skip to main content

Upper Trunk Brachial Plexopathy — SCE Neurology MCQ

Instant feedback + full explanation. One question, done properly.

HardClinical NeurophysiologyUpper Trunk Brachial PlexopathySCE Neurology

A 55-year-old man presents with a 4-month history of progressive right arm weakness and clumsiness. On examination, he has wasting and weakness of the right deltoid, biceps, and infraspinatus with reduced reflexes in the right arm. He also has a right Horner syndrome. NCS show reduced CMAP amplitudes in the right upper trunk distribution. What is the most likely anatomical localisation?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: A — Right upper trunk brachial plexopathy

The combination of weakness in C5/C6-innervated muscles from different peripheral nerves (deltoid = axillary; biceps = musculocutaneous; infraspinatus = suprascapular) with a Horner syndrome (indicating sympathetic chain involvement) localises to the upper trunk of the brachial plexus with extension to the sympathetic chain. This pattern should raise concern for Pancoast tumour or other apical pathology. A: Root avulsion would cause similar weakness but Horner syndrome suggests post-ganglionic involvement. C: Lateral cord innervates musculocutaneous and lateral pectoral nerves. D: Suprascapular neuropathy would only affect supraspinatus and infraspinatus. E: Musculocutaneous neuropathy affects biceps and brachialis only.

Reference: Preston & Shapiro – Electromyography; ABN Brachial Plexus Guidelines