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Biomedical subjects

H Feistner

Publications and source records attributed to H Feistner.

16 recordsLinked to original sources
PubMed1992

Hemodynamic and electrophysiological evaluation following extracranial/intracranial bypass surgery.

We examined 50 patients with an extracranial/intracranial bypass using transcranial Doppler blood flow mapping, somatosensory evoked potentials, and computer-assisted EEG analysis. The investigation was supplemented by temporary compression of the extracranial supplying vessel. Transcranial Doppler sonography revealed in addition to 4 patients with nonpatent anastomoses, a bypass-mediated retrograde flow in the ipsilateral middle cerebral artery beyond a depth of 40 mm in the majority of patients. In 9 patients, retrograde flow could be demonstrated in the whole proximal (M1) MCA segment. The precommunicating segment of the anterior cerebral artery (A1) could be reliably insonated in all but 5 patients. Bypass-compression dependent alterations in the SSEP and in EEG analysis were only observed in a small number of patients. Transcranial Doppler sonography, with the aid of the flow mapping system, appears therefore, to be a reliable and repeatedly performable noninvasive technique for the assessment of intracranial hemodynamics following bypass surgery.

Adult↗
PubMed1992

Computer-aided EMG-analysis in patients with neurogenic lesions.

A new system for computer aided EMG-analysis was tested in 3 groups of patients with neurogenic lesions (ALS, ulnar nerve lesions, diabetic polyneuropathy). The system entails automatic segmentation and parametrization of the single MUAP as well as the automatic classification of the MUAP into motor units. Emphasis was placed on its practicability in an everyday clinical setting. All patient groups differed significantly from normal groups in most of the computed parameters of the motor units. Moreover, on the basis of the computer-aided analysis of the MUAP up to 90% of individual patients in the ALS and ulnar nerve lesion groups and up to 40% in the diabetic polyneuropathy group, who did not have any pathological spontaneous activity or paris, could be classified as pathological. It is concluded, that computer-aided EMG-analysis has become a practical tool for routine use in the clinical laboratory simplifying early diagnosis of subtle EMG-changes, and aiding the less experienced examiner.

Action Potentials↗
PubMed1992

[Computer-assisted analysis of the electromyogram for routine clinical use].

A computerized EMG analysis system implemented on an MS-DOS computer was developed explicitly for clinical routine usage. It incorporates analysis of interference pattern as well as of motor unit action potentials (MUAPs). Key features of MUAP analysis are the automatic segmentation and parameterization of the EMG signal and the automatic assignment of MUAPs to motor units. Determination of muscle activity is based on threshold detection of the signal's first derivative, leading to the definition of a MUAPs central component. Its parameters (length, amplitude, maximal steepness, area between curve and base-line, area between first derivative and base-line, number of turns etc.) are used when comparing MUAPs. The automatic assignment of MUAPs to motor units was implemented as an iterative procedure. MUAPs are compared to a reference MUAP and eventually assigned to it if their parameters are sufficiently similar. For such a group of MUAPs the most representative MUAP is determined which is then used as new reference MUAP in the next iteration step. Most important for clinical routine usage are simple handling, speed and the clearly arranged presentation of results. The system allows for interactive modification of MUAP assignment as well as start and end points of every MUAP. Analysis results may be displayed on the screen and printed, giving the user a quick impression of the muscle under study. Thus this method meets basic requirements for computer assisted decision making in differential diagnosis.

Action Potentials↗
PubMed1991

On a method to detect long-latency excitations and inhibitions of single hand muscle motoneurons in man.

The peri-stimulus-time histogram (PSTH) analysis of stimulus-related neuronal spike train data is usually regarded as a method to detect stimulus-induced excitations or inhibitions. However, for a fairly regularly discharging neuron such as the human alpha-motoneuron, long-latency modulations of a PSTH are difficult to interpret as PSTH modulations can also occur as a consequence of a modulated neuronal autocorrelation. The experiments reported here were made (i) to investigate the extent to which a PSTH of a human hand-muscle motoneuron may be contaminated by features of the autocorrelation and (ii) to develop methods that display the motoneuronal excitations and inhibitions without such contamination. Responses of 29 single motor units to electrical ulnar nerve stimulation below motor threshold were investigated in the first dorsal interosseous muscle of three healthy volunteers using an experimental protocol capable of demonstrating the presence of autocorrelative modulations in the neuronal response. It was found for all units that the PSTH as well as the cumulative sum (CUSUM) derived from these responses were severely affected by the presence of autocorrelative features. On the other hand, calculating the CUSUM in a slightly modified form yielded--for all units investigated--a neuronal output feature sensitive only to motoneuronal excitations and inhibitions induced by the afferent volley. The price that has to be paid to arrive at such a modified CUSUM (mCUSUM) was a high computational effort prohibiting the on-line availability of this output feature during the experiment. It was found, however, that an interspike interval superposition plot (IISP)--easily obtainable during the experiment--is also free of autocorrelative features.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

[Examination of coordination of masseter muscle activity].

