Brachial Plexus Injuries: Erb's Palsy & Klumpke's

• Nerve lesions of the upper limb can result from trauma, compression, or disease, leading to motor and sensory deficits

Brachial Plexus Injuries

• The brachial plexus is a network of nerves originating in the neck and shoulder, responsible for innervating the upper limb
• Injuries can occur due to trauma, such as fractures, dislocations, or traction injuries

Upper Brachial Plexus Injury (Erb's Palsy)

• Typically involves C5-C6 nerve roots
• Mechanism: Excessive separation of the head and shoulder
• Presentation: "Waiter's tip" posture - arm adducted, internally rotated, wrist flexed
• Muscles affected: Deltoid, biceps, brachialis, brachioradialis
• Results in loss of abduction, external rotation, and elbow flexion

Lower Brachial Plexus Injury (Klumpke's Palsy)

• Involves C8-T1 nerve roots
• Mechanism: Hyperabduction of the arm, such as during a fall or difficult childbirth
• Presentation: Claw hand deformity
• Muscles affected: Intrinsic hand muscles, wrist flexors, and extensors
• Results in loss of hand function and potential Horner's syndrome (if T1 root is involved)

Long Thoracic Nerve Injury

• Long thoracic nerve roots C5-C7
• Injury to the long thoracic nerve results in a winged scapula due to paralysis of the serratus anterior muscle
• The patient has difficulty abducting the arm above 90 degrees

Axillary Nerve Injury

• Motor function involves the deltoid and teres minor muscles (shoulder abduction and external rotation)
• Sensory function affects the skin over the lateral aspect of the shoulder, causing paralysis of the deltoid muscle, leading to weakness in shoulder abduction
• Mechanism: Fracture of the surgical neck of the humerus or shoulder dislocation

Radial Nerve Injury

• The radial nerve is the largest branch of the brachial plexus, supplying the posterior compartment of the arm and forearm
• Motor function affects the triceps brachii, brachioradialis, supinator, wrist extensors, and digital extensors
• Sensory function affects the posterior arm and forearm, and dorsolateral hand

High Radial Nerve Injury (at the spiral groove of humerus)

• Affects all muscles innervated by the radial nerve distal to the triceps; triceps function may also be affected
• Presentation: Wrist drop (inability to extend the wrist and fingers)
• Loss of sensation in the posterior arm and forearm, and dorsolateral hand

Superficial Radial Nerve Injury

• Affects sensory branch only
• Sensory loss over the dorsolateral aspect of the hand, excluding the fingertips

Posterior Interosseous Nerve (PIN) Injury

• Purely motor branch of the radial nerve in the forearm
• Affects wrist and finger extensors
• Presentation: Finger drop (inability to extend the fingers at the metacarpophalangeal joints) with some wrist extension preserved (ECRB function); no sensory loss

Median Nerve Injury

• The median nerve innervates most of the forearm flexors and some intrinsic hand muscles
• Motor function affects forearm flexors (except flexor carpi ulnaris), thenar muscles (thumb abduction, flexion, opposition), lumbricals I and II
• Sensory function affects the palmar aspect of the thumb, index, middle, and radial half of the ring finger

High Median Nerve Injury (at the elbow)

• Affects all muscles innervated by the median nerve in the forearm and hand
• Presentation: Weakness in wrist flexion, pronation, finger flexion (digits I-III), and thumb opposition; ape hand deformity (flattening of the thenar eminence)
• Sensory loss in the palmar aspect of the radial side of the hand and digits
• Possible pronator syndrome (compression between heads of pronator teres)

Carpal Tunnel Syndrome

• Compression of the median nerve within the carpal tunnel at the wrist
• Presentation: Numbness, tingling, and pain in the median nerve distribution of the hand
• Thenar muscle weakness may occur in chronic cases
• Special tests: Phalen's test, Tinel's sign

Anterior Interosseous Nerve (AIN) Injury

• Purely motor branch of the median nerve in the forearm
• Affects flexor pollicis longus, flexor digitorum profundus (index and middle fingers), and pronator quadratus
• Presentation: Inability to flex the distal interphalangeal joint of the index finger and thumb; "OK" sign cannot be formed; no sensory loss

Ulnar Nerve Injury

• The ulnar nerve innervates some forearm flexors and most intrinsic hand muscles
• Motor function involves the flexor carpi ulnaris, flexor digitorum profundus (ring and little fingers), hypothenar muscles, interossei, lumbricals III and IV, adductor pollicis
• Sensory function involves the palmar and dorsal aspects of the little finger and ulnar half of the ring finger

High Ulnar Nerve Injury (at the elbow)

• Affects all muscles innervated by the ulnar nerve in the forearm and hand
• Presentation: Weakness in wrist flexion and adduction, finger adduction and abduction, and flexion of the ring and little fingers; claw hand deformity (hyperextension of MCP joints and flexion of IP joints of digits IV and V)
• Sensory loss in the ulnar aspect of the hand and digits

Ulnar Nerve Injury at the Wrist (Guyon's Canal)

• Affects intrinsic hand muscles innervated by the ulnar nerve
• Presentation: Claw hand deformity, weakness in finger abduction and adduction
• Sensory loss may be limited to the palmar aspect of the hand, depending on the level of injury