A 28-year-old motorcyclist sustains a high-velocity injury. Examination shows absent shoulder abduction and elbow flexion with preserved forearm rotation and hand function. Horner's syndrome is present. MRI myelography demonstrates pseudomeningoceles at C5–C6. The nerve roots most likely avulsed from the spinal cord are:
- A C8–T1 (lower trunk avulsion)
- B C7 root only
- C C5–C6 (upper trunk avulsion) ✓
- D Middle trunk (C7) avulsion
Explanation
Upper plexus palsy (Erb–Duchenne pattern) affects shoulder abduction (deltoid/supraspinatus), elbow flexion (biceps), and shoulder external rotation; it corresponds to C5–C6 root avulsion. Pseudomeningoceles on MRI myelography indicate intradural root avulsion from the cord — a pre-ganglionic lesion that cannot regenerate spontaneously and requires nerve transfer (neurotization). Horner's syndrome indicates sympathetic chain involvement at T1, frequently accompanying lower plexus (C8–T1) avulsions (Klumpke pattern), but here the clinical deficit localizes the avulsion to C5–C6.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
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Written and medically reviewed by the StethoPrep medical team.