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Biomedical subjects

C H Chouard

Publications and source records attributed to C H Chouard.

At least 91 records · Page 5Linked to original sources
PubMed1985

[Retrospective study of the prognostic value of histological criteria in lymphoma of the ORL region].

The histological study of 36 cases of Non-Hodgkin Lymphomas beginning for the E.N.T. area has allowed us to show that the Non-Hodgkin Lymphoma Working Formulation made for the lymph nodes may be used to ENT Localization and give a reliable prognosis. Other elements like: sex, clinical staging, treatment have no significant value concerning the survival rate in our study. This study agrees with the previous studies about the predominance cases to the high power of malignancy of these lymphomas.

Adult↗
PubMed1985

[Anatomo-pathologic study of the temporal bone in our 4 cases of sudden infant death].

A new etiopathogenic theory is proposed by the authors about four cases of sudden infant death syndrome. A new histological method on the temporal bone was used applied in these four cases. Inner ear and meningeal injuries were observed. From this observation they proposed the possibilities of brain-stem injury through neurogenic or meningeal pathways. These injuries could be responsible for apnea syndrome and loss of alertness.

Child, Preschool↗
PubMed1984

Surgical procedure and implanted material description.

The 12 intracochlear electrode placement is greatly facilitated by using our electrode-bearer which is introduced through the round window via a posterior tympanotomy approach. However, partial or complete ossification of the cochlea may oblige us to use again our first technique of one-by-one electrode placement, using Silastic pieces through 12 cochlear fenestrations. The microconnectors and the receptor are also described.

Cochlea↗
PubMed1984

Psychophysics of 12 channels implant.

A battery of psychophysic tests has been designed through a computerized command of the patient's emitter. Because of the fatigability of these implanted patients, especially in the case of deaf-mute children, and the tedious aspect of these exams only 4 tests are commonly used: the threshold level in a Békésy way, the tone decay test, the 2 channels discrimination at different intensity levels, the lowest intensity discrimination. If the electrode impedances have been per-operatively measured, these tests are useful to understand the particular phonemic discrimination difficulties of each patient.

Auditory Perception↗
PubMed1984

Description of the French 12 channel cochlear implant.

The sound information is sequentially transmitted to 12 electrodes implanted in the cochlea. An electrode bearer introduced through the round window is now commonly used. Frequencies between 100-4 000 Hz and intensities between 40-100 db are only transmitted in a 3 msec time sampling. The output signal is a positive square wave followed by an equal negative wave. Its voltage varies from 2.5 to 6.5 volts. Its duration varies from 0 to 200 microsec. Its frequency is equal or inferior to 300 Hz. The outside emitter weighs 600 g. This system has been implanted in 58 patients and allows partial speech discrimination without lipreading for more than 6 years.

Action Potentials↗
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↗
PubMed1984

Clinical results of the French multichannel cochlear implant.

Clinical assessment and results are described in 66 patients (among them 20 were less than 20 years old). Voice changes may be objectively observed on sonograms. Phonetic discrimination depends on the electrical and nervous status of the implanted deaf cochlea. Discrimination of words and sentences with reference list, but without lipreading, is commonly obtained. Discrimination of unknown words is more difficult and varies from one patient to the other. Discrimination with lipreading progress elicited by the device depends on the pre-operative status and the own possibilities of each patient. Psychoaffective improvement is evident in every case, especially in 3 cases of autistic deaf-mute children. We shall try to summarize the efficacity of the French 12-channel cochlear implant regarding the clinical results we obtained in 66 patients who have been implanted between October 1976 and September 1983. Among them, 39 suffered from pre-lingual deafness and 27 from post-lingual deafness.

Adolescent↗
PubMed1984

Implant material tolerance.

After surgical and antibiotic destruction of guinea pig cochleas non specific lesions appear which seem more due to this destruction than to the electrode implantation or chronic stimulation. Moreover, despite these lesions, the electrical threshold level value necessary to elicit brain stem evoked responses in these implanted animals does not vary in time. The electrical chronic stimulation of the newborn deafened guinea pigs cochlea prevents the cochlear nucleus atrophy observed in the non stimulated animals. In man the implanted material tolerance is perfect provided this material is covered by a Silastic or teflon sheet and is located far from the skin incision. Degradation of isolating material occurred only in case of chronic movements. For this reason device and electrodes must be placed above and behind the ear. The waterproofness of the implanted receptor is indispensable to avoid physiological liquid penetration inside the electronic device. High level voltage stimulation may involve bubble formation responsible for temporary system failure; this drawback is suppressed by enlarging the electrode tip surface allowing low level stimulation. The threshold level and the frequency discrimination of the implanted electrodes did not change for more than 6 years. Post-operative infection occurred especially in case of pre-operative chronic otitis; it may be due also to the large use of "Histoacryl". However, these infections, which never affected the threshold level voltage of the implanted electrodes, are no longer encountered since we use "Tissucol", exclude the middle ear closing the Eustachian tube, and employ our electrode bearer.

