A unilateral sympathetic blockade does not affect stress-related pain and muscle activity in patients with chronic musculoskeletal pain.

OBJECTIVE: Chronic musculoskeletal pain is often exacerbated by mental and social stress. The association between stress and musculoskeletal pain is potentially mediated by peripheral sympathetic nerves, either directly or indirectly through muscle activity. In the present study we wanted to determine whether sympathetic blockade could affect either the pain or the muscular activity experienced during mental stress in patients with chronic musculoskeletal pain. METHODS: We performed a unilateral anaesthetic blockade of the lower cervical sympathetic ganglion (ganglion stellatum) in 18 patients with chronic musculoskeletal pain (10 with fibromyalgia and eight with chronic shoulder/neck pain). After the blockade the patients performed a 60-minute stressful task with low-grade mental stress that has induced pain and muscle activity in earlier experiments. Surface electromyography (SEMG) of the forehead, temples, neck, and shoulders, and heart rate and blood pressure were recorded together with ratings of pain. RESULTS: We did not find any side or sidextime effect for pain or muscular activity in any of the four muscle groups (p>0.12). CONCLUSION: We investigated the potential involvement of peripheral sympathetic nerves in stress-related musculoskeletal pain. A peripheral sympathetic block did not affect pain and muscle responses to a stressful task. Other explanatory models should be implemented and tested experimentally to further investigate the clinical impression that mental stress exacerbates pain in patients with chronic musculoskeletal pain.

Stress-induced pain and muscle activity in patients with migraine and tension-type headache.

We recorded deep pain and surface electromyographic (EMG) responses to stress in 22 migraineurs during headache-free periods, 18 patients with tension-type headache (TTH), and 44 healthy controls. Sixty minutes of cognitive stress was followed by 30 min relaxation. EMG and pain (visual analogue scale) in the trapezius, neck (splenius), temporalis and frontalis areas were recorded. TTH patients had higher pain responses in temporalis and frontalis (with similar trends for trapezius and splenius) and more potentiation of pain during the test than controls. Migraine patients developed more pain in the splenius and temporalis than controls. Muscle pain responses were more regional (more pain in the neck and trapezius compared with the temporalis and frontalis) in migraine than in TTH patients. TTH patients had delayed pain recovery in all muscle regions compared with controls, while migraine patients had delayed pain recovery in a more restricted area (trapezius and temporalis). EMG responses were not different from controls in headache patients, and EMG responses did not correlate with pain responses. TTH patients had delayed EMG recovery in the trapezius compared with controls and migraine patients. These results support the concept that (probably central) sensitization of pain pathways and the motor system is important in TTH. Less pronounced and more regional (either peripheral or central) trigeminocervical sensitization seems to be important in migraine. Surface-detectable muscular activation does not seem to be causal for pain during cognitive stress either in migraine or in TTH.