1. The lateral cord encompasses the thumb and index finger and splits the middle finger
2. The medial cord splits the third finger to the unlar side and encompasses the ring and pinky fingers and medial forearm.
3. The lower trunk innervates the fourth and fifth fingers and continues up the forearm
4. The ulnar nerve innervates only a small triangular region across the wrist, as well as the ulnar distributed area on the hand.
5. Schwartzman describes additional techniques for the exam of plexus: The Roos abduction maneuver== holding hands up to imitate a goal post elicits numbness after 30 seconds
6. The Wright maneuver-- holding hands straight up, does same
7. The plexus can be palpated at various points: in the supraclavicular fossa (upper trunk); between the clavicle and the first rib; the neurovascular bundle against the medial humerus; at the elbow in the arcade of Frohse (entry of radial sensory and posterior interosseous nerves);
8. The intercosticobrachial nerve, from the medial cord, innervates the anterior chest and can be misdiagnosed as cardiac disease. acid reflux, gall bladder disease (if on the right) or costochondritis.
1. Upper trunk pain (C5-6 roots) radiates across trapezius ridge and down medial scapula, whereas radiculopathic pain from c6-7 GOES DOWN SPINE. Upper trunk is palpable in supraclavicular fossa, and radiation to tip of scapula (notalgia) is usually painful.
2. Middle trunk persterior cord plexus radiations are on dorsal arm across triceps, enters the forearm through the arcade of Frohse (medial to the lateral epicondyle) to innervate the forearm, and extensor surface of the thumb, index and third fingers.