Median Nerve vs Ulnar Nerve
Median Nerve vs Ulnar Nerve
The median and ulnar nerves are the two major nerves supplying the hand. Understanding their distinct territories and clinical presentations is essential for diagnosing hand weakness and sensory loss. The median nerve controls the "LOAF" muscles and lateral 3.5 digit sensation, while the ulnar nerve controls most intrinsic hand muscles.
Comparison Table
Key Differences
- →Median = LOAF muscles + lateral 3.5 digits; Ulnar = most intrinsics + medial 1.5 digits
- →Median entrapment at wrist (carpal tunnel); Ulnar at elbow (cubital tunnel)
- →Median injury = hand of benediction (making a fist); Ulnar = claw hand (at rest)
- →Ulnar nerve controls finger abduction/adduction (interossei); median controls thumb opposition
Clinical Relevance
- •Carpal tunnel syndrome (median): Numbness in lateral 3.5 digits, thenar weakness, positive Phalen's/Tinel's
- •Cubital tunnel syndrome (ulnar): Numbness in medial 1.5 digits, weak grip, interosseous atrophy
- •Froment's sign (ulnar): Compensatory thumb IP flexion when pinching (adductor pollicis weak)
- •Hand of benediction (median): Can't flex index/middle fingers when making a fist (FDS/FDP paralyzed)
Study Tips
- ✓LOAF = Median: Lumbricals 1-2, Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis
- ✓Ulnar = all the small hand muscles EXCEPT LOAF
- ✓Split the ring finger for sensory: radial half = median, ulnar half = ulnar
- ✓Think "median" = "middle" fingers (1-3), "ulnar" = "ulnar" side (4-5)
FAQs
Common questions about this comparison
The ulnar paradox refers to the observation that claw hand deformity is MORE pronounced with LOW ulnar nerve lesions (at wrist) than HIGH lesions (at elbow). This is because high lesions also paralyze FDP to digits 4-5, preventing IP flexion. Low lesions spare FDP, allowing the clawed fingers to flex at the IP joints.
When attempting to make a fist, the paralyzed FDS and lateral FDP (to digits 2-3) cannot flex the index and middle fingers. The ring and little fingers can still flex (ulnar-innervated FDP). The result looks like the hand position used in giving a blessing.