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Biomedical subjects

M Zrunek

Publications and source records attributed to M Zrunek.

At least 19 recordsLinked to original sources
PubMed1999

Battery-powered miniature implant for electrical nerve stimulation.

The range of application of implantable stimulators in functional electrical stimulation (FES) for therapeutic purposes and for the restoration of lost or damaged functions has steadily grown within the last 20 years. Each time a clinically used method is improved, a new field of FES application explored or basic research conducted, animal experiments are needed to check and evaluate the findings and results. It is precisely for this use that the stimulation system described in this paper was developed. The battery-powered single-channel stimulator can be used for the excitation of motor and sensory nerves with monophasic or biphasic impulses. All parameters and functions are programmable via the bidirectional telemetry circuit. Implant programming is achieved by a laptop computer, supported by a graphical user interface, instead of by a specially designed programmer. The maximum settings of the stimulation parameters are: frequency 100 Hz, monophasic pulse duration 0.8 ms, biphasic pulse duration 1.6 ms, stimulation current 3 mA. The implant volume was reduced to 2 cm3 (length 23 mm, width 13 mm, height 7.5 mm), lowering the weight to 3.6 g. Due to this small volume the implant can be used in small animals. The power supply via battery obviates the need for transcutaneous tunneling or permanent external high-frequency senders and facilitates the keeping of the animals.

Animals↗
PubMed1996

Flexible fiberoptic endoscopy and laser surgery in obliterated cochleas: human temporal bone studies.

BACKGROUND AND OBJECTIVE: The use of conventional drilling procedures in cochlear implant surgery of ossified cochleae poses special risks to the facial nerve and the carotid artery. This study evaluated the alternate use of flexible fiberoptic endoscopy and mid-infrared laser surgery for recanalization of partially and artificially obliterated cochleae in freshly dissected human cadavers. STUDY DESIGN/MATERIALS AND METHODS: A pulsed Holmium:YAG-laser (lambda = 2120 nm) was used in the free-running mode (1180 mJ, 250 microseconds pulse, 5 Hz). A 660 microns optic quartz fiber was positioned in the center of the round window niche and slowly--endoscopically guided--advanced in contact shooting over 1.5 cm, creating by vaporization and photoablation a passage through the artificial bony occlusion in the basal segment of the cochlea. RESULTS: In all experiments, laser application (110-130 pulses) resulted in complete recanalization of the bony occlusions without damaging surrounding structures. The microendoscopy proved capable of guiding the laser fiber through the curved segment of the basal turn allowing identification of normal bone, bone cement, and laser-treated bone cement. CONCLUSION: If partial ossification of the basal turn is present, this technique could give access to place analog as well as digital implants deep within the cochlea.

Cochlea↗
PubMed1994

Holmium: YAG laser surgery in obliterated cochleas: an experimental study in human cadaver temporal bones.

A pulsed holmium:YAG laser (lambda = 2120 nm) was used to reopen the basal turn of artificially obliterated human cochleas in freshly dissected cadavers. This allowed intracochlear insertion of the stimulation electrode of a cochlear implant under simulated surgical conditions. Laser energy was transmitted through a 400-microns nylon fiber via the opened facial recess directly to the round window niche. At an energy level of 500 mJ per 2.5 microseconds pulse, a repetition rate of 2 Hz, and an exposure time of 20-30 s, the photo-ablative mechanism of laser-bone interaction led to a 8-10 mm recanalization of the basal turn of the cochlea without damaging surrounding structures. The artificial bony occlusion and the recanalized basal turn of the cochlea were visualized by means of computed tomography and studied under light microscopy, using a histologic thin-section technique.

Aluminum Silicates↗
PubMed1994

[Experimental laser surgery of the ossified cochlea].

A pulsed holmium: YAG-laser (lambda = 2120 nm) was used to reopen the basal turn of artificially obliterated human cochleas in freshly dissected cadavers for intracochlear insertion of the stimulation electrode of a cochlear implant under simulated surgical conditions. Laser energy was transmitted through a 400 microns nylon fibre via the opened facial recess directly to the round window niche. At an energy level of 500 mJ/2.5 microseconds pulse, a repetition rate of 2 Hz, and an exposure time of 20-30 s, the photo-ablative mechanism of laser-bone interaction, which has only a limited thermal component, led to recanalisation of the basal turn of the cochlea in a length of 8-10 mm without damaging the surrounding structures. Light microscopic changes in the cochlea were evaluated following laser recanalisation. The artificial bony occlusion and the recanalised basal turn of the cochlea were visualised by means of computed tomography and histological thin section technique.

