Gisle Djupesland

Middle Ear Muscle Reflexes Elicited by Acoustic and Nonacoustic Stimulation

The function of the tensor tympani muscle has been studied by direct observation of its tendon. Results of this study together with a survey of the middle ear muscle reflexes in man are reported.

Size And Duration of Acoustically Elicited Impedance Changes in Man

The results of the present investigations show:1) The threshold for the acoustically elicited impedance changes is lower for white noise and low frequency stimuli than for high frequency stimuli.2) The size of the acoustically elicited impedance changes is larger for low frequency stimuli than for high frequency stimuli of the same intensity above the impedance threshold.3) The increase of impedance change as a function of increased stimulus intensity is faster for low frequency stimuli than for high frequency stimuli.4) The duration of the acoustically elicited impedance changes is longer for continuous low frequency stimulation of the same intensity above the impedance threshold.5) As far as the impedance change of the middle ear is considered a protective mechanism for noise induced hearing loss, our results indicate that the inner ear in this respect is better protected when exposed to low frequency sound than to high frequency sound.

TEMPORAL SUMMATION IN THE ACOUSTIC STAPEDIUS REFLEX MECHANISM

Temporal summation in the acoustic stapedius reflex mechanism was studied by monitoring acoustic impedance changes at the ear-drum. The results show that the duration of short acoustic stimuli (“white noise” and 1/1 octave bands of noise) has a pronounced effect on the stapedius reflex response. For a ten-fold increase of stimulus duration the intensity level had to be lowered by about 22 dB in order to elicit the criterion response (50% of maximal obtainable impedance change). For stimulus durations shorter than 5&80 ms, the relationship between sound intensity and stimulus duration was about the same for all types of stimuli, indicating that for such short stimuli temporal summation in the acoustic stapedius reflex is independent of the type of stimulus. For longer durations, several time constants of summation were found. The time constants were largely dependent on the type of stimulus. Possible explanations of these findings are discussed.

Intra-Aural Muscular Reflexes Elicited by Air Current Stimulation of the External Ear: Preliminary Report

A review is given of the intra-aural muscular reflexes elicited by air current stimulation of the external human ear. Air current stimulation is advantageous compared with acoustic stimulation, being independent of the hearing in the contralateral ear, provided the reflex path is intact. The diagnostic scope of impedance measurements is thus substantially increased.

A Comparison Between Middle-Ear Muscle Reflex Thresholds For Bone- And Air-Conducted Pure Tones

The middle-ear muscle reflex threshold for bone-conducted pure tones (250–6 000 Hz) was compared with the corresponding threshold for air-conducted tones. In normal-hearing subjects a significant difference (5–25 dB) was found. Possible causes for this discrepancy were studied.

Impedance changes elicited by electrocutaneous stimulation.

Electrical stimulation of the skin in the cavum conchae is followed by bilateral changes in the acoustic impedance of the ear due to reflex contraction of the stapedius muscle. A stimulator and a special surface electrode for electrical stimulation of the skin have been developed. The apparatus produces square-wave constant-current pulses independent of the electrical impedance of the electrode and the skin, and its hazard-proof. The effect of five independently variable stimulus parameters upon the elicited impedance changes has been examined in order to find a stimulus producing a large and reproducible impedance change without causing discomfort to the subject. Although a pronounced habituation phenomenon tends to mask the cause to effect relation of the various parameters, the results indicate that an appropriate stimulus is a pulse train of 0.5 s duration, consisting of individual pulses of a frequency of 200 Hz and 1 ms duration. The stimulus is applied at 10-second intervals.

Registrierung Von Intra-Auralen Muskelreflexen Durch Cutane Reizung Bei Menschen

Die Haut des Gehorganges und des ausseren Ohres mit der nachsten Umgebung ist beim Menschen mit sensorischen Fasern des n. facialis, n. trigeminus, n. vagus und n. glossopharyngicus ausgerustet. Die Nervenfasern dieses Hautbezirkes enden bei Ratten im Nucleus tractus solitari. Von da aus konnen die Impulse wahrscheinlich durch Zellen der reticularen Substanz auf die motorischen Facialis-und Trigeminuskerne uberfuhrt werden.Durch Luftstimulation des oben erwahnten Hautbezirkes haben wir eine klinisch einfach anwendbare Methode gefunden, mit der man beim Menschen nicht-akustische intraaurale Muskelreflexe hervorrufen kann. Die Reflexbahnen sind wahrscheinlich die gleichen wie bei Ratten. Die vorlaufigen Untersuchungen deuten darauf hin, dass der Stapediusreflex sowohl gekreuzt als ungekreuzt ist, wahrend der Tensorreflex im wesentlichen ungekreuzt ist.

Effect of Human Fibrin Adhesive on the Ear An Electrophysiological Study of Auditory Function in the Guinea Pig Correlated to Light and Electron Microscopy of Middle Ear Mucosa and Inner Ear Structures

The effect of human fibrin adhesive applied to the middle ear has been studied in guinea pig. Auditory function was measured using acoustically evoked brainstem responses. Middle and inner ear structures were studied with light, transmission and scanning electron microscopy. A transitory conductive hearing loss was observed, but after 8 weeks the auditory function appeared normal. Microscopy of the middle and inner ear failed to show any tissue damage.

Morbus Menière — Cerebral Atrophy: A Preliminary Report

At Rikshospitalet in Oslo, 20 randomly selected patients with a classical picture of Menieres disease have been investigated. The results indicate that the tissue damage and functional disturbances giving rise to Menieres disease are not limited to the labyrinth alone, but that the central nervous system is also the seat of pathologic changes. Further investigations are being carried out.

Herzversagen und Lungenödem Als Folge Von Asphyxie Bei Fremdkörpern in Den Luftwegen

Unser Fall hat gezeigt, dass Sauerstoffmange] bei Obstruktion der Luft-wege Herzversagen und hochgradiges Lungenodem mit fatalem Ausgang hervorrufen kann. Das Krankheitsbild stimmt mit bei Tieren experimentell hervorgerufener Asphyxie uberein. Das Krankheitsbild sollte alien Arzten bekannt sein. Bei unserem Patienten ware die richtige Behandlung eine erneute Bronchoskopie gewesen, Absaugung der Odemflussigkeit aus den Luftwegen und Sauerstoffzufuhr im geschlossenen System mit 2-4 cm Wasseruberdruck (12). Auf diese Weise hatte die Moglichkeit bestanden, die Herzfunktion zu bessern und das Lungenodem zu beseitigen. Die anwe-senden Fremdkorper waren dann leichter zu finden gewesen.