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At least 703 records · Page 39Linked to original sources
PubMed1980

Extent of reaction capacity of the vestibulo-ocular reflex.

On theoretical grounds, a high capacity of the vestibulo-ocular reflex, compensating for head velocities above 300 degrees/s, is assumed. However, in man the maximum eye speed, induced by solely vestibular stimuli, is only 100 degrees/s. With the usual clinical tests is seems impossible to get a sufficient strength of stimulus that would correspond to a strong physiological stimulus. With a systematic investigation with fistula symptoms finally a patient was found with an ideal mechanism of release of the fistula symptom. The maximum eye speed of the compensatory phase was 315 degrees/s. In this case, the vestibular phase was quicker than the so-called rapid phase. This now proven high reaction capacity constitutes the "missing link" between the hypothetical high capacity of the systems concept and the until now measured, only limited reactions after solely vestibular stimulation. For most physiological stimuli, i.e., quick head movements, the system can act as a simple reflex organ, being a velocity transducer with linear function thus successfully maintaining ocular fixation.

Aged↗
PubMed1981

[Lipoproteins in cochleovestibular disorders (author's transl)].

Forty-nine patients with neuro-otologic symptoms were examined with regard to their risk factors, especially their lipoproteins. No essential differences were found in the serum triglyceride and serum cholesterol levels. LDL-cholesterol and the quotient LDL-cholesterol/HDL-cholesterol were significantly higher in the group of patients. We consider this an indication for a relation between arteriopathy and cochleovestibular disorders.

Adult↗
PubMed2001

Morphological alterations in the inner ear of the arylsulfatase A-deficient mouse.

Metachromatic leukodystrophy of humans is an inherited sulfatide lipidosis due to deficiency of arylsulfatase A (ASA). As an animal model, ASA(-/-) mice have been generated. A previous study showed that the mice lose most of their spiral (acoustic) ganglion cells and develop deafness by the end of the first year of life. The present report describes the sulfatide histochemistry and ultrastructure of the inner ears of ASA(-/-) mice at 0.5-26 months of age. Lysosomal accumulation of sulfatides was observed in various cell types such as Schwann cells that maintain the myelin sheaths around the spiral and vestibular ganglion cells, periaxonal Schwann cells, macrophages, and spiral and vestibular ganglion cell perikarya. In the spiral ganglion, the only surviving neurons were those which are primarily non-myelinated (type 2 cells). However, the myelinated spiral neurons and their processes were rarely encountered within the process of dying, suggesting that this was a rather rapid process. Since the myelin sheaths around dying perikarya and axons appeared structurally normal, the primary cause of the neuronal cell death seems to reside in the neuron. In contrast to the spiral ganglion, the vestibular ganglion as a whole survived throughout the period of observation. The organ of Corti and the vestibular apparatus appeared preserved at the light microscopic level, despite massive sulfatide storage in the vestibular hair cells.

Animals↗
PubMed2005

The effect of superior canal dehiscence on cochlear potential in response to air-conducted stimuli in chinchilla.

A superior semicircular canal dehiscence (SCD) is a break or hole in the bony wall of the superior semicircular canal. Patients with SCD syndrome present with a variety of symptoms: some with vestibular symptoms, others with auditory symptoms (including low-frequency conductive hearing loss) and yet others with both. We are interested in whether or not mechanically altering the superior canal by introducing a dehiscence is sufficient to cause the low-frequency conductive hearing loss associated with SCD syndrome. We evaluated the effect of a surgically introduced dehiscence on auditory responses to air-conducted (AC) stimuli in 11 chinchilla ears. Cochlear potential (CP) was recorded at the round-window before and after a dehiscence was introduced. In each ear, a decrease in CP in response to low frequency (<2 kHz) sound stimuli was observed after the introduction of the dehiscence. The dehiscence was then patched with cyanoacrylate glue leading to a reversal of the dehiscence-induced changes in CP. The reversible decrease in auditory sensitivity observed in chinchilla is consistent with the elevated AC thresholds observed in patients with SCD. According to the 'third-window' hypothesis the SCD shunts sound-induced stapes velocity away from the cochlea, resulting in decreased auditory sensitivity to AC sounds. The data collected in this study are consistent with predictions of this hypothesis.

Acoustic Stimulation↗
PubMed1983

Inner ear pathology associated with Reye's syndrome.

Severe pathological changes were observed in the inner ear tissues of a 2-month-old patient who died of Reye's syndrome after 5 days of hospitalization. In the organ of Corti, the inner hair cells appeared to be more severely damaged than the outer hair cells. Various degrees of degeneration were observed in all non-sensory epithelial cells lining the cochlear duct. In most turns of the cochlear duct, Reissner's membrane was ruptured and/or collapsed onto the organ of Corti. Likewise, both sensory and non-sensory cells of the vestibular end organs were markedly degenerated. These observations suggest that the inner ear tissues are acutely affected in patients with Reye's syndrome, and that the changes may cause impairment of hearing and/or equilibrium in patients who recover.

