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Biomedical subjects

B Conrad

Publications and source records attributed to B Conrad.

At least 163 records · Page 9Linked to original sources
PubMed1988

[Fractionated determination of central motor conduction times using stimulation of the cortex, spinal tract and spinal nerve roots: possibilities and limits].

Two different approaches of determining central motor conduction times were investigated. Both methods were based on calculations of latency differences of muscle compound action potentials. First, using multilocal stimulation of the descending motor system at different levels (motor cortex, motor tracts at spinal level, motor roots) and recording from one reference muscle (Figs. 1 and 2). Second, using unilocal stimulation over the motor cortex and recording from a number of paravertebral muscles at levels from C7 to L5 (Figs. 3 and 4). With multilocal stimulation of the motor pathways, muscle response potentials are observed which differ in amplitude, duration and configuration depending on the site of stimulation (Figs. 1 and 2). This finding points to the incongruency of excited fibres within the descending motor pathways. The causes underlying this phenomenon and the resulting limitations for determining central motor conduction times are discussed. The new approach using recordings of cortically evoked responses on different levels in paravertebral muscles does not suffer from the methodical limitations of the multilocal stimulation and may be of higher clinical validity for the localization of circumscript spinal processes.

Adult↗
PubMed1988

[Changes in multi-locally recorded muscle responses following cortex stimulation in patients with multiple sclerosis].

The application of transcranial brain stimulation widens the range of neurophysiological tools available for the diagnostic evaluation of impaired function in central conduction pathways. A standardized examination of 25 patients with multiple sclerosis (diagnoses of different certainties using the classification by Bauer) was performed with electrical brain stimulation and EMG recordings from 3 muscles in each of the upper and lower extremities (Fig. 2). The occurrence and the change (amplitude, latency) of abnormal cortically evoked muscle responses correlated with the distribution and the severity of the clinical motor deficits respectively (Fig. 1 to 4 and Tab. 1). Furthermore, in some cases, abnormal responses were found in clinically unaffected limbs. Non-invasive stimulation of the motor cortex may reveal lesions affecting the function of the fast conducting component of the corticospinal tract even when there is no pathological clinical finding. In patients suspected of having multiple sclerosis the use of this technique may allow greater diagnostic certainty or even an early diagnosis.

Electric Stimulation↗
PubMed1988

[The role of magnetic stimulation in diagnosis of the peripheral nervous system].

Magnetic stimulation has recently been introduced as a new method for stimulation of neuronal tissues. Up to now most investigators were emphasized the advantages of this method for the investigation of the central nervous system. With this paper we want to show that magnetic stimulation may also be useful for the examination of the peripheral nervous system. Both, magnetic and electrical stimulation, seem to employ the same stimulation mechanisms in the nervous tissue. The results obtained with both methods should therefore be comparable. By measuring EMG-latencies after electrical and magnetic stimulation (Fig. 1) the exact site of magnetic stimulation can be determined. Magnetic stimulation offers major advantages over electrical stimulation: 1) Magnetic stimulation is a painless method even when high stimulus intensities are used. 2) Magnetic stimulation can reach deep neuronal structures that are not easily accessible using electrical stimulation (Fig. 2, Fig. 3). 3) Using a wide range of stimulus intensities (Fig. 4, Fig. 5) magnetic stimulation provides a much better descrimination of different components of the compound muscle action potential than electrical stimulation. Magnetic stimulation seems to be a promising new method for the electrodiagnostic examination of pain- sensitive patients, especially when deep-lying peripheral nerves have to be investigated.

Electric Stimulation↗
PubMed1988

[Transcranial brain stimulation. Methods and results].

Since the end of last century direct electric brain stimulations have produced remarkable neurophysiological results. Unfortunately, this method can be used only during neurosurgical operations. With the introduction of transcranial electric brain stimulation in 1980, for the first time, it became possible to perform brain stimulations on non-anaesthetized subjects. Magnetic brain stimulation, available since 1985, allows brain stimulation without any discomfort of the subject. This paper is dealing with methodological aspects of both methods and presents first results of neurophysiological and clinical applications.

Brain↗
PubMed1988

[Assessment of motor cranial nerve functions using transcranial magnetic stimulation].

Transcranial magnetic stimulation applied over one cerebral hemisphere evokes bilateral responses in the muscles supplied by cranial nerves (masseter, mentalis, sternomastoid, genioglossus) (Tabl. 1). The relatively long latencies of these responses and the influence that preactivation of the muscle has on them, suggests that they are cortically evoked. Shorter latency and exclusively ipsilateral responses can be obtained if the position of the stimulating coil over the head is more lateral. These responses are uninfluenced by pre-activation of the muscle which suggests that they arise from stimulation of the peripheral nerve itself. By considering the conduction velocity of the nerve and the response latency such stimulation probably occurs in the proximal intracisternal segment (Fig. 2). The results obtained using magnetic stimulation of the cortex in patients with unilateral cerebral hemisphere lesions lend support to the idea of a bilateral projection from each cerebral hemisphere to the motor nuclei of the facial and hypoglossal nerves on both sides: stimulations over the intact hemisphere produces bilateral responses, whereas stimulations over the damaged hemisphere produce no responses (Fig. 1). In patients with idiopathic facial palsy no short latency responses were obtained on the affected side either during the acute (less than 10 days) or during the chronic phase (greater than 3 months) of the illness-despite clinical improvement during the chronic stage (Fig. 3, 4). However cortically evoked responses were obtainable in patients seen during the chronic phase indicating that facial motoneurones could be excited transsynaptically (Fig. 3).(ABSTRACT TRUNCATED AT 250 WORDS)

Cerebral Infarction↗
PubMed1988

[Form of manifestations and course of brachial plexus lesions following medial sternotomy].

