Biomedical subjects
Publications and source records attributed to P Govaerts.
A 45 y old man suffered since a long time from right-sided hearing loss, tinnitus and, very recently, facial palsy. CT-scanning and MRI showed a very large intrapetrous lesion centered on the jugular foramen suggestive for a glomus tumor. During surgery a facial schwannoma was disclosed. The management and therapy of this lesion is discussed.
The LAURA Cochlear Implant Program at the University of Antwerp was initiated 5 years ago. Up to now 50 children have received the LAURA cochlear implant (Philips Hearing Implants). Our accumulated experience in selecting the patients, counselling their parents, implanting and fitting the device allowed us to gradually modify the inclusion/exclusion criteria for cochlear implantation and achieve very rewarding results. The most important change was the gradual shift towards a younger age at implantation, our youngest implantee being 11 months old. In this paper we describe the rationale for this change, as well as the prerequisites for a successful pediatric cochlear implant program.
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.
Major breakthroughs in implantology and prosthetic materials, but also in reconstructive surgery of the auricle, have opened new possibilities in the rehabilitation of patients with an absent auricle. The management of such cases and the surgical results in 62 cases are presented. Thirty-five bone-anchored prostheses have been adapted and 27 total auricular reconstructions performed. As long as the conditions of osseo-integration are respected, surgery for an epithesis is easy and comprises no major risks. The side effects of the percutaneous connection (mainly skin reactions) are often minor. All patients are satisfied with their prosthesis and wear it all day long. For the total auricular repair, mainly in major congenital malformations, two techniques were adopted: first the Brent technique followed by the Nagata technique, preferred nowadays. The Brent technique was found safe with good results, but the modification by NAGATA offered two additional advantages: a reduction of the operative stages from 4 to 2 and a better definition of the auricular reliefs by the more elaborate fabrication of the framework. With increasing experience the results of the total auricular reconstructions improved significantly and became more predictable. Also the advantages and disadvantages of both (the reconstructive and prosthetic) approaches are discussed.
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.
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.
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.
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.
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.
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.
The bone anchored hearing aid (B.A.H.A.) has been fitted to 10 of our patients presenting a bilateral profound conductive hearing loss and who were unable to wear a classical hearing aid. The group of patients with bilateral inoperable aural atresia (n = 5) formed the main indication and were found to give the best results. Cases with bilateral chronic otitis media (n = 5), presenting otorrhea each time a classical hearing aid was worn, formed the second indication. Audiometric performances are dependent on the bone conduction thresholds. The auricular epithesis has been adapted in 11 cases, mainly for atretic ears. The surgery for B.A.H.A. and epithesis is now routinely performed in one stage and has been found safe and reliable. The skin reactions around the abutments (total number fixtures = 32) were found to be rare and often easy to treat. Only around one abutment further subcutaneous tissue reduction was necessary to stabilize the skin. The B.A.H.A. and auricular epithesis are valuable alternatives in those cases where the limits of reconstructive (middle or outer ear) surgery are reached.