Focused examination of individual upper limb peripheral nerves including median, ulnar, radial, and musculocutaneous nerves with specific motor and sensory testing.
Peripheral nerve examination requires knowledge of individual nerve motor and sensory territories. Examiners expect you to differentiate between median, ulnar, and radial nerve lesions based on examination findings, and to localize the level of injury (high vs low lesion).
High-Yield Exam Summary
Muscles Supplied:
At/Below Wrist (LOAF):
Above Wrist (Anterior Interosseous - AIN):
In Forearm (High Lesion):
Test APB and opponens pollicis
Weak or absent opposition
Median nerve motor deficit (LOAF muscles)
Ability to detect true positives
Ability to exclude false positives
Test anterior interosseous nerve function
Triangle sign (flat index DIP, flat thumb IPJ) instead of circle
Anterior interosseous syndrome - FPL and index FDP weakness
Ability to detect true positives
Ability to exclude false positives
Muscles Supplied (All Intrinsics Except LOAF):
Hand Muscles:
Forearm (High Lesion Only):
Test adductor pollicis (ulnar nerve)
Flexion of thumb IPJ (using FPL instead of weak adductor pollicis)
Ulnar nerve palsy with adductor pollicis weakness
Ability to detect true positives
Ability to exclude false positives
Test dorsal interossei (ulnar nerve)
Weakness of finger abduction compared to other side
Ulnar nerve palsy - dorsal interosseous weakness
Ability to detect true positives
Ability to exclude false positives
Test ulnar nerve function
Little finger abducted, cannot be held adducted
Ulnar nerve palsy - weak third palmar interosseous
Ability to detect true positives
Ability to exclude false positives
Muscles Supplied:
In Arm (High Lesion):
In Forearm:
Posterior Interosseous Nerve (PIN):
Test radial nerve function
Wrist drops, cannot extend against gravity
High radial nerve palsy
Ability to detect true positives
Ability to exclude false positives
Test PIN or radial nerve
Cannot extend fingers at MCP joints
Radial nerve (high) or PIN (low) lesion
Ability to detect true positives
Ability to exclude false positives
Test extensor pollicis longus
Cannot lift thumb off table
EPL rupture or radial nerve/PIN lesion
Ability to detect true positives
Ability to exclude false positives
Motor:
Sensory:
Clinical Features of Lesion:
| nerve | highLesion | lowLesion |
|---|---|---|
| Median | Hand of Benediction, no FPL/index FDP | Thenar wasting, weak opposition only |
| Ulnar | Less claw, no FCU/ulnar FDP | Worse claw, dorsal sensation may be spared |
| Radial | Wrist drop + finger drop | Finger drop only (PIN), or sensory only (superficial) |
Quick Differentiation:
Sensory Key Points:
Upper Trunk (Erb's C5-6):
Lower Trunk (Klumpke's C8-T1):
Posterior Cord:
"35-year-old man presents 3 months after humeral shaft fracture with inability to extend wrist."
High-Yield Exam Summary