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Biomedical subjects

E Offeciers

Publications and source records attributed to E Offeciers.

15 recordsLinked to original sources
PubMed1998

New developments in cochlear implants.

Essential to improve the performance with cochlear implants is a better control of the electrode-nerve interface. The long-term stability of the electrode characteristics has to be guaranteed. Most important herein is to have a low and stable electrical impedance and to prevent fibrosis. Results of electrode coating and fibrosis-inhibiting products are described. To assess the properties of the electrode-nerve interface such as stimulation threshold, spatial selectivity and channel interaction, the electrically evoked compound action potential is measured. The measurement paradigm and the first results are described. Models of auditory nerve response to electrical stimulation can be used as a tool for cochlear implant fitting. A simple model is proposed and its predictions are compared with measured responses.

Cochlear Implantation↗
PubMed1998

Growth factors in tympanic membrane perforations.

OBJECTIVE: Little is known about the arrested healing of chronic central tympanic membrane perforations and the mechanism involved in this process. Some authors have traced the failure to a growth factor deficiency at the perforation margin. In addition, recently, several growth factors have been tried out to improve tympanic membrane (TM) closure in animals. The authors sought to determine the expression of some well-known growth factor peptides in normal human TM and in TMs with a chronic central perforation. MATERIALS AND METHODS: Total TM specimens were obtained from patients with a normal TM (N = 10) soon after death and from patients with a chronic perforation (N = 20) undergoing myringoplasty with use of an allograft TM. Formaldehyde solution-fixed TMs were analyzed after immunohistochemical staining using highly purified monoclonal antibodies to determine whether epidermal growth factor receptor (EGF-r), transforming growth factor-alpha (TGF-alpha), basic fibroblast growth factor (b-FGF), or transforming growth factor-beta 1 (TGF-beta 1) was expressed in the TMs. RESULTS: The distribution pattern for EGF-r, TGF-alpha, and b-FGF was similar in perforated and nonperforated TMs. In contrast to this, TGF-beta 1 staining was markedly different in perforated and nonperforated TMs. No or minimal TGF-beta 1 was observed in normal TMs, whereas TGF-beta 1 staining was prominent in perforated membranes, mostly at the perforation border. CONCLUSIONS: The authors experimental findings imply that EGF-r, b-FGF, and TGF-alpha expression are not significantly different in TMs with and without a central chronic perforation. However, for TGF-beta 1, the authors found an increased staining pattern in perforated TMs when compared with that of normal TMs, and staining at the fibrotic and scarred perforation margin was pronounced. Based on these findings, the authors speculate on the possible role of TGF-beta 1 in the development of the fibrotic scar at the perforation margin explaining the deficient healing pattern of tympanic membranes in chronic otitis media. Possible clinical implications for the future, including growth factor therapy, are discussed.

Antibodies, Monoclonal↗
PubMed1997

Revision stapes surgery.

This paper reports on the analysis of 332 otosclerosis revision operations. The results have been evaluated with reference to the type of the procedure at primary surgery, the alleged cause of failure and the applied technical solution. The need for revision surgery was found higher after primary total stapedectomy (3.4 per cent) than after partial stapedectomy (2.2 per cent) or stapedectomy (two per cent). The reason for revision varied according to the originally applied technique eg a migrated piston, a too short piston and a lateralized graft are almost exclusively found after total stapedectomies. The median hearing gain after revision of stapedectomy and partial stapedectomy was higher (20 dB and 18 dB respectively) than that after revision surgery for total stapedectomy (12 dB), but significantly lower than hearing gain after primary surgery (32 dB). Revisions yielded better results in the case of primary interventions with the use of a piston or pistonwire than in the case of primary interventions with a wire-type prosthesis. The risk for sensorineural loss (one per cent) was not higher than in primary surgery.

Adolescent↗
PubMed1997

Treatment of chronic postoperative otorrhea with cultured keratinocyte sheets.

