Cubital tunnel syndrome
Several months of weakness in the left ring and little fingers. No trauma. Nerve conduction study suggested ulnar nerve compression at the elbow. Referred for ulnar nerve ultrasound.
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Ulnar nerve shows continuity. There is no nerve lesion. The nerve is edematous just proximal to the elbow. There is an accessory muscle overlying the ulnar nerve at the cubital tunnel. There is severe compression of nerve with elbow flexion. However, there is no compression of nerve with elbow extension.
A diagnosis of ulnar neuropathy was suspected. Ultrasound shows cubital tunnel syndrome due to an accessory anconeus epitrochlearis muscle. With complete flexion of the elbow, the ulnar nerve is compressed by muscle.
Cubital tunnel syndrome is the second most common nerve entrapment syndrome in upper extremity after carpal tunnel syndrome 3. Accessory anconeus epitrochlearis muscle bridges olecranon and medial humeral epicondyle; this lies superficial to the nerve nerve 2. This muscle is the most common structural abnormality of the cubital tunnel causing ulnar neuropathy 2.
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