PubMed Health⌕ Search

Biomedical subjects

A Struppler

Publications and source records attributed to A Struppler.

At least 19 recordsLinked to original sources
PubMed1992

Motor cortex transcranial magnetic stimulation topography assessed by distribution and size of evoked potentials.

25 volunteers aged 18 to 70 were examined. Bilateral EMG was performed of m. m. biceps brachii et flexores digitorum profundus using surface pick-up electrodes. The evoked potentials were recorded on Nicolet Pathfinder II. Magstim 200 Novametrix was used for stimulation with A and B sides of a coil with mean diameter of 9 cm. The examinees were sitting on chairs, their forearms flexed voluntarily to approximately 90 degrees, resisting a standing pressure of 5 Nm exerted by the torque motor. Three groups were examined. In the first, we recorded the amplitude, the latencies and spreading of potentials in the muscles on the left and right stimulating with the A and B sides and positioning the coil on the vertex (Cz), 2 and 4 cm forwards and backwards. Moving the coil away from Cz brought about reduction of the amplitudes of the evoked potentials or resulted in the disappearance of potentials. This was better seen in backward shift of the coil. The latencies did not change. The responses were bilateral in 10 out of 11 subjects the amplitudes being higher on the side corresponding to the destination of stimulation. In the second group we wanted to see what the effect of the shift of stimulation away from the meddle line would be. C-P1, C-P2, Cz1 and Cz2 are not suitable sites for obtaining potentials. Stimulation at C-F1 and C-F2 yielded potentials which, contrary to the expectation, evoked ipsilateral responses. In the third group stimulation was combined with focal sensor influence. At the beginning it was a focused attention which, however, was difficult to define.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

[Control of isometric muscle contraction in muscle hypotonia of central origin: EMG mapping analysis].

Electromyographic and mechanographic investigations in patients with muscular hypotonia, which is, for instance, a side-effect after stereotactic treatment of tremor syndromes, permit the presumption that in this sensomotor open-loop situation the decreased muscular resistance to stretching during isometric contraction (initial stiffness) is caused by changes of muscular innervation pattern. Probably, the innervation pattern during tonic activity is changed by a shift of a more tonic motoneurone behaviour to motoneurone activities with predominantly phasic characteristics. In 17 controls and 4 patients with muscular hypotonia caused by stereotactic lesions of VIM area (treatment of tremor syndromes) the EMG of right and left side forearm flexors (especially the activity of the M. biceps brachii) was investigated by a sophisticated, topographically oriented 16-channel-surface-EMG-technique ("EMG-Mapping") during slight isometric contraction. EMG-Maps of forearm flexors (especially of M. biceps brachii) in patients with centrally evoked muscular hypotonia demonstrate that in these open-loop conditions the motor control is changed. For this the reason could be a shift of the activated motor units from a predominantly static to a more phasic functional behaviour. The latest results on muscular activation processes in cats support this presumption.

Adult↗
PubMed1991

[Electrophysiologic diagnosis of peripheral nerve lesions].

In the last two decades the surgical treatment of peripheral nerve lesions has improved considerably, mostly because of the introduction of the microsurgical technique. It was not until the introduction of microsurgery that the surgeon was able to achieve restoration at the level of the nerve fasciculi. The simultaneous use of electrophysiological techniques can improve the results of the reconstruction and especially the extent of functional outcome of nerve restoration. Electrophysiological methods allow detailed and objective assessment of the site, extent, and cause of the lesion and are therefore crucial for the decision upon the appropriate therapeutic procedure and for the success of the operation. The aim of the review is the demonstration of: 1. Today's understanding of peripheral nerve function/ 2. The neurophysiological mechanism of denervation and renervation/ 3. The different electrophysiological methods/ 4. The indications and 5. Application of these techniques in the context of reconstructive surgery.

Electrodiagnosis↗
PubMed1991

Changes in the response to magnetic and electrical stimulation of the motor cortex following muscle stretch in man.

1. The effect of muscle stretch on the EMG response from the stretched muscle to transcranial magnetic stimulation of the motor cortex was studied in eight subjects. Muscle stretch was produced by increasing the torque of a motor acting through a lever which was held at constant position by a flexion force of the index and middle fingers. EMG responses were recorded from fine-wire electrodes inserted into flexor digitorum profundus muscle in the forearm. They consisted of a spinal latency component and a long-latency component which could in some subjects be separated into an early and a late phase. 2. In four subjects, four intervals between the stretch and the cortical stimulus were explored using three intensities of cortical stimulation. At all three intensities, when the magnetic cortical stimulus was timed to produce an EMG response in the period of the later part of the long-latency stretch reflex the response was larger than when it was timed to produce a response in the period of the short-latency spinal reflex or when superimposed on the tonic muscle activity used to resist the standing torque of the motor. 3. When the intensity of magnetic cortical stimulation was reduced so that it was just below threshold to produce an EMG response in the short-latency reflex period or on the background tonic EMG activity, it still was capable of producing a response when superimposed on the long-latency stretch reflex. 4. In four subjects the time course of this effect was studied in more detail using only one intensity of magnetic cortical stimulus set to be just above threshold to produce a response in tonically active muscles. The time course of the facilitatory effect was similar to the time course of the later part of the long-latency stretch reflex. From these data it was not possible to determine whether the early part of the long-latency stretch reflex also was accompanied by the facilitatory effect since this component was present in only one of the four subjects. 5. The facilitatory effect persisted after the ulnar and median nerves were totally blocked at the wrist by injections of local anaesthetic. This suggests that inputs from muscle receptors of the stretched muscle contribute to the effect.4=

