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Biomedical subjects

D Claus

Publications and source records attributed to D Claus.

At least 73 records · Page 4Linked to original sources
PubMed1995

[Quality control in pediatric radiology].

The authors recall the fundamentals of an adequate use of the X-rays considering to the ALARA (As Low As Reasonably Achievable) principle. The article deals more specifically with radiation protection and quality control in radiopediatrics, as this age group is essentially concerned with stochastic hazards, i.e. cancer induction and genetic injurious effects. The major elements of X-ray equipment are reviewed, including the X-ray generator, device, film-screen, radiogenic tube, automatic exposure device, and so on... The influence of technical parameters on dosimetry in terms of radiation protection as well as dosis variation, according to the type of disorder, are demonstrated. Reference is made to the radiologic techniques proposed by the Lake Starnberg Group.

Child↗
PubMed1995

[Value of proximal conduction block study in diagnosis of inflammatory neuropathies].

Conduction block is a common finding in inflammatory neuropathies, indicating circumscribed demyelination. Since demyelination and conduction block are often localized proximally, the whole ulnar nerve including its proximal segments was studied fractionally in 31 patients with inflammatory neuropathies. In 5 of 15 patients with Guillain-Barré syndrome, conduction block at the spinal roots was the first electrophysiological finding indicating demyelinating neuropathy. Segmental conduction blocks were also found in 8 of 9 patients with chronic inflammatory demyelinating polyneuropathies (CIDP) and 4 of 4 patients with atypical neuropathies. In 3 patients, multifocal motor neuropathy (MMN) could only be differentiated from motor neuron disease by recording proximal conduction block. Corresponding to clinical recovery, conduction block improved with immunoglobulin therapy in CIDP and MMN patients. The technique of proximal conduction block studies clearly improves the diagnosis of focal demyelination in inflammatory, treatable neuropathies. They should be performed particularly in patients with atypical neuropathies in whom electrophysiological tests of distal nerve segments show normal results.

Adolescent↗
PubMed1995

Comparison of different algorithms for evaluation of respiratory sinus arrhytmia: cross-correlation function histogram analysis and regression analysis.

Three algorithms for assessment of respiratory sinus arrhythmia (RSA) have been evaluated: cross-correlation function, histogram analysis and regression plot. The algorithms were tested experimentally in a group of 11 subjects. A cross-correlation function with a high time resolution (1 ms) was used for investigation of the time lag between instantaneous heart rate and respiration (CTL). This time lag was not affected by the breathing rate in a range of 8 to 29 breaths per minute. A mathematical model of CTL compared with experimental results indicates that respiratory sinus arrhythmia is probably modulated directly by the respiratory network in the brainstem rather than by a baroreflex in the range of breathing rate investigated. Histogram analysis reflects the impact of inspiration and expiration on respiratory sinus arrhythmia. For this purpose heart rate changes were separated into two distributions (inspiration-expiration). The result value (U-VAL) of the Mann-Whitney U-test reflects the impact of respiration on heart rate variability. Regression analysis of heart rate versus respiration shows that the heart rate increase is more closely coupled to inspiration than the heart rate decrease to expiration. Both, CTL and U-VAL are thought to be useful parameters for clinical investigation of RSA.

Adult↗
PubMed1994

Screening method for the determination of volatiles in biomedical samples by means of an off-line closed-loop trapping system and high-resolution gas chromatography-ion trap detection.

A method is described for the analysis of volatile organic compounds in biological matrices (faeces and urine). The technique is based on off-line preconcentration by means of a closed-loop trapping system followed by high-resolution gas chromatography-ion trap detection (HRGC-ITD) for separation and identification of the compounds. The technique has been validated for pattern recognition in faecal and urine samples from healthy volunteers. It is considered a very promising tool in metabolic research.

Carbohydrates↗
PubMed1994

Central motor conduction time to upper and lower limbs in cervical cord lesions.