Cultured allogeneic ear keratinocyte sheets were used to treat 26 ears presenting with long-standing (average 37 months) chronic otorrhea, resistant to regular treatment, long after surgery for atresia (n = 8), cholesteatoma (n = 10), and chronic otitis media (n = 8). Complete epithelial healing and cessation of otorrhea were obtained in 18 cases (69%), following an average of 2.2 weekly applications. Temporary epithelial healing lasting at least 3 months was observed in 3 patients (12%) subsequently needing repeated applications. Lack of complete epithelialization was documented in 5 cases (19%). In 3 of those 5 cases, a reason could be determined. The authors speculate that the allocultured keratinocytes are able to promote migration and proliferation of resident cells at the wound edges, despite their short survival time, by release of keratinocyte-stimulating factors.

Adolescent↗
PubMed1997

Stimulation of epithelial healing in chronic postoperative otorrhea using lyophilized cultured keratinocyte lysates.

OBJECTIVE: After tympanoplasty, despite a closed tympanic graft, some patients continue to have persistent otorrhea due to insufficient epithelial healing and granulation tissue formation in the depths of the outer ear canal. When all medical therapies fail, many otologists undertake revision surgery, usually with free skin grafting. To avoid surgery, the authors sought to improve this condition with a lysate of lyophilized cultured allogeneic keratinocytes. STUDY DESIGN AND PATIENTS: In this prospective pilot study, lyophilized cultured allogeneic keratinocyte lysates have been administered in 27 patients. These patients had uncontrollable otorrhea that resisted medical (topical) therapy for at least 6 months. MAIN OUTCOME MEASURE: The criterion of success was a complete epithelialization and cessation of otorrhea. RESULTS: After an average of 2 applications, cessation of otorrhea was achieved in 20 cases (74%). Three patients (11%) relapsed after 3 months. The other ears (63%) still were dry at the 1-year final evaluation. CONCLUSIONS: These results are similar to those obtained after application of sheets of viable cultured keratinocytes of autologous as well as of allogeneic origin. Because the soluble lysate can be incorporated into ototopical drops, the lysate technique is more "user-friendly" and can be applicable in any outpatient clinic. Because keratinocytes contain many growth factors (e.g., epidermal growth factor, basic fibroblast growth factor, platelet-derived growth factor, transforming growth factor), the authors speculate that the release of those intracellular growth factors is responsible for the observed therapeutic effect. This form of therapy by its combination of several growth factors might be considered a more physiologic method than the, also still experimental, growth factor therapy in which high doses of only single growth factor are used.

Adolescent↗
PubMed1996

Lysates from cultured allogeneic keratinocytes stimulate wound healing after tympanoplasty.

In the past, cultured keratinocyte allografts have been used with benefit in the treatment of burn wounds and leg ulcers. Since in burn wounds autologous and allogeneic fresh keratinocyte cultures were found to give similar favorable results as lysates of allogeneic cultured cells, the authors investigated whether this lysate mixed in an antibiotic suspension would also accelerate the epithelial healing after routine tympanoplasty. In a double blind setting the healing process in 50 consecutive tympanoplasty ears was studied: an acceleration of healing of 8 days was observed in the lysate-treated group (39.25 days) as compared with the control group (47.23 days). The percentage of ears which healed within 6 weeks (after 5 weekly applications of 200 microliters suspension in both groups) was significantly higher in the treated group (61%) than in the control population (36%). Although the therapeutical effect of the keratinocyte lysate in this study is believed to be due primarily to its mitogenic activity through growth factors or cytokines, at present it is still unclear which growth factors are involved and which combinations of these factors have to be present to modulate the different stages of the complex healing processes.

Administration, Topical↗
PubMed1996

Hearing preservation surgery for acoustic neuroma.

