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Biomedical subjects

H C Diener

Publications and source records attributed to H C Diener.

At least 19 recordsLinked to original sources
PubMed1992

The coordination of posture and voluntary movement in patients with cerebellar dysfunction.

Postural adjustments associated with the task of rising on tiptoes were investigated in a reaction time paradigm in 10 normal subjects and 18 patients with cerebellar disorders. Cerebellar dysfunction was due to either degenerative cerebellar disease, tumor, or ischemia. Displacements of the center of foot pressure (CFP) were recorded. The task, accomplished by the triceps surae muscle (executional activity, mean latency of 411 ms), is mechanically effective only if the center of gravity has been shifted forward in advance. To this effect, a phasic burst of preparatory EMG activity in the tibialis anterior normally occurs at a mean latency of 163 ms, shifting the center of gravity forward. Shortly thereafter, activity of the quadriceps femoris (175 ms) extends the knee and aids the forward shift of the center of gravity. Different aspects of this motor sequence were disturbed in individual patients: Latencies of preparatory and executional activity were uncorrelated in 15 of the 18 patients. Executional (n = 16) or preparatory (n = 13) EMG activity was tonic instead of phasic. Latencies of either preparatory or executional EMG activities or both were prolonged (n = 10). The time interval between motor preparation and execution was increased (n = 9). The trial-to-trial variability of biomechanical parameters and EMG latency was increased. Preparatory EMG activity in the quadriceps was entirely missing (n = 9), resulting in knee bending at the unsuccessful attempt to rise on tiptoes. Patients who were most severely affected had no preparatory activity at all (n = 2), and therefore were unable to perform the task.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Pathophysiology of cerebellar ataxia.

Human and animal experiments performed recently have resulted in a more detailed understanding of limb movement and body posture disorders associated with cerebellar dysfunction. The delay in movement initiation can be explained by a delay in onset of phasic motor cortex neural discharge owing to decreased input from the cerebellar hemispheres. Disorders of movement termination (dysmetria), which can occur for movements at proximal and distal joints, result from disturbances of the timing and intensity of antagonist electromyographic (EMG) activity necessary to break the movement. Disorders in velocity and acceleration of limb movements result from muscular activity that is smaller in amplitude and more prolonged. The cerebellum is important for control of constant force but not for generation of maximal force. Dysdiadochokinesia is explained by a combination of the above mentioned mechanisms. During complex movements in three-dimensional space, the cerebellum contributes to timing between single components of a movement, scales the size of muscular action, and coordinates the sequence of agonists and antagonists. The basic structure of motor programs is not generated in the cerebellum. Hypotonia can be observed only in acute cerebellar lesions. Cerebellar tremor appears to result from a central mechanism, but is modulated or provoked through increased long-loop EMG responses. The common assumption that cerebellar ataxia of stance does not improve with visual feedback is true only of vestibulocerebellar lesions, not for ataxia resulting from atrophy of the anterior lobe of the cerebellum.

Cerebellar Ataxia↗
PubMed1992

[Various ultrasound methods for studying the vertebral artery--a comparative evaluation].

In a prospective study 451 patients were examined with extracranial continuous-wave (CW) Doppler sonography, transcranial Doppler sonography and color coded duplex sonography in order to evaluate the diagnostic accuracy of the three methods for vertebral artery pathology (hypoplasia, proximal and distal stenosis and occlusion). Color duplex sonography was used as the reference method. CW-Doppler sonography (mastoidal slope) had a sensitivity of 100% and a specificity of 27% for the detection of pathological changes in vertebral arteries (VA). For suboccipital transcranial Doppler sonography these values were 38% and 58%. Extracranial Doppler sonography and transcranial Doppler sonography are often unsuitable for differentiating between proximal stenosis and hypoplasia of VA. Transcranial Doppler sonography of the terminal segments of VA resulted in normal flow parameters in 27% of cases with proximal stenosis and in 50% in cases of proximal occlusion. Flow was normal in these particular cases owing to a more distal collateralisation of the VA. The terms "hypoplasia" and "asymmetric" of VA are discussed.

Adult↗
PubMed1992

[Doppler and duplex sonography of the vertebral arteries].

