Courtesy: Prof Nabil Ebraheim, University of Toledo, Ohio, USA

Basic Structure of the Brachial Plexus

• Brachial plexus formed from nerve roots C5–T1.
• Organization follows: Roots ? Trunks ? Divisions ? Cords ? Branches.
• Five roots: C5, C6, C7, C8, T1.

Trunks

• C5 + C6 join to form the Upper trunk.
• C7 continues alone as the Middle trunk.
• C8 + T1 join to form the Lower trunk.

Divisions

• Each trunk divides into an anterior and posterior division.
• Posterior divisions of all three trunks unite to form the Posterior cord.
• Anterior divisions of upper and middle trunks form the Lateral cord.
• Anterior division of the lower trunk forms the Medial cord.

Cords

• Named according to relation to the axillary artery.
• Lateral cord – lateral to axillary artery.
• Posterior cord – posterior to axillary artery.
• Medial cord – medial to axillary artery.

Branches from Roots (Preclavicular Branches)

• Dorsal scapular nerve (C5) – supplies rhomboids and levator scapulae.
• Long thoracic nerve (C5–C7) – supplies serratus anterior.
• Injury causes medial winging of the scapula.

Branches from Upper Trunk

• Suprascapular nerve – supplies supraspinatus and infraspinatus.
• Nerve to subclavius.

Branches from Lateral Cord

• Lateral pectoral nerve.
• Musculocutaneous nerve.
• Lateral root of the median nerve.

Branches from Posterior Cord

• Upper subscapular nerve – supplies subscapularis.
• Thoracodorsal nerve – supplies latissimus dorsi.
• Lower subscapular nerve – supplies subscapularis and teres major.
• Axillary nerve – supplies deltoid and teres minor.
• Radial nerve – supplies posterior arm and forearm muscles.

Branches from Medial Cord

• Medial pectoral nerve.
• Medial cutaneous nerve of arm.
• Medial cutaneous nerve of forearm.
• Ulnar nerve.
• Medial root of the median nerve.

Median Nerve Formation

• Formed by union of lateral root (from lateral cord) and medial root (from medial cord).

Preganglionic vs Postganglionic Brachial Plexus Injury

• Preganglionic injury occurs proximal to dorsal root ganglion (root avulsion).
• Involves central nervous system.
• Has poor prognosis and no potential for recovery.
• Postganglionic injury occurs distal to dorsal root ganglion.
• Involves peripheral nervous system.
• Has potential for regeneration and better prognosis.

Signs of Preganglionic Injury

• Horner syndrome (ptosis, miosis, anhidrosis, enophthalmos).
• Medial scapular winging due to long thoracic nerve involvement.
• Rhomboid paralysis due to dorsal scapular nerve injury.
• Supraspinatus and infraspinatus weakness.
• Sensation preserved because dorsal root ganglion intact.

Signs of Postganglionic Injury

• Both motor and sensory deficits present.
• Injury usually post?clavicular.
• EMG shows intact cervical paraspinal innervation.

Erb’s Palsy

• Injury to upper trunk (C5–C6).
• Causes weakness of deltoid, rotator cuff, elbow flexors, and wrist extensors.
• Arm position: adducted, internally rotated shoulder, extended elbow, pronated forearm.
• Classic appearance called ‘Waiter’s tip’.
• Most common obstetric brachial plexus injury.
• Recovery assessed by return of biceps function by 3 months.

Klumpke’s Palsy

• Injury to lower trunk (C8–T1).
• Produces claw hand deformity.
• Weakness of intrinsic hand muscles and wrist flexors.
• Often associated with Horner syndrome.
• Prognosis usually poor.

Total Brachial Plexus Injury

• Involves C5–T1 roots.
• Arm becomes completely flaccid.
• Both motor and sensory loss.
• Has the worst prognosis.

Treatment of Brachial Plexus Injuries

• Initial management: observation and physiotherapy.
• If no recovery (especially biceps function) by 3 months ? suspect root avulsion.
• Surgical options include nerve grafting for postganglionic injuries.

Nerve transfers (neurotization) used for preganglionic injuries