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Biomedical subjects

H Scherer

Publications and source records attributed to H Scherer.

At least 109 records · Page 6Linked to original sources
PubMed1986

European vestibular experiments on the Spacelab-1 mission: 3. Caloric nystagmus in microgravity.

Response to caloric stimulation was examined in two subjects in the weightless environment of orbital flight. Using air insufflation, a binaural temperature stimulus profile was performed twice on each subject during flight. In all but one test, which was carried out on the first mission day, a caloric nystagmus was registered. This zero-g nystagmus was similar to ground-based pre- and postflight responses with regard to its intensity, its temporal correlation with the stimulus profile (nystagmus was always directed towards the warmer ear) and the subjective sensations reported by the tested subjects. These findings demonstrate that mechanisms other than thermoconvection are involved in the elicitation of the caloric nystagmus response. At each stage of the temperature stimulus profile, linear acceleratory stimulation was presented in the form of oscillations in the X-axis. Some differences were found between one-g and zero-g conditions in the resultant modification of the nystagmus response.

Caloric Tests↗
PubMed1986

[Electric stimulation of a sensory nerve with 70-micrometer electrodes].

Using the device of an implant (Fig. 1) for direct stimulation of the eighth cranial nerve (Zwicker et al., 1986) measurements have been performed after implantation of one electrode in the nervus suralis of the first author. The results show that threshold of sensation is reached at voltage amplitudes of about 600 mV for sinusoidal stimuli almost frequency independent in the range between 100 Hz and 3 kHz (Fig. 2). The impedance of the electrode (Fig. 3) was found to be remarkably smaller compared with values measured by Zollner (1982) in Ringer's solution. No clear relation between threshold value or impedance and active electrode area could be detected. However, there was a clear dependence of the threshold voltage on the angle between the direction of puncture of the electrode and the direction of the nerve. Parallel puncturing resulted in a 13 dB less sensitive threshold in relation to perpendicular puncturing. The practical dynamic range between the threshold of sensation and the threshold of pain was found to be 10 to 12 dB.

Auditory Perception↗
PubMed1986

[Side effects of drugs on the equilibrium].

Side effects of drugs on the vestibular system may occur when a drug is injected too fast during chronic application of drugs after discontinuation of drugs Dizziness due to ototoxic drugs is rare because of the symmetric influence on the vestibular system. The oculomotor system most often is found being reversible or irreversible damaged by chronic drug effects especially from barbiturates, psychopharmacologic drugs, anticonvulsives and some antiarrhythmics, whereas the vestibular organs and their pathways usually remain unaffected except from ototoxic drugs. An isolated oculomotor disfunction therefore could be an indication for a drug side effect.

Anti-Arrhythmia Agents↗
PubMed1986

[Experiences with the implantation of a multichannel electrode in the acoustic nerve].

The authors developed a surgical approach to the acoustic nerve enabling the introduction of an electrode into the acoustic nerve. A multichannel electrode was implanted by this method in a deaf patient. The receiver casing for percutaneous transmission was fixed in the mastoid. Encouraging hearing results were obtained over a period of two months by electrical stimulation of the acoustic nerve.

Auditory Perception↗
PubMed1986

[Dangers in the use of gas-sterilized materials].

After gas sterilisation of synthetic materials, some traces of the gases employed (ethylene oxide; formaldehyde) can remain in the sterilised material, and, in the case of moist materials, in drops of water. These gases are carcinogenic and, in case of contact to tissue, can lead to fibrinous inflammation and consequently to stenotising scars. Two cases of laryngotracheitis are described, in which insufficiently aired tracheal tubes were used. On contact with material containing chloride ions, e.g. PVC or body fluids, ethylene oxid can be converted to highly toxic ethylene chlorohydrine. For this reason, it is prohibited to sterilise synthetics containing chlorine ions with ethylene oxide.

Ethylene Oxide↗
PubMed1985

[Neck-induced vertigo].

Cervicogenic vertigo can be elicited by hyperactivity of spinovestibular afferents and, much more seldomly, by episodic reduction of blood flow in the vertebral artery. The afferent hyperactivity to the vestibular system derives from a "circulus vitiosus" involving false posture, pain, joint dysfunction, which in turn exacerbates the false posture - and so on. This is to be observed in the joints CO/C1 and C1/C2 and their short muscles. This dysfunction of the upper cervical spine can be determined by exact anamnesis, careful investigation of neck mobility, joint play and muscle tension. The cervical nystagmus observed during the neck torsion test is short (seconds) in functional diseases (hyperactivity) and longlasting (minutes) in cases of vascular disorder. Cervical vertigo should be differentiated from other atactic disorders, especially those arising from benign paroxysmal positional vertigo and from Menière's disease.

Brain↗
PubMed1985

[Physiology of the caloric equilibrium reaction. Consequences from results of space experiments in Spacelab 1, December 1983].

A caloric nystagmus was observed during weightlessness in orbital flight. This cannot be reconciled with the classical convection theory of the caloric mechanism. Alternative hypotheses are discussed. It appears that a direct thermal effect on the canal afferents could only play a small part. It is suggested that a stronger effect is produced by the temperature-mediated volume change in the horizontal semicircular canal, the asymmetric stimulation of the canal ring leading to volume displacement towards the cupula. On earth, the convective torque produced by redistribution of endolymph mass may be considered as a secondary effect, comparable to a stimulus producing a nystagmus threshold response. Modulation of the caloric and rotatory nystagmus by body position and the role of the otoliths are also discussed.

