The ulnar nerve lies medial to the brachial artery to the mid-brachium where it penetrates the medial intermuscular septum. It runs between the septum and medial head of the triceps to the groove between the medial epicondyle of the humerus and ulnar olecranon (cubital tunnel). It traverses the forearm between the flexor carpi ulnaris and flexor digitorum profundus and comes to lie superficial and lateral to the tendon of flexor carpi ulnaris above the wrist. Potential points of compression include the superior thoracic aperture, medial intermuscular septum, elbow and wrist.
At the wrist, the palmar branch of the ulnar nerve accompanies the ulnar artery through the tunnel between the volar carpal ligament and transverse carpal ligament (Guyon's canal) where it can also be compressed.
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