About The Brachial Plexus

The lower 4 cervical nerves (C5, C6, C7, C8) and 1st thoracic nerve (T1) emerge from the inter vertebral foramina; the anterior rami of these 5 nerves undergo a characteristic fusion which is known as the Brachial Plexus, which is a network of nerves which supply the upper limbs. It also receives contributions from the anterior primary rami of C4 and T2. It can be prefixed or post fixed. It is said to be prefixed when the contribution by C4 is large and that from T2 is absent. In the Post fixed variety, contribution from T1 is large, T2 is always present, C4 is absent and C5 is reduced in size. The C5 and C6 roots join to form the upper trunk. C7 root forms the middle trunk. C8 and T1 join to form the lower trunk. Each trunk divides into ventral and dorsal divisions. These divisions join to form cords. The cords are named as lateral, medial and posterior based on their relation to the axillary artery. The lateral cord is formed by the union of the ventral divisions of the upper and middle trunks. The medial cord is formed by the ventral division of the lower trunk. The posterior cord is formed by the union of the dorsal divisions of all the three trunks.

Nerves arising from the Brachial Plexus and their root value:

Long thoracic nerve (C5, 6, 7)

Suprascapular (C5, C6), Dorsal scapular nerve (C5)

Nerve to the subclavius (C5, 6),

Thoracodorsal nerve (C6, 7, 8), two subscapular nerves (C5, 6),

Axillary nerve (C5, 6),Ulnar nerve (C8, T1)

Medial pectoral nerve (C8, T1), lateral pectoral nerve (C5, 6, 7)

Medial cutaneous nerve of the arm (C8, T1),

Medial cutaneous nerve of the forearm (C8, T1)

Median nerve (C5, 6, 7, 8, T1), Radial nerve (C5, 6, 7, 8, T1)

Musculocutaneous nerve (C5, 6, 7)

Common Injuries and characteristic defects produced:

Erb’s paralysis: Is caused due to injury to the upper trunk. Nerve roots involved mainly C5 and partly C6 of the Brachial Plexus. Injuries wherein the head gets separated far from the shoulder, like an accidental fall, birth injury sustained due to shoulder dystocia etc. The muscles that get paralysed are biceps, deltoid, brachialis and brachioradialis. Partly supraspinatus, infraspinatus and supinator. The affected limb hangs to the side, is adducted and medially rotated, due to paralysis of the deltoid, biceps and brachialis. The forearm is extended and pronated. This deformity is called ‘policeman’s tip hand’ or ‘porter’s tip hand’ owing to the characteristic position of the affected limb.

Injury to nerve to Serratus Anterior: This nerve can be damaged if there is a sudden weight lifted on the shoulders. It causes ‘Winging of the scapula’ that is the medial border of the scapula becomes prominent. Symptoms will be loss of overhead abduction (patient will be unable to lift his arm over his head) and loss of pushing and punching actions.

Klumpke’s paralysis is caused due to injury to the lower part of the plexus and causes claw hand and Horner’s syndrome.

Some injuries of the Brachial Plexus are minor and will completely recover in several weeks; others however may be severe enough to cause permanent disability. Factors that may affect the results following injury are age, the type, severity and location of the injury. Several surgical techniques can be used to treat and help recovery, in cases where improvement is possible.

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