brachialplexen

Brachialplexen, or the brachial plexus, is a network of nerves that supplies the upper limb. It arises from the ventral rami of spinal nerves C5 through T1 in the lower neck and upper thorax, with occasional contributions from adjacent levels in anatomical variants. The plexus travels between the scalene muscles in the neck, crosses the first rib, and enters the axilla near the axillary artery.

Traditionally, the plexus is described as five roots, three trunks (upper, middle, lower), six divisions, and three cords (lateral, posterior, medial). From these arise the five terminal branches—musculocutaneous, axillary, radial, median, and ulnar—and numerous other muscular and cutaneous nerves. Some branches originate directly from roots or trunks, including the dorsal scapular, long thoracic, suprascapular, subscapular (upper and lower), thoracodorsal, and pectoral nerves.

Functionally, the brachialplexen provides motor innervation to most shoulder and arm muscles and sensory supply to the upper limb, particularly its lateral aspect. The terminal nerves control elbow flexion and extension, forearm rotation, and hand movements, while various branches innervate muscles around the shoulder girdle and arm.

Clinical relevance: Injury to the brachialplexen can result from trauma, entrapment, or obstetric causes. Erb-Duchenne palsy (C5–C6) produces weakness of proximal arm muscles and a characteristic “waiter’s tip” posture; Klumpke palsy (C8–T1) affects intrinsic hand muscles and may accompany sympathetic signs. Diagnosis is based on clinical examination and electrodiagnostic studies; treatment ranges from physical therapy to surgical nerve repair or grafting, depending on severity and timing.