Comparison of the Efficacy of the Ultrasound With Fluoroscopy in Guidance of Lumbar Sympathetic Block

Inclusion Criteria: * Patients who have sympathetically-mediated pain and are supposed to undergo LSB procedure (e.g. pain with asymmetric skin temperature of lower limb in previous thermography, small fiber disorder in previous quantitative sudomotor axon reflex test (QSART), vascular insufficiency in lower extremities, diabetic polyneuropathy, postherpetic neuralgia, complex regional pain syndrome, cancer-related neuropathic pain such as chemotherapy-induced peripheral neuropathy, other lower extremity neuropathies, lower extremity crush injury etc.) * Numeric rating scale (NRS) ≥ 4/10 * Failure of previous conservative treatments, such as physiotherapy, oral medication, or other noninvasive treatment Exclusion Criteria: * Previous lumbar sympathetic neurolysis * Bleeding tendency * Local infection * Allergy to local anesthetics or contrast media * Pregnancy * Severe variation near procedure site-scoliosis, tumor, abdominal aneurysm, etc. * BMI ≥ 30 kg/m2 * Cognitive dysfunction