A prospective study is reported of the prevalence, the clinical picture and the course of plexus brachialis lesions following median sternotomy during heart operations. The study comprises 1,585 patients. In 22 patients (1.39%) a lesion of the lower plexus brachialis was found postoperatively. In 12 patients the plexus lesion was combined with an ipsilateral Horner syndrome. The present study suggests that in spite of cautious use of the sternal retractor, the appearance of a postoperative plexus lesion cannot be completely avoided. In contrast to a cranial incision of the retractor, which can be associated with a posterior fracture of the first rib, a caudal placement of the retractor seems to induce a superior luxation of the first rib and local hematoma without concurrent fracture. Re-examinations of the patients demonstrated a good prognosis of these plexus lesions, the Horner syndromes, however, may remain for a longer time period. It is advisable that patients who have to undergo a heart operation with median sternotomy should be informed beforehand about the possible side-effects described here.

Aortic Valve↗
PubMed1987

Intracranial flow patterns at increasing intracranial pressure.

In the course of a pilot study, changes in intracranial pressure were compared with the transcranial Doppler findings of the middle cerebral artery. The cases of five patients were discussed who developed dissociated brain death in spite of intensive therapeutic measures. The studies showed that changes of the intracranial pressure influenced the flow patterns considerably: at increasing intracranial pressure (decreasing cerebral perfusion pressure) a progressive reduction of the systolic and above all diastolic flow velocities and finally a pendular flow occurred. These changes could be recorded quantitatively by means of the "Pourcelot index" and the mean flow velocity. Acute changes of the intracranial pressure can be detected at an early stage by noninvasive transcranial Doppler studies and can be followed by adequate intensive therapy.

Adult↗
PubMed1987

Electromagnetic articulography: use of alternating magnetic fields for tracking movements of multiple points inside and outside the vocal tract.

The purpose of this paper is to present a new electromagnetic device which uses alternating magnetic fields for tracking movements of multiple points inside and outside the vocal tract. It is biologically safe, noninvasive, it does not interfere with speech movements, allows for multiple recording in the same subject, and for easy collection of large amounts of data. It is especially suitable for evaluation of patients with speech motor impairments.

Electromagnetic Fields↗
PubMed1987

[Possibilities and limits of determining central motor conduction latencies in the human].

It was the aim of the present study to define the normal range of latencies to muscle compound action potentials of different muscles in the upper and lower extremity elicited by transcranial cortex stimulation (see Tab. 1). It was demonstrated that parameters, such as voluntary background innervation (see Fig. 1) and stimulation strength (see Fig. 2) have great influence on both the latencies and the amplitudes of these responses (see Figs. 3 and 4). Thus, as a prerequisite for an interpretation of latencies to cortically evoked responses as being normal or abnormal is a detailed description of the conditions under which the responses have been obtained. Additionally the individual conduction distances along the central and peripheral motor pathways have to be taken into account (see Fig. 5). Furthermore it is shown that the combination of cortex stimulation and stimulation on spinal level with the aim of a fractionated determination of central motor conduction velocities suffers from several limitations. The main limitation arises from the observation that the excited parts of the motor system are non-congruent (see Fig. 6). Isolated high-cervical tract stimulation exciting motoneurones of the upper extremity frequently could not be performed since the excitation threshold of the motor roots is much lower than that of the descending motor tracts (see Fig. 6 and 7).

Body Height↗
PubMed1987

[Cutaneo-muscular reflexes of the human hand. II. Neurophysiologic aspects of reflex organization and coordination].

The organization and coordination of cutaneo-muscular reflexes of human finger and arm muscles to electrical stimulation of the digital nerves were investigated in 14 healthy volunteers. Thumb and finger muscles, although antagonists, showed homonymous reflex effects whereas the wrist and elbow muscles exhibited an reciprocally alternating reflex pattern in pairs of antagonists (Fig. 1). The mechanographical correlate of the homonymous reflex activity in distal muscles was a short release (Fig. 6). The receptive field for evoking such reflex effects covered both the palmar and dorsal surfaces of the fingers (Fig. 2). However, with stimulation of the thumb, the muscles of the fingers and of the wrist showed reflex reversal (Figs 3, 5). If the stimulus was moved from the second to the fifth fingers, a successive attenuation of the transcortical reflex component was seen (Fig. 4). It is concluded that the reflexes investigated are complex flexor reflexes comprising both a distal release and a proximal flexion synergy. According to opposition of the thumb in grasping, the receptive field terminates between thumb and index finger. These reflexes are supposed to have no assisting function during corticalized manipulatory movements--in contrast to the long-loop reflexes evoked by epicritic sensibility. The transcortical servo is blocked if the eliciting stimulus is contaminated by nociceptive signals; its receptive field is confined to those fingers used in the precision grip.