Adult↗
PubMed1990

Responses of human muscle spindle afferents during isotonic position holding and active movements.

Discharge characteristics of muscle spindle primary afferents from human finger flexors were investigated during load-bearing isotonic position holding, and intentional shortening or lengthening contractions. During position holding, units mostly showed a negative relationship between muscle length and impulse rate, particularly when the load was small. When the load was increased, Ia-discharge rates increased more in the elongated than in the shortened muscle, and the inverse position response became less pronounced. During active lengthening contractions, a stretch response pattern was sometimes absent or could be abolished by increasing the load.

Adult↗
PubMed1990

Amyotrophic lateral sclerosis: macro-EMG and twitch forces of single motor units.

Macro-EMG potentials (MEP)s and twitch contractions (spike-triggered-averaging) of single motor units (MUs) have been recorded in the first dorsal interosseus muscle (FDI) of 10 control subjects and 20 patients with amyotrophic lateral sclerosis (ALS). MUs over the full range of voluntary recruitment thresholds were studied. Patients with slightly affected FDIs (5) mainly showed MUs with enlarged MEPs and increased twitch forces. In contrast, the patients with more severely affected FDIs (15) revealed decreased twitch forces, especially in the MUs with higher thresholds. The corresponding MEPs could be enlarged as well as normal. It appears that MU sprouting and the resulting increase of twitch force can compensate for the loss of motoneuron in early stages of ALS. In more advanced stages, however, a decline of the force of the surviving MUs, especially of those with higher thresholds, seems to contribute to the progressive muscle weakness, in addition to the corticospinal degeneration and the reduction in the number of motoneurons.

Action Potentials↗
PubMed1990

Stereoencephalotomy and control of skeletal muscle tone.

Stereotactic interventions at the thalamic or subtalamic level for treatment of pathological hyperkinesias provide a good model for investigation of the systems controlling tonic innervation in the alert subject. It is suggested that the poststereotactic muscular hypotonia observed contralaterally to the lesion is due to changes in the tonic innervation pattern caused by interruption of a proprioceptive feedback loop.

Dominance, Cerebral↗
PubMed1990

Discharge pattern of tonically activated motor units during unloading.

In order to analyse the EMG pattern during unloading of brachial biceps muscle, the interference EMG and single motor unit activity were investigated. The measurements were done on seven healthy subjects with two types of unloading techniques: a) active unloading, when the subjects resisted against an external load (10, 20, 30 and 40 N) which is suddenly released, and b) passive unloading, performed by low inertia torque motors with independently adjustable background extension and suddenly applied flexion torques. Following active unloading the silent period duration, the amplitude of the rebound and its segmentation into consecutive bursts is changing with initial load, whereas the silent period latency remains constant. Following passive unloading the acceleration influences predominantly the amplitude of the rebound, without changing its latency and silent period duration. The initial voluntary activity influences both silent period duration and rebound parameters (latency, amplitude and duration).

Action Potentials↗
PubMed1989

Response of human muscle spindle afferents to abrupt load perturbations.

Response patterns of single muscle spindle primary afferents to abrupt load perturbations inflicted upon the contracting finger flexors were investigated in awake human subjects using the technique of microneurography. Units showed a transient high-frequency discharge in the rising phase of the stretch. No repeated burst activity attributable to irregularities of the stretch velocity or to mechanical oscillations of the muscle could be detected.

Action Potentials↗
PubMed1989

Painful dysaesthesias following peripheral nerve injury: a clinical and electrophysiological study.

Thirty-three patients with complete median, ulnar or digital nerve transections were studied 4 months to 13 years subsequent to suture or nerve grafting. In all cases, sensory disturbances, in terms of paraesthesia or hypaesthesia, were encountered. Painful or unpleasant symptoms, allodynia or hyperpathia, were observed most frequently in patients with poor recovery. The clinical findings and the patients' subjective complaints were correlated to microneurographic single fibre recordings of regenerated cutaneous mechanoreceptors. In more than 80% of the recordings, discharge properties of regenerated receptors, thresholds and a variety of other electrophysiological data were similar or equal to normal controls. Less than 20% of the receptors exhibited atypical properties suggesting defective steady-state regeneration. The ratio of rapidly adapting (RA-units) to slowly adapting mechanoreceptors (SA-units) was inverse in relation to normals. The density of regenerated RA-receptors was higher in the proximal than in the distal part of the reinnervated area. This paralleled the clinical finding of reduced sensory discrimination in these cases and suggests that SA-units may regenerate preferentially. In painful conditions no single fibres could be recorded, reflecting the relative paucity of fibres and probably the atrophy of the nerve. The results of the microstimulation experiments, although less reliable, revealed some evidence that the central processing of regenerated units is abnormal. Clinical and electrophysiological data supported this concept of central changes underlying some of the phenomena observed during peripheral nerve regeneration.

