[Suitability of various lasers for interventions from the tympanic membrane to the foot plate (Er:YAG, argon, CO2 s.p.--, Ho:YAG laser]. / Eignung verschiedener Laser für Eingriffe vom Trommelfell bis zur Fussplatte (Er:YAG-, Argon-, CO2 s.p.-, Ho:YAG-Laser.

The Erbium:YAG-laser is a good tool for microresection of bone and soft tissue from the ear drum, to the ossicles and extending to the footplate. The mechanism of ablation is based on the fact that the emission of infrared light is of the same wavelength at which water has its peak of optimal light absorption. 14% of bone is water, just sufficient force for ablation. At 50 mJ impulses the temperature in the centre stays below the coagulation point. 500 impulses of 50 mJoule definitely remain below the acoustic risk. In 44 guinea pigs 500 x 50 mJ caused a temporal threshold shift of maximal 38 dB at 2000 cps which recovered after 90-135 min. In 60 tympanoplasties neither tinnitus nor audiological side effects of the laser application were measured. The ear drum is perforated by 1 (-3) impulses. This can be done even in children after superficial anaesthesia (2% pantocaine drops) to drain the middle ear. The laser perforation of 0.3 mm [symbol: see text] will close after a day and has to be re-opened in the office to avoid tubes. We do not yet know how often general anaesthesia and removal by suction of too viscous mucus remain nevertheless necessary. With the Er:YAG laser parts of the ossicles can be cut out of the intact chain, without contact and trauma, nearly without loss of bone tissue. This allows better radicality in removing cholesteatomas or scars with less destruction. 500 impulses of 50 mJ ablate 32 mg of bone, i.e. the weight of an incus.(ABSTRACT TRUNCATED AT 250 WORDS)

[The human stapedius reflex by ipsilateral electrical stimulation of the auditory meatal skin (author's transl)]. / Stapediusreflex des Menschen bei ipsilateraler elektrischer Reizung im Gehörgang.

A modified method for eliciting a stapedius reflex by electrical stimulation of the meatal skin is presented. In contrast to the acoustically elicited stapedius reflex, the electrically-induced response is only ipsilateral, and can be ablated by anesthesia of the meatal skin. Contralateral acoustical and ipsilateral electrical stimulations lead to a summation effect of the amplitude off the stapedius reflex. When presented simultaneously, subthreshold electrical and acoustical stimulations may produce a reflectory contraction of the stapedius muscle. Similar responses can be found in diseases of the middle ear and the facial nerve. The method described is not difficult to perform, is painless to the patient, and can be used objectively in neurotologic testing.