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Biomedical subjects

J Siegfried

Publications and source records attributed to J Siegfried.

At least 19 recordsLinked to original sources
PubMed1991

Thalamic stimulation for the treatment of tremor and other movement disorders.

Thalamic stimulation for the treatment of tremor and other motor movement disorders is attractive in view of the fact that it is a non-destructive procedure. With the experience of 26 cases indications can be defined. The method is an alternative for treatment of tremor only when thalamotomy carries a high risk of complications. Not only is the cost a limiting factor but also repeated operations for replacing the neuro-pacemaker and thus the risk of infection have to be taken in consideration.

Brain Damage, Chronic↗
PubMed1990

Transfection of cytochrome P450 cDNAs into mammalian cells used in mutation and transformation assays.

The present work demonstrates that cDNAs coding for cytochrome P450 enzymes can be transfected into mammalian cells and expressed. In the present studies, two different cell systems were used for transfection: 10T1/2 cells which can be used to study initiation and promotion (Diamond, 1984) and AHH-1 cells which can be used to study mutation and clastogenesis (Crespi and Thilly, 1984, Crespi and Penman, 1989). Thus, a diversity of endpoints can be studied in cells which have increased metabolic capability. By increasing the metabolic capability of the target cell, the effects of nongenotoxic as well as genotoxic chemicals, can be examined in the appropriate in vitro systems. For example, the 10T1/2 cells can be treated with a nontransforming dose of an initiator followed by continuous treatment with a second chemical that requires cytochrome P450 specific metabolism to manifest its promoting activity. By this approach, greater insight into the role of chemical metabolism in the promotion process (and presumably other nongenotoxic effects) can be obtained. Additionally, the role of specific cytochrome P450s in the metabolism of different classes of carcinogens/drugs can be elucidated. A major advantage of having the metabolizing enzymes actually present in the target cell is that effects of chemicals can be studied in long-term, low-dose exposure protocols which will eliminate the acute toxic effects which are associated with many current protocols. Thus, more realistic environmental exposure conditions can be achieved by using these in vitro systems containing endogenous metabolism systems.

Animals↗
PubMed1989

[Palliative neurosurgical treatment of chronic pain following peripheral nerve lesions].

Pathogenesis of pain after traumatic or iatrogenic lesions to peripheral nerves as well as local and conservative therapeutic possibilities are briefly reviewed. If pain subsides or in the case of relapse with establishment of a chronic pain-state the therapy of choice consists in implanting a programmable neuro-stimulator with the electrodes placed near the dorsal sensory roots in the cervical epidural space for the upper extremities or along the posterior columns of the medulla in the thoracic epidural space for the legs. With a success rate for long term pain control of approximately 80% this reversible method which is well tolerated by the nervous system should always be considered for deafferentation-pain (neurogenic pain).

Chronic Disease↗
PubMed1989

[Neurosurgical indications in the treatment of chronic pain].

Better knowledge in the transmission of pain signals, clinical analysis of pain allowing its aetiopathogenic interpretation (neurogenic pain, somatogenic pain), and technical improvements in neurosurgical interventions that have now become non-traumatic, increasingly selective with less and less general anaesthesia and without prolonged hospitalization, most often allowing precise postoperative control of the intervention, have given neurosurgery a fresh impetus and a major place in the multidisciplinary therapeutic approach to chronic pain. From being exclusively destructive, the neurosurgery of chronic pain has acquired a resolutely conservative orientation with a neurophysiological approach (therapeutic neurostimulation methods) as well as a broader range via a biochemical approach (drug application in the vicinity of neuromediator receptors).

Analgesia, Epidural↗
PubMed1988

Electrostimulation and neurosurgical measures in cancer pain.

Neurosurgery for cancer pain may always be considered when the pain no longer responds to conservative treatment methods or only at the cost of undesirable side-effects. Almost all these operations that can be considered for the cancer patient can be performed percutaneously, without general anaesthesia, without loss of blood, and with short hospitalization. Chronic pain has to be differentiated according to whether it is somatogenic or neurogenic. For somatogenic pain (pain without any neurological deficit), intrathecal or intraventricular administration of morphine-like substances through an implanted drug delivery system is the most attractive method. The classical neurosurgical interruption of a tract conducting pain between the periphery and the cerebral integration centers is an almost obsolete method, and percutaneous cordotomy can only be discussed when the pain is strictly unilateral and the prognosis of the disease relatively favorable. For neurogenic pain (pain with sensory disturbances) the only method which can be helpful is electrical stimulation with an implanted neuropacemaker connected to an electrode in the dorsal columns of the cord or in the sensory thalamic nucleus (depending on the location of the pain), since morphine has at best only a poor analgesic effect on deafferentation pain.

Electric Stimulation Therapy↗
PubMed1988

Intrathecal application of drugs for muscle hypertonia.

The literature regarding the intrathecal use of morphine, baclofen, and midazolam to treat spasticity is reviewed. Nine patients with significant spasticity due to different etiologies were treated. Morphine and midazolam decreased spasticity but did not change the patient's functional status. Baclofen improved patient status, but was associated with significant CNS depression in two cases.

Baclofen↗
PubMed1987

Intrathecal application of baclofen in the treatment of spasticity.

