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Biomedical subjects

H Feistner

Publications and source records attributed to H Feistner.

At least 37 records · Page 2Linked to original sources
PubMed1997

[Surgical decompression of bilateral, compression-induced damage to the posterior interosseous nerve. A case report].

Bilateral posterior interosseous nerve palsy is a rare case of radial nerve entrapment. The patient is unable to extend the fingers in the metacarpophalangeal joints. Extension of the interphalangeal joints is preserved due to the intrinsic muscles. Neither the extensor carpi radialis longus and brevis muscles are affected nor the brachioradialis muscle. However, extension of the wrist may be weak. There is no sensory loss. The neurophysiological examination underlines the clinical findings. In our case compression is caused by the arcade of Frohse and the vessels of the recurrent radial artery. A good recovery of nerve function is seen after surgical decompression.

Decompression, Surgical↗
PubMed1996

A trend-detection algorithm for intraoperative EEG monitoring.

Intraoperative EEG-monitoring needs to discriminate random fluctuations from real systematic variations (trends). This task is made more difficult by several types of artifacts. With the goal of supporting visual EEG evaluation, a new trend-detection algorithm is presented which is based on spectral analysis and a post-processing dynamic linear model, the latter introduced by Harrison and Stevens. A gradient value provided by this model is exploited to determine the onset and relative extent of an existing trend. Artifacts are detected by several threshold measures for the original signal and its first derivative. The system was validated using a set of intraoperative EEGs recorded during carotid endarterectomy.

Algorithms↗
PubMed1995

Laser-excited fluorescence studies of mitochondrial function in saponin-skinned skeletal muscle fibers of patients with chronic progressive external ophthalmoplegia.

The functional behavior of mitochondria in skeletal muscle of patients with chronic progressive external ophthalmoplegia was studied by laser-excited fluorescence measurements of NAD(P)H and flavoproteins in saponin-skinned fibers. Variations in the mitochondrial content and the presence of partially respiratory chain-inhibited mitochondria can be detected using this novel method.

DNA, Mitochondrial↗
PubMed1995

Comparison of single motor unit responses to transcranial magnetic and peroneal nerve stimulation in the tibialis anterior muscle of patients with amyotrophic lateral sclerosis.

Responses of single tibialis anterior motor units to transcranial magnetic stimulation and to a synchronized Ia volley evoked by peripheral nerve electrical stimulation were obtained in amyotrophic lateral sclerosis (ALS) patients and normal controls. Whereas the units of normal subjects exhibited rather stereotyped short-latency spike density peaks in response to both types of stimulus, the responses of ALS patient units were much less uniform. All ALS patient units exhibited a response to the synchronized Ia volley indistinguishable from that of normal subjects, indicating that the investigated spinal motoneurons are capable of normal excitatory responses in ALS patients. More than half of the ALS patient units responded to the transcranial magnetic stimulus with prolonged spike-density peaks appearing at a latency consistent with the notion that these pathological peaks are evoked by some relatively hyperexcitable structures presynaptic to the corticomotoneurons.

Adult↗
PubMed1994

Correlations between size parameters and the amplitude of the excitatory postsynaptic potential evoked by magnetic brain stimulation in human hand muscle motoneurons.

According to the size principle for motoneurons one would expect that an excitatory stimulus given to a motoneuronal pool should evoke small excitatory postsynaptic potentials (EPSPs) in large and large EPSPs in small motoneurons of the pool. In this study this expectation was tested for the motoneuron pool of the first dorsal interosseus muscle of man excited by a magnetic stimulus given to the contralateral motor cortex. In total, 60 first dorsal interosseus motor units from three healthy volunteers were investigated. For each unit the EPSP size induced by the magnetic brain stimulus was assessed indirectly through a cross correlation of magnetic brain stimuli with motor unit discharges during a slight voluntary contraction. In addition to the indirect measurement of EPSP size, three indicators of motoneuronal size were obtained for each unit: the area the macroelectromyogram (Macro EMG) of the unit encloses with the baseline, the peak-to-peak amplitude of the Macro EMG, and the "true" latency from the magnetic stimulus to the motor unit which in turn provides an indirect estimate for the conduction velocity of the motoneuronal axon. It was found that all three measures of motoneuron size were significantly negatively correlated with the estimates of EPSP amplitude. Such significant negative correlations were found not only in the pooled data but also in the data from each subject individually. These correlations reveal that a magnetic brain stimulus induces small EPSPs in large and large EPSPs in small motoneurons of the first dorsal interosseus muscle of man.

Adult↗
PubMed1994

Quantification of D- and I-wave effects evoked by transcranial magnetic brain stimulation on the tibialis anterior motoneuron pool in man.