Cochlea↗
PubMed1994

The Vienna Cochlear Implant in patients with obliteration of the cochlea.

Twelve deaf patients with obliterated or ossified cochleas received the extracochlear version of the Vienna Cochlear Implant. Four patients, 1 of them a child, developed open speech comprehension. Obliteration of the cochlea could not always be predicted by conventional tomography of the temporal bone. Short duration of deafness, wide dynamic range, and good ability of time resolution (small temporal difference limen [TDL]) are predictors for good postoperative results. Obliteration or ossification of the cochlea per se is no contraindication to cochlear implantation.

Adult↗
PubMed1994

Long-term results after stapedectomy versus stapedotomy.

In a retrospective study postoperative hearing results after stapedotomy were compared with those after stapedectomy. Of 117 patients suffering from otosclerosis, 93 percent were primarily successfully operated between 1980 and 1990 in the ENT department of the University of Vienna. Long-term results from 35 stapedotomies and 22 stapedectomies were compared. Stapedotomy gave better results for high frequencies than stapedectomy. Whereas after stapedotomy no case of hearing loss could be observed, the incidence of anacusis after stapedectomy was 1.7 percent. Therefore, it is concluded that stapedotomy should be the preferred surgical technique in the treatment of otosclerosis.

Aged↗
PubMed1993

[Manifestation of malignant lymphomatous polyposis of the nasopharynx].

A 66 year old male patient with malignant lymphomatous polyposis of the gastrointestinal tract showed a manifestation in the nasopharynx. After 6 cycles of chemotherapy according to the CHOP-Scheme complete remission could be observed. 9 months after therapy no signs of recurrence were evident.

Aged↗
PubMed1993

[Chondromatous tumors of the larynx based on three case reports with special reference to magnetic resonance tomography].

Cartilaginous tumours of the larynx are rare, altogether about 250 cases being reported in the literature. These tumours typically grow slowly and malignant types usually show only local infiltrative growth. Distant metastases are rarely observed. Up until the present CT has been the main diagnostic tool due to its excellent demonstration of intra-tumoral calcifications. In the German literature Grevers et al. reported on MRI in cases of laryngeal tumours. Since we do not know of any reports discussing the special situation of cartilaginous tumours in this location, we present three cases of cartilaginous tumours outlining the effectiveness of MRI.

Biopsy↗
PubMed1992

[Malignant lymphomatous polyposis of the gastrointestinal tract].

Two years after endoscopic excision of several polyps of the colon (histological examination revealing infiltration by a malignant non-Hodgkin lymphoma) a 67-year-old man was again found to have blood and mucus in his stool. Because local recurrence was suspected a coloscopy was performed. This revealed multiple polyps throughout the entire colon, predominantly in the sigmoid and rectum. Biopsy showed focal infiltration of the submucosa and mucosa with centrocytic non-Hodgkin lymphoma, compatible with the diagnosis of malignant lymphomatous polyposis of the gastrointestinal tract. Gastroduodenoscopy then demonstrated duodenal polyps and massive coarsening of the gastric folds due to infiltration. For the first time tumour masses were also found in the epipharynx. After 6 chemotherapy cycles according to the CHOP scheme (day 1: cyclophosphamide, 1500 mg, adriblastin, 100 mg and vincristine, 2 mg; days 1-5: prednisolone, 100 mg) all lymphoma infiltrates regressed completely. The patient has been symptom-free for 9 months.

Aged↗
PubMed1991

A laryngeal pacemaker for inspiration-controlled, direct electrical stimulation of the denervated posterior cricoarytenoid muscle in sheep.

Bilateral recurrent nerve palsies were induced in four sheep and unilateral nerve palsy in one sheep. Vocal cord abductions were achieved by direct electrical stimulation of the posterior cricoarytenoid muscles (PCMs). By means of the diaphragmatic myogram, respiratory synchronous activation of the glottis opening musculature was shown possible. In all cases an adequate glottis opening for respiratory function was achieved during a maximum period of stimulation of 5-8 h in each animal. Abductor movements of the vocal cords were documented with video laryngoscopy. Using digital image processing, the areas of the open glottis were measured at rest and during bilateral direct electrical stimulation of the PCMs.

Animals↗
PubMed1991

[Functional and electromyographic long-term results following primary microsurgical repair of the recurrent laryngeal nerve].

