Brachial plexus injury !

A brachial plexus injury is damage to the network of nerves from the neck to the arm, usually by stretching; it causes weakness and numbness of the arm.

Updated 2026-10-29

Structures involved

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Why it happens

What it is

Damage to the network of nerves formed by the C5–T1 roots that supplies the upper limb, usually from traction. The classic patterns are Erb palsy (upper plexus, C5–C6) and Klumpke palsy (lower plexus, C8–T1).

Who gets it

In adults most injuries follow high-energy trauma, above all motorcycle crashes, a major cause in Colombia and Latin America. In newborns obstetric injury follows difficult deliveries, especially shoulder dystocia.

Causes

Traction from forced separation of the head and shoulder (motorcycle falls, falls onto the shoulder)
Forced arm abduction above the head, stretching the lower plexus (grabbing a support during a fall)
Obstetric traction during delivery (shoulder dystocia, breech delivery)
Penetrating wounds, clavicle fracture, shoulder dislocation, tumours or radiation

Risk factors

Motorcycle riding
Contact sports (stingers or burners)
Macrosomia, maternal diabetes and shoulder dystocia (obstetric injury)
Previous radiation to the axilla or neck

Pathophysiology

Traction can stretch the nerve (neurapraxia), break the axons (axonotmesis), rupture the nerve (neurotmesis) or tear the roots from the spinal cord (avulsion), which cannot repair itself. Upper plexus injury (C5–C6) weakens shoulder abductors, external rotators and elbow flexors. Lower plexus injury (C8–T1) weakens the intrinsic hand muscles; T1 avulsion can damage the sympathetic chain and cause Horner syndrome.

Classification

Erb-Duchenne (upper, C5–C6, sometimes C7): waiter's tip posture
Klumpke (lower, C8–T1): claw hand, sometimes with Horner syndrome
Total (pan-plexus) injury: flail, numb arm
Preganglionic (root avulsion) versus postganglionic (rupture or stretch)
Seddon or Sunderland nerve injury grades

Symptoms and signs

Erb: arm hanging adducted and internally rotated, elbow extended, forearm pronated, wrist flexed (waiter's tip)
Klumpke: claw hand with weak intrinsic hand muscles and numbness on the ulnar forearm and hand
Ptosis, miosis and anhidrosis on the same side if T1 is involved (Horner)
Burning (neuropathic) pain in the arm, typical of root avulsion
In newborns: reduced movement of one arm and an asymmetric Moro reflex

Diagnosis

Clinical: Detailed motor and sensory mapping by root, trunk and cord. Weak serratus anterior (winged scapula), rhomboids or a Horner sign point to a preganglionic lesion. Tinel sign along the plexus is followed over time.
Tests: Electromyography and nerve conduction studies, usually after a few weeks; preserved sensory potentials in a numb area suggest root avulsion.
Imaging: X-rays of the cervical spine, shoulder, clavicle and chest (a raised hemidiaphragm suggests phrenic involvement). MRI or CT myelography looks for pseudomeningoceles from root avulsion; angiography if vascular injury is suspected.

Differential diagnosis

Spinal cord injury
Cervical radiculopathy
Isolated peripheral nerve injury (axillary, radial, suprascapular)
Rotator cuff tear or shoulder dislocation
Neuralgic amyotrophy (Parsonage-Turner syndrome)
Clavicle or humerus fracture causing pseudoparalysis (in newborns)

Goal of treatment

Recover the most useful functions (elbow flexion, shoulder stability, hand sensation), control pain and prevent contractures.

Treatment

Acute: In trauma, initial care follows trauma protocols: airway, bleeding control, cervical spine protection and repair of vascular injuries.
Follow-up: Closed stretch injuries are usually observed with serial examination and electromyography, because many recover over months.
Surgical: Surgery for open injuries, avulsions or failed recovery: nerve repair, nerve grafts, nerve transfers and later tendon or free muscle transfers; timing matters because muscles lose reinnervation potential.
Rehabilitation: Physiotherapy and occupational therapy to keep joints mobile, prevent contractures and retrain function; in babies, parents learn gentle range-of-motion exercises.
Medical: Neuropathic pain medications such as anticonvulsants or antidepressants of the neuropathic pain classes.

Complications

Permanent weakness or paralysis of the arm
Chronic neuropathic pain
Joint contractures and shoulder deformity (internal rotation contracture in children)
Limb length or size difference in obstetric palsy
Psychological and occupational impact

Prognosis

Depends on the level and type of injury. Most neonatal Erb palsies recover well in the first months. Upper plexus injuries recover better than lower ones, and root avulsions do not recover without surgery.

Prevention

Helmets, protective gear and road safety for motorcyclists
Recognition and management of shoulder dystocia in delivery rooms

Test yourself

Think of the answer, then tap the question to see it.

Which roots are injured in Erb palsy, and what posture does it produce?

C5–C6 (upper trunk). The arm hangs adducted and internally rotated, with the elbow extended and the forearm pronated: the waiter's tip posture.

Which roots are injured in Klumpke palsy, and what are its main signs?

C8–T1 (lower trunk). Claw hand with weak intrinsic muscles, ulnar-side numbness and, if T1 is involved, Horner syndrome.

Why does Horner syndrome suggest a severe brachial plexus injury?

It means the T1 root is injured near the spinal cord, damaging sympathetic fibres; this often indicates a preganglionic root avulsion.

What mechanism causes most adult brachial plexus injuries in Latin America?

High-energy traction injury, typically a motorcycle crash that forces the head and shoulder apart.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: Brachial Plexus Injuries (StatPearls (NCBI Bookshelf), 2026).

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Representative model, for educational purposes only.

Brachial plexus roots highlighted on the Durgical 3D model