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Biomedical subjects

T Lenarz

Publications and source records attributed to T Lenarz.

At least 127 records · Page 7Linked to original sources
PubMed1997

Cochlear implants: what can be achieved?

Cochlear implants in children are effective in terms of speech perception and production. Onset of deafness, date of implantation, and duration of deafness are important prognostic factors for long-term results. Sophisticated intraoperative and postoperative device control measurements enable detection of partial or total device failure and calculation of the reliability of the implant. However, the present technological status is far from an optimal device. Future developments will include improvements of both electrode design and speech processing. The number and separation of channels will be increased, and the pattern of stimulation will approach the natural excitation pattern of the auditory nerve. Behind-the-ear implants or totally implantable devices will further increase the acceptance and reliability of this technology. The implant systems will become more versatile and adaptable to the physiological conditions of the individual patient. Apart from these technological improvements, rehabilitation and proper selection of patients will still play a major role in successful implantation in children. Outcome studies are necessary to calculate the cost-benefit ratio and justify a further extension of implantation. We are still on the way toward the artificial ear.

Child↗
PubMed1997

Intracochlear, electrical, multichannel stimulation effects on the development of auditory system in neonatally deafened kittens.

OBJECTIVE: To investigate the effect of chronic electrical stimulation in acoustically deprivated animals during maturation. MATERIALS AND METHODS: Latencies of EABR measurements from acoustically deprivated and acoustically deprivated, but electrically stimulated animals were compared with ABR from normal hearing cats. In addition, morphological analyses of the cochlear nuclei and the auditory cortex and their subdivisions were done. RESULTS AND DISCUSSION: EABR latencies demonstrated that the most peripheral auditory pathway is more independent from the normal auditory or external electrical stimulation than the more central regions. Morphological analysis also demonstrated the reverse of the acoustically deprivation effect during maturation in the auditory cortex via intracochlear electrical stimulation.

Animals↗
PubMed1997

Optical imaging of cat auditory cortical organization after electrical stimulation of a multichannel cochlear implant: differential effects of acute and chronic stimulation.

OBJECTIVE: To study the effects of electrical stimulation on cortical activation patterns. MATERIALS AND METHODS: Optical imaging of auditory cortex in cats that are acutely and chronically electrically stimulated with cochlear implants. RESULTS: Chronic electrical stimulation results in expansion of cortical territory and overlap. CONCLUSION: Effects of chronic electrical stimulation are comparable to use-dependent cortical plastic reorganization.

Animals↗
PubMed1997

Acute effects of electrical intracochlear multichannel high-rate stimulation of the auditory nerve of cats.

OBJECTIVE: To investigate the short-term effects of electrical stimulation of the cochlea in cats. MATERIALS AND METHODS: Deafened cats were implanted with human cochlear electrodes, electrical stimulation at clinical levels was given, and evoked auditory brain stem responses (EABR) were recorded. RESULTS AND DISCUSSION: No long-term reduction in the excitability of the auditory nerve or in brain stem responses was seen.

Animals↗
PubMed1997

Measurements of threshold shifts observed when using normal and preformed electrodes.

OBJECTIVE: To investigate the efficacy of short-term electrical stimulation with different human electrodes using high stimulation rates and different electrode designs. MATERIALS AND METHODS: Human electrodes of two different designs were implanted in cats, and electrically evoked auditory brain stem responses (EABR) were recorded. RESULTS AND DISCUSSION: Thresholds from the EABR recordings at the apical end of the electrode array were comparable in both types of implants. There were significantly higher thresholds at the basal end than at the apical end of the electrodes in both types of electrodes.

Acoustic Stimulation↗
PubMed1997

Nucleus double electrode array: a new approach for ossified cochleae.

INTRODUCTION: The ossified cochlea is still a special surgical issue that requires a special surgical procedure. The current cochlear implants only have one electrode lead, which can be placed only partially in the drilled out basal turn. The small number of used active electrodes leads to worse performance as compared with patients with full insertion. METHODS: To overcome this limitation, a special electrode was developed consisting of two arrays. One array with 11 active electrode rings is placed in the drilled out basal turn, the second array with 10 active electrodes in the opened second turn. The number of inserted electrodes can be significantly increased. The surgery is similar to that in nonossified cochleae. After the posterior tympanotomy, the bridge is removed and the incus is located. A cochleostomy is performed at the basal turn and the new-built tissue removed. A second cochleostomy is placed below the cochleariform process. In most cases, the second turn is not obliterated and the second electrode array can be fully inserted. RESULTS: The surgical procedure was in all nine cases uneventful. Intraoperative stapedius reflex could be recorded with elevated thresholds. The wide variety of stimulation modes and sites allows an individual fitting to maximize the performance. All patients show a gap in the pitch scale between the apical and the basal array. The pitch variation is much smaller in the apical array. All patients have some benefit from the additional apical array and an improved performance. CONCLUSION: The nucleus double electrode array is an advanced treatment option for patients with ossified cochleae. The receiver/stimulator is a regular nucleus cochlear implant.

