Image Interpretation: Focal enlargement and dynamic dislocation of the left ulnar nerve at the level of the medial epicondyle, consistent with left ulnar mononeuropathy at the elbow.
Teaching Pearl: Cubital tunnel syndrome is a peripheral neuropathy caused by chronic compression or repetitive trauma of the ulnar nerve at the elbow between the medial epicondyle of the humerus and the olecranon process of the ulna.
Nerve irritation can be caused by anatomic damage from fracture of the medial epicondyle, osteophytes, infection, soft tissue mass or synovitis at the elbow joint. The nerve may also be damaged due to compression from tight or thickened surrounding tissues. Symptoms often occur with prolonged periods of elbow flexion like sleep, exercise, driving, typing or talking on a phone.
Congenital laxity of the cubital tunnel retinaculum can result in hypermobility of the ulnar nerve, which can lead to repetitive subluxation when then elbow is flexed.
In this case, the ulnar nerve is recurrently dislocated and relocated with flexion and extension (respectively) of the elbow, resulting in a tractional and frictional neuritis.
Consider ulnar nerve instability when patients present with recurrent numbness/tingling and pain with flexion of the arm, especially with curling movements.