Six patients with unilateral recurrent nerve paralysis underwent phoniatric follow-up after neurolysis or primary microsurgical repair of the recurrent laryngeal nerve. Four patients were controlled by electromyography of the vocal muscle 14 to 80 months post-operatively. In six patients the paralyzed vocal cords were in median to paramedian position with sustained muscle tonus. Phoniatric parameters were found to be close to the average range in healthy persons. EMG findings indicated degenerative neurogenous paralyses in two patients, signs of reinnervation in another. In one case biphasic action potentials could be recorded.

Adult↗
PubMed1988

Isomyosin changes after functional electrostimulation of denervated sheep muscle.

Isomyosin analyses by biochemical, immunochemical, and histochemical investigations have been carried out in five sheep following unilateral recurrent laryngeal nerve paralysis and direct functional electrostimulation of the denervated cricoarytenoid posterior muscle. Myosin light chains were identified by two-dimensional gel electrophoresis. Myosin heavy chains were analyzed by one-dimensional SDS-polyacrylamide gel electrophoresis. Slow myosin heavy chain was identified by orthogonal peptide mapping and immunochemistry. The stimulation effect at cellular level was determined using adenosine triphosphatase (ATPase) histochemistry. A dramatic increase of the type 1 fiber area (slow, fatigue-resistant fibers) could be seen after many weeks of an increasing regime of low-frequency direct electrical stimulation. Biochemically, the amount of slow myosin was always higher than in normal muscles. Some muscles were transformed almost completely to the slow type. At the time they were studied and with the methods employed, the expression of embryonic isomyosin was not observed. In conclusion, after numerous weeks of maintained functional activity, elicited by direct electrostimulation, the denervated muscle regionally showed areas of hypertrophy or at least lack of atrophy of slow myofibers without major signs of muscle damage.

Animals↗
PubMed1986

[Acute loss of vestibular function: an emergency for patient and physician].

The dramatic symptomatology of sudden loss of vestibular function alarms the patient and the physician who is consulted in an emergency situation. The continuous vertigo is often accompanied by marked autonomic symptomatology, so that heart and cerebral diseases as well as acute intoxication are often primarily diagnosed. The differential diagnosis, clinical features, course of the disease and treatment are presented in this study of 54 patients treated in our department between 1980 and 1985. Aetiology and pathogenesis are discussed on the basis of the literature.

Acute Disease↗
PubMed1986

[Realtime sonography in the diagnosis and follow-up of malignant tongue tumors. II. Detection and staging].

92 sonographic examinations performed in 62 patients were evaluated to determine the possible application of sonography in the diagnosis and follow-up of malignant tumours of the tongue. Squamous cell carcinomas were by far dominant and proved to be hypoechoic, mainly inhomogeneous and ill-defined masses. In most cases, they ranged between 2 and 4 cm. in diameter. In 50% of the lesions an infiltration of the pharynx wall was confirmed, and exulcerations were correctly detected by sonography in 75%. In preoperative determination of the size of the tumour, sonography correctly detected the size in 93% of the cases and was thus markedly superior to the clinical palpatory examination, which determined a mere 43% correctly. Sonography should be included in the pretherapeutic staging of tumours of the tongue to objectify the clinical findings. It is also adequate to document tumour behaviour during radiation.

Aged↗
PubMed1986

[Differences in the neuromuscular blockade of the larynx and thenar muscles following relaxation with vecuronium].

To objectivate the clinical impression of different neuromuscular depression in the larynx- and limb-musculature, an attempt was made in 5 patients to quantify laryngeal muscle relaxation by electromyographic recordings of evoked responses from the vocalis muscle during endolaryngeal microsurgery. Mechanographic and evoked electromyographic recordings of the thenar muscles were obtained simultaneously. Nearly total suppression of evoked responses at the peripheral muscle site was observed after a bolus dose of either 60 micrograms/kg or 100 micrograms/kg of the nondepolarising muscle relaxant Vecuronium. However, the vocalis muscle was not blocked completely. The neuromuscular depression ranged from 61 to 92% depending on the dose. In no case was the recommended intubating dose (ED 95) of 60 micrograms/kg sufficient for complete relaxation of the vocalis muscle. The present results do not support that the extent and/or time course of intrinsic laryngeal muscle relaxation correlates with peripheral neuromuscular depression in a quantitative manner. The different degree of relaxation achieved by Vecuronium in the hand and larynx is probably due to their different content of acetylcholine receptors.

Adult↗