Search PubMed⌕ Search

Biomedical subjects

Ralf Baron

Publications and source records attributed to Ralf Baron.

32 records · Page 2Linked to original sources
PubMed2004

Mechanistic and clinical aspects of complex regional pain syndrome (CRPS).

Complex regional pain syndromes (CRPS, reflex sympathetic dystrophy, causalgia) are painful disorders that develop after trauma affecting a limb with (I) or without (II) nerve injury. Clinical features are pain, impairment of motor function, swelling and autonomic abnormalities (changes in sweating and blood flow). Autonomic abnormalities. The maximal skin temperature difference between the affected and unaffected extremity that occurs during a controlled thermoregulation can be used as a diagnostic tool. SMP. Sympathetic outflow to the painful extremity was experimentally activated. The intensity as well as area of spontaneous pain and mechanical hyperalgesia increased considerably in patients that had been classified as having SMP by positive sympathetic blocks. A pathological interaction between sympathetic vasoconstrictor and afferent neurons within the affected skin is the likely explanation for SMP in CRPS patients. Motor abnormalities. Kinematic analysis of target reaching as well as grip force analysis showed a pathological sensorimotor integration located in the parietal cortex. Furthermore, MEG studies demonstrated a continuous inhibition of the primary motor cortex. Neurogenic inflammation. Some features of acute CRPS (vasodilatation, swelling, pain) indicate a localized inflammatory process. Transcutaneous electrical stimulation of nociceptive C-fibre provoked protein extravasation into the interstitial fluid (microdialysis) only in CRPS patients and not in controls.

Animals↗
PubMed2003

Efficacy of lidocaine patch 5% in the treatment of focal peripheral neuropathic pain syndromes: a randomized, double-blind, placebo-controlled study.

Peripheral neuropathic pain syndromes (PNPS) are difficult to treat because commonly used analgesics are often ineffective when, for example, touch-evoked allodynia, hyperalgesia, and pain paroxysms are present. To investigate whether lidocaine patch 5% treatment is also effective in postherpetic neuropathy (PHN) and in other PNPS, 40 patients with various forms and localizations of PNPS completed a prospective, randomized, placebo-controlled, two-way, cross-over study in three medical hospitals. Patients suffering from pain in a localized skin area with intensity above 40 mm visual analog scale (VAS) and a stable consumption of pain medication were included in this study. The study was divided into four phases: 3-day run-in phase, treatment phase 1, wash-out period, and treatment phase 2, each lasting 1 week. At the discretion of the patients, up to four patches (covering a maximum of 560 cm2) were applied onto the maximally painful area for 12 consecutive hours daily, always either by day or at night. Throughout the four phases, ongoing pain, allodynia, quality of neuropathic symptoms, quality of sleep, and adverse events were assessed. When, after the wash-out period, the pain intensity scores did not return to the pre-treatment values (+/-20%), these patients were excluded from the study. The present study revealed that, as an add-on therapy, the lidocaine patch 5% was clearly effective in reducing ongoing pain (P=0.017) and allodynia (P=0.023) during the first 8 h after application and that the patches also worked well over a period of 7 days (P=0.018) in diverse focal PNPS. Calculation of the numbers needed to treat (NNT) to obtain one patient with more than 50% relief of ongoing pain revealed that the NNT of 4.4 in the present study compared reasonably well with other studies of PHN, such as topically applied capsaicin (NNT: 5.3-infinity) or systemic treatment with gabapentin (NNT: 3.2-5.0).

Administration, Topical↗
PubMed2003

Complex regional pain syndrome: mystery explained?

Complex regional pain syndrome (CRPS) is the result of changes to the somatosensory systems that process noxious, tactile, and thermal information; to the sympathetic systems that innervate skin (blood vessels, sweat glands); and to the somatomotor systems. The changes suggest that the CNS representations of the systems have been altered. Patients with CRPS also have peripheral changes (eg, oedema, signs of inflammation, sympathetic-afferent coupling [the basis for sympathetically maintained pain], and trophic changes) that cannot be explained by central changes. On the basis of clinical observation and research in human beings and animals, we hypothesise that CRPS is a systemic disease involving the CNS and peripheral nervous system. The most important question for future research is what causes CRPS? In this article, we suggest a change to the focus of research efforts and treatment. We also suggest there be diagnostic reclassification and redefinition of CRPS.

