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and analgesic procedures. Myoclonus after regional anesthesia has rarely been reported, but there have been a few reports of myoclonus after a peripheral nerve block. We report a very rare case of myoclonus after a supraclavicular brachial plexus block in a healthy patient with a brief review of literature. A 22-year-old woman (height: 160 cm, body weight: 46 kg, American Society of Anesthesiologists physical status I) was scheduled for a capsular release operation. There was nothing specific in her past medical history. She had previously undergone an uncomplicated left hand procedure under general anesthesia with no anesthesia-related adverse events. Preoperative evaluations were also normal. A supraclavicular brachial plexus block was planned for the anesthesia. Electrocardiography, noninvasive blood pressure, and pulse oximetry were monitored. Before induction of anesthesia, midazolam 2 mg and fentanyl 50 μg were intravenously injected for sedation and pain relief. At the beginning of nerve block, her blood pressure and heart rate were 120/75 mmHg and 65 beats/min. A supraclavicular brachial plexus block was performed under ultrasonographic guidance with a 5 cm standard bevel needle (Profi needle, Shinchang medical Co., Seoul, Korea). We injected 1.5% mepivacaine 40 ml after confirming no aspiration of blood. She did not complain of any severe paresthesia or injection pain during the procedure. Fifteen minutes after procedure, we confirmed successful sensory and motor block of brachial plexus and 5 L/min of oxygen was supplied via facial mask during the operation. An additional 1 mg of midazolam was given intravenously for sedation. The patient was stable during the surgery and the duration of surgical procedure was about 40 minutes. After the surgical procedure, the patient was transferred to a recovery room. One hour after the injection of the local anesthetic, she showed a shivering motion without any chilling sensation. The body temperature was 36.7°C. Meperidine 25 mg was intravenously injected to relieve shivering and 5 L/min of oxygen was supplied via facial mask. However, her shivering continued for about 15 minutes and the patient began to show mild agitation. Thirty minutes after meperidine injection, she showed involuntary movement of left arm, while the other body parts were under control (Video 1). The patient was unable to suppress the movement intentionally but remained conscious and communicated appropriately. She did not complain of pain or any other discomfort and there were no other neurologic symptoms. The driving force for the abnormal movement was from the surrounding muscles of the shoulder with some contribution from the muscles of the elbow joint. We consulted to neurology and the patient was treated with an intravenous injection of midazolam 5 mg but it was not effective. The movement continued while patient was sedated with midazolam. The neurologist examined the patient and about 20 minutes after midazolam injection, lorazepam 4 mg was administered intravenously but it was also not effective. The abnormal movement did Letter to the Editor