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Biomedical subjects

D Dressler

Publications and source records attributed to D Dressler.

At least 19 recordsLinked to original sources
PubMed1992

Effect of digital nerve stimuli on responses to electrical or magnetic stimulation of the human brain.

1. Reflexes were elicited in the first dorsal interosseous muscle of seven normal subjects by electrical stimulation of the digital nerves of the index finger at 3 times perceptual threshold while subjects maintained a constant voluntary contraction of the muscle. The average response in the surface-rectified electromyogram (EMG) consisted of an early inhibitory (I1) component followed by a later excitation (E2). 2. Low intensity anodal electrical or magnetic scalp stimuli were given over the motor cortex in order to elicit muscle responses within the period of the I1 and E2 reflex components. 3. Compared with control responses elicited in the absence of digital nerve stimulation, responses to electrical cortex stimulation were suppressed in the I1 period and facilitated during the E2 period of the reflex. In contrast, responses evoked by magnetic stimulation were suppressed during I1 and also for the first 10 ms or so of the E2 response. Magnetically evoked responses were facilitated during the later part of the E2 reflex. 4. Similar effects were seen when the probability of firing of single motor units was studied. 5. In three subjects, small taps were given to the abducted index finger in order to stretch the first dorsal interosseous muscle and evoke reflexes which were of comparable size to the E2 reflex evoked by digital nerve stimulation. In contrast to the experiments in which digital nerve stimuli were given, responses evoked by magnetic stimulation over motor cortex were facilitated at all times during the course of the reflex evoked when the muscle was stretched. 6. We conclude that single electrical stimuli applied to the digital nerves can reduce for a short period the excitability of motor cortex to magnetic stimulation. This occurs at a time when the same stimulus is evoking an excitatory (E2) reflex in the average surface-rectified EMG.

Adult↗
PubMed1992

[Gilles-de-la-Tourette syndrome].

Gilles de la Tourette's syndrome, a combination of multiple chronic tics and vocalizations, usually first occurring during childhood, is described in its history, symptomatology, genetics, etiology and therapy. Traditionally TS has been viewed either as an organic or as a psychogenic disorder. We propose an integrative concept combining both aspects. During a vulnerable phase in childhood a hypersensitivity of dopamine 2-receptors, induced by gene defects or perinatal trauma, leads to a lack of suppression of subcortical programs which discharge as tics. Tics are modified by multiple psychological contents (aggressive or sexual impulses, imitation of others) which tend to become independent of their origin. Severity of tics in the course of the illness is often dependent on the emotional status of the patient. Recent research focuses on the search for a major gene locus and the relationship between dopamine-receptor hypersensibility and the disturbances of other neurotransmitter systems (norepinephrine, serotonin, endorphin).

Combined Modality Therapy↗
PubMed1991

Further observations on the facilitation of muscle responses to cortical stimulation by voluntary contraction.

The effect of voluntary contraction on the discharge of single motor units following electrical and magnetic stimulation of the motor cortex was examined using the post-stimulus time histogram (PSTH) technique. The latencies of responses in single motor units of the first dorsal interosseous muscle to cortical stimulation were 2-4 msec shorter when the muscle was contracting than when at rest in 9 of 10 units studied. These latency differences are comparable with those recorded by surface electromyography for compound muscle action potentials following cortical stimulation in relaxed and active muscles. The new findings are that the intensity of cortical stimulation required to discharge a resting motor unit to produce a single PSTH peak produced multiple PSTH peaks when the same unit was contracting. The timing of the PSTH peak of relaxed motor unit discharge corresponded to one of the later PSTH peaks (usually the second) when the motor unit was voluntarily activated. These findings are in keeping with our previous suggestions that the longer latency of responses in relaxed muscles is due to the time taken for temporal summation of multiple descending corticospinal volleys at the cortico-motoneurone synapse. Facilitation produced by voluntary contraction occurs at least in part at the level of the spinal cord by lowering motoneurone threshold to enable discharge on the initial descending volley. The higher threshold of relaxed muscles is related to the higher intensities of stimulation needed to recruit multiple descending volleys and discharge resting motoneurones.

Adult↗
PubMed1991

Hyperkinesias after hypoglossofacial nerve anastomosis--treatment with botulinum toxin.

