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Biomedical subjects

D Claus

Publications and source records attributed to D Claus.

At least 91 records · Page 5Linked to original sources
PubMed1993

Short-term memory: no evidence of effect of rapid-repetitive transcranial magnetic stimulation in healthy individuals.

The effect of rapid-repetitive transcranial magnetic stimulation (rr-TMS) on the immediate verbal and visuospatial memory span was assessed by computerized neuropsychological testing in 11 healthy volunteers. The objective was to test whether rr-TMS may be utilized as a non-invasive tool for evaluation of memory function. The subjects had to memorize series of numbers (Digit-Span test) or the position of cubes (Corsi-Block test) shown to them on a computer screen and actively reproduce them immediately after the presentation. Synchronous with the appearance of each item an rr-TMS train of 550 ms duration was delivered to the left or right anterolateral parietal as well as superior and posterior lateral temporal region at 50 Hz and with approximately 1.0 T stimulation intensity. Statistical comparison of memory performance during rr-TMS and baseline testings without stimulation revealed no significant changes. No adverse effects were observed. Thus, rr-TMS does not affect short-term memory performance in healthy individuals under the stimulation conditions described above.

Adult↗
PubMed1993

Influence of repetitive magnetic stimuli on verbal comprehension.

The influence of repetitive magnetic transcranial stimulation over the temporo-parietal cortex on verbal comprehension was investigated in 44 healthy subjects. In right-handed subjects, trains of 50 Hz magnetic stimuli over the left hemisphere produced more errors than stimulation over the right hemisphere. The result is not very clearcut, however; thus the test cannot be used for diagnostic investigation of language dominance.

Adolescent↗
PubMed1993

Resistance to ischaemic nerve-fibre block in diabetes mellitus and in mitochondrial encephalomyopathies.

Thermal thresholds were measured during ischaemic compression block in the left forearms of 26 healthy subjects, 10 patients with diabetes mellitus and 6 patients suffering from different kinds of mitochondrial disorders. Cold and warm thresholds in the 6 patients with deficiencies in the respiratory chain increased earlier than in normals. When cold perception was impaired, cold stimuli were perceived as warmth and pinprick perception attenuated. In diabetics cold thresholds were less elevated during ischaemic block than in controls. This was paralleled by tingling paraesthesiae in all groups. The findings show that higher resistance to ischaemic nerve-fibre block in diabetes mellitus is not exclusively based on increased anaerobic metabolism.

Adult↗
PubMed1993

Electrophysiologic evidence for a toxic polyneuropathy in rats after exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD).

At present, experimental data on the neurotoxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin are still lacking. Therefore, electrophysiologic studies were performed in 80 adult, male Han/Wistar rats intraperitoneally injected with a single, low dose of TCDD (8.8, 6.6, 4.4 or 2.2 micrograms/kg) dissolved in corn oil. 20 control animals received corn oil only. The typical 'wasting syndrome' of high-dose TCDD-intoxication was therefore not observed. Motor and sensory nerve conduction velocities in the right sciatic nerve showed dose-dependent and statistically significant slowing in TCDD-exposed rats as compared to controls. Spontaneous activity in the flexor digitorum muscle of the right hind paw and in tail muscles could be seen in the electromyogram of TCDD-group 1 (100%), group 2 (93%), groups 3 and 4 (87% each). This was significantly less frequent in the controls (21%). These findings give electrophysiologic evidence for a toxic polyneuropathy in rats after a single, low dose of TCDD.

Animals↗
PubMed1993

[Peripheral nerve entrapment syndrome in musicians].

This survey article discusses entrapment syndromes of nerves in instrumentalists. There is no specific susceptibility of musicians to peripheral nerve lesions. They are, however, very sensitive to symptoms caused by entrapment neuropathies. In pianists the right arm is more often affected and in violinists the left. Some typical syndromes are described such as the thoracic outlet syndrome, carpal tunnel syndrome, anterior and posterior interosseus syndrome, as well as ulnar neuropathies at elbow and wrist. The symptoms of peripheral nerve entrapment can interfere with playing the instrument in such a way that musicians have to give up their career. The results of conservative and surgical treatment are, however, favourable.

Humans↗
PubMed1993

Hyperventilation and transcranial magnetic stimulation: two methods of activation of epileptiform EEG activity in comparison.