Transcranial stimulation in man evokes multiple descending volleys in the spinal cord giving rise to multiple subpeaks in a peri-stimulus-time histogram (PSTH) obtained from a cross-correlation of motor unit discharges with transcranial stimuli. The first volley is termed the D wave, as it is assumed to be evoked by direct excitation of pyramidal tract neurons, whereas the subsequent I waves appear to be generated by indirect excitation of the pyramidal tract neurons via cortical interneurons. It was the aim of this study to obtain an estimate of the effect induced by multiple volleys evoked by transcranial magnetic stimulation on the entire motoneuron pool of the tibialis anterior in awake subjects. A considerable part of a particular motoneuron pool was investigated by sampling responses of a large number (at least 19) from each muscle investigated. In total, three tibialis anterior muscles from three normal volunteers were studied. From each of the 63 units included in this study, a PSTH to 100 transcranial magnetic stimuli and a PSTH to 100 electrical stimuli given to the peroneal nerve were compiled. From the motor unit response to the peripheral nerve stimulation, the latency of the single-unit H reflex peak was obtained. This yielded, the timing of the subpeaks in response to the magnetic stimulation relative to the timing of the H reflex of the same unit, thus eliminating the influence of the peripheral conduction time from the motoneuron to the recording electrode. It was found that 50 (79%) of the motor units exhibited at least two subpeaks in response to the cortical stimulus.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

The relationship between estimates of Ia-EPSP amplitude and conduction velocity in human soleus motoneurons.

There are several parameters associated with motoneuron size, among which are the conduction velocity of the axon as well as the size of the excitatory postsynaptic potential (EPSP) induced by stimulation of Ia afferents in the corresponding muscle nerve. In particular, it has been established in animal experiments that small motoneurons with a low conduction velocity exhibit large Ia EPSPs, whereas large motoneurons with a high conduction velocity show small Ia EPSPs. Thus small motoneurons are recruited earlier than large ones. In this study, we investigated whether such a relationship between motoaxon conduction velocity and size of the Ia EPSPs could also be found for human soleus motoneurons. In total, 36 motor units from six healthy volunteers were activated by a slight voluntary contraction and exposed to 200 stimuli of the tibial nerve in the popliteal fossa. Stimuli were delivered using a special stimulus protocol ensuring a constant pre-stimulus spike density along with a constant rate of discharge of the investigated unit. From the stimulus-correlated spike train data a measure of Ia-EPSP amplitude was obtained, along with the single-unit H-reflex latency. Additionally, for each unit, the so-called surface macro EMG was recorded, which measures the complete electrical activity attributable to the unit investigated. From the macro EMB, the intramuscular delay from arrival of each action potential at the soleus muscle and the detection of the muscle-fiber action potential picked up by the recording needle electrode were measured. All single-unit H-reflex latencies were corrected for the corresponding intramuscular delays. From the corrected latencies, single-unit conduction velocities were obtained.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Abnormal EPSPs evoked by magnetic brain stimulation in hand muscle motoneurons of patients with amyotrophic lateral sclerosis.

Using cross-correlation between magnetic brain stimulation and discharges of a motoneuron made active by a slight voluntary contraction, an indirect estimate of the EPSP evoked by magnetic brain stimulation in single hand muscle motoneurons was obtained in patients with amyotrophic lateral sclerosis (ALS) and normal controls. In total, 60 motoneurons of 3 normal subjects and 70 motoneurons of 7 patients with ALS were investigated. All motoneurons of normal subjects responded to the magnetic brain stimulus with a short-latency EPSP with a rise time between 1 and 5 msec. In contrast, only 67% of the motoneurons from ALS patients responded with an EPSP while the remaining 33% exhibited a clear short-latency inhibition in response to the brain stimulus. For those units of ALS patients showing an EPSP, both latency and EPSP amplitude were indistinguishable from those of normal subjects. The EPSP rise time, however, was massively prolonged in some units (up to 18 msec). These results provide a physiological basis for the interpretation of surface EMG responses in patients with ALS.

Action Potentials↗
PubMed1993

Single potential analysis of cavernous electrical activity. Four years' experience in more than 500 patients with erectile dysfunction.

Since the recent introduction of cavernous electromyography by Gerstenberg and Wagner, a new too for the study of erectile dysfunction in man is available. The refinement of this method, single potential analysis of cavernous electrical activity (SPACE), offers a straightforward approach to the diagnosis of cavernous autonomic neuropathy and smooth muscle myopathy by minimal invasive means. SPACE was done in more than 500 consecutive patients with erectile dysfunction and in 85 normal control subjects. With increasing experience the methodology was refined with respect to the used hardware as well as cut-off frequencies. In normal control subjects, SPACE showed a reproducible regular activity with potentials of low frequency and electrical silence inbetween. The potentials were synchronous throughout the cavernous bodies. In patients with peripheral autonomic denervation, asynchronous potentials with higher frequencies and irregular shape were found. Normal and abnormal potentials were found in patients with upper spinal cord lesions. Recordings obtained with surface electrodes showed similar characteristics when compared with recordings obtained with needle electrodes. Recent studies show that SPACE provides independent information about the autonomic and myogenic intactness of the cavernous tissue. Currently, a computerized expert system and a graded classification for easier interpretation is being developed with first results. We conclude that cavernous electrical activity can be recorded. SPACE is a reproducible diagnostic tool for erectile dysfunction.

Action Potentials↗
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↗