Hypoglossofacial nerve anastomosis is a successful method for restoration of facial nerve function. Facial hyperkinesis, however, are a common side effect of this therapy and have been a major therapeutical problem ever since. We are reporting a patient whose facial hyperkinesias responded favourably to botulinum toxin carefully injected into the most affected muscles. EMG studies are illustrating the effect of botulinum toxin on the facial hyperkinesias as well as on voluntary muscle activation.

Anastomosis, Surgical↗
PubMed1990

Safety aspects of transcranial brain stimulation in man tested by single photon emission-computed tomography.

Single photon emission-computed tomography (SPECT) using 99mTc-labelled hexamethylpropyleneamine oxime (99mTc-HMPAO), a new method to visualize regional cerebral blood flow (rCBF) and epileptogenic foci, was used to study acute and long-term effects of transcranial brain stimulation. Magnetic and electric brain stimulation increase rCBF not more than voluntary muscle activation mimicking the motor effects of transcranial brain stimulation. Focal rCBF increase, typical for epileptogenic foci, or other pathological findings could not be detected even when the subject had received several thousand stimulations in the past. Transcranial brain stimulation does not produce rCBF patterns indicating acute or chronic adverse effects.

Adult↗
PubMed1990

Botulinum toxin to suppress hyperkinesias after hypoglossal-facial nerve anastomosis.

Facial hyperkinesias are a common side effect of hypoglossal-facial nerve anastomoses. We report a patient whose facial hyperkinesias were suppressed by botulinum toxin injections a treatment recently introduced in the therapy of craniocervical dystonias. EMG studies are used to document the effect of botulinum toxin on the facial hyperkinesias as well as on voluntary muscle activation.

Anastomosis, Surgical↗
PubMed1990

Central motor conduction time to bulbocavernosus muscle: evaluation by magnetic brain stimulation and testing of bulbocavernosus reflex.

Magnetic brain stimulation and bulbocavernosus reflex (BCR) testing were performed to evaluate the central motor conduction time (CMCT) to the bulbocavernosus muscle (BC). In six healthy subjects CMCT ranged from 13.81 ms to 16.9 ms with a mean value of 15.77 ms (SD 1.38 ms). This equals a central motor conduction velocity of about 40 m/s, which can only be realized in fast conducting pyramidal tract fibres. Testing of pyramidal tract function by BC-CMCT might improve the diagnosis of male sexual dysfunction.

Adult↗
PubMed1990

99mTc-hexamethylpropylene amine oxime SPECT and X-ray CT in acute cerebral ischaemia.

Early diagnosis of acute cerebral ischaemia is still unsatisfactory, because X-ray computed tomography (CT) does not reveal the site and extent of hypoperfusion within the first 24 h. Single photon emission computed tomography (SPECT) using 99mTc-hexamethylpropylene amine oxime (HMPAO) may offer earlier information, since the distribution of HMPAO follows the actual cerebral perfusion pattern. We therefore investigated 53 patients suffering from acute cerebral ischaemia (10 with transient ischaemic attacks, 9 with prolonged ischaemic reversible neurological deficits, 34 with completed stroke). SPECT and CT examinations were performed on days 1, 3, and 14. On day 1, SPECT revealed hypoperfused areas in 42 patients, whereas CT showed hypodensities only in 5. The sensitivity of SPECT was higher in cortical compared with subcortical ischaemia. In patients suffering from reversible neurological deficits SPECT normalized in the follow-up, corresponding to clinical improvement. In completed stroke, SPECT demonstrated variable perfusion patterns with hypo-, normo-, and hypoperfused areas on day 3 and especially on day 14. In contrast to CT, HMPAO SPECT leads to early diagnosis of cerebral ischaemia, in particular within the cerebral cortex.

Aged↗
PubMed1990

Polyradiculoneuritis following botulinum toxin therapy.

The development of Guillain-Barré syndrome is reported in a patient, who had previously received botulinum toxin type A injections into both orbicularis oculi muscles to treat idiopathic blepharospasm. The possibility of a causal relationship is discussed with consideration of the literature on adverse effects of vaccinations and of Clostridium botulinum and its toxin.

Blepharospasm↗
PubMed1989

Changes of transcranially evoked motor responses in man by midazolam, a short acting benzodiazepine.