Nowadays smaller acoustic tumors are being detected earlier. We started to remove these tumors with attempt of preservation of hearing in 1994. Since 1994, in an attempt to preserve hearing, the retrosigmoid approach was used. Our first results are presented and criteria of preoperative selection and postoperative evaluation are discussed. A fair chance to keep a useful hearing can be given to a patient with a small tumor, preferrably smaller than 1,5 cm and provided that the average hearing levels differ by no more than 30 dB from the other ear. In all the other cases the translabyrinthine route remains the preferred approach.

Adult↗
PubMed1994

Statistical analysis of otosclerosis surgery performed by Jean Marquet.

The early and long-term hearing results of 1,681 primary otosclerosis operations performed by the same surgeon, Jean Marquet, were reviewed retrospectively and analyzed with very strict statistical standards. Significantly better short- and long-term results were achieved with the stapedotomy technique compared to total stapedectomy, mainly at the higher frequencies (4 and 8 kHz) important for speech discrimination. Whatever technique was used to open the footplate (micropick, microdrill, or laser), no statistical audiometric difference could be found. The results were equal whether or not the stapedial tendon was preserved. Perioperative problems like pronounced oozing, difficult anatomic relationships, and accidental perilymph aspiration could affect hearing at higher frequencies. The calibrated hole technique was equally as good as conventional oval window sealing in sealing of the fenestra to prevent fistula. The stapedotomy technique was found the safest, having fewer complications.

Adolescent↗
PubMed1993

A digital speech processor and various speech encoding strategies for cochlear implants.

We distinguish two main categories in the speech decoding strategies: those based on feature extraction and those based on time information of the filtered incoming signal. In the first group only those electrode pairs corresponding to the localisation of the four or more, maximum spectral peaks or the formants of the speech signal are stimulated. The second category is essentially based on the timing information that is included in the filter outputs of the filtered speech signal. The Laura implant has the capability to be programmed to the different decodings-strategies. To understand the potential possibilities the main features of the implant are discussed.

Acoustic Stimulation↗
PubMed1990

Two-stage repair of extensive subglottic tracheal stenosis.

The authors describe an open technique that has been used over the past 25 years to reconstruct the subglottic tracheal region in two stages after extensive laryngotracheal stenosis. After submucosal resection of fibrous tissue and reconstruction of the subglottic and tracheal skeleton by means of two autologous osseous grafts, a large laryngotracheostomy is created during the initial stage. Some weeks later, in the second stage, the anterior wall is closed, using two cervical hinge-door flaps. Ten patients have undergone this procedure, with a minimum follow-up of 3 years. All of the patients were decannulated upon completion of the treatment without recurrence of stenosis during the follow-up period.

Bone Transplantation↗
PubMed1989

[2-stage reconstruction of extensive subglottic tracheal stenosis].

The authors describe an open technique, used over the past 25 years to reconstruct the subglottic region in two stages after extensive laryngo-tracheal stenosis. After submucosal resection of fibrous tissue and reconstruction of the subglottic-tracheal skeleton by means of two autologous osseous grafts, a large laryngo-tracheostomy is created during the initial stage. A few weeks later, in a second stage, the anterior wall is closed using two cervical hinge-door flaps. Ten patients underwent this procedure and have had a minimal follow-up of 3 years. All ten patients could be decannulated after completion of the treatment and no recurrence of a stenosis could be observed during the follow-up.

Adult↗
PubMed1980

[Diagnosis and therapy of incus luxation].

Diagnosis and treatment of dislocation of the incus are discussed, and three fully described cases are reported. The author emphasizes the need of a multidirectional serial tomography for a correct radiological diagnosis. The reliability of routine impedance measurement for this diagnostical problem is questioned. A systematization of the surgical procedure is proposed. The importance of an optimum and lasting solution is stressed. In this context the author emphasizes the advantages of the anatomical reposition of the incus, the function and adequate application of Histo-Acryl, and the incus remodelling technique following J. Marquet. The success rate in a series of 9 cases is reported regarding the type of ossicular lesion and the used technique.

Acoustic Impedance Tests↗