LAUSR

A 39-year-old man presented with fluctuating muscle tightness in the right upper extremity, most prominent around digit 3–5 with episodic paresthesias. Nerve conduction studies (NCS) and electromyography (EMG) were performed with the concern of ulnar neuropathy but they were unremarkable (Fig. 1A). He tried physical therapy and pharmacologic intervention (gabapentin and cyclobenzaprine) with limited benefit. Laboratory workup included normal CK, ESR, and vitamin B12. MRI of the cervical spine and brachial plexus showed no accountable lesions. Neuromuscular ultrasound showed accessory epitrochlearis anconeus muscle, also confirmed by MRI (Fig. 1B–D). Neuromuscular ultrasound (NMUS) is increasingly being used in neuromuscular medicine. NMUS can help in cases of non-localized ulnar neuropathy based on NCS/EMG [1]. Epitrochlearis anconeus muscle is an accessory muscle which originates from the medial humeral epicondyle and attaches to the olecranon; it can be present in 9% of patients with cubital tunnel syndrome and lead