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Aminoglycoside ototoxicity.

The author participated in two prospective studies of patients receiving aminoglycoside antibiotics. In the first study, 54 patients received amikacin, and 54 received gentamicin. In the second study, 61 patients received gentamicin, 50 received netilmicin, and 52 received tobramycin. The studies were randomized and the investigator was blinded when evaluating auditory and vestibular toxicity and nephrotoxicity. All patients had pure tone audiometric evaluations, and two thirds of the patients had vestibular function tests consisting of an electronystagmogram performed with 30 degrees C and 44 degrees C water. Nephrotoxicity was measured by changes in serum creatinine levels. The incidence of gentamicin toxicity in the first study was 11 per cent, and it was 18 per cent in the second study. Amikacin was ototoxic 12.9 per cent of the time, whereas the incidence of tobramycin ototoxicity was 11.5 per cent, and the incidence of netilmicin ototoxicity was 2 per cent. Cases of unilateral, delayed-onset, and reversible auditory and vestibular toxicities were seen in all drug treatment groups. Nephrotoxicity was rare with amikacin usage. Gentamicin, on the other hand, produced a 18.6 per cent, tobramycin a 25 per cent, and netilmicin a 21.3 per cent rate of nephrotoxicity.

Amikacin↗

Quantitative vestibular testing.

Our standard rotational test battery includes tests of optokinetic nystagmus (OKN), the vestibulo-ocular reflex (VOR), and visual-vestibular interaction. Lesions of the peripheral vestibular system characteristically impair only the VOR, whereas lesions of the central system impair OKN and visual-vestibular interaction. The pattern of abnormal responses can help localize lesions within the central vestibular pathways.

Electronystagmography↗

Evaluation of patients with acoustic neuroma with dynamic posturography.

The purpose of the present work was to consider the use of posture tests in patients who had known acoustic tumors. The results suggest that it might be possible to determine whether the tumor is on the inferior or superior branch of the vestibular nerve. This would have clinical significance for planning a surgical approach to the tumor.

Aged↗

Predictive monitoring of high-frequency vestibulo-ocular reflex rehabilitation following gentamicin ototoxicity.

Nine patients exposed to gentamicin ototoxicity were tested with active head movements to determine their high-frequency (2-6 Hz) horizontal and vertical vestibulo-ocular reflex (VOR) responses. Results showed a common pattern documenting patients' reports of oscillopsia during walking: gains of 0.5 or less, and phases less than 180 degrees. A subset of these patients undergoing exercise rehabilitation therapy were tested repeatedly during follow-up visits to monitor changes in their VORs. VOR improvements toward reduced oscillopsia were correlated with patients' reported reduction of symptoms. Each patient's VOR changes over time were monitored with a quantitative least-squares method which predicted results of the next test, based on trends from three or more previous tests. The method was tested by comparing predicted results with actual test results, following the next test. Preliminary results show relatively accurate predictions up to 6 weeks in advance of actual tests, at least when trends of recent, previous tests were in a consistent direction. We conclude that predictive monitoring of changing VOR states can be useful for continuing, or modifying, the course of vestibular rehabilitation therapy, by providing quantitative prediction estimates of future results.

Anti-Bacterial Agents↗

Randomized perturbed posturography in abstinent chronic alcoholics.

Equilibrium is maintained by visual, proprioceptive and vestibular afferent influx, central coordination and motor efferents. Eleven male abstinent chronic alcoholic volunteers aged 44-65 years (mean 57 years) were investigated by randomized perturbed posturography. They had all been long time heavy drinkers. Ocular smooth pursuit and visual suppression of the vestibulo-ocular reflex showed abnormalities in a previous study, but they had no signs or symptoms of polyneuropathy. The current study demonstrated larger (but generally not significantly so) sway areas, and in all tests on the randomly moving support surface the sway velocities were significantly larger than in the controls. It is concluded that randomized perturbed posturography is valuable in dysequilibrium assessment in chronic alcoholics.

Adult↗

[Does optokinetic stimulation modify directional hearing?].

The directional hearing of 20 healthy test persons, all with normal hearing abilities, was tested using a special self constructed equipment. Under the repeated influence of an optokinetic stimulation (rotating light beams on a semicircular screen in a completely darkened room) no statistically significant deviation of the directional hearing reactions could be detected.

Adolescent↗

Autonomic nervous system disturbance as etiological background of vertigo and dizziness.

