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Biomedical subjects

H J Gerhardt

Publications and source records attributed to H J Gerhardt.

At least 19 recordsLinked to original sources
PubMed1998

[Lymphoma of the cerebellopontile angle as etiology of retrochochlear damage. Case report and review of the literature].

The clinical features of progression sensorineural hearing loss and vertigo in combination with the radiologic finding of a contrast-enhancing mass within the inner auditory canal are suggestive of an acoustic neuroma. We report our findings in a 57-year-old woman with known mixed connective tissue disease who was presumed to have a neuroma. A large malignant lymphoma of the cerebellopontine angle presented clinically with a primary acoustic none palsy and no other central neurological deficits. Both the primary radiological examinations and the exclusively peripheral nerve palsy failed to indicate manifestations of a lymphoma. The development of a progressive facial palsy within 8 weeks of presentation and an atypical occipital headache were uncommon findings for an acoustic neuroma. Such changes in symptoms despite the occurrence of cardinal symptoms require further diagnostic measures. Manifestations of a malignant lymphoma in the cerebellopontine angle are extremely rare. To our knowledge a case of an intracerebral lymphoma in a patient with Sjögren's syndrome has never been reported before.

Cerebellar Neoplasms↗
PubMed1998

[Long-term results after modified Réthi-plasty in childhood].

BACKGROUND: Laminotomy as described by Réthi has proved useful in the treatment of laryngotracheal stenoses. Using this technique in children poses the question as to whether it interferes with the growth of the larynx and trachea. The aim of our study was to verify the influence of this operative procedure on the structure and function of the restored airway. PATIENTS: Fifteen children between the ages of 2 and 16 with severe laryngotracheal stenoses (Cotton Grade III and IV) underwent reconstruction with interposition of a piece of costal cartilage in the posterior cricoid plate. Indications for this procedure included the presence of severe circumferential subglottic stenosis in combination with stenosis of the posterior glottis (8 children) and complete atresia (4 children). RESULTS: In endoscopic follow-up examinations (2-12 years follow-up), complete epithelization with light stenosis in the subglottis was demonstrated in all cases. Airway ventilation tests showed a slight or moderate central obstruction in nearly all cases. No disturbance of growth of the larynx was noted. CONCLUSIONS: This technique is a safe and successful method for repairing severe subglottic stenoses in children. Although there are some structural and functional problems during the long term follow-up, this is not considered a significant disadvantage.

Adolescent↗
PubMed1995

[Epithelialization of porous biomaterials with isolated respiratory epithelial cells in vivo].

Extensive tracheal defects after prolonged assisted ventilation, trauma or large resections in tumor surgery are a challenge in plastic and reconstructive surgery. Defects which cannot be satisfactorily repaired reguine near of an alloplastic tracheal replacement. Previous experimental and clinical experiences in the development of an alloplastic tracheal prosthesis have demonstrated that the main cause for failure is the lack of an epithelial lining of luminal surfaces and inadequate biophysical properties of the prosthesis. With the use of a cell-seeding technique tested in vitro on biomaterials epithelialization of tracheal prostheses can be tested in vivo. In animal experiments isolated respiratory cells were seeded into implanted tubular prostheses of porous polyurethane or expanded polytetrafluorethylene. Light and scanning microscopic investigations then showed the tendency of epithelialization to occur on the luminal surfaces. Vigorous squamous epithelium cell layers that were single and (predominantly) multiple layers were found. Differentiated cilated or mucous cells were not detected in any case. The present results have shown that epithelialization of incorporated porous implants is possible. The realization of usable tracheal replacement for clinical practice must still be tested in further experiments.

Animals↗
PubMed1991

A new concept for reconstruction of atresias of larynx and trachea: lining of wound surfaces with autologous isolated respiratory epithelial cells.

A new method, first applied two years ago in our clinic, has proved to be reliable for achieving a rapid reepithelialisation of epithelial defects after scar removal inside the trachea. The defect is seeded with isolated respiratory epithelial cells harvested the day before from the ethmoid. Isolation of epithelial cells was achieved by keeping the mucosa in 0.25% trypsin buffer solution under room temperature for about 16 h. Afterwards, the epithelial layer was separated from the submucosa using small forceps and knife. Cells were then isolated by pipetting. For seeding the wound the surface was covered with silastic sheeting and the cell suspension then injected into the cleft between both of them. Cell distribution occurred by capillary attraction. The tracheal lumen was maintained by inserting a silastic stent for about three weeks. So far, 10 patients between 6 and 45 years have been treated in this way. In 4 patients the tracheal wall additionally had to be stabilized using rip cartilage. Only in one case above the tracheostoma, considerable scar formation occurred again requiring a second operation some months later. In 8 patients decannulation was meanwhile possible.

Adolescent↗
PubMed1991

[The surgical approach to the cochlear nucleus area].