The present study investigated the effects of midazolam, a short acting benzodiazepine, on muscle responses elicited by magnetic brain stimulation. During continuous midazolam infusion (0.3 mg/kg/h for up to 30 min) amplitudes and durations of transcranially elicited compound muscle action potentials decreased progressively while latencies remained unchanged. The results can be accounted for by midazolam enhancement of the inhibitory action of GABAergic cortical interneurons, which decreases the excitability of pyramidal cells and reduces the number of neurons available for generation of descending pyramidal tract activity.

Action Potentials↗
PubMed1989

The development of an epileptogenic focus. A case study with 99mTc-HMPAO SPECT.

A patient is described who developed complex partial seizures with secondary generalization 3 years after a severe viral encephalitis with a CT and EEG identified lesion in the left insular cortex and its surrounding structures. When the seizures first occurred CT and MRI as well as repeated interictal conventional EEG recordings were entirely normal. Single photon emission computed tomography (SPECT), however, revealed an area of increased 99mTc-hexamethyl propyleneamine oxime (HMPAO) uptake in the left insular cortex. After anticonvulsive therapy the seizures and the SPECT findings disappeared. 99mTc-HMPAO SPECT is a highly sensitive method for the demonstration of functional alterations in brain tissue. It can improve diagnosis of epilepsy and may provide additional information to monitor anticonvulsive therapy.

Adult↗
PubMed1989

[Narcolepsy syndrome--clinical aspects, diagnosis, therapy].

The present paper gives an updated overview over the clinical symptomatology, diagnostic procedures and therapy of the narcolepsy syndrome as a variable, disabling condition, whose diagnosis is sometimes not easy to make. Special attention is paid to new and promising diagnostic developments.

Arousal↗
PubMed1989

Electric and magnetic stimulation of human motor cortex: surface EMG and single motor unit responses.

1. The effects of different forms of brain stimulation on the discharge pattern of single motor units were examined using the post-stimulus time histogram (PSTH) technique and by recording the compound surface electromyographic (EMG) responses in the first dorsal interosseous (FDI) muscle. Electrical and magnetic methods were used to stimulate the brain through the intact scalp of seven normal subjects. Electrical stimuli were applied either with the anode over the lateral central scalp and the cathode at the vertex (anodal stimulation) or with the anode at the vertex and the cathode lateral (cathodal stimulation). Magnetic stimulation used a 9 cm diameter coil centred at the vertex; current in the coil flowed either clockwise or anticlockwise when viewed from above. 2. Supramotor threshold stimuli produced one or more narrow (less than 2 ms) peaks of increased firing in the PSTH of all thirty-two units studied. Anodal stimulation always produced an early peak. The latencies of the peaks produced by other forms of stimulation, or by high intensities of anodal stimulation, were grouped into four time bands relative to this early peak, at intervals of -0.5 to 0.5, 1-2, 2.5-3.5 and 4-5.5 ms later. Peaks occurring within these intervals are referred to as P0 (the earliest anodal), P1, P2 and P3 respectively. 3. At threshold, anodal stimulation evoked only the P0 peak; at higher intensities, the P2 or more commonly the P3 peak also was recruited. The size of the P0 peak appeared to saturate at high intensities. 4. In five of six subjects, cathodal stimulation behaved like anodal stimulation, except that there was a lower threshold for recruitment of the P2 or P3 peak relative to that of the P0 peak. In the other subject, the P3 peak was recruited before the P0 peak. 5. Anticlockwise magnetic [corrected] stimulation, at threshold, often produced several peaks. These always included a P1 peak, and usually a P3 peak. A P0 peak in the PSTH was never produced by an anticlockwise stimulation [corrected] at intensities which we could explore with the technique. 6. Clockwise magnetic [corrected] stimulation never recruited a P1 peak; in most subjects a P3 peak was recruited first and at higher intensities was accompanied by P0 or P2 peaks. 7. On most occasions when more than one peak was observed in a PSTH, the unit fired in only one of the preferred intervals after each shock. However, double firing was seen in five units when high intensities of stimulation were used.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1989

[Botulinum toxin in therapy of craniocervical dystonia].

Craniocervical dystonias are a major therapeutic problem, since in the majority of cases various drug regimens as well as surgical interventions either fail or are accompanied by serious side effects. Botulinum toxin, well known as a biological toxin which blocks the cholinergic neuromuscular synapse, proved to be a new and successful concept in the treatment of these disorders. In the present study, mechanisms of action, clinical indications and practical use of botulinum toxin are described.

Botulinum Toxins↗