In order to investigate whether dysautonomia lies behind vertigo and/or dizziness in the neurotological clinic, an electrocardiogram (ECG) R-peak to R-peak test (R-R test) along with the Schellong test were simultaneously performed in 136 subjects. ECG data were analyzed by a microcomputer, and R-R intervals were calculated. In a dynamic test performed during postural changes from the supine to the standing position, there were 23 of 55 (41.8%) positive test results in patients with peripheral vestibular disorders, 28 of 51 (54.9%) with central vestibular disorders, and 15 of 18 (83.3%) with spinocerebellar degeneration. In a static test with the patient in the standing position, there were 13 of 55 (29.1%) positive test results in patients with peripheral vestibular disorders, 16 of 51 with central vestibular disorders, and 8 of 18 (44.4%) with spinocerebellar degeneration. A significant difference in the positive rate between spinocerebellar degeneration and both other central and peripheral vestibular disorders in the dynamic test was observed. These results also demonstrated that dysautonomia upon postural changes might play an important role in the development of vertigo and dizziness and that it is provoked by disorders of the autoregulatory mechanisms of the cerebral blood flow. This test is presumed to be excellent for detecting dysautonomia by virtue of being non-invasive, having good reproducibility and being readily available to quantitative evaluation by using a microcomputer.

Autonomic Nervous System↗

[Effects of color visual background on nystagmus components].

The paper deals with the problem of vestibular-visual interactions. It was found that color background has a marked influence on nystagmus components depending on the spectral characteristics. Yellow-green background is recommended as optimal in the performance of the rotation test. Patients with vestibulopathy can benefit from wearing yellow-green glasses in every day life. In patients with Meniere's disease and cochleovestibular neuritis color background produced specific changes in the principal parameters of the nystagmus.

Adult↗

Quantitative evaluation of the Vestibular Autorotation Test (VAT) in normal subjects.

UNLABELLED: The Vestibular Autorotation Test (VAT) is a relatively easy method for testing the Vestibulo Ocular Reflex (VOR) at higher frequencies by asking the patient to actively shake his/her head from side to side (jaw) with increasing frequency. In this study we investigated reproducibility and clinical applicability of this method and quantified gain and phase of the VOR in normal subjects. We studied the VOR in 33 subjects over a frequency range from 2 to 6 Hz. Ten subjects were investigated with an angular rate sensor mounted on a headband. In this group the velocity gain tended to decrease at higher frequencies and phase lag increased slightly. In a second experiment (2 subjects) head velocity was detected simultaneously by an angular sensor fixed to a headband and an identical sensor attached to a bite board. It was shown that the gain of the VOR in the first group was underrated and phase shift overrated due to slippage of the headband fixed rate sensor. Therefore in a third experiment, 21 subjects were investigated with the rate sensor attached to a bite board only. In this group VOR gain was close to unity and phase was close to 0 degrees (180 degrees out of phase) from 2 up to 6 Hz. In contrast to other studies, a considerable number of subjects were unable to reach shaking frequencies above 4 Hz. Our results agree with those of recently published reports and disagree with others, both using a headband. This is interpreted as being due to difficulties in sensing head velocity accurately. CONCLUSION: vestibular autorotation is an accurate and reproducible way of testing the high frequency range of the vestibulo-ocular reflex, provided that head velocity is measured by a bite board. Our present work is focused on determining the high frequency characteristics of the VOR in patients suffering from vertigo.

Adult↗

Influence of cerebrospinal fluid tapping on dynamic equilibrium in suspected hydrocephalus.

Thirty-nine patients aged 21-82 years (mean 62 years) under investigation for suspected acquired hydrocephalus were investigated by dynamic posturography before and 6-8 h after a cerebrospinal fluid tap of 20-40 ml. Dynamic posturography comprises a sensory organization (SO) part in which the platform and visual surround are either stable or referenced to the patient's sway. The eyes are closed or open. In a movement coordination (MC) part the platform makes active movements, thus introducing external disturbances in the procedure. The patients improved their balancing ability in all tests on the sway referenced platform in SO, while MC remained unaffected. It is concluded that dynamic posturography is valuable for dysequilibrium assessment in clinical evaluation of suitable candidates for ventricular shunts in acquired hydrocephalus.

Adult↗

Intratympanic gentamicin in monolateral Meniere's disease: our experience.

