- The brachial plexus arises from the anterior rami of the cervical spine roots of (C5 – C6 – C7 – C8 – T1).
- Sometimes C5 receives some fibers from C4 and T1 also receives some fibers from T2.
- Shortly after leaving the intervertebral foramen, each root receives its sympathetic component via a gray ramus.
- The cervical roots receive their sympathetic components from one of the lower cervical sympathetic ganglia and the T1 root from its own sympathetic ganglion after contributing a white ramus to it.
- The brachial plexus begins to form distal to the scalene muscle.
- Brachial Plexus palsy can be seen in infant after birth or in adult patient after trauma or accidents.
Parts of Brachial Plexus:
- The Brachial Plexus consists of ( 5 Roots – 3 Trunks – 6 Divisions – 3 Cords – 5 Terminal Branches) respectively :
- Roots are the anterior rami of (C5 – C6 – C7 – C8 – T1) as mentioned above.
- Trunks are ( Upper – Middle – Lower trunk).
- Divisions are anterior and posterior of each trunks.
- Cords are ( Lateral – Posterior – Medial)
- The only nerves that arise from the root directly are:
- Dorsal scapular nerve: arises from C5 root, it’s the first important branch seen when the plexus is explored superior to the clavicle.
- The Long Thoracic nerve arises from C5 – C6 – C7 cervical roots.
- There are three trunks formed from the united of the roots.
- They proceed infero-laterally behind the clavicle:
- The three trunks are:
- The Upper trunk is formed by the united of C5 & C6 cervical roots.
- The Middle trunks is formed by the C7 cervical root alone.
- The Lower trunk is formed by the united of the C8 & T1.
- The upper trunk gives arise to:
- Suprascapular nerve.
- Subclavius nerve.
- Each trunk is divided into two divisions:
- Anterior Division.
- Posterior Division.
- No Nerves arise from the divisions.
- The Lateral Cord is formed by the united of the anterior divisions of the upper and middle trunks, it gives arise to the:
- Lateral Pectoral Nerve (C5 – C6 – C7).
- The Posterior Cord is formed by the united of the three posterior divisions, , it gives arise to the (Respectively from proximal to distal):
- Upper Subscapular Nerve (C5 – C6)
- Thoracodorsal (Middle Subscapular) Nerve (C6 – C7 – C8).
- Lower Subscapular Nerve (C5 – C6).
- The Medial Cord is formed by the anterior division of the lower trunk alone, it gives arise to the (Respectively from proximal to distal):
- Medial Pectoral Nerve (C5 – C6 – C7).
- Medial Brachial Cutaneous Nerve (T1).
- Medial Antebrachial Cutaneous Nerve (C8 – T1).
- These cords is named based on their relationship with the axillary artery:
- Lateral Cord is located lateral to the axillary artery.
- Posterior Cord is located posterior to the axillary artery.
- Medial Cord is located medial to the axillary artery.
Notice: The lateral pectoral nerve and the medial pectoral nerve communicate by an anastomotic loop.
- The Musculocutaneous Nerve (C5 – C6 – C7): arises from the lateral cord.
- The Axillary Nerve (C5 – C6): arises from the posterior cord.
- The Radial Nerve (C5 – C6 – C7 – C8 – T1): arises from the posterior cord.
- The Median Nerve (C5 – C6 – C7 – C8 – T1): arises from the lateral & medial cord.
- The Ulnar Nerve (C7 – C8 – T1): arises from the medial cord.