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Biomedical subjects

M Tos

Publications and source records attributed to M Tos.

At least 127 records · Page 7Linked to original sources
PubMed1992

The early stages of polyp formation.

The purpose of this study is to describe polyp formation in the mucosa of the middle ear as a possible model for the pathogenesis of nasal polyps. In 65 Wistar rats, the eustachian tube was occluded on the left side for up to 20 months; 60 right-sided, nonoccluded ears served as controls. Following occlusion, the middle ear mucosa was examined for signs of polyps. Signs of polyp formation or fully developed polyps were seen in 14 (22%) of the middle ears, and were only seen in middle ears with signs of actual or previous infection. It was established that the first stages of polyp formation include epithelial rupture, proliferation of fibrous tissue through the epithelial defect, and epithelialization of the prolapsed fibrous tissue by proliferation and migration of epithelial cells from the surrounding epithelium until there is full epithelial covering of the polyp. This report discusses whether the described middle ear model may form basis for the explanation of the pathogenesis of nasal polyps.

Animals↗
PubMed1992

Incidence and progression of myringo-incudo-pexy after secretory otitis.

A cohort of originally 327 healthy children born in 1975 was followed by repeated otomicroscopies and tympanometries from age 5 to age 16 years, in total 9 otomicroscopies. Prevalence of drum pathology, especially myringo-incudo-pexy was investigated. Prevalence of myringo-incudo-pexy was 0.5% at age 5 years, 2.5% at age 7 and 4.2% at age 16. Forty percent of pexies were stable; 36% fluctuated and 26% disappeared. Hearing was surprisingly good at age 16, but the pexy represents a risk for progression.

Acoustic Impedance Tests↗
PubMed1992

Suboccipital acoustic neuroma surgery: results of decentralized neurosurgical tumor removal in Denmark.

From 1979 to 1990, a series of 59 patients with 59 acoustic neuromas were operated on in five departments of neurosurgery by at least five different neurosurgical teams, employing the suboccipital approach. Perioperative mortality rate was 8.5%. Complications including hematoma, ventricular hemorrhage, meningitis, hemiparalysis, abducens nerve paralysis, recurrent nerve paralysis, postoperative wound infection and CSF leak were observed in 21 patients (35.6%). Total tumor removal was not possible in 17 patients (28.8%). Converting the postoperative facial nerve function to House-Brackmann (HB) classification, 34 patients (57.6%) were regarded as HB 6. Reconstruction of the facial nerve was attempted in 19 patients (32.2%). Attempts at hearing preservation were unsuccessful in all patients. Failure to attain better results and the importance of centralized treatment of acoustic neuroma are emphasized.

Adult↗
PubMed1992

Daily impedance audiometric screening of children. Validity of impedance tympanoscope ZS331 compared with impedance audiometer AZ7.

The purpose of the present study was to test a fully automated screening impedance tympanoscope against a clinical impedance audiometer. Previous studies have indicated a relatively high incidence of type B tympanograms when using the tympanoscope and in addition shown a surprisingly large number of type B curves of one day's duration. The present study was based on 51 otherwise healthy children attending kindergartens (100 ears) who underwent daily tympanometric screening with both the impedance tympanoscope ZS331 and the impedance audiometer AZ7. The tympanoscope indicated a significantly larger number of type B tympanograms, and in 16 cases the type B curves could be demonstrated on only one day, resulting in significantly higher point and period prevalences of type B tympanograms. The difference is mainly attributable to the different ways in which a type B tympanogram is defined by the two instruments. On the basis of the present study we conclude that the impedance tympanoscope is not well suited for this type of study.

Acoustic Impedance Tests↗
PubMed1992

Incidence of acoustic neuromas.

The annual incidence of diagnosed acoustic neuromas in Denmark during two 7-year periods from June 1976 to June 1990 was compared, collecting all operated and non-operated tumors from the entire country. During the first period 278 tumors were diagnosed with an annual incidence of 38 tumors or 7.8 tumors per million per year. During the second period the annual incidence rose to 48 tumors and 9.4 tumors per million per year. There was a significant decrease of extrameatal tumor size from 33 to 26 mm and diminishing of giant tumors.

Denmark↗
PubMed1991

[False-positive diagnostic findings in acoustic neurinomas].