The coordination of masseter muscle contraction is inseparably wrapped up in the occlusal elements. This study measured bilaterally the masseter muscle activity of 22 subjects without temporomandibular joint disease. The EMG recordings of the left and the right masseter muscles were repeated 20 times to test symmetry, reproducibility and appearance of silent periods. In 6 subjects the beginning of the muscle contraction showed laterality characteristics depending on handedness. The complex processes of recorded mandibular movements showed more biological variations than the recording patterns of occlusal indicator foils may disclose. That indicates the possibility of pseudocontact markings. The occluding surfaces therefore should allow free mandibular movements.

Adult↗
PubMed1991

[Experience with computer-assisted EMG analysis: reference values for four muscles].

The characteristics of a newly developed computerized EMG-analysis system are lined out. The analysis steps include segmentation and parametrization of digitized EMG segments followed by automatic classification of single potentials into motor units. Comparison of parameters is used rather than a template matching algorithm for classification. For each motor unit a set of parameters can be computed in addition to duration and amplitude. Normative data are given for four muscles. 60 normal volunteers (50% female, 50% below age 50) were recorded from for each muscle. The recording conditions required to move the electrode until a motor unit could be recorded with its individual maximum. Furthermore, it was attempted to attain the maximum discharge rate of a particular motor unit. A highly significant correlation of the amplitude of the motor unit potentials with age was found for all four muscles. For the duration of the potentials a correlation with age was found only for the M. ext. digitorum brevis. Significant sex differences were found for nearly all parameters and all muscles. Pairwise comparisons of the muscles revealed significant differences of all muscles. The analysis showed, that a muscle can be regarded pathological if more than two of a total of seven recorded motor units show pathological parameters.

Age Factors↗
PubMed1990

Physiological regulation of circadian and pulsatile thyrotropin secretion in normal man and woman.

The circadian and pulsatile TSH secretion profiles were investigated in 5 females at the time of menstruation and 21 healthy males by sampling blood every 10 min for 24 h. Computer-assisted analysis, i.e. the Cluster and Desade programs, revealed means of 9.9 +/- 1.7 (Cluster) and 11.4 +/- 3.9 (Desade) pulses/24 h. More than 50% of the TSH pulses were detected between 2000-0400 h. Male and female subjects showed no significant difference in the basal mean and pulsatile secretion of TSH or in the TSH response to TRH (200 micrograms). Repetition of the TSH secretion analysis in 4 healthy subjects after 1, 2, and 6 months (2 subjects) revealed a significantly better cross-correlation within than between individuals (P less than 0.0001). We modulate the circadian TSH secretion pattern by acute sleep withdrawal or prolonged sleep after a night of sleep withdrawal in six healthy male volunteers. Sleep withdrawal augmented the nightly TSH secretion (mean serum TSH, 2.1 +/- 1.3 mU/L; mean TSH in sleep, 1.3 +/- 0.5 mU/L; P less than 0.05), whereas sleep after sleep withdrawal almost completely suppressed the circadian variation (mean TSH, 1.1 +/- 0.7 mU/L; P less than 0.01). This modulation is due to a significant decrease in pulse amplitude, but not to an alteration in the frequency or temporal distribution of TSH pulses.

Adult↗
PubMed1990

[Studies on the cybernetic aspects of occlusal splint therapy].

This study was focussed on the effects of changes in interocclusal clearance on the activity of oral muscles. Two types of occlusal splints were incorporated in 20 subjects without TMJ-syndrome. Their muscle reactions were recorded electromyographically in the masseter muscle. The results show 5 groups of muscle reaction correlated with the mean postural face height. The changed height of the postural position has a significant influence on the control pattern of the masticatory system.

Adult↗
PubMed1989

Post-irradiation lesions of the caudal roots.

The article reports on 3 patients suffering from muscular atrophy after radiotherapy of the para-aortal lymph nodes for malignant testicular tumor without any sensory, bladder, or bowel disturbances. By neurophysiological examination, a lesion of the lumbal plexus and the peripheral nerves of the lower extremities were excluded. On EMG-examination there were no giant motor unit potentials, as they can be found in anterior horn cell lesions. Though there were no sensory deficits, a distinct prolongation of latencies and reduction of amplitudes could be found for lumbar dermatomal somatosensory evoked potentials (SSEP) and those after stimulation of some peripheral nerves of the lower extremities.

Adult↗
PubMed1986

[Familial polyneuropathy with a disposition to pressure paralyses. A contribution to the differential diagnosis of mononeuropathies].

When a young woman admitted for recurrent peripheral nerve palsies was suspected to suffer from hereditary polyneuropathy with liability to pressure palsies, 8 members of her family were examined diagnostically. Only one of these had a history of a transient mononeuropathy. A neurophysiological examination demonstrated peripheral nerve lesions not only in the patients father but also in 5 of her brothers and sisters. In presenting the data for this family the characteristics of hereditary polyneuropathy with liability to pressure palsies and the most important differential diagnostic aspects are discussed.

Adult↗
PubMed1979

Semliki forest virus: cause of a fatal case of human encephalitis.

A fatal case of human encephalitis has been observed for which our results indicate that Semliki Forest virus (SFV) was the etiologic agent. This is surprising in view of the fact that this virus, which has been widely studied, was believed to be one of the arboviruses nonpathogenic for man. Described are the clinical course, the virological examinations performed, and the histopathological findings in the central nervous system.

Adult↗