Neuropathic and Myopathic Pain.

The evaluation and management of childhood pain syndromes of neuromuscular origin have distinct challenges, as the patterns of disease presentation and the ability of a child to describe symptoms may differ from that of an adult. Advances in scientific and clinical knowledge are leading to significant progress in the care of affected children. The genetic origins of Fabry disease and the inherited form of erythromelalgia are better understood. The increasing interest in neuroimmunology among pediatric neurologists has led to more sophisticated diagnostic and therapeutic approaches. Treatment protocols for complex regional pain syndrome have become more standardized. In addition, investigations continue into potential new interventions for metabolic muscle diseases such as McArdle disease and carnitine palmitoyl transferase deficiency type II. In the years to come, children with pain of neuromuscular origin will have access to more precise diagnostic tools and novel therapies that would alleviate this particularly distressing category of disease.

Relationships between Irritable Bowel Syndrome Pain, Skin Temperature Indices of Autonomic Dysregulation, and Sensitivity to Thermal Cutaneous Stimulation.

This study evaluated relationships between irritable bowel syndrome (IBS) pain, sympathetic dysregulation, and thermal pain sensitivity. Eight female patients with diarrhea-predominant IBS and ten healthy female controls were tested for sensitivity to thermal stimulation of the left palm. A new method of response-dependent thermal stimulation was used to maintain pain intensity at a predetermined level (35%) by adjusting thermal stimulus intensity as a function of pain ratings. Clinical pain levels were assessed prior to each testing session. Skin temperatures were recorded before and after pain sensitivity testing. The temperature of palmar skin dropped (1.5°C) when the corresponding location on the opposite hand of control subjects was subjected to prolonged thermal stimulation, but this response was absent for IBS pain patients. The patients also required significantly lower stimulus temperatures than controls to maintain a 35% pain rating. Baseline skin temperatures of patients were significantly correlated with thermode temperatures required to maintain 35% pain ratings. IBS pain intensity was not significantly correlated with skin temperature or pain sensitivity. The method of response-dependent stimulation revealed thermal hyperalgesia and increased sympathetic tone for chronic pain patients, relative to controls. Similarly, a significant correlation between resting skin temperatures and thermal pain sensitivity for IBS but not control subjects indicates that tonic sympathetic activation and a thermal hyperalgesia were generated by the chronic presence of visceral pain. However, lack of a significant relationship between sympathetic tone and ratings of IBS pain casts doubt on propositions that the magnitude of IBS pain is determined by psychological stress.

Hypersensitivity to cutaneous thermal nociceptive stimuli in irritable bowel syndrome.

Irritable bowel syndrome (IBS) is a common intestinal ailment of which the pathophysiological mechanisms are not well understood. Most IBS patients demonstrate enhanced perception, visceral hypersensitivity, in response to distension of the gut lumen but there are conflicting results about changes in somatic sensitivity. This study focused on the possible contribution of abnormal pain sensitization due to positive feedback (vicious pain cycle) that affects somatic tissues due to viscero-somatic convergence. The specific objectives were to measure cutaneous thermal pain sensitivity along the segmental axis, including in dermatomes that are remote from the visceral pain focus. Pain sensitivity was probed with cutaneous thermal stimulation to the lower and upper extremities and the face in nine diarrhea-predominant IBS patients (diagnosed with ROME II criteria) and 12 healthy female controls. The stimuli were administered with a contact thermode, assuring that size of the stimulated area and stimulus duration were clearly defined and identical in all locations. Sensitization of IBS patients was not limited to symptomatic dermatomes (calf) but extended evenly across the body, including to the face (no sensitization gradient from foot to face). Also, the difference between IBS and control groups did not depend on the evoked pain intensity level, i.e. the degree of sensitization of IBS patients was similar near threshold (10% on the visual analog scale) and at higher intensities. Lastly, no correlation was found between IBS subjects' pain sensitivity of any of the three test sites and their ratings of spontaneous pain.