Symptoms of cubital tunnel syndrome include numbness and paresthesias of the fifth (small finger) and part of the fourth digit (ulnar half of the ring finger) as well as the ulnar dorsal hand. Motor findings include a weak pinch and/or a weak grasp. Eventually, atrophy of the intrinsic or extrinsic hand muscles may be visible.
Cubital tunnel syndrome can be caused by trauma at the elbow as well as by a chronic process of ulnar nerve destabilization, repetitive elbow overuse, and injury of the nerve against the retinaculum. It is usually caused by repetitive elbow flexion, eg, due to an occupation, throwing (athletes), talking on a mobile phone, or sleeping with the elbow flexed.
There are many different anatomic sites of compression of the ulnar nerve proximal to the wrist. The cubital tunnel itself has the following boundaries:
- Medial – medial epicondyle of humerus
- Lateral – olecranon process of ulna
- Roof – formed by fascia of flexor carpi ulnaris and Osborne's ligament (goes from medial epicondyle to olecranon)
- Floor – formed by posterior and transverse bands of the medial collateral ligament and the elbow joint capsule