Cochlea↗
PubMed1997

Complications of cochlear implant surgery in children.

OBJECTIVE: To evaluate the intraoperative problems and postoperative complications in children receiving cochlear implants. STUDY DESIGN: A retrospective analysis of the clinical records of 366 children, aged 1 to 14 years, who had received cochlear implants. RESULTS: Intraoperatively, obliteration of the cochlea occurred in 66 patients, cochlear dysplasia in 8, and CSF leakage in 7, and nearly 5% of patients had signs of infection in the mucosa of the middle ear. Postoperatively, early complications occurred in 1% to 2.5% of patients: flap complications, electrode dislocation, facial nerve problems, and incorrect insertion of the electrode. Delayed complications included otitis media and stimulation of the facial nerve. CONCLUSION: Proper preparation of the implantation site, experienced and well-trained surgeons, and awareness of the operative and postoperative risks are necessary.

Adolescent↗
PubMed1997

Malformations in cochlear implant patients.

OBJECTIVE: To report on cochlear implantation in children with bony inner ear malformations. PATIENTS: 30 children with bony inner ear malformations who have received cochlear implants. INTERVENTIONS: High-resolution spiral computed tomography is used to identify malformations. Magnetic resonance imaging is used to detect the presence of an acoustic nerve and determine the integrity of the auditory pathway and central nervous system structures. Both imaging techniques may be used intraoperatively, as well as facial nerve monitoring and electrical auditory brainstem response monitoring. Three-dimensional reconstructions are helpful in preoperative planning. Large vestibular aqueducts and vestibular malformations can be successfully managed. RESULTS: Postoperative results have been encouraging, although children with malformations tend to occupy the lower third of rehabilitation results of all children with implants.

Child↗
PubMed1997

Comparison of preoperative electrostimulation data using an ear-canal electrode and a promontory needle electrode.

OBJECTIVE: To compare the electrical stimulation results of the ear-canal electrode with those of a promontory needle. PATIENTS AND METHODS: In thirty-three adult patients, the ear-canal electrode test was compared with the needle electrode promontory test with respect to sound perception, rhythm detection, frequency, and disturbing side effects. RESULTS: The ear-canal electrode test, in comparison with the needle electrode promontory test, resulted in vibrotactile sensation in addition to auditory sensation in some patients, less auditory fatigue, higher threshold levels, and lower discomfort levels. CONCLUSION: Reliable assessment of deafness in children requires, in addition to electrical stimulation, determination of the electrical evoked auditory brainstem response with the patient under anesthesia.

Adult↗
PubMed1997

Intraoperative test of auditory nerve function.

OBJECTIVE: To develop a preoperative objective test of auditory nerve function for the assessment of cochlear implant candidacy, especially in children. PATIENTS AND METHODS: We stimulated electrically with a ball electrode before insertion of the implant. First the stimulus was applied bipolar between the promontory and the round window. To record auditory brain stem responses (EABRs) very high stimulus intensities were needed, which was not possible in all patients. RESULTS: By stimulation in the basal turn of the cochlea, evoked potentials could be derived. Although in some patients the facial nerve was stimulated as a side effect, auditory evoked potentials could be recorded. A facial muscle artifact can be differentiated from the EABRs by latency and the slope of the input-output function. CONCLUSION: For the present, the only reliable test seems to be the EABR recording stimulated within the cochlea.

Adolescent↗
PubMed1997

Monitoring the electrode position during acoustic neuroma surgery.

OBJECTIVE: To obtain information about the auditory brain stem responses during auditory brain stem implantation. SETTING: Operating room during acoustic neuroma surgery. METHODS: Electrical stimulation of the auditory system during acoustic neuroma surgery, by placement of a monopolar or bipolar electrode on the nerve or nerve entry zone of the brain stem, and monitoring of the evoked auditory brain stem responses (EABR) recorded from the scalp. In some patients, a multichannel silicon electrode array was placed at the foramen of Luschka. Biphasic rectangular current pulses were applied, and EABRs were recorded. RESULTS: Usually the derived potentials consisted of three peaks with a latency below 4 ms. Sometimes we got a complex of two or more peaks. The interpeak interval between the first and second peak was about 0.7 to 1.0 ms, independently of the stimulating electrode position, but the absolute latency of the first peak increased from a minimum of 0.7 ms stimulated at the foramen of Luschka to a maximum of 1.3 ms stimulated at the nerve.

