EMG Brachial Plexus

Diagnosis starts with a focused history and neurological exam: motor strength of shoulder, arm and hand; sensory mapping and reflexes; look for Horner’s syndrome and vascular compromise. Imaging with MRI of the brachial plexus or CT myelography (for suspected root avulsion) clarifies anatomy. Electrodiagnostic testing (EMG/NCS) is done about 3 weeks after injury to assess nerve continuity and prognosis; ultrasound may help.

High-resolution MRI with a dedicated brachial plexus protocol (MR neurography) is the preferred initial imaging to evaluate nerve continuity, edema, and soft-tissue injury. If MRI is inconclusive or preganglionic root avulsion is suspected, CT myelography is the most sensitive for detecting root avulsions and surgical planning. Ultrasound can help for superficial peripheral nerve assessment.

A brachial plexus MRI typically takes about 30–60 minutes for the scan itself. If contrast (gadolinium) is required, plus IV placement, positioning and any delays, total appointment time may be 45–90 minutes. Duration varies with the number of sequences, scanner type and patient cooperation. Expect to lie very still and allow extra time for check-in and brief post-scan observation if contrast is used.

Red flags for brachial plexus injury include severe arm/shoulder pain, sudden weakness or paralysis of shoulder, arm, or hand, numbness/tingling, and loss of reflexes. Look for drooping shoulder, inability to move fingers, Horner’s signs (ptosis, miosis, anhidrosis), recent major trauma or penetrating injury, expanding hematoma, or progressive neurological deficit—seek urgent evaluation.

Electromyography (EMG) and nerve conduction studies can detect brachial plexus injury by showing denervation (fibrillations/positive sharp waves), reduced motor unit recruitment, and altered conduction. These changes usually become evident 2–3 weeks after injury, so very early tests may be normal. EMG helps localize lesion level and assess severity; sensory studies and MRI often complement the evaluation for root avulsions.

Tinel’s sign is a commonly used special test for nerve injury: light percussion over a nerve (e.g., at the wrist or elbow) produces tingling or “pins and needles” in the nerve’s sensory distribution, suggesting nerve irritation or regeneration. It’s a quick bedside screen; electrodiagnostic tests (nerve conduction studies and EMG) are then used to confirm and quantify the injury.