Animals↗
PubMed2002

Effect of sympathetic muscle vasoconstrictor activity on capsaicin-induced muscle pain.

Neuropathic pain syndromes with sympathetically maintained pain are often associated with a deep somatic pain component. An adrenergic interaction between sympathetic vasoconstrictor neurons and cutaneous afferents has been demonstrated. To determine whether a sympathetic-afferent interaction exists in deep somatic tissues, we investigated the effect of sympathetic muscle vasoconstrictor activity on experimentally induced pain. In 12 healthy volunteers, capsaicin was infused into the anterior tibial muscle. Intensity and quality of muscle and referred pain were assessed. The analyses were performed during the presence of low sympathetic muscle vasoconstrictor activity induced by breathing 100% O(2) gas (normocapnia), and during high activity induced by inspiration of 95% O(2) and 5% CO(2) (hypercapnia). The degree of sympathetic muscle vasoconstrictor discharge was monitored indirectly by measuring systemic blood pressure and end-expiratory CO(2) and by performing duplex sonography of muscle resistance vessels. The intensity, quality, and spatial distribution of muscle and referred pain were not significantly different during resting and increased sympathetic muscle vasoconstrictor discharge, indicating that such activity does not influence pain after intramuscular infusion of capsaicin.

Adult↗
PubMed2002

Complex regional pain syndrome is a disease of the central nervous system.

Complex regional pain syndrome (CRPS) is clinically characterized by pain, abnormal regulation of blood flow and sweating, edema of skin and subcutaneous tissues, trophic changes of skin, appendages of skin and subcutaneous tissues, and active and passive movement disorders. It is classified into type I (previously reflex sympathetic dystrophy) and type II (previously causalgia). Based on multiple evidence from clinical observations, experimentation on humans, and experimentation on animals, the hypothesis has been put forward that CRPS is primarily a disease of the central nervous system. CRPS patients exhibit changes which occur in somatosensory systems processing noxious, tactile and thermal information, in sympathetic systems innervating skin (blood vessels, sweat glands), and in the somatomotor system. This indicates that the central representations of these systems are changed and data show that CRPS, in particular type I, is a systemic disease involving these neuronal systems. This way of looking at CRPS shifts the attention away from interpreting the syndrome conceptually in a narrow manner and to reduce it to one system or to one mechanism only, e.g., to sympathetic-afferent coupling. It will further our understanding why CRPS type I may develop after a trivial trauma, after a trauma being remote from the affected extremity exhibiting CRPS, and possibly after immobilization of an extremity. It will explain why, in CRPS patients with sympathetically maintained pain, a few temporary blocks of the sympathetic innervation of the affected extremity sometimes lead to long-lasting (even permanent) pain relief and to resolution of the other changes observed in CRPS. This changed view will bring about a diagnostic reclassification and redefinition of CRPS and will have bearings on the therapeutic approaches. Finally it will shift the focus of research efforts.

Central Nervous System↗
PubMed2002

Skin temperature side differences--a diagnostic tool for CRPS?

Complex regional pain syndrome type I (CRPS I) is a chronic painful disease of one extremity that may develop as a disproportionate consequence of a trauma affecting the limbs without overt nerve injury. It is clinically characterized by sensory, motor and autonomic symptoms including vascular abnormalities. Previously, we have reported that pathophysiological alterations of the ongoing sympathetic activity play a crucial role in vasomotor disturbances (Brain 124 (2001) 587). As a companion article, the aim of this study was to evaluate the diagnostic value of skin temperature side differences in consideration of the spontaneous sympathetic vasoconstrictor activity. Twenty-five patients with CRPS I were studied. Fifteen patients with painful limbs of other origin and 20 healthy individuals served as controls. Controlled thermoregulation was performed to change cutaneous sympathetic vasoconstrictor activity by the use of a thermal suit: skin sympathetic vasoconstrictor neurones were activated by whole-body cooling and nerve activity was abolished by whole-body warming. Skin temperature at the affected and unaffected limbs (infra-red thermometry) was measured under resting conditions and continuously monitored during controlled modulation of sympathetic activity. The results showed only minor skin temperature asymmetries between both limbs under resting conditions in most CRPS patients. However, during controlled thermoregulation temperature differences between both sides increased dynamically and were most prominent at a high to medium level of vasoconstrictor activity. In both control groups, there were only minor side differences in temperature both in rest and during thermoregulatory changes of sympathetic activity. When comparing the diagnostic value of skin temperature asymmetries in CRPS I, sensitivity was only 32% under resting conditions, but increased up to 76% during controlled alteration of sympathetic activity. Specificity was 100% at rest and 93% at controlled thermoregulation. We concluded that the degree of unilateral vascular disturbances in CRPS I depends critically on spontaneous sympathetic activity. Taking this into consideration, skin temperature differences in the distal limbs are capable of reliably distinguishing CRPS I from other extremity pain syndromes with high sensitivity and specificity.