The aim of this study was to verify the efficacy of a modified Odkvist titration protocol of intratympanic gentamicin application in the control of vertigo attacks and the effects on the auditory and vestibular function in a group of 71 patients affected by monolateral MD resistant to medical therapy. All the patients underwent an intratympanic administration of a 1-ml solution containing 26.6 mg of gentamicin sulfate. The treatment protocol provided one to three injections for a total amount of gentamicin varying from 26.6 to 80 mg. Five days after the first gentamicin administration, cochlear and vestibular function tests were performed. The worsening of the PTA greater than 15 dB, the appearance of clinical signs of vestibulotoxicity such as imbalance or persistent spontaneous nystagmus beating away from the injected ear or of a "curative vertigo" were the criteria taken into consideration to stop the treatment. In the absence of any sign, a second and third injection were performed. The presence of an unchanged frequency of the attacks at least 3 months after the previous cycle was the parameter considered to perform a second or third cycle. Seventeen (24%) patients were submitted to a second cycle of therapy and two (3%) to a third cycle. After a mean follow-up period of 20.3 months (range: 3 to 48) all 71 patients experienced good control of the vertigo attacks: grade A in 46 cases and grade B in 25 cases according to the AAO-HNS CoHE criteria. The pure tone average (PTA) hearing threshold (500-3,000 Hz) worsened in 19 patients, improved in 5 and was unchanged in 47. On the basis of the experience acquired during the treatment, we progressively decreased the number of injections from 3/cycle to a 1-2/cycle of therapy. Moreover, in the later phase of the study re-injections were administered 1 or 2 weeks after the previous application and avoided in the presence of signs of depression of the vestibular and/or cochlear function. A residual caloric excitability was found in 30% of the cases. Vertigo control doesn't seem to be linked to the achievement of vestibular inexcitability. The marker of successful gentamicin treatment at short-term is the appearance of signs of curative vertigo and/or vestibular imbalance, and at long-term the disappearance of vertigo attacks.

Adult↗

[Diagnostic and therapeutic problems in dissociated forms of Menière's disease].

The authors report the cases of 5 subjects who presented with incapacitating vertigo which was attributed to a dissociated form of Meniere's disease. They stress the difficulty, in these circumstances, in making a precise diagnosis which can only in fact be confirmed with the benefit of a longer follow up. They stress the value of systematically combining frequency analysis with measurement of maximal slow phase velocity during vestibular testing. This allowed better precision in terms of topographical diagnosis. All subjects underwent vestibular neurotomy via the retro-sigmoid approach. The procedure did not alter hearing and compensation occurred within the usual delay. The question therefore arises as to when is the best time to intervene in patients presenting with vertigo of peripheral origin with preserved hearing.

Audiometry↗

[Herpetic vestibular neuronitis: a hypothesis].

Abundant experimental research has shown the potentially damaging effects that the herpes simplex virus (HSV) may have on peripheral or central nervous pathways. Fifty subjects (ages 20-45) with labial herpes virus (HSV-1) and 15 (ages 25-35) with genital herpes virus (HSV-2) were studied through recording spontaneous and optokinetic nystagmus (OKN) and using the eye-tracking-test (ETT) by means of electronystagmography (ENG). Recording was carried out during the first two days after vesicular eruption and seven days later, when cutaneous manifestations had disappeared. Thirty-five of the 50 subjects with HSV-1 showed spontaneous nystagmus, frequently with a vertical component, which in most cases had disappeared by the seventh control day. We recorded qualitative alterations of OKN as well as ETT in 19 patients while in 3 subjects only ETT was abnormal. All the subjects were normal on the seventh control day. At no time did any of the patients with HSV-2 show objective signs involving the peripheral or central vestibular system. Our research shows that HSV infection, especially HSV-1 infection, determines subclinical alterations of the vestibular function, probably due to the involvement of the brainstem. Therefore the virus is to be taken into account in establishing the etiology of "unknown" vertigo.

Adult↗

Neurotologic evidence of central and peripheral involvement in patients with vestibular neuronitis.

Quantitative vestibulo-oculomotor tests and auditory brain stem responses were studied in 22 patients with vestibular neuronitis in a search for evidence of CNS affection. Such evidence was found in 16 of the 22; only in the other six could the examination findings be regarded as the result of damage limited to vestibular neuroepithelium or nerve. It is concluded that vestibular neuronitis can cause CNS signs by itself, probably because of inflammation in the vicinity of the vestibular nerve.

Adolescent↗

Studies on the integrative activity of the vestibular nuclei complex.

Central mechanisms currently used in clinical vestibular tests are far more complex than generally thought. The first synaptic station, the vestibular nuclei, represents a sensory-motor centre integrating vestibular impulses with proprioceptive afferents from muscles and joints. This convergence can be found on cells with long axons projecting to the oculo-motor system, to the spinal cord and to the thalamus as well as on cells without long projecting axons. There are also vestibulo-motor cells transmitting pure vestibular information.

Humans↗

A new method for determining impulsive time constants and their application to clinical data.

We have developed an accurate, convenient method for determining unique values of vestibular time constants from impulsive tests. The method was used to determine the mean values and standard deviations of 36 normal subjects. A comparison between these normal values and data from patients with cerebellopontine (CP) angle tumors or unilateral peripheral vestibular lesions showed no significant difference in the values of the time constants. We conclude that shape-descriptive parameters such as time constants cannot differentiate between subjects and patients.

Adaptation, Physiological↗