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Biomedical subjects

M C Dahm

Publications and source records attributed to M C Dahm.

At least 19 recordsLinked to original sources
PubMed2000

Comparison of electrode position in the human cochlea using various perimodiolar electrode arrays.

OBJECTIVE: This study was conducted to evaluate the insertion properties and intracochlear trajectories of three perimodiolar electrode array designs and to compare these designs with the standard Cochlear/Melbourne array. BACKGROUND: Advantages to be expected of a perimodiolar electrode array include both a reduction in stimulus thresholds and an increase in dynamic range, resulting in a more localized stimulation pattern of the spiral ganglion cells, reduced power consumption, and, therefore, longer speech processor battery life. METHODS: The test arrays were implanted into human temporal bones. Image analysis was performed on a radiograph taken after the insertion. The cochleas were then histologically processed with the electrode array in situ, and the resulting sections were subsequently assessed for position of the electrode array as well as insertion-related intracochlear damage. RESULTS: All perimodiolar electrode arrays were inserted deeper and showed trajectories that were generally closer to the modiolus compared with the standard electrode array. However, although the precurved array designs did not show significant insertion trauma, the method of insertion needed improvement. After insertion of the straight electrode array with positioner, signs of severe insertion trauma in the majority of implanted cochleas were found. CONCLUSIONS: Although it was possible to position the electrode arrays close to the modiolus, none of the three perimodiolar designs investigated fulfilled satisfactorily all three criteria of being easy, safe, and atraumatic to implant.

Cochlear Implantation↗
PubMed1998

[Deafness: the right to silence or the chance to hear with a cochlear implant? Human images and medicine in the world of the deaf and in the world of the hearing].

Cochlear implantation has evolved from its experimental state into a safe and effective therapy for the treatment of profound deafness. Although not applicable to all patients, it offers an alternative to a life in silence. In particular, in early detected and treated deafness in childhood inner ear prostheses have enabled affected persons to be integrated into the world of sound. In addition to the significant impact that therapy has on the life of the individual, there is a social and cultural consequence for society. This is epitomized in the criticism by the deaf community that has resulted in the total rejection of cochlear implants. A critical analysis reveals different personal images prevailing in the deaf community. Knowledge of these differences and their relevance is important for all clinicians involved in counselling a cochlear implant candidate.

Cochlear Implants↗
PubMed1998

Acute apnea caused by an epiglottic cyst.

A life threatening complication in the course of routine sedation in a 5 year old child is reported in a case study. A retention cyst of the epiglottis was found to be responsible for obstruction of the larynx leading to acute apnea. The patient history revealed recurrent episodes of stridor previously diagnosed and treated as acute laryngotracheobronchitis as well as border line psychomotoric retardation. Cerebral magnetic resonance imaging was performed for neuroradiological evaluation. After administration of sedation the child presented with stridor and acute apnea. Emergency orotracheal intubation could prevent tracheotomy but was complicated by the unexpected presence of a tumor at the base of the tongue. Further evaluation revealed a large epiglottic cyst. After endoscopic removal of the cyst no further episodes of apnea or stridor were noted.

Acute Disease↗
PubMed1998

[Cervical manifestation of malignant schwannoma].

BACKGROUND: Malignant schwannomas are rare malignant mesenchymal tumors often associated with neurofibromatosis. They occur less frequently in the head and neck than in other regions. PATIENT: A case history of a primary malignant schwannoma of the head and neck area in a 27-year-old man is reported. The tumor was located in the left submandibular region. The patient did not have any functional deficits. The tumor was totally removed. There have been no signs of either recurrence or metastasis within the two years following diagnosis and surgery. DISCUSSION: The microscopic and immunohistochemical findings are presented, and the importance and therapy of this very rare malignant tumor of the head and neck area are discussed. CONCLUSION: Malignant schwannoma in the head and neck region is rare. Radical resection is the treatment of choice.

Adult↗
PubMed1997

[Aspects of auditory speech perception in cochlear implant and hearing aid managed children].

