Sympathetic nerve activity can be measured transcutaneously in awake patients by computer-based filtering of raw signal obtained via skin leads attached on the chest and the right arm. Electrocardiogram can be removed by applying a high-pass filter setting of 150 Hz. Electromyogram can be filtered by applying a high-pass filter setting of 500 Hz or a band-pass filter setting of 500-1000 Hz.

Currently, the therapeutic effect of stellate, thoracic, and lumbar sympathetic ganglia block (SGB, TSGB, and LSGB, respectively) in patients with chronic pain is generally evaluated by using thermogram/thermography (change in temperature of the upper or lower extremeties) or questionnaire-based scoring.

However, it is not known whether the skin sympathetic nerve activity (SKNA) can be measured in patients undergoing SGB/TSGB/LSGB and used as an alternative tool for assessing the therapeutic effect of SGB/TSGB/LSGB.

Therefore, we planned this pilot study to observe whether the SKNA can be obtained in patients undergoing SGB/TSGB/LSGB and whether it is well correlated to thermogram or questionnaire-based scoring. If the SKNA is observed and decreases after SGB/TSGB/LSGB, it will be presented in milivolt (uV) and compared to that of pre-block values.

Inclusion Criteria:

• Outpatient patients undergoing stellate, thoracic, and lumbar sympathetic block for chronic pain disease

Exclusion Criteria:

• patients denial
• peripheral vascular disease in the head and the upper extremities.
• prior thoracic sympathectomy/sympathicotomy
• prior resection or ablation (chemically or mechanically) of stellate, thoracic, and lumbar sympathetic
• coagulapathy
• infectious disease
• allergy to local anesthetics

Patients undergoing stellate, thoracic, or lumbar sympathetic block for control of chronic neuropathic pain