OBJECTIVE: Diagnostic value of central motor conduction time (CMCT) to upper and lower limbs in cervical cord lesions was investigated. DESIGN: A series of patients underwent transcranial magnetic stimulation. SETTING: Patients hospitalized in our department were investigated. PATIENTS: Forty-seven consecutive patients with cervical spinal lesions (31 patients with myelopathy due to cervical spondylosis, eight with syringomyelia, eight with tumors) were tested. MAIN OUTCOME MEASURES: Compound muscle action potentials were recorded from the abductor digiti minimi (ADM) and the anterior tibial (TA) muscles bilaterally. The CMCT was calculated after transcranial magnetic and electrical nerve root stimulation. Correlation of abnormal CMCT to radiologically proved cord compression and to clinical signs of upper motor neuron involvement were tested. RESULTS: Of 37 patients with extramedullary lesions, CMCT to the ADM was abnormal in 19 cases (51%) and to the TA in 26 cases (70%). In 10 patients with intramedullary lesions, abnormal CMCT to the ADM was observed in three cases (30%) and to the TA in three cases (30%) as well. Higher sensitivity of measurements to the TA in extramedullary disorders was not significant. Abnormal CMCT correlated to cord compression and to upper motor neuron involvement. In eight patients (42%), subclinical lesions were detected by an abnormal CMCT. CONCLUSION: In extramedullary lesions, measurement of CMCT to the TA is more sensitive. The procedure is valuable in detecting subclinical lesions. Abnormal CMCT correlates with cord compression and clinical signs of upper motor neuron involvement.

Action Potentials↗
PubMed1994

Is heat hypoalgesia a useful parameter in quantitative thermal testing of alcoholic polyneuropathy?

Detection of thermal hypoaesthesia, hyperalgesia, and paradoxical sensation significantly contribute to the diagnosis of polyneuropathy (PNP). There is controversy about the clinical usefulness of detected heat hypoalgesia. In 50 chronic alcoholic patients we compared the prevalence and diagnostic value of heat hypoalgesia (HPT) to that of cold (CT) and warm (WT) hypoaesthesia using a "Marstock" thermotest. Clinical examination revealed PNP in 56%, cold hypoaesthesia was present in 62%, warm hypoaesthesia in 24%, paradoxical thermal sensation in 10%, cold and heat hyperalgesia in 12%, and heat hypoalgesia in 22%. Only 1 patient (2%) presented with heat hypoalgesia but normal warm and cold thresholds; he reported paradoxical thermal sensation and had PNP. One patient suffered first degree burn injury from heat pain examination. Heat hypoalgesia contributed least to the diagnosis of polyneuropathy (HPT versus CT: P < 0.001). In patients with sensory loss, testing heat hypoalgesia bears some risk of burn injury. In contrast to thermal hypoaesthesia and hyperalgesia, it does not significantly enrich the diagnostic workup of alcoholic polyneuropathies.

Adult↗
PubMed1994

Investigation of parasympathetic and sympathetic cardiac innervation in diabetic neuropathy: heart rate variation versus meta-iodo-benzylguanidine measured by single photon emission computed tomography.

In diabetic neuropathy disturbed autonomic cardiac innervation is associated with shortened life expectancy. Sympathetic dysfunction is likely to play a role in cases of cardiac death. The quantitative uptake of the radiopharmaceutical iodine-123-meta-iodo-benzylguanidine (MIBG) can be measured by single photon emission computed tomography (SPECT). It is an index of the functional integrity of sympathetic neurones in the heart. The respiratory heart rate variation--as assessed by a computerized device--reflects mainly parasympathetic cardiac innervation. In 25 diabetic patients and 19 healthy subjects MIBG-SPECT and heart rate variation tests were carried out. MIBG scans in all normal subjects showed homogeneous uptake of activity. In 12 out of 25 patients at least two heart rate variation tests were abnormal. MIBG-SPECT was more sensitive (abnormal in 17 out of 25). The lack of correlation between MIBG-SPECT results and spectral analysis of heart rate variation suggest that spectral analysis alone should not be regarded as an indicator of sympathetic cardiac innervation.