In a prospective study, we compared the established method for an activation of epileptiform activity in EEG, hyperventilation (HV), with the recently presented new activational technique of transcranial magnetic stimulation (TMS) in 10 patients with drug-resistant partial epilepsies. Long-term EEG recordings included subdural electrodes in the course of presurgical evaluation. Epileptiform activity was evaluated visually 500 s before, during, and 500 s after stimulation, and the results were compared statistically. TMS was not better than HV: HV caused an activation of the epileptogenic foci in 6 of 10 cases, TMS only in 3 of 10. Seizures could be induced by HV in 2 of 10, by TMS in no cases. In 2 of 10 cases, TMS even caused a significant reduction of epileptiform activity.

Adolescent↗
PubMed1993

Histologic evidence for a toxic polyneuropathy due to exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in rats.

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a considerable environmental hazard in industrial societies. Its toxic effects on animals and humans are numerous, but little is known about its neurotoxicity. We studied the neurotoxic effects of TCDD in 80 male, adult Wistar rats. The substance was dissolved in corn oil and a single dose injected intraperitoneally (8.8 micrograms, 6.6 micrograms, 4.4 micrograms or 2.2 micrograms/kg). Neurophysiological examinations proved a dose-related, statistically significant slowing of sensory and motor conduction velocities. Ten months after the application of TCDD peripheral nerves showed a progressive, and proximally accentuated neuropathy. The extent of changes, however, differed remarkably between individual animals. Our data indicate that TCDD caused a toxic polyneuropathy in rats.

Animals↗
PubMed1993

[Central motor conduction time in diagnosis of spinal processes].

In patients with extra- and intramedullary spinal disorders (32 cases with myelopathy due to cervical spondylosis, 11 with syringomyelia and 17 with spinal tumours) central motor conduction time (CMCT) was studied after transcranial magnetic stimulation of the cortex. Compound muscle action potentials (CMAP) were recorded from abductor digiti minimi muscle (ADM) and anterior tibial muscle (TA) bilaterally. Of 37 patients with extramedullary located cervical lesions CMCT to the ADM was abnormal in 51% (n = 19) and to the TA in 70% (n = 26). In 10 patients with intramedullary cervical lesions abnormal CMCT to the ADM as well as to the TA was observed in 30% (n = 3) each. In extramedullary disorders measurement of CMCT to the TA was more sensitive in detecting impaired central motor conduction, though not significantly. Prolonged CMCT correlated to clinical signs of upper motor neuron involvement and to spinal cord compression. In addition, the method proved useful for detection of subclinical lesions of corticospinal pathways. The different results between intra- and extramedullary affections are explained by the anatomical localisation of pyramidal tract fibers.

Adult↗
PubMed1992

Isoflurane anaesthesia in the treatment of convulsive status epilepticus. Case report.

Status epilepticus may be resistant to intravenous anticonvulsive drugs. In these cases treatment with the inhalation anaesthetic agent isoflurane may be helpful in the further management. We describe a 35-year-old female patient who suffered from status epilepticus with partial seizures. In spite of therapy with benzodiazepine and phenytoin the status evolved into tonic clonic seizures. Treatment with thiopentone sodium did not stop seizure activity. Anaesthesia with isoflurane (dosage up to 1.5 vol.%) carried out twice within 72 h finally led to a termination of status epilepticus. From our own experience and reports in the literature we conclude that general anaesthesia with isoflurane can and should be used in the treatment of severe status epilepticus that does not respond to intravenous anticonvulsive agents.

Adult↗
PubMed1992

Corticospinal conduction studied with magnetic double stimulation in the intact human.

A group of 8 healthy normal subjects (24-36 years old, mean age 29 years) were investigated. Transcranial magnetic double stimulation of the motor cortex was carried out at different interstimulus intervals. With both stimuli suprathreshold, an attenuation of the test response was found at interstimulus intervals of less than 200 msec (target relaxed or contracted). The manifestation of this attenuation correlated with central signs in 31 patients with multiple sclerosis. This phenomenon is (at least at longer intervals) probably not a result of the refractory spinal motoneuron pool, but of a supraspinal inhibitory mechanism or lack of corticospinal drive caused otherwise. At interstimulus intervals between 10 and 30 msec, the test response increases significantly (magnetic double stimulation 10% suprathreshold, target relaxed). This result is also seen with voluntary muscle contraction and with vibration applied to a relaxed target muscle. The facilitatory effect is probably caused by slowly conducted corticospinal volleys enabling summation, with descending impulses generated by the test stimulus. With the conditioning stimulus subthreshold and target muscle relaxed an intracortical inhibition of the test response could be confirmed at short interstimulus intervals.

