Upper Limb Nerve Injuries

Overview

Upper limb nerve injuries produce predictable, topographically consistent motor and sensory deficits based on the anatomical territories of the radial, median, and ulnar nerves. These are increasingly characterised by MRI neurography and high-frequency ultrasound.

Radial Nerve

• Common injury site: Midshaft humeral fracture (in the spiral groove), or axillary compression ('saturday night palsy').
• Motor deficit: Wrist drop (loss of wrist and finger extension at MCP joints). 'Finger drop'.
• Sensory deficit: Dorsolateral hand — anatomical snuffbox and dorsum of the first web space.
• Imaging: MRI shows denervation oedema (T2 hyperintensity + swelling) in brachioradialis and wrist/finger extensors.

Median Nerve

• High lesion (supracondylar fracture): Loss of forearm pronation, wrist flexion (FDS/FDP index/middle), FPL, and LOAF muscles. 'Hand of Benediction' on attempted fist — index and middle stay extended.
• Low lesion (carpal tunnel): Only LOAF muscles lost. Thenar wasting. Thenar skin sensation spared (palmar cutaneous branch exits above tunnel).

Ulnar Nerve

• Common injury site: Medial epicondyle (cubital tunnel), Guyon's canal (wrist).
• Motor deficit: Loss of ALL intrinsics except LOAF. 'Ulnar claw' at rest — ring and little fingers hyperextend at MCP, flex at IP joints (FDP to these fingers is intact).
• Sensory deficit: Medial 1.5 digits and hypothenar eminence (medial palm).

High Yield Facts