Adult↗
PubMed2002

Docetaxel-induced nail changes--a neurogenic mechanism: a case report.

Docetaxel is a new taxoid widely used in chemotherapy for advanced breast cancer and other solid malignancies. Painful nail changes with onycholysis occur in about 40% of docetaxel-treated patients as a prominent adverse effect. We report a patient with a complete peripheral palsy of the right arm due to advanced breast cancer with diffuse tumor infiltration of the brachial plexus. Treatment with docetaxel led to onycholysis at all extremities except the paretic hand. Sensory and motoric innervation measured by nerve conduction studies showed a complete loss of large nerve fiber function of the right arm. Function of deep mechanosensitive A beta-fibers (quantitative vibrametry) was severely decreased, but not absent. Sympathetic reflexes (induced by deep inspiration and measured with laser Doppler flowmetry) were absent on the right side and skin temperature was decreased consistent with a complete sympathetic denervation. Small afferent fibers investigated by quantitative thermotesting revealed a total loss of thermal and pain sensation. Furthermore, iontophoresis of histamine failed to induce any axon reflex-vasodilatation indicating a complete peripheral degeneration of small fiber afferents. In summary, a severe denervation of small and large fibers of the right upper limb was revealed. These results indicate that integrity of peripheral nerves seems to be a substantial factor for docetaxel-mediated nail changes. The role of an inflammatory process in onycholysis maintained by postganglionic sympathetic terminals and nociceptive C-fiber afferents is discussed. In accordance with this hypothesis, a cyclooxygenase-2 inhibitor improved nail alterations of the non-paretic limbs.

Afferent Pathways↗
PubMedDate not supplied

Complex regional pain syndromes: the influence of cutaneous and deep somatic sympathetic innervation on pain.

OBJECTIVES: Complex regional pain syndromes (CRPS) can be relieved by sympathetic blockade. Different sympathetic efferent output channels innervate distinct effector organs (ie, cutaneous vasoconstrictor, muscle vasoconstrictor. and sudomotor neurons, as well as neurons innervating deep somatic tissues like bone, joints, and tendons). The aim of the present study was to elucidate in CRPS patients the sympathetically maintained pain (SMP) component that exclusively depends on cutaneous sympathetic activity compared with the SMP depending on the sympathetic innervation of deep somatic tissues. METHODS: The sympathetic outflow to the painful skin was modulated selectively in awake humans. High and low cutaneous vasoconstrictor activity was produced in 12 CRPS type 1 patients by whole-body cooling and warming (thermal suit). Spontaneous pain was quantified during high and low cutaneous vasoconstrictor activity. By comparing the cutaneous SMP component with the change in pain that was achieved by modulation of the entire sympathetic outflow (sympathetic ganglion block), the SMP component originating in deep somatic structures was estimated. RESULTS: The relief of spontaneous pain after sympathetic blockade was more pronounced than changes in spontaneous pain that could be induced by selective sympathetic cutaneous modulation. The entire SMP component (cutaneous and deep) changes considerably over time. It is most prominent in the acute stages of CRPS. CONCLUSIONS: Sympathetic afferent coupling takes place in the skin and in the deep somatic tissues, but especially in the acute stages of CRPS, the pain component that is influenced by the sympathetic innervation of deep somatic structures is more important than the cutaneous activation. The entire sympathetic maintained pain component is not constant in the course of the disease but decreases over time.

Adult↗