3-Iodobenzylguanidine↗
PubMed1994

Sonographic evaluation of traumatic spinal cord lesions in the newborn infant.

We present a case of spinal cord injury due to birth trauma and assess the value of sonography for diagnosis, lesion characterization, and follow-up. Sonography is a non-invasive and easily reproducible imaging method for examining a ventilated child, and its initial sensitivity is comparable to that of MRI. Sonography is the method of choice for guiding diagnosis in this type of traumatic lesion to the newborn.

Birth Injuries↗
PubMed1994

Heart rate analysis in 24 patients treated with 150 mg amitriptyline per day.

Twenty-four patients treated with 150 mg amitriptyline per day for an episode of major depression underwent a standardized heart rate analysis (HRA) before therapy and after 14 days. The battery of cardiovascular reflex tests included the determination of the coefficient of variation (CV) while resting and during deep respiration, a spectral analysis of heart rate, the heart rate response to standing, and the Valsalva manoeuvre. The results of the initial HRA did not differ from a group of 24 normal control subjects matched for age and sex. On day 14 of treatment the patients showed significantly reduced values of heart rate variability in all tests (P < 0.0001), probably due to the anticholinergic side effects of amitriptyline. Heart rate increased from 78.1 to 93.6 bpm on average (P < 0.0001). Abnormal CV at rest was registered in 96% of the patients; during deep respiration 29% showed abnormal CV results. An abnormal spectral analysis was found in 100% of the cases (low frequency peak: 42%, mid-frequency peak: 100%, high frequency peak: 79%). The heart rate response to standing was abnormal in 75% and the Valsalva test in 33% of the cases. Eighty-eight percent of the patients fulfilled the criteria of a cardiovascular autonomic neuropathy under the conditions of amitriptyline therapy. As yet, the consequences of these changes for the patients have not been sufficiently elucidated.

Adult↗
PubMed1994

Facilitation and disfacilitation of muscle responses after repetitive transcranial cortical stimulation and electrical peripheral nerve stimulation.

Compound muscle responses were recorded after repetitive electrical stimulation of the peripheral nerve and after transcranial electrical and magnetic stimulation in 5 healthy persons. The enlargement of the second response at intervals between 30 and 50 msec is more pronounced after cortical magnetic and electrical stimulation than after peripheral nerve stimulation. This difference is believed to be a result of facilitatory mechanisms involving the summation of effects from conditioning and test stimuli along the entire central motor pathway. The facilitation at 10 msec interval, which is only seen after magnetic, but not after electrical transcranial stimulation could indicate an intracortical mechanism.

Action Potentials↗
PubMed1994

[Effect of temperature on clinical electrophysiology].

Body temperature has a considerable impact on neurophysiological results. This influence of temperature is often undervalued. Abnormal findings even in healthy subjects can be caused by cold extremities only. Low surface temperature for example may lead to longer distal latencies and slower motor and sensory nerve conduction velocities. In patients with neuromuscular diseases typical results may disappear, when the examination is done beyond a standard temperature. In myasthenic patients the decrement and the jitter in single fibre electromyography decrease with temperature. In myasthenic syndrome the amplitude of the muscle compound action potentials increases and the increment at 50/s-stimulation becomes smaller at low temperature. Cold limbs lead to restoring nerve conduction in demyelinated nerve fibres; conduction block may thus disappear. Spontaneous activity becomes rare and myotonic discharges become more obvious at low temperature. In certain cases an examination at low temperatures can be helpful, e.g. for the distinction between myotonia and paramyotonia. Usually electrophysiological examinations should be done at standard temperatures.

Adult↗
PubMed1994

Heart rate variability in depressed patients and differential effects of paroxetine and amitriptyline on cardiovascular autonomic functions.