Acoustic Maculae↗
PubMed2000

Surgical treatment of labyrinthine fistula caused by cholesteatoma.

In a 144-month period, 27 cases of labyrinthine fistula (LF) were seen, and 360 mastoid operations were performed; the LF prevalence was 7.5%. Primary symptoms were hypoacusis, otorrhea, vertigo, tinnitus, and otalgia. All patients underwent preoperative CT scans and preoperative audiometry. LF diagnosis was made before surgery for 93% of patients on the basis of symptoms, signs, and imaging studies. With respect to surgical technique, the canal-wall-down procedure was performed in 92%, and the canal-wall-up procedure was performed in 8%. In 88% of patients the fistula was located in the horizontal semicircular canal. In 96% of patients the cholesteatoma matrix was removed, and the fistula was sealed; in 4% of patients the matrix was left. With a follow-up of 13 years, vertigo disappeared in 96% of patients, and hearing remained unchanged in 70% of patients. Further complications of chronic otitis media existed in approximately half of the patients with LF. Open surgery with removal of the cholesteatoma matrix and sealing of the fistula with temporalis fascia in a canal-wall-down manner is a safe procedure that can make vertigo disappear and helps to preserve cochlear function.

Adolescent↗
PubMed1980

Romberg and his test.

In the eponymous test described by Romberg in 1846, the erect patient is asked to close his eyes. If he falls, the test is positive and indicates the presence of a dorsal column lesion. Slight modifications have been described in the test but in all cases, great care must be taken to do it carefully. The test compares the stability of eye-opening with that of eye-closure. A positive test does not indicate vestibular or cerebellar disease.

Cerebellar Diseases↗
PubMed1979

Vestibular suppression in peripheral and central vestibular disorders.

Caloric tests have been carried out both in the presence of optic fixation and in total darkness upon normal subjects, patients with peripheral vestibular disorders and patients with central vestibular lesions. Nystagmic responses were recorded electronystagmographically and measurements made of latency and duration of response, maximum slow component velocity and beat frequency. The relative enhancement of the response in darkness is expressed as a fixation index: maximum slow component velocity in darkness maximum slow component velocity with fixation. Compared to the normal group the peripheral group were found to have abnormally high fixation indices, the central group abnormally low. A hypothesis has been developed of the nervous mechanisms underlying the suppressive effects of optic fixation in both peripheral and central lesions which accords well with the available clinical, anatomical and physiological data. The clinical implications of the findings are discussed both in respect of their localizing value and relevance to current innovations in the design of caloric tests.

Brain Neoplasms↗
PubMed2005

Serial audiometry in a clinical trial of AIED treatment.

OBJECTIVE: We analyzed pure-tone and speech audiometric results from a prospective trial of anti-inflammatory treatment of subjects with active autoimmune inner ear disease (AIED). We sought to characterize the pattern and size of the treatment effect as reflected in clinical audiometry and to identify audiometric predictors of response to steroid treatment of AIED. SUBJECTS: Adult participants demonstrated clinically established criteria for AIED (n = 116). Eligibility required audiometric evidence of active AIED as indicated by idiopathic sensorineural hearing loss with threshold elevations within 3 months of enrollment. METHODS: We evaluated audiometric changes after 4 weeks of treatment with pharmacologic doses (60 mg/day) of prednisone. We examined the relationship between audiometric pure-tone thresholds at baseline and changes in word intelligibility score (WIS) using parametric and nonparametric analyses. Magnitudes of change were assessed using independent or paired t-tests. Separate analyses were performed on subgroups that did or did not show improved WIS score with steroid treatment. RESULTS: Overall mean pure-tone averages improved from baseline to closeout of prednisone treatment in better hearing ears from 52.4 to 48.3 dB (p < .0001). Mean WIS improved in the better ear from 71.4% to 78.1% (p < .0001). Of pure-tone measures, only the six-tone average showed significant correlation with both the absolute improvements in WIS and with the percentage change in WIS after treatment. Individual frequencies at baseline showed no significant relationship with changes in WIS score after treatment. In 69 (59.5%) of 116 subjects, WIS improved (range, 2-80%) in the better ear. In these subjects, the baseline pure-tone thresholds and pure-tone averages correlated significantly and positively with improvement in WIS. CONCLUSIONS: Steroid treatment in AIED-mediated hearing loss produce variable but significant hearing gains. Neither a focal, cochleotopic region of greatest vulnerability to AIED nor frequency-specific amenability to treatment were evident. We did observe that analysis of predictors and the degree of treatment effect vary with different approaches to measuring change in the WIS. Depending on the approach adopted, the size of the treatment effect may be greatest across intermediate hearing levels at baseline. These observations offer an audiometric database that may enable greater precision in judging clinically meaningful parameters for future studies of AIED treatment and other interventions for sensorineural hearing loss.

Adolescent↗