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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
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↗
PubMed1986

Delayed visual evoked potentials in chronic alcoholism.

Pattern reversal visual evoked potentials (VEPs) were studied in 80 chronic alcoholics and in 43 normal subjects. In the patient group, P2 latencies and inter-eye differences were found above the 98% confidence limit in 30%, and above the 99.9% confidence limit in 10%. An abnormal waveform was observed in 12.5% and 7.5% of the patients. VEP abnormalities showed some statistical correlation with the gamma-type of alcoholism of Jellinek, but almost no correlation was observed with a variety of clinical and laboratory data. This suggest that VEP abnormalities are unrelated to other toxic effects of alcohol on the peripheral and central nervous systems or on metabolism.

Adult↗
PubMed1985

Hesitation vowels: a motor speech respiration hypothesis.

In spontaneous speech the relation of hesitation vowels 'ah' and 'mh' (filled pauses) and respiration was studied in 16 healthy native speakers of German. Hesitation vowels did not occur randomly in expiration during speech. When expiratory duration was divided into four segments of equal length, the highest incidence of hesitation vowels was to be found at early loci during expiration. As speech respiration is reset to vegetative breathing as soon as speech production stops, hesitation vowels act as phonomotoric subroutines during halting speech production to prevent the respiratory system from uneconomic air loss and to keep it in the speech respiration mode.

Adult↗
PubMed1985

Rapid goal-directed elbow flexion movements: limitations of the speed control system due to neural constraints.

In rapid goal-directed elbow flexion movements the influence of both movement amplitude and inertial load on the three-burst pattern and the consequences on movement time were studied. Subjects performed visually guided, self-paced movements as rapidly and as accurately as possible. An increase of both the movement amplitude and the inertial load were found to be interacting factors for the modulation of the three-burst-pattern and movement time. The first biceps burst progressively increased in duration and amplitude for larger movements, resulting in prolonged movement times. Surplus inertial loads further prolonged the agonist burst for large, but not for small movement amplitudes. The activity of the antagonist burst, in contrast, was largest in small movements and successively decreased at increasing movement amplitudes. Its duration, however, remained fairly constant. As was similarly observed for the agonist burst, surplus inertial loads lead to a prolongation of antagonist burst duration and an small movement amplitudes. It is suggested that in elbow flexion movements the programming of fastest goal-directed movements must take into account neural constraints and biomechanical characteristics of the agonist muscle and the antagonist muscle. Due to neural constraints of the biceps muscle, in contrast to finger movements, the concept of movement time invariance does not hold for elbow movements. Furthermore, neural constraints of the antagonist muscle lead to a limited force production of the agonist muscle at small movement amplitudes in order to avoid an overload of the braking process.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

The flexor reflex--influence of stimulus parameters on the reflex response.

The flexor reflex evoked in the tibialis anterior muscle by stimulation of the medial plantar nerve was investigated in 54 normal subjects. Three main reflex components were identified (excitation--inhibition-- excitation), the early excitation being composed of two subcomponents. Occasionally, a fourth (excitatory) reflex component was seen breaking through EMG inhibition. The individual reflex components were differentially susceptible to facilitatory influences which suggested transmission via a central multichannel system. Methodological experiments showed that the amplitudes and to some degree also the latencies of the individual reflex components were modified by both the parameters of the stimulus as well as by the degree of pre-innervation. However, the patterning of the reflex response was basically independent from methodological permutations.

Adult↗
PubMed1985

[Lesion of the intercostobrachial nerve].

After surgery in the area of the armpit, and particularly after axillary lymphonodectomy during mastectomy, severe pain and paraesthesia can occur in the region of the medial and posterior side of the proximal upper arm. It is shown by means of four case reports that this discomfort can be caused by a lesion in the intercostobrachial nerve. The differential diagnosis must consider injury to the brachial plexus or a local metastasis.

Arm↗
PubMed1984

Changes of somatosensory evoked potentials in man as correlates of transcortical reflex mediation?

Somatosensory evoked potentials (SSEP) from the scalp of the sensori-motor cortex were recorded together with long latency reflexes in the EMG of the contralateral biceps muscle in 17 human subjects, who were instructed to compensate a sudden biceps stretch. In this 'compensate' condition the earliest deviation from the shape of the SSEP obtained in a 'let go' situation (exhibiting only short latency reflexes) occurred as early as 35-40 ms. The results indicate that SSEP changes associated with the occurrence of long latency reflexes might be compatible with a transcortically mediated reflex activity.

Adult↗