Twenty-four unmedicated patients with episodes of major depression (DSM-III-R) and an age- and sex-matched group of 24 normal subjects underwent a heart rate analysis. The battery of cardiovascular reflex tests included the coefficient of variation while resting (CVr) and during deep breathing (CVdr), a spectral analysis of heart rate variability, the Valsalva test, and the posture index. The depressed patients showed no significant abnormalities in any of the tests as compared to the healthy subjects. The 24 patients were randomly allocated for treatment with either amitriptyline or paroxetine. During treatment with 20 mg paroxetine per day, patients showed no changes in cardiovascular autonomic function tests after 14 days. However, treatment with 150 mg amitriptyline per day decreased all heart rate parameters significantly due to anticholinergic side effects, except heart rate, which increased significantly. As autonomic side effects are a potential hazard of antidepressant therapy, the data suggest that paroxetine is an appropriate antidepressant for cases with pre-existing cardiovascular autonomic neuropathy.

Adult↗
PubMed1994

[The role of ultrasonography in abdominal pain in children in the emergency room].

Our retrospective study aims at defining the influence of ultrasonography on the management of acute abdominal pain in a pediatric population. This technique appears to be essential in the diagnosis of intussusception and thus, should be recommended in all cases of acute abdominal pain in the population at risk for this disorder. On the other hand, ultrasonography only plays a minor role in the management of the other diseases we observed, especially in acute appendicitis.

Abdomen, Acute↗
PubMed1994

[Disorders of autonomic heart rate regulation in patients with brain stem lesions].

The present study investigates the frequency of alterations of autonomic cardiac innervation in patients with brain stem lesions by testing cardio-vascular reflexes tests. In the neurological ICU, we tested 22 patients aged 19 to 78 years (mean age 54 +/- 17 years) suffering from ischemic brain stem lesions. The variability of heart rate was at first evaluated at rest. Mean heart rate, coefficient of variation (VK) and RMSSD (root mean square of successive differences) were calculated. In addition, a spectral analysis of the heart frequency was computed by a fast fourier transformation and the spectral powers in the frequency bands 0.02-0.09 Hz, 0.09-0.15 Hz and 0.20-0.30 Hz, respectively were determined. An atropine test was then carried out. 5 minutes after the beginning of injection of atropine sulfate, further rate and spectral analyses were again computed. The VK was pathologically diminished in 59% of the patients, the RMSSD in 55% and both, VK and RMSSD, in 45%. In 32% of the patients VK and RMSSD were within normal range. Spectral power was diminished in all three frequency bands in 4 out of 22 patients with pathological heart rate variability. Most abnormal results in spectral analysis could be obtained in the frequency band 0.09-0.15 Hz (73%), followed by the frequency band 0.20-0.30 Hz (45%) and the 0.02-0.09 Hz frequency band (32%). There were significant correlations between the heart rate variability; the spectral power in the 0.09-0.15 Hz and 0.20-0.30 Hz frequency bands (p < 0.05; Spearman). 88% of the patients with abnormal results at rest had diminished heart rate responses to atropine.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Assessment of diabetic neuropathy: definition of norm and discrimination of abnormal nerve function.

One hundred one normal subjects and 46 patients were investigated. Various objective and subjective tests for polyneuropathies were compared. Motor and sensory nerve conduction velocities are the most sensitive tests. In normals, age hardly influenced nerve conduction velocities. This is believed to be a result of the strict exclusion criteria. Diagnostic sensitivity is also high with the vibration fork test and with vibratometry at the big toe. Results with the method of limits are as reliable and sensitive as more cumbersome techniques, such as the titration method and the forced choice method. Thermal thresholds and cardiovascular tests are less sensitive. The most correct overall classification is attained with a combination of tests reflecting the function of different nerve fiber classes in the peripheral and autonomic nervous systems.

Adolescent↗