In the period from 1976 to 1990 Tos and Thomsen operated on 520 patients with acoustic neuromas using the translabyrinthine approach and five other patients were operated on via middle fossa approach. The diagnostic work up in all patients included: pure tone audiometry, tympanogram with acoustic reflexes, caloric test and brainstem audiometry. Since the late seventies, CT became the radiological investigation of choice to visualize the tumor. The first generation of CT failed to reveal tumors less than 1.5 cm in the extrameatal diameter, and pantopaque cisternography was necessary in some cases. The following generation of CT did not always reveal small intrameatal tumors, and false-negative results were reported. The incidence of false-positive CT findings in our series is calculated to be 0.6%. Three patients were operated on on account of false-positive CT. Peroperatively, adhesions in and around the internal porus were found in two cases while no pathology was found in the third case. Postoperatively, anacusis was observed in two cases. This could have been avoided if magnetic resonance imaging (MRI) with gadolinium contrast had been performed. In our opinion, MRI should be considered before a definitive surgical procedure is undertaken. Until MRI becomes more widely available, intravenous contrast-enhanced tomography followed by air cisternography is recommended in the diagnosis of small acoustic neuromas.

Adult↗
PubMed1991

Diagnostic and treatment problems in skull base meningiomas.

Two cases of combined intra- and extracranial meningiomas are presented. It both cases the middle ear problems preceded the diagnosis by several years. The diagnosis was made in one patient because of tumor invasion of the middle ear and in the other because of tumor invesion of the nasal cevity. In both instances the diagnosis was made at a stage at which total tumor removal was considered unwarranted in the light of the paucity of symptoms. A discussion of the clinical behavior of such meningiomas is given. The vast majority of co-called primary extracrenial ectopic meningiomas are not truly primary extracranial tumors, but rather extracranial extensions of intracranial lesions. The importance of computed tomography or magnetic resonance imaging examinations in patients with long-standing middle ear problems of undiagnosed etiology is stressed.

Journal Article↗
PubMed1991

Origin of nasal polyps.

The nasoethmoid complexes from 6 patients with nasal polyps were systematically examined. First, the location and place of the origin of the polyps were recorded and photographed. The polyps and their places of origin were removed, serial sectioned, and examined. In all 6 patients, the polyps originated from the nasal mucosa. Most of the polyps extended laterally from the mucosa into the anterior part of the middle meatus. Several polyps originated from the mucosa near the ethmoid cell ostium or directly from the mucosa lining the edge of the ostium. The ostia themselves were not blocked by the polyps, and there was no indication of polyp formation in the ethmoid cells.

Aged↗
PubMed1991

Inverted papilloma of the nasal cavity: pathological aspects in a follow-up study.

The initially removed tumors from 42 patients with inverted papillomas of the nasal cavity and paranasal sinuses were subjected to an extensive histopathological examination in order to define the characteristics associated with multiple recurrences and development of malignancy. Two of the patients subsequently developed squamous cell carcinoma and eight patients had more than one recurrence. No specific histological characteristic was determined to be a predictor of multiple recurrences or development of malignancy. However, three patterns of characteristics emerged from the data which were found to be related to the development of malignancy, multiple recurrences, and benign behaviour. Malignancy was found to be associated with bilateral inverted papilloma, a predominance of mature squamous epithelium, the presence of all three epithelial types (metaplastic squamous, mature squamous, and cylindrical), severe hyperkeratosis, a mitotic index greater than or equal to 2 per high-power field (HPF), absence of inflammatory polyps among the papillomas, an abundance of plasma cells, and an absence of neutrophils. Multiple recurrences (without malignancy) were associated with a mitotic index greater than or equal to 2 per HPF and an absence of inflammatory polyps. Benign behaviour was associated with predominantly mucinous tumors, a mitotic index less than 1 per HPF, a ratio of neoplastic epithelium/connective tissue stroma greater than or equal to 6, and the presence of inflammatory polyps among the papillomas.

Carcinoma, Squamous Cell↗
PubMed1991

Hearing decrease after loss of cerebrospinal fluid. A new hydrops model?