Adolescent↗
PubMed1989

Measurements of muscle stiffness, the electromyogram and activity in single muscle spindles of human flexor muscles following conditioning by passive stretch or contraction.

In experiments on adult human subjects we examined the effect on passive mechanical properties of a muscle by conditioning it with either an isometric contraction or passive muscle extension. The test measurement was the amount of muscle displacement (stiffness) and the accompanying EMG in response to a brief torque pulse. Two muscles were tested, flexor digitorum profundus (FDP) and brachialis. In FDP the discharge of single muscle spindles was recorded as well. After muscle extension and return to the initial length, passive stiffness was less than after an isometric contraction. The changes in stiffness were accompanied by changes in pattern of EMG and in the responses of muscle spindles. It is suggested that in resting muscle there are stable cross bridges between actin and myosin filaments of muscle fibres which largely determine the passive stiffness. Muscle extension leads to detachment of these cross bridges which then re-form at the longer length. Return of the muscle to its starting length leads to development of slack in muscle fibres because, stiffened by the presence of the stable cross bridges, they are unable to shorten. Slack in muscle fibres lowers their measured stiffness. Muscle contraction, on the other hand, will result in any preexisting slack being taken up by the actively shortening muscle fibres, thereby raising muscle stiffness. Stiffness in intrafusal fibres is likely to follow a similar pattern to that in extrafusal fibres, leading to changes in stretch responsiveness of muscle spindles and consequently in the reflex EMG. It is concluded that the changes in stiffness and accompanying reflexes observed in this study are likely to be seen, at least under some conditions, in normal movements.

Adult↗
PubMed1989

[Systemic pharmacotherapy in backache. Indications and practical applications].

The treatment of acute and chronic low back pain is a problem frequently encountered in the doctor's office. Selective drug therapy has a useful role to play within the framework of the overall therapeutic strategy. Indications and practical application of the major analgesic agents in various low back pain conditions are discussed.

Adrenal Cortex Hormones↗
PubMed1989

Intrathecal baclofen for long-term treatment of spasticity: a multi-centre study.

Twenty eight patients with severe, intractable spasticity have been treated by chronic intrathecal administration of baclofen. An implantable programmable drug-administration-device (DAD) was used with a permanent intrathecal catheter. Infusion of 50 to 800 micrograms/day of baclofen completely abolished spasticity. Follow-up was up to two years. Therapeutic effect was documented by clinical assessment of tone, spasms and reflexes and by electrophysiological recordings of mono- and polysynaptic reflex activity. Complications and untoward side-effects of the procedure were few. This procedure is recommended for spasticity of spinal origin refractory to physiotherapy and oral medication. It is a preferable alternative to ablative surgical intervention.

Adult↗
PubMed1989

Functional neuroanatomy of the target area for the treatment of pathological tremor: an electrophysiological approach.

Within the target area used for the stereotactic treatment of pathological tremor, recording of somatosensory evoked potentials and single units and also electrical stimulation were performed. The data were correlated with anatomical sites as demonstrated in the stereotactic atlas of Schaltenbrand and Wahren by using a computer system. The affected anatomical area was predominantly the prelemniscal radiation and adjacent thalamic nuclei. The recordings and stimulation effects indicate that a direct spinal input is involved in the control of muscle tone and manifestation of tremor.

Brain↗
PubMed1989

Stereoencephalotomy and control of skeletal muscle tone.

Following therapeutic stereotactic lesions in the ventrolateral subthalamus and adjacent nuclei there are two phenomena concerning muscle tone: decreased muscle stiffness and failure in load compensation. In order to clarify whether hypotonia is due to decreased reflex activity and/or reduced nonreflex muscle stiffness, torque-induced stretch responses in the forearm flexor muscles and muscle spindle afferent discharge were investigated. In hypotonia following these lesions, the immediate compensation of abrupt external perturbations was diminished prior to reflex onset. A special feedback system is presented which originates in skeletal muscles and which continuously controls the muscle stiffness during movements. This afferent fiber system probably has a greater representation at the thalamic level as compared to the peripheral nerve. It is assumed that the decrease in muscle stiffness as well as the failure in load compensation are due to diminished static gamma-drive. This lack in somatosensory feedback can be compensated voluntarily by changing the mode of innervation.

Electric Stimulation↗