Adult↗
PubMed1987

[Microcomputer and rehabilitation of cognitive cerebral performance disorders].

Clinical neuropsychology has so far mostly been concerned with theoretical aspects of the brain-behavior relationship, as well as the diagnosis of cognitive deficits after brain damage. Only very recently has cognitive rehabilitation of the brain injured patient become a major area of interest in neuropsychology, and computer-assisted therapy of higher cortical functions is playing an increasing role especially in the United States. A survey found that 73% of the rehabilitation centers included were using computers in delivering their cognitive rehabilitation therapy, major areas of computer-assisted therapy being deficits of eye-hand coordination, attention, concentration, orientation, visual-spatial processing, memory, discrimination, problem solving, and concept formation. Treatment of speech disorders using computers is so far limited but will improve when more efficient language analyzers and synthesizers become available. More powerful microcomputers will lead to both computer-assisted and computer-managed cognitive programs, which allow for maximum flexibility and individualization of treatment. Computer use in cognitive rehabilitation should be subject to supervision by a therapist, and the following requirements should be met: 1) detailed diagnostic analysis of the differential cognitive performance pattern of a patient; 2) individual adaptation of computer peripherals to achieve optimum patient-computer-interaction; 3) selection and adaptation of therapy software to match the individual cognitive performance profile of a patient. Cognitive computer therapy appears to be most profitable in the rehabilitation phase and in post-rehabilitation treatment.

Brain Damage, Chronic↗
PubMed1987

[Postoperatively developing serratus paresis as a legal problem].

It is demonstrated in five exemplary cases that a neuralgic amyotrophy with particular involvement of the long thoracic nerve was the cause of a postoperative serratus paresis. In any case liability claims, it is essential for an expert's opinion on postoperative serratus paresis to differentiate this pathology from intraoperative injuries caused by pressure. Above all the interval between operation and the first manifestation of symptoms, as well as the development of distinct pain count against an intraoperative plexus lesion.

Adult↗
PubMed1986

Myoadenylate deaminase deficiency.

This report concerns two unrelated males; one had sarcoidosis, sarcoid myopathy and muscle weakness, and the other had exercise-induced weakness and myalgia. Both patients had a lack of ammonia rise in their serum after an ischemic work test, minimal histochemical activity of myoadenylate deaminase in repeated muscle biopsies, and less than 5% of normal biochemical activity of myoadenylate deaminase in their skeletal muscles. These three criteria establish primary myoadenylate deaminase deficiency as a separate primary metabolic muscle disease which merits differential diagnostic consideration when patients complain of muscle weakness and cramps.

AMP Deaminase↗
PubMed1986

Aspects of speech motor control: programing of repetitive versus non-repetitive speech.

The aim of the present study was to investigate whether time to program repetitive speech movements (RS) would be distinct from time to program non-repetitive speech movements (NRS) when the length of sequences is kept constant. Using an oral reading task, latencies for the initiation of RS and NRS were measured under two conditions which allowed delineation of the time necessary for perceptual processing separated from actual motor programing. The results show that latencies for NRS were significantly longer than for RS, indicating that the nature of an utterance, not simply its length, is a determinant of program complexity.

Adult↗
PubMed1986

Improved programs for DNA and protein sequence analysis on the IBM personal computer and other standard computer systems.

We have previously described programs for a variety of types of sequence analysis (1-4). These programs have now been integrated into a single package. They are written in the standard C programming language and run on virtually any computer system with a C compiler, such as the IBM/PC and other computers running under the MS/DOS and UNIX operating systems. The programs are widely distributed and may be obtained from the authors as described below.

Amino Acid Sequence↗
PubMed1986

Neuropharmacological investigations in the stiff-man syndrome.

In a patient with the stiff-man syndrome, abnormal exteroceptive reflexes in hand and arm muscles were used as a tool for investigating the effects of various centrally acting adrenergic drugs by means of acute testing. Clonidine, tizanidine and methamphetamine induced reflex suppression whereas reserpine had a biphasic effect: transient reflex suppression and delayed reflex enhancement. The drug actions on the reflexes paralleled to some degree those on the muscle stiffness. It is concluded that alpha-adrenergic stimulation leads to reflex suppression and muscular relaxation, whereas alpha-adrenergic blockade has the opposite effect. Correspondingly, long-term oral treatment with the alpha-stimulator, tizanidine, proved successful. The hypothesis is put forward that a noradrenergic system which exerts a net inhibitory influence on muscle tone and on exteroceptive reflexes plays an important role in the pathogenesis of the stiff-man syndrome.

Adrenergic Fibers↗