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At least 523 records · Page 29Linked to original sources
PubMed1984

Implanted material tolerance studies for a multiple-channel cochlear prosthesis.

We have performed a number of temporal bone and animal studies in order to evaluate the histopathological effects of intracochlear electrode implantation and chronic electrical stimulation. Our results indicate that (a) the insertion of a free-fit scala tympani array results in minimal damage to the membranous labyrinth; (b) the materials used in the electrode array evoke mild tissue reactions when implanted subcutaneously, in muscle, or within the scala tympani; (c) intracochlear electrical stimulation for periods of 500 to 2000 hours, using carefully controlled biphasic pulses, does not adversely affect the population or neural activity of the primary auditory neurones; (d) labyrinthine infection severely reduces the number of viable spiral ganglion cells; (e) an adequate fibrous tissue seal of the round window can prevent the spread of infection from the bulla to the implanted cochlea in cats, following inoculation of the bulla cavity with bacteria; (f) bone growth is not associated with electrical stimulation per se; (g) the electrode arrays show minimal platinum dissolution and no apparent degradation of the Silastic carrier following periods of long-term intracochlear electrical stimulation.

Animals↗
PubMed1984

[Spontaneous perforation of the membrane of the round window--a major cause of sudden deafness?].

In 1983, 45 out of 63 clinically treated patients with sudden hearing loss underwent an exploratory tympanotomy. In 27 cases (60%) a perforation of the round window membrane was found, whereas in 18 cases (40%) the round window membrane was intact and there was no perilymph fistula. From 1982 to the end of 1983 30 perforations of the round window membrane were found which are reported here, most of them being spontaneous perforations without any preceding trauma. Audiometrically, hearing losses were found ranging from medium to high degree. These included all types of hard hearing, such as loss of high or low tones and losses over all frequency ranges to total deafness. All patients complained of tinnitus. One-third of the patients with perforated membrane had dizziness or vertigo combined with disturbances of balance. Treatment consisted of sealing the round window membrane with a plug of fascia or periostium. When the patients were discharged, or shortly after their discharge, audiometry revealed normal hearing in three patients, improved hearing in 8 patients, no change in 14 patients, and further deterioration in 3 patients. In 8 patients with perforated membrane, the sudden hearing loss had occurred 1 to 12 months back and in 6 patients only 8 to 30 days ago. The study will continue, but we can already see from the present results that every sudden hearing loss should be examined for a possible spontaneous perforation of the round window membrane. For this reason, exploration of the round window should be done within the first few days. The study yields new knowledge of the pathogenesis of the sudden hearing loss.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1984

Prognostic evaluation of the multichannel cochlear implant.

Preoperative appreciation of the future clinical results of the multichannel cochlear implant is important to assess in the case of pre- or post-lingual total deafness, in order to improve the patients selection. The psychological status of the future implanted is one of the main concerns because the post-operative reeducation efficacity depends on the patient's motivation. The Round Window electrical stimulation test supplies us with important and measurable data (electrical threshold level, tone decay test). The age of the patient, the age and the etiology of the deafness, the vestibular status and the cochlear tomodensitometry only offer non-decisive informations. The patient's socialisation level is a considerable factor. But per-operative observations are sometimes and surprisingly determinant (electrode impedances, ossified cochlea). Moreover immediate post-operative electrical and psychophysic data must also be considered.

Auditory Perception↗
PubMed1984

Results of the round window electrical stimulation in 460 cases of total deafness.

In order to avoid false and quantitatively unprecise responses the stimulating electrode must be directly placed on the round window membrane. That necessitates a transmeatal approach removing the eardrum, which is commonly achieved under local anesthesia. The positive response is subjectively easy to identify; it may be objectively registered by means of brain stem evoked responses; this registration is indispensable in case of children who need general anesthesia. This positive response signifies that some cochlear nerve fibers are still present, and therefore that the rehabilitation of the cochlear implant is possible. Among the 460 totally deaf, stimulated patients, more than 93% of them presented a positive response. The threshold level voltage value represents a statistically significant representation of the functional value of the electrode nerve interface. The features of the tone decay tests, which may be also subjectively or objectively performed, present important data which may be used to predict the clinical results that can be obtained by the cochlear implant.

Adolescent↗
PubMed1982

[Rupture of the round window - a cause of sudden hearing loss (author's transl)].

Rupture of the round window has been mostly described as an occasional lesion with sudden deafness and vertigo after diving, flying and physical stress, usually according to the patient's history. It also seems to be the cause of sudden progressive hearing loss of so-called idiopathic origin as shown by the findings in 6 out of 9 patients with perilymphatic fistulas. Therefore, transtympanic endoscopic evaluation of the round window is performed in the author's clinic as a routine measure in patients with sudden complete deafness or severe progressive loss of hearing even without any pointer to a possible trauma.

Adult↗
PubMed1981

Experimental round window membrane rupture.

An increase of perilymphatic fluid pressure was found to be an important factor in the aetiology of round window membrane rupture. The critical pressure causing membrane rupture, as determined in anaesthetized cats, was in the range of 10-30 mm Hg (mean, 23.4 +/- 17.1). This value was compared to the pressure increases caused by thoracic and abdominal compression, cervical strangulation, forced Trendelenburg position, coughing, and sneezing.

Animals↗
PubMed1980

Effect of round window removal on auditory thresholds in cats.

Round window fistula is a recognized and proven pathological entity that can cause sudden hearing loss. The study reported here, using cats, measured changes in the brainstem evoked response threshold to click stimuli after total removal of the round window membrane. The results showed an immediate 25 dB threshold decline followed by a further 35 dB decline over four hours. The response threshold then remained constant for 20 hours. In one animal there was no response to a stimulus of 110 dB SPL immediately post-op, and this animal, on re-examination, had a hole in the basilar membrane. In two animals, a membrane formed spontaneously over the round window area. In one, the response threshold did not change postoperatively, and in the other the threshold partially recovered following an initial decline.

Animals↗
PubMed1995

Prognostic indicators of speech recognition performance in adult cochlear implant users: a prospective analysis.

In a previously reported retrospective study of 32 prelingually and postlingually deaf adult Nucleus 22-channel cochlear implant users, multiple parameters were analyzed to determine which were predictive of postimplant speech recognition. Duration of deafness divided by age at implantation, and the psychophysical measures of 1) the threshold slope function (50 to 400 Hz) and 2) detection threshold at 400 Hz obtained preimplantation by means of a round window ball electrode were found to correlate most highly with postimplant performance. A more recent prospective study of 22 consecutive perilingually and postlingually deaf adult Nucleus users has reaffirmed the previous findings. Results revealed a highly significant correlation (r = .873, p < .0001, df = 20) between estimated and realized speech perception. In view of these findings, it would appear that there are variables that can be used preoperatively to predict perilingually and postlingually deaf adults' speech performance. The implications of these findings with respect to patient counseling and realistic expectations both for the patient and the implant team are obvious.

Adult↗