M. Zrunek

Comparative Anatomy of Human and Sheep Laryngeal Skeleton

In a macroscopical study the dimensions of the adult laryngeal skeleton of man and sheep were compared. In both species the data for male and female were evaluated separately. In contrast to pronounced differences in size between male and female human larynges, the dimensions of both sexes in sheep proved to be very similar. In respect of 7 size values, the sheep larynx falls in the range between the male and female human larynx. This applies to most values for height, the antero-posterior diameter and the inferior breadth of the thyroid cartilage. In the sheep cricoid, the height of the lamina and the inner transverse diameter correspond closely to the human counterpart. The most conspicuous differences vis-à-vis the human larynx are the narrowing of the upper portion, the absent upper incisure of the thyroid and the relatively large dimensions of the arytenoid cartilages in sheep. Since in sheep the dimensions at the level of the glottis and of the subglottic space are within the range of the human larynx, the suitability of the sheep larynx as a model for experimental clinical laryngology is discussed.

Comparative Histochemistry of Human and Sheep Laryngeal Muscles

Four laryngeal muscles of human male, human female and sheep female cadavers were evaluated by histological, histochemical and quantitative techniques. The muscle fibre sizes showed significant differences between human male, female and sheep. Fibre diameters of male human laryngeal muscles were 2 to 4 microns larger than in female human and 11 to 13 microns larger than in sheep muscles. In the group of human laryngeal muscles, the posterior cricoarytenoid muscle contained the highest percentage (65%) of type I fibres. In sheep, the homologous muscle consists only of 45% type I fibres. On the other hand, in sheep the cricothyroid muscle showed significantly more type I fibres (58%) than the human counterpart (43%). In both species the vocal muscles had a rather low content of type I fibres (26 to 37%).

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

SummaryBilateral 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.

Laryngeal Pacemaker: Activity of the Posterior Cricoarytenoid Muscle (PCM) and the Diaphragm during Respiration in Sheep

Electromyograms (EMG) of the PCM and the diaphragm were evaluated in 6 sedated female sheep. Corresponding pneumatograms were recorded simultaneously by means of thermocontrolled respiration flowmeter. Evidence was obtained on considerable intra- and inter-individual differences in the duration of respiratory cycles as well as PCM- and diaphragmatic activity. Most of the evaluated respiratory periods showed either a phase coincidence between the PCM and the diaphragm, or a leading edge of about 40-80 ms of the posticus muscle. Due to this minimal phase shift, the diaphragmatic myogram seems to be a valuable trigger for an external PCM stimulation unit in bilateral recurrent nerve palsy.

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.

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

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.

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

A pulsed holmium: YAG laser (λ = 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-μm nylon fiber via the opened facial recess directly to the round window niche. At an energy level of 500 mJ per 2.5 μs 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.

Experimentelle Laserchirurgie bei ossifizierter Kochlea

Die Ergebnisse nach Versorgung tauber Patienten mit intracochlearen Implantaten sind denen nach extracochlearer Implantation uberlegen. Patienten mit ossifizierter Cochlea werden bislang extra-cochlear oder im Falle der Moglichkeit der Eroffnung der basalen Schneckenwindung mit konventionellem Instrumentarium partiell intracochlear plazierte Elektroden implantiert. Die Verwendung von Lasern mit Abtragen von Hartgewebsstrukturen im Mittel- und Innenohr ist bei Verwendung herkommlicher fasergangiger ARGON, KTP oder Nd-YAG-Laser-Systeme aufgrund ausgedehnter Schadigungszonen nicht moglich.

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.

Zwerchfellsynchrone funktioneile Stimulation der Glottisöffnung

Das Versuchsprogramm zur Synchronisation mit der Atmung wird von Zrunek et al. im Rahmen der vorliegenden Publikation dargestellt 12}. Der gegenständliche Artikel beschreibt die Gewinnung des Steuersignales für das Stimulationsgerät aus dem Zwerchfellmyogramm. In der Folge wurden an fünf Schafen Recurrensdurchtrennungen durchgeführt, Stimulationselektroden in die Mm. postici und Ableitelektroden in das Zwerchfell implantiert. Mit den Experimenten wurde zwischen 8 Stunden und 7 Tagen nach der Denervation begonnen; es wurde zwischen 5 und 8 Stunden lang atemsynchron stimuliert. Die morphometrische Vermessung der Glottisfläche nach Videodokumentation mit Hilfe eines Lupenlaryngoskopes zeigt durchwegs eine Flächendifferenz von ca. 40% zwischen stimuliertem und relaxiertem Zustand.