import { HighYieldBox, ExamCheatSheet, Tabs, Tab, ComparisonTable, VivaScenario, ContentSection, SpecialTestCard , MedicalImage} from '@/components/content' # Upper Limb Peripheral Nerve Examination 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). ## Quick Reference One-Pager ## Median Nerve **Muscles Supplied:** **At/Below Wrist (LOAF):** - **L**umbricals 1 and 2 - **O**pponens pollicis - **A**bductor pollicis brevis (APB) - **F**lexor pollicis brevis (superficial head) **Above Wrist (Anterior Interosseous - AIN):** - Flexor pollicis longus (FPL) - Flexor digitorum profundus (index and middle) - Pronator quadratus **In Forearm (High Lesion):** - Pronator teres - Flexor carpi radialis - Palmaris longus - Flexor digitorum superficialis - Above plus AIN muscles **Palmar Surface:** - Lateral 3.5 digits (thumb to radial half ring finger) - Palm over thenar eminence - Palmar cutaneous branch arises proximal to carpal tunnel **Dorsal Surface:** - Distal phalanges of lateral 3.5 digits - Fingertips only (not back of hand) **Key Test Point:** - Index finger pulp (most reliable) **High Median Nerve Lesion:** - Hand of Benediction (trying to make fist) - Cannot flex IPJ thumb and DIP index/middle - Loss of forearm pronation **Low Median Nerve Lesion (at wrist):** - Thenar wasting (ape hand deformity) - Weak thumb opposition - Sensory loss palm and digits **Anterior Interosseous Syndrome:** - Pure motor (no sensory loss) - Cannot make OK sign ## Ulnar Nerve **Muscles Supplied (All Intrinsics Except LOAF):** **Hand Muscles:** - Interossei (all 4 dorsal, all 3 palmar) - Lumbricals 3 and 4 - Adductor pollicis - Flexor pollicis brevis (deep head) - Hypothenar muscles (ADM, ODM, FDM) **Forearm (High Lesion Only):** - Flexor carpi ulnaris (FCU) - Flexor digitorum profundus (ring and little fingers) **Distribution:** - Medial 1.5 digits (little finger + ulnar half ring) - BOTH palmar AND dorsal surfaces **Key Test Point:** - Little finger pulp **Dorsal Branch:** - Arises 5cm proximal to wrist - Sensory to dorsal medial hand - Spared in wrist-level injury **High Ulnar Nerve Lesion:** - Ulnar claw LESS pronounced (ulnar paradox) - FCU and ulnar FDP also weak - Cannot flex DIP ring/little fingers **Low Ulnar Nerve Lesion (at wrist/hand):** - Ulnar claw deformity MORE pronounced - MCP hyperextension, IPJ flexion (ring, little) - Intrinsic minus posture - Dorsal cutaneous sensation may be SPARED **Ulnar Paradox:** - High lesion = less clawing (FDP paralyzed too) - Low lesion = more clawing (FDP works, pulls IPJ into flexion) ## Radial Nerve **Muscles Supplied:** **In Arm (High Lesion):** - Triceps - Brachioradialis - ECRL (may be spared as branch early) **In Forearm:** - ECRB - Supinator - Extensor digitorum communis - Extensor digiti minimi - Extensor carpi ulnaris - Abductor pollicis longus - Extensor pollicis brevis - Extensor pollicis longus - Extensor indicis **Posterior Interosseous Nerve (PIN):** - Pure motor branch - All extensors below supinator **Distribution:** - Posterior arm and forearm (radial nerve proper) - Dorsum of hand, lateral 3.5 digits (superficial radial) **Key Test Point:** - First dorsal web space **Superficial Radial Nerve:** - Pure sensory - Emerges from under brachioradialis - Dorsum of hand sensory **High Radial Nerve Palsy (Spiral Groove):** - Wrist drop - Finger drop - Loss of thumb extension - Weak brachioradialis (elbow flexion) - Triceps SPARED (branch proximal) **PIN Syndrome (Forearm):** - Pure motor (no sensory loss) - Finger drop - Weak wrist extension (ECU weak, but ECRL works) - Wrist deviates radially on extension - No wrist drop **Superficial Radial Nerve:** - Pure sensory - First web space numbness - No motor loss ## Musculocutaneous Nerve **Motor:** - Biceps brachii (main elbow flexor and supinator) - Brachialis - Coracobrachialis **Sensory:** - Lateral cutaneous nerve of forearm - Lateral forearm sensation **Clinical Features of Lesion:** - Weak elbow flexion (biceps and brachialis) - Weak supination - Numbness lateral forearm - Absent biceps reflex ## Distinguishing Lesion Levels **Quick Differentiation:** - **Can't make fist (IF, MF)** = Median (high) - **Can't spread fingers** = Ulnar - **Can't extend wrist/fingers** = Radial - **Can't flex elbow** = Musculocutaneous **Sensory Key Points:** - **Index pulp** = Median - **Little finger pulp** = Ulnar - **First web space dorsum** = Radial ## Combined Lesions **Upper Trunk (Erb's C5-6):** - Weak shoulder abduction, external rotation - Weak elbow flexion - Waiter's tip posture **Lower Trunk (Klumpke's C8-T1):** - Intrinsic hand weakness - Ulnar sensory loss - May have Horner's syndrome **Posterior Cord:** - Radial + axillary nerves - Wrist drop + weak shoulder abduction ## Summary Presentation ## Examination Sequence 1. **Inspection**: Wasting, deformity, trophic changes 2. **Median motor**: Opposition, APB, OK sign 3. **Ulnar motor**: Finger abduction, Froment's, Wartenberg 4. **Radial motor**: Wrist extension, finger extension, EPL 5. **Median sensory**: Index finger pulp 6. **Ulnar sensory**: Little finger pulp, dorsal (check level) 7. **Radial sensory**: First dorsal web space 8. **Reflexes**: Biceps, triceps 9. **Compare sides**: Every finding 10. **Localize level**: High vs low based on pattern ## Examiner Tips