The stimulation of the proximal auditory nerve or the Cochlear Nuclear Complex (CNC) situated in the lateral recess of the fourth ventricle is a possibility of hearing rehabilitation for patients suffering from bilateral deafness by bilateral cerebellopontine-angle tumors or by transsections of cochlear nerves on both sides. Using such anatomical landmarks as proximal cochlear nerve, flocculus, choroid plexus and taenia the surgeon can locate exactly the CNC for this stimulation. We investigated location, diameter and surrounding structures of the CNC on 10 human brains fixed in 10% formalin-solution and on 9 histological series of these subjects.

Acoustic Stimulation↗
PubMed1990

[Menière's disease. An analysis of clinical findings].

During a period of about 25 years 500 patients with Ménière's disease underwent treatment for their disease in the ENT clinic of the Charité Hospital in Berlin. In a long-term follow-up study of the course of the disease, 170 patients (80 female, 90 male) with a minimum duration of illness of 5 years could be registered. The detailed analysis based on differentiation of vertigo attacks, audiological and vestibular findings offered 3 different phases of the natural course of Méniére's disease: 1. Early phase: Vertigo attacks and fluctuating hearing loss mainly in the low-tone frequencies; 2. Chronic phase: Decrease of frequency and duration of attacks; 3. Late chronic phase: Hearing loss of nearly 50-60 dB and loss of vestibular excitability (caloric response, side difference ca. 50%). In consideration of neurological symptoms in the late chronic phase symptoms of Ménière's disease are changing into symptoms of vertebrobasilar insufficiency. The natural course of Ménière's disease and resulting therapeutical and diagnostical aspects require long-term therapeutic planning. An appropriate schedule is suggested.

Adult↗
PubMed1990

[Congenital epidermoid tumors of the temporal bone. 1: Pathogenesis].

Epidermoids (congenital cholesteatomas) of the mastoid air cells lying behind an intact tympanic membrane are not as rare as previously supposed. We discuss the current hypotheses of their pathogenesis critically, and favour the hypothesis of germ scattering. We summarize some not so well known details of the early stages of development of the normal involution of the first branchial cleft and of the first pharyngeal pouch as well as the subsequent development of the external meatus, the tubotympanic recess and the pneumatized spaces of the temporal bone. On this basis the transfer of ectodermal cells to the entoderm, the subsequent transmission from the embryonal closing membrane to the definite pneumatic spaces of the middle ear, and the variable frequency of recurrence of epidermoids in these diverse spaces are explained.

Cholesteatoma↗
PubMed1990

[Surgical anatomy of the petrous canal and posterior cranial fossa in relation to hearing preservation in surgery of acoustic neuroma].

The suboccipital (retrosigmoid) and the middle fossa routes are recommended for preservation of hearing in surgery for acoustic neuroma. We carried out a comparative study of the critical distances and bony landmarks on 520 petrous bones. Unlike the transtemporal route, the suboccipital approach offers no landmarks for identification of the common crus, the vestibule or the facial nerve; the lateral portion of the internal auditory canal is not always seen. The fundus can be seen in only 50% of bones without opening the labyrinth.

Adolescent↗
PubMed1989

[The immunohistochemistry of pituitary adenomas].

A great deal of progress has been achieved in recent years in the field of immunohistochemistry of pituitary adenoma. Continued use of more new antisera and monoclonal antibodies against numerous hormones in the adenohypophysis have resulted in new approaches to classification of pituitary adenoma. However, new problems have been discovered, on the other hand, by large-scale studies in recent years. The great number of multihormonal pituitary adenomas and possible change of the immunohistochemically detectable hormone status in cases of recurrent tumours have particularly re-emphasised the need for new thinking about patterns of classification. It would appear somewhat problematic, in this context, to uncritically accept terms, such as ACTH cellular adenoma or GH cellular adenoma. Reference is also made to the distribution pattern of cell and tissue markers in pituitary adenomas. The paper is based on thorough literature screening as well as on experience obtained by the authors from 450 cases of pituitary adenoma of which 260 had been analysed by immunohistochemistry, 131 by morphometry, and 80 by electron microscopy.

Adenoma↗
PubMed1989

[Action and biocompatibility of two collagen-based hemostatics in animal experiments].

Efficacy and biocompatibility of two collagen hemostatic wound dressings (usual agent: Collastypt, fluid-stabilised agent: Lyostypt) were compared. In a prospective randomized study the local hemostatic effect (bleeding time and blood loss) of the two agents were investigated after liver trauma of 45 rats. Liver wounds which remained untreated served as controls. Both preparations significantly reduced bleeding. The fluid-stabilised agent was significantly superior to the second collagen agent of different manufacturing.

Animals↗
PubMed1988

One hundred and seventy-five surgically treated malformations of the external and middle ear: findings and results.

