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Biomedical subjects

M Gersdorff

Publications and source records attributed to M Gersdorff.

At least 19 recordsLinked to original sources
PubMed1992

Macroporous biphasic calcium phosphate efficiency in mastoid cavity obliteration: experimental and clinical findings.

Following our previous experimental studies on the performance of macroporous biphasic calcium phosphate (MBCP) in canine mastoid cavities, we used this material in patients requiring surgical intervention. Twenty-two cases were selected, and in eight specific cases a biopsy specimen was taken. Histologic, ultrastructural, and microanalysis studies were performed. This study demonstrates the effectiveness of MBCP implants as bone graft substitutes for mastoid cavity obliteration. Clinical evaluation of the series and histologic and ultrastructural results demonstrated the bioactivity and osteo-conduction of this material, with partial transformation of MBCP granules into lamellar bone after several months.

Adolescent↗
PubMed1992

[Contralateral ear in cholesteatoma].

The authors examine 224 contralateral files of patients suffering from cholesteatoma. They record that the systematic study of the opposite ear can prove to be of interest, given the numerous anomalies found. One ear in two has a contralateral pathology. In 32% of the cases, there is a retraction pocket, and in 14% a cholesteatoma. The mean time for a cholesteatoma to appear from a retraction pocket varies by 24 months in 44% of the cases, thus demonstrating the necessity of examining the opposite ear, as a dynamic evolution exists. Of these pockets, 2% in fact evolved, these statistics, to a true cholesteatoma.

Adolescent↗
PubMed1992

[Primary meningioma of the geniculate ganglion: apropos of a case].

Based on a clinical observation and a literature review, etiologic hypothesis, clinical, radiological and therapeutics characteristics of intratympanic primitive meningioma are described. Those tumors arise from arachnoid cells, some may be carried along the nerve sheath within the Fallopian canal during embryology.

Adult↗
PubMed1992

[Acute vertigo caused by cerebellar vascular accident].

At the beginning, small cerebellar strokes may present only with acute onset of vertigo, unsteadiness and unidirectional nystagmus, like a vestibular neuritis. In some cases, it is associated with tinnitus and hearing disturbance, like an endolymphatic hydrops. Other cases may mimic a benign cupulolithiasis, with only a paroxysmal positioning vertigo. Attention should be focused on transient associated symptoms: headache and blurred vision. One should not wait for classical cerebellar clinical signs: they are subtle and they appear late. Within a few days, the clinical picture will change: vertigo will disappear, while unsteadiness will progress. The electronystagmography confirms the integrity of the vestibular peripheric system. The cerebral CT Scan will show the ischaemic lesions only several days after the onset of the symptoms. A magnetic resonance imaging is far more efficient. Small cerebellar strokes have a good prognosis: complete recovery may be hoped with acetylsalicylic acid treatment and kinesitherapy.

Acute Disease↗
PubMed1992

[Somatosensory evoked potentials in peripheral diseases of the facial nerve: a new investigation method].

In 1988, at the Facial Nerve Congress in Rio de Janeiro, results of facial nerve somatosensory evoked potentials (SEPs) by electrical stimulation of the Ramsay-Hunt zone were presented. In the clinical phase of this work, we have tested 8 normal subjects and 5 patients with unilateral peripheral facial palsy by the SEP method. Significant and reproducible responses were obtained in the normal nerves; general wave-form and different parameters are described: latency of different activities, differences inter and intra-subjects. In one case, we performed a brain mapping by stimulation of the Ramsay-Hunt zone to improve the localization of the different activities and to differentiate them from a possible auditory response to the electrical stimulation. In the pathological nerves, we observed significant changes in the morphology of the cortical waves with regards to the healthy nerves. Detailed results are presented in two cases with a long-term follow-up. We concluded that the electrical stimulation of the Ramsay Hunt zone evokes a cortical response like the electrical stimulation of other cutaneous zones. This response is significantly altered in peripheral facial palsy. Following studies should define the prognostic value of such modifications.

Adult↗
PubMed1992

[Etiology of deafness in children].

A retrospective etiological study of 112 files of deaf children is presented. A prenatal etiology is found in 42.8%, a perinatal in 19.6% and a postnatal in 13.4% of the cases. No cause was suspected in 30.3% of the cases. These results emphasise existing literature.

Chromosome Aberrations↗
PubMed1992

[Value of evoked somatosensory potentials of the facial nerve].

We assessed the somatosensory evoked potentials (SEP) contribution to the evaluation of peripheral pathologies of the facial nerve. SEPs to electrical stimulation of the internal face of the auricle (Ramsay-Hunt zone) were recorded in 8 normal subjects and in 6 patients with unilateral peripheral facial palsy. Significant and reproducible cortical responses were obtained in all normal subjects and to stimulation of the healthy facial nerve in all patients. Brain mapping performed in one normal subject allowed us to locate the different activities on the cortex and to differentiate those from a possible auditory nerve response to electrical stimulation. When stimulating the pathological side, the cortical activities were altered when compared with those obtained by stimulation of the healthy side. In conclusion, the stimulation of the Ramsay-Hunt zone evokes a cortical response like those obtained by somatosensory stimulation of other cutaneous territories. These responses are significantly altered in peripheral facial palsy. Additional studies are needed to establish the prognostic value of these abnormalities.

Adult↗
PubMed1991

[Implantable hearing aids].