Baclofen, a derivative of g-aminobutyric acid (GABA) has been known for many years to be a useful drug in the treatment of spinal spasticity. However, when the spasticity is severe, the systemic administration has to be increased, often without therapeutic effects but frequently with central side-effects. Baclofen given intrathecally however, in microgram doses has been previously reported to be effective and safe. A personal experience is reported of 9 severely spastic patients residing in chronic care facilities who were treated from July 1984 to March 1986 with intrathecal baclofen. The spasticity was causing significant nursing care problems, and 6 patients were reduced to a completely bedridden state. Each patient initially received a percutaneous intrathecal drug injection of 0.2-0.7 mg of baclofen to test its efficacy. A subcutaneous intrathecal system for further injections was placed in 6 patients. In 3 patients a decreased level of consciousness was observed. In the 3 cases of multiple sclerosis, intrathecal baclofen resulted in significant reduction of spasticity for 24 to 48 hours after each injection. The spasticity was improved in only one of the 2 cases of posttraumatic paraplegia. The effect was not convincing in the 2 cases of spinal cord tumour, and in the case of cerebral palsy the effect was improvement in spasticity, but also significant drowsiness. Baclofen, in comparison with some other drugs such as morphine or midazolam, also tried intrathecally by the authors, is the most effective in reducing spasticity. Its use however warrants caution, for it can cause decreased consciousness, and there is currently no antagonist.

Adolescent↗
PubMed1987

Fluctuations of visual evoked potential amplitudes and of contrast sensitivity in Uhthoff's symptom.

Visual evoked potentials (VEPs) to pattern reversal and psychophysical contrast sensitivity (CS) were tested in five patients with Uhthoff's symptom before and after exercise. Four of the cases were related to a demyelinating disease and one patient had a severe brain injury. Uhthoff's symptom occurred also in neuropathies without previous clinical neuritis and in eyes with normal latency time of the VEPs. A depression of CS was observed by all five patients after exercise; a transient "overshoot" of CS following the depression was present in three of the patients. VEP amplitudes were reduced by exercise in three cases. Responses by stimulation with small checks were more affected. Paradoxical increased VEP amplitudes after exercise in the presence of a loss of psychophysical CS were found in one case.

Adult↗
PubMed1987

Sensory thalamic neurostimulation for chronic pain.

Among all kinds of pain, deafferentation pain is the most physically and mentally debilitative; this affliction is often resistant to medications and to the effects of ablative neurosurgical procedures. Since the introduction of neurostimulation as a method of treatment of pain, stimulation of the sensory thalamic relay nucleus has been proven effective in the majority of cases of patients suffering from deafferentation pain. The method used for thalamic stimulation and the results obtained in a series of 89 patients treated from October 1978 to October 1985 will be presented. Postherpetic trigeminal pain has the best chance of responding to thalamic stimulation with a long-term success rate of 80%. This is also true for anesthesia dolorosa of any origin (after ablative surgery, nerve lesions, paraplegia). In the opposite, only 50% of patients with either brachial plexus avulsion or thalamic pain syndrome will have a significant benefit from thalamic stimulation. It would appear that the success of thalamic stimulation in these disorders may be dependent upon the extent of the central lesion from the periphery up to the thalamic regions (dorsal horn destruction, lesions of the thalamus).

Chronic Disease↗
PubMed1987

Therapeutic value of Madopar HBS: judgment after 2 years experience.

The study included 19 parkinsonian patients presenting with fluctuations in motor performance after L-dopa therapy (9.9 years on average, range 6 months to 17 years) and 2 other patients not pretreated with L-dopa. In all patients of the first group, after 3 months on stable 'optimal' dosage schedule, the previous L-dopa treatment was abruptly replaced, dose for dose, from one day to another by Madopar HBS, a new controlled-release form of Madopar. The first clinical assessment was performed just before the beginning of the HBS treatment. Then, 4-6 weeks were allowed to optimize the dosage schedule of Madopar HBS before performing a second assessment. Long-term therapeutic effects were systematically evaluated after 6 and 12 months. Catamnestic evaluation took place at the last check-up for patients treated for more than 1 year. Of the 19 patients with fluctuations 1 dropped out after 7 days due to lack of cooperation. Thus, 18 of these patients were evaluable. At the end of the dose adaptation phase 12 patients (2/3) were better controlled by the new dosage form and were eligible for a long-term follow-up aiming to evaluate the maintenance of the benefit. It was concluded that in most of the patients the initial benefit was maintained during 1 year and even up to 2 years and 7 months for some of them. The best results were obtained in patients with mild to moderate forms of fluctuations (early stage). Positive results in de novo cases need confirmation.

Adult↗
PubMed1987

Ventricular cerebrospinal fluid concentrations of putative amino acid transmitters in Parkinson's disease and other disorders.

Concentrations of putative neuroactive substances glutamate, aspartate, gamma-aminobutyric acid, glycine, proline and ethanolamine were determined in ventricular cerebrospinal fluid collected in patients suffering from Parkinson's disease, pain syndromes or cerebellar tremor. Values are similar to those given in the literature for lumbar cerebrospinal fluid. A decrease in gamma-aminobutyric acid in Parkinson patients, as reported in lumbar cerebrospinal fluid, could not be observed. Further evidence for a rostro-caudal gradient for gamma-aminobutyric acid is supplied. New insights into pathophysiological mechanisms in any of the investigated syndromes may not be derived.

Adult↗