Caloric Tests↗
PubMed1985

[Frequent errors in neuro-otologic diagnosis].

A number of characteristic sources of error during the testing of vestibular function, originating from anamnesis, equipment and examination, are described. It is stressed that false-positive findings are often due to the influence of alcohol and that false-negative findings may be the result of tiredness or sedative drugs. With regard to the caloric test, it is recommended that water provides a better stimulus than air, and that the warm caloric stimulus is more valid than the cold caloric stimulus. Attention should be paid to the ENG-recorders, particularly to an adequate writing breadth, and to time constants. Different parameters in use for quantitative analysis of the intensity of vestibular reactions are discussed. If the findings are vague, repeated examination will often help to clarify matters. The regular use of Frenzel glasses is of great importance, since otherwise examination of the vestibular organs must be considered incomplete.

Alcohol Drinking↗
PubMed1984

Effects of rectilinear acceleration and optokinetic and caloric stimulations in space.

During the flight of Spacelab 1 the crew performed a number of experiments to explore changes in vestibular function and visual-vestibular interactions on exposure to microgravity. Measurements were made on the threshold for detection of linear oscillation, vestibulo-ocular reflexes elicited by angular and linear movements, oculomotor and posture responses to optokinetic stimulations, and responses to caloric stimulation. Tests were also conducted on the ground, during the 4 months before and on days 1 to 6 after flight. The most significant result was that caloric mystagmus of the same direction as on the earth could also be evoked in the weightless environment.

Acceleration↗
PubMed1984

The European vestibular experiments in Spacelab-1.

A series of experiments were performed in the Spacelab-1 mission on November/December, 1983, pre-, in-, and postflight. These experiments covered various aspects of the functions of the vestibular system, the inflight tests comprising threshold measurements for linear movements in three orthogonal axes, optokinetic stimulation, vestibulo-ocular reflexes under linear and angular accelerations, caloric stimulation with and without linear accelerations; pre- and postflight tests repeated the inflight protocol with the addition of subjective vertical and eye counter-rotation measurements using a tilt table. One of the most surprising and significant results was the caloric test: strong caloric nystagmus on the two subjects tested was recorded inflight; this was contrary to what was expected from Barany's convection hypothesis for caloric nystagmus.

Adaptation, Physiological↗
PubMed1984

[Standardization of electronically evaluated Romberg tests].

A procedure is presented here permitting calibration of examinations recording postural changes. With the help of physical calibration a "posturographic unit" (PU) can be defined. "Biological" calibration is not only facilitated for shifting of the centre of gravity of the body, resulting in swaying, but also practically for all other parameters describing postural stability. The advantages of this method are demonstrated. It is pointed out that it is now possible to compare the results of various authors using different measuring devices.

Adult↗
PubMed1984

[A simple measuring device for nystagmus amplitude. A contribution to rapid, exact and inexpensive evaluation of electronystagmograms].

Different parameters in use for quantitative analysis of ENG recordings are being discussed. Special importance can be attributed to the slow-phase velocity of the nystagmus and above all to the total amplitude. However, measurement of the total amplitude via digital computers is very expensive. Hence we present a device to measure amplitudes by means of a potentiometer. This is easy to handle, works accurately and is inexpensive.

Electronystagmography↗
PubMed1984

[Treatment possibilities for malignant melanomas of the palate, nasal cavity and paranasal sinuses].

Malignant melanomas of the mucous membranes are rare. Statistics reveal an incidence of 8-9% in all head and neck melanomas. The tumour predominates in the nasal cavity and the paranasal sinuses in the statistic compiled by Eneroth and Lundberg and in our patients (60%), while Conley found that in the USA the oral cavity contains half of the melanomas. 34% only were situated in the nose. The prognosis is very poor, because of the hidden localisation, insufficient signs and high malignancy of these tumours. The five-year survival rate is 15-17%. The treatment of choice is extensive local electrodesiccation together with a radical neck dissection, or local cryosurgery. Maximal attention has to be given to the topmost lymph nodes at the base of the skull in melanomas of the nasal cavity. They can be removed after resection of the digastric muscle and elevation of the parotid gland. In case of a massive involvement of the lymphatic tissue at the skull base, the dorsal half of the vertical mandibula can be removed to gain broad access to the skull base, the pterygoid fossa and the retro-mandibular space. Neck dissection in cases of tumours of the buccal region and the alveolus must include the buccal lymph nodes concomitant with the facial vein. They are situated lateral to the horizontal part of the mandible.

Aged↗
PubMed1983

[Modification of vestibular tests by alcohol].

Besides the positional alcohol nystagmus, PAN I and PAN II, alcohol in conventional doses causes marked side differences in experimental vestibular and oculomotor tests together with qualitative and quantitative alterations of the experimental nystagmus. These toxic, false positive results cannot be distinguished from post-traumatic central and peripheral pathological findings. When writing an expertise, we must therefore prevent a social insurance pension based on alcohol effects, by analysing the concentration of alcohol in the blood.

Adult↗