In a prospective study 451 patients were examined with extracranial CW-Doppler sonography (mastoidal slope), suboccipital transcranial Doppler sonography and colour-coded duplex sonography to evaluate unusual vertebral arteries (hypoplasia, stenosis and occlusion). Colour duplex sonography was used as reference method. CW-Doppler sonography had a sensitivity of 100% and a specificity of 27% for the detection of an unusual vertebral artery. For transcranial Doppler sonography these values are 38% and 58%. Our study showed that CW-Doppler is a useful screening examination for identifying pathological findings of vertebral arteries. In case of abnormalities in CW-Doppler, duplex sonography, especially colour-coded duplex sonography, should be added.

Adult↗
PubMed1992

Comparison of multicenter study designs for investigation of carotid endarterectomy efficacy.

BACKGROUND: Our report summarizes and compares the characteristics of six prospective, multicenter, randomized clinical trials of carotid endarterectomy underway in North America and Europe. SUMMARY OF REVIEW: Three trials are designed to evaluate the safety and efficacy of endarterectomy in patients with asymptomatic carotid artery stenosis. The other three trials enroll patients who have had transient ischemic attacks or a minor cerebral infarction in the distribution of the randomized artery. Considered together, these six clinical trials span the range of candidates for carotid endarterectomy. The inclusion and exclusion criteria, methodology, and statistical considerations of each study are detailed in tables. CONCLUSIONS: The results from these trials will be helpful in resolving some of the questions surrounding endarterectomy, provided the similarities and differences in the study designs are considered when interpreting the results.

Carotid Arteries↗
PubMed1992

[Prospective follow-up of neuropsychological deficits after cervicocephalic acceleration trauma].

30 patients with acute cervico-cephalic syndrome following whiplash injury (neck and head pain, vegetative symptoms and subjective complaints of impaired mental functions) without neurological deficits were investigated in a prospective follow-up of 3 months with neuropsychological examination in the acute phase (x = 5.7 days) and again 6 and 12 weeks after the accident. Attention, concentration, cognition and verbal and visual memory functions were quantified by neuropsychological tests, and changes over the observation period were analysed. In the acute phase all neuropsychological functions were below the individual's normal level. Deficits in attention and concentration recovered within the first 6 weeks. Further recovery within the following 6 weeks were observed in visual memory, imagination and analytic capacity. The capability of verbal memory and abstraction, cognitive selectivity and information processing speed was impaired for a longer time and first recovered after 12 weeks. In conclusion, intraindividual neuropsychological deficits following whiplash injury can be quantified and monitored to show the time course of recovery. Thus in clinical and forensic practice the diagnosis of a pseudoneurasthenic or even "neurotic" syndrome in acute whiplash injury should be made with caution.

Accidents, Traffic↗
PubMed1992

[Acute plexus lesions in heroin dependence].

A wide spectrum of acute and chronic neurological syndromes are associated with heroin addiction. We report two cases with acute brachial/lumbar plexus lesions, with details of the clinical findings, diagnostic procedures and therapy. Possible causes are allergic or toxic reactions to heroin or added substances, as well as nerve compression due to local muscle swelling in connection with rhabdomyolysis. The extent of paresis which occurs is also determined by this compression.

Acute Kidney Injury↗
PubMed1992

Color-coded duplex sonography in the evaluation of vertebral arteries.

The vertebral arteries of 100 healthy subjects were studied with color-coded duplex sonography. All subjects experienced no clinical symptoms attributable to the vertebrobasilar system. Diastolic and systolic flow velocities could be measured in color-coded duplex sonography in 94% of the right and 92% of the left vertebral arteries. The anechogenic band between the transverse processes of the cervical spine which helps to identify the vertebral artery could not be discerned reliably in 18% of the subjects. In these cases the colored blood flow signals were used as a guide line to place the doppler sample volume exactly within the arterial lumen. Thus color coded duplex sonography is a useful tool for a rapid and definitely identification of vertebral artery and for pulsed Doppler flow measurements with velocity spectrum. For measurements in diameter of hypoplastic and normal vertebral arteries gray scale methodic is a more accurate assessment, as some artifacts of color-coded duplex sonography exist.

Adult↗
PubMed1991

Direction and amplitude precuing has no effect on automatic posture responses.

Automatic postural responses of leg muscles to the sudden displacement of standing support were investigated under four different conditions of information given to subjects in advance. Results from three groups of subjects were compared: 6 normal subjects, 10 patients with cerebellar disease, and 9 patients with Parkinson's disease. Specifically, each subject was provided with visual information about the direction and/or the amplitude of an upcoming platform tilt. For the control situation no advance information on the characteristics of platform tilt was provided. Neither the latencies nor the integrals of postural EMG-responses showed alterations with advance information. In contrast, in a control experiment in which 3 normal subjects had to perform large or small forward or backward voluntary movements of the body around the ankle joint, shorter onset-latencies of leg muscle EMG responses were observed with increasing complexity of the advance information. These results suggest that, unlike voluntary movements, postural responses to rapid surface tilts do not benefit from advance visual information on direction or amplitude of a postural disturbance.

