Biomedical subjects
Publications and source records attributed to H Gerhard.
In strong static magnetic fields as used by NMR for clinical diagnosis we found oscillations in somatosensory evoked potentials of man when stimulating the Nervus medianus at the wrist joint. These new signals are to register only, when the head of the test person is inside of the magnetic field. A magnetic influence only of the stimulated arm has no effect of the normal SEP-signal.
Diagnosis of Parkinson's disease is not yet possible with neurophysiological methods. Therefore we investigated the median somatosensory and visually evoked potentials (SEP and VEP) to single and double stimulation, VEP using a special stimulation technique and motor evoked potentials (MEP) employing spinal and transcranial stimulation. In Parkinson's disease the absolute and relative refractory periods of cortical N1 peak of SEP did not differ from that of normal subjects. After single stimulation the cortical N20 latencies were only in 2 of 17 cases delayed. In 8 of 10 cases central conduction time was normal. Also the SEP peaks of brain stem were normal and there was no correlation between symptomatology and SEP results. The data of motor evoked potentials (MEP) demonstrated in all patients a normal central motor conduction time of 5.0 msec. In 30% of patients the VEP data showed a significant delay of P2 latency, independently of clinical status or age. But there were no more P2 alterations after special visual stimulation techniques. In contrast to a good clinical effect in 14 of 19 patients with end-off-dose akinesia, an improvement of P2 delay could not be noticed during a chronic L-dopa and deprenyl therapy.
A muscular action potential (MAP) following transcranial and spinal stimulation can be recorded from most of the striped muscles. The motor central conduction time after transcranial and spinal stimulation can be determined at cervical 6/7. It is at 5.0 ms in normal subjects. This was demonstrated in four normal subjects. After spinal stimulation at cervical 6/7 a motor evoked potential can also be recorded from the scalp. It has a latency that is comparable to motor conduction time. In animal experiments in examining ten rabbits a motor evoked potential to stimulation at several levels of the spinal cord could also be determined.
The importance of the parameters stimulation rate, filter, stimulation- and recording place is presented; thus, a reduction in the low-pass filter frequency produces an increase in latency and an increase in the high-filter a decrease in latency of all SEP-components. A proper choice of the filters leads to a selection of the relevant signals; in a topic classification of the SEP generator the referential electrode must in any case be taken into consideration.
Ten normal subjects of the age of 21 to 57 years were examined with single stimulus- and double stimulus-VEP following checkerboard whole field stimulation, foveal stimulation with a small checkerboard and flash. The latencies of the VEP following foveal stimulation are longer than those following whole field stimulation. There could not be determined a relative refractory period following checkerboard whole field stimulation at double stimulation. There is a relative refractory period following foveal stimulation between 80 and 100 ms. With retrobulbar neuritis at a late stage the relative refractory period is prolonged and it appears at about 150 ms.
Somatosensory evoked potentials (SEP) of the tibial nerve are of diagnostic value, if the recording points nearest to the spinous process are used. In cases with space-occupying lesions of the spinal cord, conduction block or amplitude reduction is the most common abnormality. In contrast in inflammatory diseases like spinal MS the most common abnormality is marked latency delay.
The CPK-determination in the serum immediately before and 4 hours after the intravenous Prednisolon injection does not furnish any diagnostically relevant different results in the single forms of myopathy. In accordance with Czyzewski we cannot confirm the assumption of Takahashi et al. (1975) that the Prednisolon-test is suitable to the differentiation of myopathies and polymyositis. It must still be left undecided whether conductors of the Duchenne muscular dystrophy in the scope of the heterocygoty diagnostic could have a diagnostic relevant increase in CPK only after Prednisolon injection.
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In 33 normal subjects aged between 15 and 60 years, the cortical somatosensory evoked potentials (SEP) recorded above the mastoid process, HWK2, LWK1, and the nerve action potential above the poplitea were examined following single stimulation of the tibial nerve at the medial malleolus. There is a correlation between size and N1, P1 latencies of the cortical SEP, but no relationship was found between age and N1, P1 latencies. The spinal conduction velocity determined as the difference between HWK2 and LWK1 did not show any correlation with age. The double stimuli examination showed a rise in the N1, P1 latencies within the relative refractory period on shortening of the interstimulus time. The cerebral relative and absolute refractory times were higher than those of the median nerve.