During 10 years 222 patients suffering from malformation of the external and/or middle ear came for treatment to our clinic. One hundred and fifty-seven have been operated on, 139 on one side, 18 bilaterally. This report is based therefore upon 175 cases and deals especially with findings seen during operation, methods of reconstruction and results achieved. Thirty-six patients showed a stenosis of the external meatus, 78 had a partial or complete aplasia. In 61 ears exclusive malformation of middle ear structures was the cause of hearing loss (anomalies of malleus 58.2%, of incus 58.8% and of the stapes nearly always: 172 out of 175 ears). Combinations were frequent. Three structures may affect the development of the ossicular chain, when showing abnormal development themselves: 1) facial nerve, 2) a persistent stapedial artery and 3) the chorda tympani. Anomalies of the course of the facial nerve have been found in 87 ears. In 60 cases these deviations of the course caused obviously a malformation of the ossicular chain, too. A persistent stapedial artery has been seen in six ears. The stapes footplate was always fixed. In four patients a lateral deviation of the chorda tympani's course caused an interruption of the ossicular chain, mainly between the head and the handle of the malleus. The long process of the incus was involved, too, in different degree. The ratio between one-sided and bilateral aplasias was about 2:1. Our method to reconstruct the external meatus is described in detail. The functional results were very satisfying in exclusive anomalies of the ossicular chain.(ABSTRACT TRUNCATED AT 250 WORDS)

Ear, External↗
PubMed1988

Long-term implantation of a system of electrical stimulation of paralyzed laryngeal muscles in dogs.

Electrical stimulation of the posterior cricoarytenoid muscle, synchronized with inspiration, was achieved in dogs utilizing a radio frequency stimulus triggered by a chest wall expansion transducer. This system brings about abduction of the paralyzed vocal cord for the entire duration of inspiration, which allows a normal flow of air through the larynx. The implantable part of that system was tested successfully in chronic experiments (up to 11 months) in dogs with experimental paralysis of the recurrent laryngeal nerve. We feel that the system may be suitable for pacing the paralyzed human larynx.

Animals↗
PubMed1987

Inhibition of inner ear ornithine decarboxylase by neomycin in-vitro.

We quantitated the activity of ornithine decarboxylase (ODC) in homogenates and subcellular fractions of inner ear tissues from the rat and guinea pig and demonstrate inhibition of cochlear ODC by the aminoglycoside neomycin. Subcellular fractionation showed the enzyme associated with the post-mitochondrial supernatant fraction in each of the tissues: Specific activities of ODC, defined as alpha-difluoromethylornithine (DFMO)-sensitive decarboxylation of ornithine, in the supernatant fractions of combined inner ear tissues were: guinea pig = 44 +/- 4 pmoles CO2 produced/hour/mg protein, and rat = 133 +/- 30. In the guinea pig, supernatant fractions of the lateral wall tissues (stria vascularis and spiral ligament) had specific activities of 62 +/- 25, those of the organ of Corti (plus VIIIth nerve) 64 +/- 41. The ototoxic aminoglycoside neomycin produced a dose-dependent inhibition of ODC with half-maximal inhibition observed at 50 microM drug and almost complete inhibition at 100 microM. This is the first report of the presence of ODC in the inner ear and its inhibition by neomycin. Since both the ODC-inhibitors, DFMO and neomycin, can cause hearing loss in patients and experimental animals it is suggested that inhibition of ODC may be an important factor in the ototoxicity of these drugs.

Animals↗
PubMed1984

Pathogenesis of dysplasias of the face and the ear and dystopias of the temporal region.

Dysplasias of the face and ear are supposed to be caused by a premature involution of 3 different embryonal arteries of the branchial arches: (1) Dysfunction of the mandibular artery causes the otocephalia syndrome; (2) that of the stapedial artery causes dysplasias of the face; (3) dysfunction of the hyoid artery entails dysplasias of the ear; and (4) combination of (2) and (3) (dysfunction of truncus hyostapedialis) results in simultaneous dysplasias of the face and the ear. The earlier the deficiency of blood supply occurs the more serious the resulting dysplasias are. The dystopias in the temporal region (auricles, facial nerve, ossicles, petrous bone) are the consequence of an overbending of the proximal hyoid arch caused by a retardation in the development (shortening) of the mandibular arch. Therefore, dystopias of the ear always occur together with dysplasias of the face. Phenotype and appearance on radiographs are discussed.

Adolescent↗
PubMed1984

Respiratory rhythmically regulated electrical stimulation of paralyzed laryngeal muscles.

Electrical stimulation of the posterior cricoarytenoid muscle, synchronized with inspiration, was achieved in dogs, utilizing a radio frequency stimulus triggered by a chest wall expansion transducer. This system brings about the abduction of the paralyzed vocal cord for the entire duration of inspiration, which allows a normal flow of air through the larynx. The stimulation system could be tested successfully in actual experiments in dogs with artificial paralysis of the recurrent laryngeal nerve. Its effectiveness could be proved through observation of the vocal cord movements (photographic documentation) and recording subglottic pressure variations. Transmission of stimulation energy is effected by electrical induction.

Animals↗