Adult↗
PubMed1991

Ergotamine, flunarizine and sumatriptan do not change cerebral blood flow velocity in normal subjects and migraneurs.

Changes in the diameter of extracranial and intracranial arteries resulting in changes in cerebral blood flow have previously been assumed to be the most important pathophysiological factor in migraine. To test this hypothesis 20 normal subjects, and three groups of patients (n = 29) with migraine were investigated by means of transcranial Doppler sonography. Blood flow velocities in the middle cerebral (MCA) and in basilar (BA) arteries were measured. Data from patients were obtained in the interval between migraine attacks, during migraine attacks and following treatment with either ergotamine (0.5 mg i.m.; n = 10); flunarizine, a calcium overload blocker (20 mg i.v.; n = 13); or a 5-HT1-like agonist (sumatriptan, 4 mg s.c.; n = 6). Ergotamine and sumatriptan are constrictors of cerebral arteries in animal experiments. The arithmetic mean of flow velocity in the BA was reduced in normal subjects (45 cm/s) as compared with patients with migraine measured in between attacks (53 cm/s). Mean flow velocity in MCA was not different in normals (72.5 cm/s) as compared with migraineurs (75 cm/s). Neither ergotamine nor the 5-HT1 agonist and flunarizine resulted in a significant change in blood flow velocity in MCA and BA. This was true irrespective of whether the drugs were given in the headache-free period, during a migraine attack or during the withdrawal phase of drug-induced headache. Ergotamine was effective in improving headache during migraine attacks and sumatriptan attenuated headache during drug withdrawal from chronic analgesic intake. These results indicate that the action of ergotamine and the 5-HT1-receptor agonist is probably not mediated by their vasoconstrictor action on cerebral arteries.

Adult↗
PubMed1991

Responders and non-responders to metoprolol, propranolol and nifedipine treatment in migraine prophylaxis: a dose-range study based on time-series analysis.

The aim of the present study was to ascertain, on the basis of single case statistics and time-series analysis, responder and non-responder rates for metoprolol, propranolol and nifedipine in migraine prophylaxis. In addition, an attempt was made to identify the dose relationship for the various drugs on headache parameters. In a double-blind dose-finding study, 58 patients were treated in five consecutive dosage steps each lasting 1-3 months. All patients kept a headache diary before, during and after treatment. Serum drug levels were also determined. The data were assessed by time-series analysis, as well as by multiple regression and analysis of variance. A significant improvement was noted in 54.4% of patients with migraine during treatment with metoprolol. The study did not confirm the high success rates in migraine prophylaxis of nifedipine and propranolol quoted in the literature. Administration of nifedipine led to an increase in migraine attacks in 71% of the patients. Nifedipine was of no value in the prophylaxis of migraine. Only 32% of patients showed a reduction in frequency of migraine attacks during administration of propranolol. The analysis of variance failed to show any significant difference between the responder rates for metoprolol and propranolol. Higher doses of propranolol and metoprolol were more effective. Multiple regression analysis explained a considerable part of variance for propranolol (but not for metoprolol) as a result of reduced intake of ergotamine preparations and analgesics. It can therefore be concluded that part of the prophylactic effect of propranolol is attributable to a reduction in the use of migraine medication.

Adolescent↗
PubMed1991

Subcutaneous sumatriptan in the treatment of headache during withdrawal from drug-induced headache.

In a pilot study (5 patients) we investigated the effects of subcutaneous sumatriptan, a 5-HT1-like receptor agonist, on headache experienced during the withdrawal period of drug-induced headache. The pilot study indicated that the substance was effective mostly in patients who originally suffered from migraine. In a patient with tension headache the substance was less effective. In a second double-blind study on six migraine patients with severe drug-induced headache, the drug was highly effective in ameliorating headache and autonomic disturbances. Blood flow velocities measured in extracranial parts of internal and external carotid arteries by duplex-sonography and in middle cerebral and basilar arteries by transcranial Doppler showed no changes after administration of sumatriptan or placebo. This result suggests sumatriptan does not act primarily via constriction of the large cerebral arteries.

Adult↗