Cochlear Implantation↗
PubMed1997

Performance of the new Clarion speech processor 1.2 in quiet and in noise.

OBJECTIVE: To evaluate the benefit of the new Clarion speech processor 1.2. STUDY DESIGN: Fifty-two subjects who received a Clarion cochlear implant during 1993 and 1995 were upgraded with the new Clarion speech processor 1.2. All subjects were tested with a speech test battery in quiet and in noise, first with the 1.0 processor and 1 month later with the new 1.2 processor. To avoid ceiling or floor effects, the subjects were divided into three groups according to their test results with the Freiburger Monosyllabic Word Test (group A < 10%, group B 10-50%, and group C > 50%). RESULTS: The results indicated that all subjects had an improvement with the new speech processor. This improvement was statistically significant (p < 0.05) for group C in all conditions, and for group B in the tests with noise. CONCLUSION: While the better and good performers improved their test scores significantly, low performers seemed to derive little benefit from the technical improvements of the same speech processing strategy. Perhaps this group might gain more from a different processing scheme.

Child, Preschool↗
PubMed1997

Preliminary conversation with the parents before cochlear implantation.

OBJECTIVE: To provide parents of hearing-impaired children about to undergo cochlear implantation with an opportunity to discuss their expectations and the pedagogical implications of surgery. SETTING: Parents and children participate in discussions at the medical center where the cochlear implantation will take place. PATIENTS: More than 700 children and their parents have participated. OUTCOMES: Parents of congenitally deaf children differ somewhat in their expectations and behavior from the parents of postlingually deafened children.

Child, Preschool↗
PubMed1997

[Axillary metastases of oropharyngeal carcinoma after pectoralis major flap].

Reconstruction of defects after resection of advanced head and neck tumours with the pedicled myocutaneous pectoralis-major-flap is a well established method of regional plastic surgery. A 66 year old female patient with an oropharyngeal squamous cell carcinoma was treated by surgery and radiotherapy in curative intention. A few months later a local recurrence could be resected by a lateral pharyngotomy while the defect was reconstructed with a myocutaneous pectoralis-major-flap. Together with another local relapse at the pectoralis-major-flap in the oropharynx a painless tough swelling developed in the ipsilateral axilla which revealed histologically as a lymph node metastasis of a squamous cell carcinoma. Because no second malignoma as a source for this metastasis could be found, a lymphogenous spread of the oropharyngeal carcinoma along the pedicle of the flap could be the most probable explanation for this rare event. As a conclusion of this observation all patients with pedicled reconstructions after resection of head and neck cancer should not only be examined in the tributary lymph node levels of the neck but also in the axilla during oncological follow up.

Aged↗
PubMed1996

[The Clarion cochlear implant--technical principles, initial clinical experiences and results].

BACKGROUND: Certain design characteristics of the Clarion device (Advanced Bionics Corp.) make it significantly different from other cochlear implant systems. It has a preformed electrode array to be placed closer to the modiolus, thus providing a more efficient coupling of the electrical signal to the auditory nerve; a telemetric function which permits the evaluation of the implant electronics; and two different speech processing strategies. The strategies are continuous interleaved sampling (CIS) and compressed analog (CA); both can be programmed into the same speech processor and alternatively selected by the patients, as they desire. The surgical procedure is only slightly different from the procedure familiar from the Nucleus system with the exception of a significantly larger cochleostomy. PATIENTS: The results of a series of speech tests designed to evaluate benefit in terms of speech understanding were administered to the first ten Clarion patients and compared to the results of a similar group of patients using the Nucleus system and the M Peak method. From a data-base of more than 300 Nucleus users, it was possible to select ten subjects who had near-equivalent data for onset of deafness, duration of deafness, and age at implantation (so-called matched pairs). In the majority of cases, etiology and course of deafness (progressive or sudden) could also be matched. RESULTS: It was found that the Clarion patients had higher test scores than the Nucleus patients after two weeks, three months, and six months after implantation. This positive experience with the Clarion device encouraged us to continue implanting this system in patients. As of September 1995, 106 patients (including 35 children between the ages of two and fourteen) are currently enrolled in the study. CONCLUSIONS: A final assessment of results with the Clarion implant is not possible because of the short follow-up. In any case, it appears that the patients with this implant system achieve faster open-set speech understanding and that it is accomplished with less effort in programming and shorter rehabilitation time.

Adolescent↗