Brachial Plexopathy

Brachial plexopathy is dysfunction of the brachial plexus (C5 to T1), causing arm weakness and sensory loss in several nerve distributions. Causes are trauma (traction, motorcycle accidents, birth injury), neuralgic amyotrophy (idiopathic and hereditary), tumour infiltration (Pancoast tumour, breast cancer, lymphoma), radiation, thoracic outlet syndrome, surgery and anaesthesia positioning, penetrating injury and inflammation.

Pathophysiology. Stretch, compression, direct infiltration, radiation fibrosis or immune mediated inflammation damages the plexus.

Upper plexus (C5 to C6, Erb): shoulder abduction and elbow flexion weakness (waiter's tip posture). Lower plexus (C8 to T1, Klumpke): hand weakness, claw deformity, Horner syndrome. Neuralgic amyotrophy: sudden severe shoulder pain lasting days, followed by weakness and wasting, often after infection, vaccination or surgery. Tumour: constant pain, lower trunk involvement and Horner syndrome. Radiation: painless, with upper trunk involvement and arm swelling.

Red flags.

• Horner syndrome with arm pain (Pancoast tumour).
• Hand ischaemia or vascular signs (thoracic outlet).
• Severe trauma with arm paralysis and avulsion.

Electromyography and nerve conduction studies after 3 weeks localise the lesion and distinguish root avulsion (normal sensory potentials) from plexus lesions. MRI of the brachial plexus and cervical spine, chest imaging (apical lordotic view or CT) for tumour, and ultrasound. CT myelography for avulsion. Vascular imaging for thoracic outlet syndrome. Genetic testing of SEPT9 for hereditary neuralgic amyotrophy.

Differential diagnosis.

• Cervical radiculopathy, rotator cuff tears and shoulder pathology.
• Cervical myelopathy, motor neuron disease and syringomyelia.
• Peripheral nerve injury (axillary, suprascapular, long thoracic).

Traumatic. Early exploration for open injury, vascular injury or no recovery. Closed traction injuries are observed for 3 to 6 months, then nerve grafts or transfers if no recovery (best performed within 6 months).

Neuralgic amyotrophy. Analgesia and early corticosteroids (prednisolone 1 mg/kg daily for 5 to 7 days, then taper) for severe pain; intravenous immunoglobulin or high dose steroid in some, with limited evidence. Physiotherapy, shoulder support and range of motion. Recovery over 1 to 3 years, with about 70 to 90% having good recovery.

Tumour. Oncology treatment (radiotherapy, chemotherapy or surgery) and pain control.

Thoracic outlet syndrome. Physiotherapy, and surgery (rib resection) for vascular or true neurogenic types.

Neuropathic pain. Gabapentin, pregabalin, amitriptyline, duloxetine, and opioids for cancer pain.

Rehabilitation. Physiotherapy, splinting, occupational therapy and shoulder protection.

Monitoring. Strength, electromyography, and imaging in malignancy.

Referral and escalation. Refer urgently to neurology and peripheral nerve surgery for traumatic and tumour causes.