In a prospective study of 12 patients undergoing operation for acoustic neuromas the hearing on the contralateral ear was tested before and systematically day by day after operation. In 11 cases a perceptive loss of at least 20 dB was found at one or more frequencies during the first 2 postoperative weeks. A maximal average threshold decrease of 16.5 dB was found in the treble (2.4, 8 kHz average), while a tendency of a more pronounced decrease of 19.6 dB was seen in the low frequencies (125, 250, 500 Hz average). After 3 months the hearing had normalized in all cases. The explanation for the transitional loss supports the present theory: The loss of cerebro-spinal fluid during operation diminishes the CSF pressure. This decrease is transmitted to the perilymph via the cochlear aqueduct producing a transitory perilymphatic hypotonia, which in turn hydromechanically results in a relative endolymphatic hypertension mimicking an endolymphatic hydrops thus representing a human hydrops model.

Adult↗
PubMed1991

Polyp formation by experimental tubal occlusion in the rat.

The purpose of this study was to show the early stages of polyp formation, as part of our studies on the pathogenesis of nasal polyps. Two and 4 weeks after experimental tubal occlusion in 18 Wistar rats, 13 showed signs of bacterial infection, respective acute otitis media. In the majority of these rats polypouslike protrusions of the middle ear mucosa were found in whole-mount specimens. All polypouslike protrusions were investigated by cross sections, which revealed localised accumulation of fluid and inflammatory cells in the lamina propria. The polyps were covered with a flattened epithelium, compared to the epithelium in the surroundings. In some of the bigger polyps the apical part was without epithelial covering. The findings suggest that the epithelium by fast polyp growth may be distended and may burst, or that a primary epithelial defect has not been sufficiently covered.

Animals↗
PubMed1991

Cerebrospinal fluid leak from nontumor ear after acoustic neuroma surgery: diagnostic and therapeutic problems.

An unusual case of CSF leak from the nontumor ear after removal of a 3-cm acoustic neuroma is presented. Prior to tumor removal a ventricular-peritoneal shunt was established because of increased intracranial pressure. After the shunt was clamped the patient twice developed rhinoliquorrhea and underwent in both instances unsuccessful closure of the leak on the tumor side. Finally the leak was established in the nontumor ear, most likely due to sequelae after a hunting accident 20 years before, where a projectile created a defect in the tegmen tympani. The CSF leak was probably provoked by the pressure changes following tumor removal and shunt treatment.

Brain↗
PubMed1990

Gastrin, cholecystokinin and their precursors in acoustic neuromas.

Using sequence-specific radioimmunoassays the occurrence of 4 neuropeptides (cholecystokinin (CCK), gastrin, somatostatin, substance P and some of their precursors) was examined in 19 human acoustic nerve tumors and corresponding normal tissue. The normal acoustic nerve tissue obtained by autopsy contained traces of CCK, somatostatin, and substance P (less than or equal to 0.5 pmol/g), but neither proCCK, gastrin nor progastrin. In contrast 8 tumors expressed proCCK (range 0.2-4.5 pmol/g), 3 tumors gastrin (0.1-7.3 pmol/g) and 14 tumors progastrin (0.6-2.2 pmol/g). Traces of somatostatin were present in two and substance P in one tumor. The results show that acoustic neuromas often express the homologous CCK and gastrin genes, but process their propeptides poorly to transmitter-active peptides. The tumor synthesis of gastrin/progastrin contrasts to the rare, sporadic expression of the gastrin gene in normal nerve tissue.

Adult↗
PubMed1990

[Postoperative hyperkinetic arrhythmias treated with amiodarone].

Twenty eight patients have been treated; 8 patients had atrial fibrillation (FA) and 20 supraventricular paroxysmal (SVPT) tachycardia. Both diseases followed interventions of major surgery. No patient had myocardial ischemia and/or damaged conduction system, took any heart-related drug, or showed any risk factor. The posologic plans was as follows: a) bolus i.v. (three minutes) with 2 Amiodarone vials and electrocardiographic monitoring, then b) 10-20 mg/kg/day for three days with electrocardiographic monitoring. Within 5 days, all patients attained the total recovery from SVPT; AF regressed during the bolus injection in 1 patient, on the first day in 5 patients, and on the third day in the remaining 2 patients. During the hospitalization no important side effects occurred, except for transient hypotension in three subjects. The 6 months follow up did not reveal signs of intolerance, either. Amiodarone thus showed to be useful and well tolerated in the treatment of post-surgical hyperkinetic arrhythmias in patients undergoing major surgery.

Amiodarone↗