The regeneration of nevus cells after shave biopsy was investigated by means of fluorescence-histochemical and electron microscopic methods. A prerequisite for the regeneration of pigmented nevi seems to be the retention of their deepest part. It appears that the remaining nevus cells primarily induce proliferation of pigment-producing dendritic cells in the epidermis. These dendritic cells form nest-like conglomerations at the dermal-epidermal junction, which eventually separate from the epidermis during a process called "dropping off". The fluorescence-histochemical and electron-microscopic results lead to the conclusion that under these circumstances melanocytes are transformed into nevus cells.
During the years of 1978 to 1981, a pilot study was conducted with 210 patients suffering from 235 tumors. The treatment included localized high-frequency hyperthermia alone or combined with radiotherapy and/or chemotherapy. The final evaluation of 164 tumors with different sites, sizes and histologic findings shows that even if the patients collective is unfavorably selected (nearly all tumors in an advanced stage), an increased palliative effect exceeding the clinical effect expected for radiotherapy alone was reached in 60 to 70% of all cases. 45% of the patients showed curative effects in the sense of an objectively improved tumor remission. At the same time, a significant reduction of local side effects of radiotherapy was achieved by the hyperthermic treatment. Localized hyperthermia until 42/43 degrees C has only a small rate of complications, even if it is applied in the abdominal region. Within the relatively short follow-up period, an increased rate of metastases after therapy combinations with hyperthermia was not observed.
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29 normal persons at the age of 19 to 70 years were examined. Checker-board stimulation with a revolving mirror technique was used. The P2-latencies of the visually evoked potentials showed no relation to age. The changes of P2-latencies within the relative refractory period were so small, that a relative cerebral refractory time could not be determined. The absolute refractory time was at 16,7 +/- 11 ms. With MS-patients with retrobulbarneuritis pathologically lengthened absolute cerebral refractory times were found. The relative refractory time could not be determined. With patients with certain multiple sclerosis without anamnestic retrobulbarneuritis the determination of the absolute cerebral refractory time could improve the diagnostic accuracy in comparison to single stimulus examination.
Exercise-induced asthma can appear as one of many forms of airway hyperreactivity or as a unique clinical entity. Simple spirometry confirms the suspected clinical diagnosis in most instances, although more sensitive measurements of airway obstruction may be required. In general, the asthmatic need not restrict physical activity because of exercise-induced attacks. The disease responds well to prophylactic management with a wide variety of antiasthmatic agents, such as theophylline preparations, beta-agonists, and cromolyn sodium.
On the wrist the median nerve of 42 normal subjects was stimulated by single and double stimuli and the contralateral cortical evoked potentials (SRAP) were evaluated with regard to peak-latencies, amplitudes and refractory period. SRAP after single nerve stimulations has 4-6 peaks in the first 100 ms, in 19 of 42 subjects there is an early peak ("peak 14-15") of the brain stem. The peak-latencies of minimum 1, maximum 1 and minimum 2 increase with the age not significantly. There are no right/left differences of the SRAP-amplitudes or -latencies. The duration of the relative refractory period was determined through the lengthening of latency respectively through the loss of minimum 1. The relative refractory time is independent of age, the absolute refractory time increase with advanced age. The refractory times of the first 4 peaks are not different for the right and left hemisphere. A slow alpha-rhythm correlate significantly with a higher absolute refractory time.
The duration of the refractory period of the somatosensory system was determined through the lengthening of latency respectively through the loss of Minimum 1 and Maximum 1; the median nerve was stimulated by single and double stimuli of variable interval, the somatosensory evoked potentials (SRAP) were averaged contralateral. The relative refractory time is independent of age, the absolute refractory time increased with advanced age. In genuine epilepsy with 3/s spike-waves the relative refractory period is shortened compared with the reference group of normal subjects. In multiple sclerosis the relative refractory time is distinctly increases in sign of demyelination on conduction in the central nervous system. The most distinct delays of refractory period are in cases with cerebrovascular disease and brain atrophy. The correlation between the clinical and neurophysiological results shows, that the single and double stimulation of the median nerve, combined with the analysis of the evoked potentials and the cerebral refractory period, is a good neurophysiologic cerebral function-test.