The purpose of these hearing aids is to improve the quantity and quality of amplification of the sound wave. Their operating principle is based on the existence of a transducer which transforms the electric signal captured by the microphone into a mechanical, vibrating wave. This transducer can act either directly on the temporal bone by short-circuiting the middle ear (and is then called a bone conduction implant) or directly on the ossicular chain (in which case it is called an ossicular transduction implant). A) There are 2 types of bone conduction implant: the "Audiant Bone Conduction" system of Hough-Vernon (Xomed), where an outside electromagnetic coil sends signals transcutaneously to a magnetic screw embedded on the temporal bone. Bone conduction must be normal. The "Bone Anchored Hearing Aid" (Nobelpharma) where the outside electromagnetic coil sends signals directly to the magnetic screw that is percutaneous. The mean thresholds in bone conduction can reach up to 45 dB. The drawbacks of this system lie in its inaesthetic appearance and the risk of infection. B) With ossicular transduction implants, the transducer may be: either an electromagnetic coil influencing a magnet fixed to the tympanum, on the ossicular chain, or replacing an element of the ossicular chain (these hearing aids are marketed by Richards); or a piezo-electric crystal which produces vibrations when it is subjected to an AC current, and which can be positioned on the stapes (Yanagihara). This system consumes less energy, gives excellent results for the high frequencies, but is more cumbersome.

Bone Conduction↗
PubMed1991

Results of cochlear implants in children.

About 700 children throughout the world have been implanted to date. Placing a cochlear implant represents no particular problem in the child. The incidence of complications is not high, being of about the same proportion as that in the adult. To obtain the best results, the selection of patients must be correct and carried out by a multi-disciplinary team of specialists, while the operated child must be subject to regular and intensive rehabilitation. The results appear to have become more satisfactory since the duration of sensory deprivation has been made shorter. In cases of congenital deafness in prelingual children, implantation should, ideally, take place before the age of six.

Age Factors↗
PubMed1991

[Limits of the study of early auditory brainstem responses in the diagnoses of childhood deafness].

The author presents the results of his experience concerning brain stem evoked response in children. 122 cases are put forth. It shows that although behavioral audiometry is impossible in 7% of the cases, the BERA (Brain stem Evoked Response Audiology) is not reliable in 26.5% of the treble frequencies and 36% of the bass frequencies. Thus, it is not possible to equip children with hearing aids based on this given alone.

Adolescent↗
PubMed1991

Ossiculoplasty: some physical and physiological considerations.

Numerous techniques and many materials are available to the surgeon for the reconstruction of defects of the tympano-ossicular system. The author would like modestly to recall certain aspects of middle-ear physiology and physics, and the impact that a knowledge of these ought to have in the mind and in the action of a surgeon about to practise an ossiculoplasty. The ideal for an ossiculoplasty would be to respect the ossicular joints, to remember that sound transmission at the level of the footplate falls within the field of quantic mechanics. The stapes transmits sound energy to the inner ear virtually without movement. Let us pay the greatest respect to the malleus and make use of the tympano-mallear complex during ossicular reconstruction. Let us remember that the middle ear is an adaptor for acoustic impedance. Let us respect the resonance frequencies of the ear, by avoiding an increase in the mass with unnecessarily heavy devices, or an increase in the stiffness, and let us seek to have a well-ventilated middle ear and a reconstruction without excessive tension. Let us use materials that are as physiological as possible in the field of impedance and speed of sound transmission. Finally, let us try to reconstitute the most physiological ossicular chain possible, using three ossicles whenever we can, using the malleus and avoiding if possible direct drum footplate contacts.

Acoustics↗
PubMed1990

Long-term results of various surgical treatments for cholesteatoma.

The authors have studied 11 series of results following cholesteatoma surgery by closed or open technique. The closed technique was performed in 77%. The notion of surgical revision is not accepted by all surgeons; it is practised with an average of 59% for the whole series. Residual cholesteatoma and/or recurrences are observed in 34% of the cases of which 20% have been discovered at the time of revision surgery. Surgical revision appears mandatory to the authors.

Cholesteatoma↗
PubMed1989

Bone allografts in reconstructive middle ear surgery.

The authors present their current experience with stored bone grafts, using allografts shaped from the cortices of long bones for reconstructing the tympano-ossicular chain. The materials and the methods are described. The anatomical results have been good in 97% of the cases, while the functional results are as satisfactory as those obtained with bioceramics. In addition to ossiculoplasty, the bone allografts can also be used in otology for reconstructing large bony defects of the temporal bone.

Bone Transplantation↗
PubMed1989

New perspectives on lyophilized bone allografts.

In 1987, at the Congress of Implants in Otology in Venice, Italy, we first presented our experiences with stored lyophilized bone allografts for reconstruction of the tympano-ossicular chain. Since then, we have extended our experiences to include reconstruction of the external bony ear canal, the filling of defects in the mastoid bone, reconstructive nasal surgery and rehabilitation of major bony defects of the face. Additionally, we have tried to improve the preparation of the bony implants used clinically and have started a multicenter collaboration with other European universities.

Bone Transplantation↗
PubMed1989

[Lyophilized homologous bone grafts in middle ear surgery: new perspectives].

The authors share their experience of the use of allografts in the reconstruction of the tympano-ossicular chain. The implants were cut from the cortical substance of the long bone in patients deceased for a maximum of six hours; the donors were tested for syphilis, hepatitis, AIDS, systemic diseases or a neoplasm. These bone allografts were cut to size, degreased, demineralized, frozen and then lyophilized in order to be presented to the surgeon in a sterile container (Bone Bank). The implants were all tolerated well. The anatomical results were satisfactory. Optical microscopic studies showed that the implant was: a) covered with mucosa, b) full of osteoblasts and c) the site of a bone neoformation. Experimental research is currently underway in order to perfect the implant preparation methodology.

Bone Transplantation↗