CH Park, et al / Pulsed RF Under US Guided to Trapezius Muscle 53 was undergoing psychiatric treatment for depression and had been diagnosed with ossification of the posterior lon- gitudinal ligament (OPLL) for neck pain that had continued for 15 years. One year before visiting our clinic, she had undergone an operation in a neurosurgery clinic. The symptom did not significantly improve after the surgery and the pain continued. Thus, she underwent continuous rehabilitation therapy and physical therapy under the di- agnosis of failed back surgery syndrome. When the patient came to the clinic, she complained of tearing pain concentrated in the neck and both nuchal regions. This pain became more severe when the patient was doing more than the usual household chores. The visual analogue scale (VAS) score of the pain was as high as 8 and was accompanied by sleep disorders. The physical ex- amination showed pain during neck flexion and extension as well as direct tenderness at both trapezius muscles and the levator scapular muscle. A simple C-spine X-ray test and a laboratory test found no explanation for the pain. TPI was then performed, under the assumption that the myofasical pain syndrome originated in the trapezius and the surrounding muscles. Medication for failed back surgery syndrome was sug- gested, but the patient rejected it since the previously used analgesic anti-inflammatory agent had had no effect on her and she was taking an antidepressant and other drugs. Hence, as an outpatient,a small dose (12.5 μg/hr) of fen- tanyl patch (Durogesic D-transⓇ, JanssenPharmaceutica N.V, Tumhoutseweg, Belgium), which is a narcotic analgesic, was given, and TPI was performed on the trapezius muscle. When the patient returned as an outpatient after the treatment, the patient stated that the VAS score had de- creased from 8 to 4-5 for 2-3 days following the TPI but later returned to previous levels. The patient did not show any side effects from the fentanyl patch. TPI was repeated three times, but the pattern of improvement for 2-3 days and exacerbation, thereafter, continued. Treatment meth- ods such as botulinum toxin injection were considered but pulsed RF treatment to the trapezius muscle was per- formed first due to its lower cost and the fact that it could be used in outpatient treatment. Following betadine disinfection in the prone position, the accurate trigger point was located by means of an ad- ditional physical examination. Then, skin wheal infiltration was performed with local anesthetics. To verify the accu- rate needle position, 10 cm-RF needles (22 gauge, straight, Fig. 1. Insertion of radiofrequency (RF) needle at the tra- pezius muscle under ultrasound guided. 5 mm active-tip) were inserted into both trapezius muscles under ultrasound (S-nerve, SonositeⓇ, Bothell, WA, USA) guidance. Following sensory stimulation performed at 50 Hz with a potential less than 1V, pulsed RF (PMG230, Baylis medical company Inc, Montreal, Quebec, Canada) treat- ment was performed two times for each muscle (120 s, 20 ms, 2 Hz, 42oC, impedance below 400 ohms) (Fig. 1). When the patient returned as an outpatient one week after the pulsed RF treatment, the pain at both nuchal re- gions was much relieved as reflected in the VAS score of 1-2. This pain relief was continuously maintained. Thus, we decided to use only the fentanyl patch. Since the VAS score has been in the range of 2-3 for about two months after the pulsed RF treatment, TPI is no longer performed. DISCUSSION RF thermocoagulation is a method of pain treatment that has been used for more than 30 years. The basic principle is to prevent nociceptive input using the thermo- coagulation of nerve tissues. Recently, another hypothesis suggested that the pain analgesic effect of RF thermocoa- gulation is not only caused by tissue destruction but also by the strong magnetic field that is formed around the treated region [1]. Pulsed RF treatment, which is used as an alternative to nerve destruction, employs the same fre- quency as RF thermocoagulation. However, the difference is that pulsed RF uses a high voltage energy burst for 20 msec to reduce nerve destruction compared to RF thermo- coagulation uses heat that causes nerve destruction by in- creasing tissue temperature. Thus, pulsed RF treatment has been used in the treatment of dorsal root ganglion,