Adult↗
PubMed1992

The influence of the shape of mechanical stimuli on muscle stretch reflexes and SEP.

Stretching of human thenar muscle was carried out using mechanical stimuli of different amplitudes and velocities in 50 normal subjects. Amplitudes of early M1 and late M2 reflex responses as well as cortical evoked potentials were recorded. M1 and M2 increased with a larger mechanical stimulus. Steeper mechanical stimuli generated larger M1 amplitudes, whereas M2 remained unaffected. Amplitudes of early cortical evoked potentials increased with increase of both rise-time and amplitude of muscle stretch. The shape of the mechanical stimulus is critical for the resulting reflex response. The different behaviours of M1 and M2 with increasing stimulus velocity are in favour of their different origins. Our results support a participation of slowly conducting muscle spindle afferents in the generation of the late M2 response in distal human hand muscles.

Adult↗
PubMed1992

Influence of caffeine, sweating and local hyperemisation on "Marstock" thermotesting.

Marstock thermotesting evaluates A-delta- and C-fiber functions. To optimize this method, intraindividual variations of vasodilatation, blood flow and sympathetic activity probably biasing thermotest results were imitated by exogenous stimuli which strongly exaggerated these intraindividual variations. In 20 healthy subjects, warm (WT), cold (CT), and heat-pain (HT) thresholds were determined in the morning at the thenar (th), the volar wrist (wr), and behind the malleolus internus (mi). Thresholds at the thenar and the volar wrist were compared with those during severe sweating induced by Minor's test, and to those measured when sympathetic activity had been increased by the ingestion of a high dose of caffeine (0.5 g). Furthermore, the intraindividual variation of local capillary blood flow and vasodilatation was imitated by a rubefacient liniment (Forapin) applied to the three sites. After a local hyperemisation had been induced thermal thresholds were measured and compared to those measured without any stimulation. Local hyperemia did not influence thermal thresholds significantly. Sweating only lowered cold thresholds at the thenar significantly and only slightly raised warm and heat-pain thresholds at the thenar. Caffeine significantly lowered warm thresholds and raised heat-pain thresholds at the thenar. To conclude, the tested exogenous interferences do not disturb thermal perception markedly, especially when testing is not performed at the thenar, but at the volar wrist and when the testing-procedure and parameters are standardised.

Adult↗
PubMed1992

[Peripheral facial paralysis as the first symptom of unknown metastatic primary tumor].

The spread of metastases to the brain and the leptomeninges is usually a terminal event in patients with known malignancies. We report on two patients, in whom the diagnosis of a diffusely metastasizing carcinoma was considerably delayed by the initial symptom of a peripheral facial nerve paralysis. The clinical, neuroradiologic and cerebrospinal fluid findings are discussed. A malignant neoplasm with diffuse or focal metastasis to the leptomeninges is a rare cause of peripheral facial paralysis of unclear genesis. The necessity of a lumbar puncture plus magnetic resonance imaging of the brain to enable an early diagnosis is emphasized.

Adenocarcinoma, Mucinous↗
PubMed1991

Motor potentials evoked in tibialis anterior by single and paired cervical stimuli in man.

Latencies of compound muscle action potentials evoked in lower limb muscles after transcranial stimulation shorten and amplitudes enlarge when the target muscle is contracted. After transcutaneous stimulation of the cervical cord with single electrical stimuli, the latency is not affected by muscle contraction. This is thought to be due to a lack of temporal summation at the spinal motoneurones. Results are different when paired stimuli are used. With contraction most motoneurones respond to the first cervical stimulus while in a relaxed condition they respond to the second. Temporal summation brings motoneurones to their firing threshold. Therefore, cervical double stimulation is more effective than single stimuli. It is however less powerful than cortical stimulation. Paired stimuli are most powerful at an interval of 2 ms similar to the D I-wave interval after cortical stimulation.

Action Potentials↗