Speech perception is a valuable tool for the assessment of auditory (re-)habilitation of children with hearing impairments. We tested 3 groups of prelingually deaf children. For the evaluation of speech recognition abilities the test of auditory perception of speech in children (TAPS) was used. Hearing aid fitted children of a school for hard of hearing and school of the deaf (n = 12 and n = 10, respectively) and cochlear implant users (n = 12) of the same age group were tested. A positive correlation of the speech perception abilities with the aided thresholds was found. Hearing aid fitted children of the school of hard of hearing with aided thresholds between 20 and 40 dB HL including 4000 Hz showed best results. Students of the same school with aided thresholds in the range of 45 to 70 dB HL performed comparable to the lesser cochlear implant users fitted with a single channel analogue system. Hearing aid fitted students of a school for the deaf with the same degree of hearing loss and amplification showed significantly poorer results.

Auditory Threshold↗
PubMed1997

Submillimeter imaging and reconstruction of the inner ear.

OBJECTIVE: To present new radiological developments using high-resolution magnetic resonance imaging (MRI). MATERIALS AND METHODS: Using heavily T2-weighted sequences at a 1.5 Tesla scanner, maximum-intensity projections (MIP) of the inner ear were generated. The imaging time was less than 20 minutes, and imaging could be performed with adults and children of all age groups alike. This method enables us to visualize and identify the different neural structures of the internal auditory canal. Aplasia or schwannoma of a single or a variation of nerves could be clearly demonstrated. RESULTS: Three-dimensional reconstruction enabled unprecedented clear and precise presentation of the fluid content of the inner ear. The size and shape of 2 to 2 1/2 turns of the cochlea could be routinely demonstrated and analyzed in 45 subjects. Eight patients subsequently received an intracochlear implant electrode, and the intraoperative findings correlated with the imaging. CONCLUSION: The most recent high-resolution MRI techniques provide reliable visualization of submillimeter anatomical structures of the inner ear and auditory nerve.

Adult↗
PubMed1994

Silastic with polyacrylic acid filler: swelling properties, biocompatibility and potential use in cochlear implants.

We present a new hygroscopic implant material which consists of high-molecular-weight polyacrylic acid (PAA) as a filler in a Silastic matrix. The mixture swells upon immersion in bodily fluids; the degree of swelling depends on the ratio of PAA to Silastic and allows the design of implants that will achieve their final shape and size only after the implantation procedure. In vivo and in vitro biocompatibility tests reveal no adverse cellular or tissue responses. In cochlear implant development the material has been experimentally incorporated into intracochlear electrode arrays which curl after insertion, and in bacteriostatic devices for electrode fixation.

Acrylic Resins↗
PubMed1994

Cochlear implantation in children: labyrinthitis following pneumococcal otitis media in unimplanted and implanted cat cochleas.

Pneumococcal otitis media is frequent in young children and could lead to labyrinthitis post-implantation. To assess the risk, and methods of minimizing it by a graft to the round window around the electrode entry point, we have used a cat animal model of pneumococcal otitis media. Twenty-one kittens were used in the study. Thirty-two cochleas were implanted when the kittens were 2 months of age. Fourteen cochleas were implanted without using a graft (12 were available for study); 9 had a fascial graft, and 9 a Gelfoam graft (7 were available for study). The implanted kittens had their bullae inoculated with Streptococcus pneumoniae 2 months after implantation and were sacrificed 1 week later. There were also 9 unimplanted control ears which were inoculated when the animals were 4 months of age. Labyrinthitis occurred in 44% of unimplanted control, 50% of implanted ungrafted, and 6% of implanted grafted (fascia and Gelfoam) cochleas. There was no statistically significant difference between the unimplanted control and the implanted cochleas (p < 0.05). There was, however, a difference between the implanted-ungrafted and implanted grafted cochleas, but not between the use of fascia and Gelfoam to graft the round window entry point. As a result, the data indicates that cochlear implantation does not increase the risk of labyrinthitis following pneumococcal otitis media, but it is desirable to use fascia as a graft to the round window around the electrode entry point.

Animals↗