Animals↗
PubMed1984

Sound signal processing.

In the CHORIMAC-12, the French device, the whole speech information despite its redundancy is transmitted to the few cochlear nerve fibers that are still present. Only loud speech intensities between 40 db and 100 db are introduced in a filter battery which gives out the frequency information in 12 channels including the 100-6000 Hz. This 60 db intensity scale is transmitted in a compression rate of about 6 db. The time sampling is 3 msec. A 12 electrode bearer or 12 separate electrodes (in case of ossified cochlea) transmit the electrical information. The electrical stimulus is a square wave: its frequency is equal or inferior to 300 Hz; its voltage may vary between 2.5 and 6.5 volts; its duration may vary between 0 and 200 mu sec. The performances of the system is demonstrated by means of a system of computerized psychophysic tests and speech intelligibility tests.

Cochlear Implants↗
PubMed1983

[Treatment of total deafness. Indications for and results of the multi-electrode cochlear implant].

Most cases of total deafness are due to destruction of Corti's organ leaving some of the auditory nerve fibres untouched. When these fibres are electrically stimulated the patient may perceive sounds the pitch of which depends upon the location of the stimulated nerve-endings along the cochlea. An intracochlear electronic device with 12 electrodes implanted in different areas and driven from outside by a portable radiofrequency emitter provides the patient with new hearing and some speech intelligibility. After several months' training words and sentences can be recognized without having recourse to lip reading. Performances depend upon a variety of factors, many of which can be determined prior to implantation. The long-term results obtained in 54 totally deaf patients are reported.

Cochlear Implants↗
PubMed1983

Long-term results of the multichannel cochlear implant.

Clinical results obtained with the multichannel cochlear implant are described in 48 cases of total deafness (27 cases of prelingual and 21 cases of postlingual deafness). The tolerance for implanted material and the survival of the electrode-nerve interface have not yet been altered after more than 5 years. After some months of training the patients, the percentages of phoneme-, word-, and sentence-recognition vary from one patient to another, but depend approximately on the value of the threshold level of the round-window stimulation test, and the degree of socialization of each patient. These results suggest that the multichannel cochlear implant may now be considered as a useful tool in the rehabilitation of totally deaf persons.

Adolescent↗
PubMed1983

[Effect of chronic electric stimulation of the auditory nerve on the development of the cochlear nuclei in guinea pigs].

14 newborn guinea pigs have been deafened three days after birth by bilateral destruction of the organ of Corti, and among them 8 have been supplied with a chronic auditory electric stimulation by mean of an intra-cochlear implanted electrode. The histological study and the anatomical reconstructions of these animals' cochlear nuclei demonstrate that this chronic stimulation prevent at least partially these auditory pathway medullary formations from the atrophy due to the cochlear destruction.

Animals↗
PubMed1982

[Electrical stimulation of the middle ear in total deafness: results in 375 cases (author's transl)].

Electrical stimulation of the middle ear can provoke sound sensations in 90 p. cent of patients with total deafness, as shown by auditory evoked potentials brain stem recordings. This signifies that cochlear nerve destruction is not complete, and rehabilitation by multiple electrode cochlear implants is possible. The liminal stimulation threshold level appears to be inversely proportional to the functional quality of the electrode-nerve interface obtained by the implants. The electrical stimulation of the middle ear test is therefore essential for selection of patients for operation, and for predicting the quality of rehabilitation that will be obtained.

Adolescent↗
PubMed1982

[Treatment of tinnitus by mean of electric transcutaneous stimulation (author's transl)].

In about a third of cases transcutaneous stimulation during a few minute by mean of electric square waves substantially improves severe tinnitus. This very simple treatment must be frequently repeated two or three times to be successful. If a notable improvement is not obtained after two or three attempts, failure must be considered as certain. The parameters of these stimulation are described and clinical results are reported. The mechanism of these improvement is uncertain.

Adult↗
PubMed1982

[Microcomputer applications in otorhinolaryngology (author's transl)].

Two main types of utilisation of microcomputers in otorhinolaryngology are envisaged: instrumentation and medical audit. The modes of employ of the material in these fields are briefly exposed, followed by the presentation of several examples of its employ and functioning. Practical notions are discussed, particular emphasis then being placed on theoretical considerations involved in the use of such equipment. Of primary importance are strictly medical reflections, problem solving being facilitated (by suppressing or diminishing routine tasks) but never simplified.

Computers↗