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Biomedical subjects

P Govaerts

Publications and source records attributed to P Govaerts.

At least 19 recordsLinked to original sources
PubMed2005

[Loss and uncontrolled use of radioactive sources].

In the course of history, exposure to radioactive sources escaping regular control, has been the main cause of fatal accidents, with the exception of the reactor accident at Chernobyl. After the disintegration of the Soviet Union, numerous lost sources have been found, sometimes with serious physical damage. The attacks of September 11, 2001 have focussed the attention on the possibility of nuclear terrorism. Although the risks of fatal consequences are rather limited, the possible uncontrolled exposure to ionizing radiation has an important psycho-social impact on the population. After a brief survey of the types of radioactive sources for medical and industrial applications and a discussion of the risks and exposure routes, possible scenarios are illustrated by well documented case histories. The main conclusions of this analysis are: Radioactive materials are not unique as a potential threat by toxic materials. The most serious consequences for individuals occur as the result of external radiation, mostly with skin contact with medium-active sources which are relatively easily accessible. The collective impact is mostly psycho-social and is more important for a dispersed contamination of the environment. Many sources are detected via medical complaints. The knowledge of the specific symptoms is consequently very important. A dispersion of radioactive contamination has usually considerable economic consequences. Accidents occur particularly, but certainly not exclusively, in relatively unstable countries. Change of owner or final evacuation of the source constitute a critical phase in many scenarios.

Humans↗
PubMed2001

CT and MR imaging of congential abnormalities of the inner ear and internal auditory canal.

The embryology of the inner ear must be known as many of the inner ear malformations present as a result of the arrest during the various stages of embryology. These malformations are described in this "embryologic" perspective and specific names for certain malformations are no longer used. Both CT and MR can be used to look at inner ear malformations but often both techniques are complementary. However, CT is preferred when associated middle- or external ear malformations must be excluded. Magnetic resonance is preferred when subtle changes in the membranous labyrinth or abnormalities of the nerves in the internal auditory canal must be visualised. The CT and MR technique must however be adapted as more and more subtle congenital malformations can only be seen when the right technique is used. The heavily T2-weighted gradient-echo or fast spin-echo MR techniques are mandatory if malformations of the inner ear must be excluded. The purpose of this paper is to describe the techniques used to study these patients and to give an overview of the most frequent and important congenital malformations which can be found in the inner ear and internal auditory canal/cerebellopontine angle.

Ear, Inner↗
PubMed2001

Prognostic value of magnetic resonance imaging findings in hearing preservation surgery for vestibular schwannoma.

OBJECTIVE: The purpose of this study was to determine whether three magnetic resonance imaging (MRI) findings (tumor size, extension to the fundus, intralabyrinthine signal intensity) have a predictive value to hearing preservation in vestibular schwannoma surgery. STUDY DESIGN: A retrospective study was conducted of preoperative high-resolution MR images in a series of consecutive hearing preservation attempts for vestibular schwannomas. PATIENTS: Twenty-six consecutive records of patients with an acoustic tumor removed via a retrosigmoid transcanal approach were analyzed, and the MR images were reviewed blindly and compared with postoperative hearing. SETTING: The study took place in a tertiary referral center. Imaging Techniques: The MR sequences used in this study were unenhanced and gadolinium-enhanced T1-weighted spin-echo images and gradient echo images (3DFT-CISS). MAIN OUTCOME MEASURES: The predictive value of three MRI signs was analyzed: tumor size, lateral extension of the tumor (with and without obliteration of the fundus), and the maintenance of, or decrease in, the intralabyrinthine signal intensity on the affected side in comparison with the signal intensity on the opposite normal side as seen on 3DFT-CISS images. RESULTS: The tumor size in ears in which hearing was preserved averaged 15 mm and was 17 mm in those cases where hearing was not preserved. Hearing was preserved in 50% of ears when the tumor did not extend to the fundus but in only 33% when the fundus was obliterated by tumor. A "normal" intralabyrinthine signal on CISS images (being an isointense signal when compared with the contralateral unaffected ear) was followed by hearing preservation in 82% of ears, whereas in cases where the intralabyrinthine signal was low, hearing was preserved in only 20%. This correlation was statistically significant (p < 0.05). CONCLUSION: The intralabyrinthine signal intensity on 3DFT-CISS gradient-echo images is a valuable additional tool for determining candidacy for hearing preservation surgery. In two cases with preoperative decrease in signal intensity of the intralabyrinthine fluids, control MRI after surgery showed spontaneous recovery of normal intralabyrinthine signal intensity. The authors hypothesize that vascular compression in the internal auditory canal by the tumor is responsible for the observed intralabyrinthine signal decrease.

Adult↗
PubMed2001

Giant congenital intracranial epidermoid tumor: a case report.

A case of a large epidermoid tumor in a middle-aged woman with limited symptomatology is reported. Intracranial epidermoid tumors are slow growing and benign lesions. Although the treatment of choice consists in complete resection, partial removal may be preferred in some very extended cases presenting with minimal symptomatology because of the lower morbidity involved. This case illustrates a key-hole approach via a retrolabyrinthine route with preservation of all labyrinthine structures, including the endolymphatic sac and duct. The epidermoid was partially removed by extensive intracapsular debulking under endoscopic control with the aim of decreasing cerebral compression. All cranial nerve functions were preserved and the 6 month postoperative imaging has remained unchanged over a 2-year long follow-up period. The literature regarding this rare pathology is also reviewed.

Adult↗
PubMed1999

Large intrapetrous facial schwannoma presenting as a glomus tumor.

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.

Diagnosis, Differential↗
PubMed1998

The LAURA Pediatric Cochlear Implant Program in Antwerp: what have we learnt in 5 years?

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.

Belgium↗
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

Total auricular repair: bone anchored prosthesis or plastic reconstruction?

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.

Adult↗
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↗
PubMed1994

The bone anchored hearing aid and auricular prosthesis.

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.

Adolescent↗