used for the latter, such as positioning and rotational tests, are unable to provide information about the degree of compensation reached in the VSR. The examinations used in the different modalities of sensory interaction can show the presence of influences of ocular fixation and changes of head position. We have observed three types of deviant interaction. Our posturographic data have allowed us to assess functional situations in a more precise way. Any rehabilitation exercises used should be adapted according to these data.

Humans↗
PubMed1986

Vestibulospinal function in otoneurology.

The vestibulospinal level of vestibular function is commonly neglected in the evaluation of dizzy patients. Posturography provides a measuring technique for this function (static balance), and thus becomes a counterpart of electronystagmography, and proves to be an indispensable complement in the evaluation of a number of cases. It enables one to make a better assessment of the patient's condition and to obtain decisive indications for his treatment. Detailed analysis of the posturographic recording indicates several patterns of vestibulospinal dysfunction and allows one to evaluate the sensory interaction. The data point to the necessity of adjusting the treatment schedule accordingly.

Humans↗
PubMed1985

[Posturography in peripheral vestibular pathology. Its contribution in the functional diagnosis and rehabilitation therapy].

Vestibulospinal examination has been neglected in the evaluation of vertigo. The clinical experience gives a loft of evidence that this level of balance function is very important. Even in peripheral cases, this function may be disturbed as has been shown by a systematical application of posturography. In this way the pattern of balance dysfunction can be characterized in a more thorough way. The data obtained by posturography, and especially during follow-up, allow to adapt the rehabilitation exercises in order to reach more efficiency.

Adult↗
PubMed1984

Posturography and vestibular compensation.

In unilateral vestibular hypofunction, compensation has to be achieved at the several levels of the balance function. The development of compensation at each level has not necessarily a parallel course. Accordingly, a thorough evaluation of the functional state of the patient, requires a separate assessment for each level. In clinical practice, compensation is evaluated by the testing of provoked vertigo (with eventual positional nystagmus) and by the rotation test results. To these data a measurement of the vestibulospinal level has to be added. Posturography provides this assessment and in this way the global functional state is completed. In many cases the complaints can be objectified and the elaboration of adequate rehabilitation exercises can be founded upon these posturographic data. The detailed analysis of the posturograpohic curves furnishes a diversification of the dysfunctional patterns at this balance level, with also emphasis upon the sensory interaction.

Adaptation, Physiological↗
PubMed1983

Evaluation of the vestibulospinal reflex by posturography. New perspectives in the otoneurology.

The vestibulospinal aspect of the vestibular function has been neglected in the evaluation of a patient with balance troubles. The attention is focused on vertigo rather than on problems of instability and ataxia, whereas also the examination of the patient is based upon the evaluation of the vestibulo-ocular reflex. Recent technical progress allows us to assess the vestibulospinal reflex in the global balance regulation of the standing patient by means of posturography, i.e. the recording and micro-computer analysis of the postural sway. In this way a precise description of this function is obtained and can be used in the approach to the patient, especially for a functional follow-up.

Humans↗
PubMed1982

On-effect in brainstem electric response audiometry. Consequences for the use of tone-bursts.

The nature of the auditory brainstem potentials is studied, referring to the theory of the on-effect. The following stimuli are used: a click, a tone-burst of 3 kHz with a rise-decay time of 2 ms and a plateau of 1 ms, and finally different initial parts of the former tone-burst (the first 8, 4, 2, 1 cycles). Together with the electrical waveforms, the acoustic forms of the stimuli are described and the frequency spectra are measured. The auditory brainstem potential appears to be a pure onset response with a very short integration time. Only the initial part of the tone-burst (mainly the first oscillation) is responsible for eliciting the response. The consequences for the audiometric use of short tonal stimuli are discussed. Measurements of intensities or frequency spectra, technically or subjectively, of the whole tone-bursts are inappropriate, because the intensity and frequency content of the effective stimulus must be considered. The real frequency specificity then becomes much poorer and differs little from the click stimulation.

Adult↗
PubMed1980

Distortion products f1 + fh and 2f1 + fh in the inner ear.

The ear introduces spectral components which are not present in the stimulating sound. These components are commonly attributed to nonlinearities in the inner ear. In this paper it is shown that the sum product of f1 + fh and cubic sum product 2f1 + fh, perceptively measured, do behave as predicte d by the conventional distortion theory of a power series nonlinearity and that they are most likely masked by the d.c. component generated by the same nonlinearity. We present a model in an attempt to explain the data.

Ear, Inner↗