import { HighYieldBox, ExamCheatSheet, Tabs, Tab, ComparisonTable, VivaScenario, ContentSection, SpecialTestCard , MedicalImage} from '@/components/content' # Hand Nerve Examination Hand nerve examination requires systematic assessment of the three main nerves: median, ulnar, and radial. Examiners expect you to know the motor and sensory distributions of each nerve, perform provocative tests correctly, and differentiate between high and low nerve lesions. ## Quick Reference One-Pager ## Anatomy Overview **Median Nerve (C6-T1):** - Enters hand through carpal tunnel - Motor: APB, opponens pollicis, FPB superficial head, lumbricals 1-2 - Sensory: Palmar thumb, index, middle, radial half ring finger - Anterior interosseous nerve (AIN): No sensory, pure motor (FPL, FDP 1-2, PQ) **Ulnar Nerve (C8-T1):** - Enters hand through Guyon's canal - Motor: All interossei, hypothenar muscles, adductor pollicis, FPB deep head, lumbricals 3-4 - Sensory: Little finger, ulnar half ring finger (dorsal and palmar) - Dorsal cutaneous branch: Dorsal ulnar hand (leaves proximal to wrist) **Radial Nerve (C5-T1):** - No intrinsic hand muscles - Posterior interosseous nerve (PIN): No sensory, pure motor (finger/thumb extensors) - Superficial radial nerve (SRN): Sensory to dorsal first web space, dorsum of hand **Memory Aid - "LOAF" Muscles (Median Nerve):** - **L**umbricals 1 and 2 - **O**pponens pollicis - **A**bductor pollicis brevis (most important/first affected) - **F**lexor pollicis brevis (superficial head) Everything else in the hand is ULNAR! ## Median Nerve Examination **Abductor Pollicis Brevis (APB):** - Most important muscle to test (first affected in CTS) - Place palm up, thumb pointing to ceiling - Ask patient to lift thumb straight up against resistance - Observe and palpate thenar eminence **Opposition:** - Touch thumb tip to little finger tip - Make a complete circle (pulp-to-pulp contact) - Test against resistance **Anterior Interosseous Nerve (AIN):** - "OK Sign" test - Patient makes circle with thumb and index finger - Should be round circle (FPL and FDP to index) - Pinch test: Abnormal pinch = flat (uses EPL and FDS compensation) **Distribution:** - Palmar thumb - Palmar index finger - Palmar middle finger - Radial half of ring finger (palmar) **Best Test Area:** - Tip of index finger (most reliable) - Autonomous zone = volar index finger tip **Note:** Palm is spared in carpal tunnel syndrome (palmar cutaneous branch exits proximal to tunnel) ### Carpal Tunnel Provocative Tests ## Ulnar Nerve Examination **First Dorsal Interosseous (FDI):** - Place palm flat on table - Abduct index finger (spread away from middle finger) - Resist abduction - Palpate muscle bulk in first web space **Finger Abduction/Adduction:** - "Spread your fingers apart" (interossei) - "Squeeze fingers together" (interossei) - Note first dorsal interosseous wasting **Adductor Pollicis:** - Froment's test (see below) **Hypothenar Muscles:** - Abduct little finger (ADM) - Compare bulk with contralateral side **Distribution:** - Little finger (both dorsal and palmar) - Ulnar half of ring finger **Best Test Area:** - Tip of little finger - Autonomous zone = volar little finger tip **Key Point:** - Dorsal sensation preserved if lesion distal to dorsal cutaneous branch (which exits proximal to wrist) ### Ulnar Nerve Provocative Tests **Froment's Sign Explained:** - Normal: Pinch with extended IP joint (adductor pollicis) - Positive: Thumb IP flexes (using FPL - median nerve - to compensate) - Indicates adductor pollicis weakness (ulnar nerve) - May also see hypothenar and interosseous wasting ## Radial Nerve Examination **Wrist Extension (ECRL, ECRB, ECU):** - Patient extends wrist against resistance - With high radial nerve palsy = wrist drop **Finger Extension (EDC):** - Extend MCP joints against resistance - Note: IP extension preserved (interossei, lumbricals) **Thumb Extension (EPL):** - Extend thumb IP joint against resistance - Place palm flat, lift thumb off table **Posterior Interosseous Nerve (PIN):** - Pure motor branch - Finger and thumb extension weakness - Wrist extension preserved (ECRL takes off proximal to PIN) - "Finger drop" with preserved wrist extension **Superficial Radial Nerve (SRN):** - Dorsal first web space (autonomous zone) - Dorsum of thumb, index, and middle finger (proximal phalanx) - Radial half of dorsum of hand **Note:** - SRN palsy = sensory loss only (no motor) - PIN palsy = motor only (no sensory) ## Claw Hand Deformity **Classic Ulnar Claw:** - MCP hyperextension (loss of lumbrical MCP flexion) - IP flexion (unopposed FDP) - Ring and little fingers affected (lumbricals 3-4 are ulnar) **Ulnar Paradox:** - LOW ulnar lesion = MORE obvious claw (FDP intact, working) - HIGH ulnar lesion = LESS obvious claw (FDP also paralyzed) **Bouvier's Test:** - Block MCP hyperextension passively - Can patient now extend IP joints? - If yes: Simple claw (lumbricals only) - If no: Complex claw (intrinsic tightness, other pathology) ## Differentiating Lesion Levels ## Summary Presentation ## Examination Sequence 1. **Observation**: Thenar/hypothenar wasting, interosseous wasting, claw deformity 2. **Median Motor**: APB (thumb abduction), opposition, OK sign (AIN) 3. **Median Sensory**: Index finger tip 4. **Median Provocative**: Phalen's, Tinel's, Durkan's 5. **Ulnar Motor**: FDI, finger abduction, Froment's 6. **Ulnar Sensory**: Little finger tip 7. **Ulnar Provocative**: Elbow flexion test, Tinel's at elbow 8. **Radial Motor**: Wrist extension, finger extension 9. **Radial Sensory**: First web space dorsally 10. **Compare with contralateral side** ## Examiner Tips