SN3
SHORT NOTE
5M
★ High-yield
Describe the carpal tunnel with its contents. Discuss carpal tunnel syndrome.
Definition
Carpal tunnel syndrome = compression of the median nerve beneath the flexor retinaculum at the wrist.
- The commonest entrapment neuropathy
The Carpal Tunnel
| Boundary | Formed by |
|---|---|
| Floor and sides | Concavity of the carpal bones |
| Roof | Flexor retinaculum |
| Retinaculum attachments — medial | Pisiform and hook of the hamate |
| Retinaculum attachments — lateral | Scaphoid tubercle and trapezium |
- Median nerve
- Four tendons of flexor digitorum superficialis
- Four tendons of flexor digitorum profundus
- Tendon of flexor pollicis longus
- Structures passing superficial to the retinaculum (not through the tunnel) — ulnar nerve and artery (in Guyon canal), palmaris longus tendon, palmar cutaneous branches of median and ulnar nerves
Causes
| Category | Causes |
|---|---|
| Idiopathic | The commonest; middle-aged women |
| Endocrine | Pregnancy, hypothyroidism, acromegaly, diabetes, obesity |
| Inflammatory | Rheumatoid arthritis, tenosynovitis, gout |
| Traumatic | Colles fracture, dislocation of the lunate, scaphoid fracture |
| Occupational | Repetitive wrist movement, vibrating tools, typing |
| Infiltrative | Amyloidosis, ganglion, lipoma |
Clinical Features
- Pain and paraesthesiae in the lateral three and a half digits
- Characteristically worse AT night, waking the patient, who shakes the hand for relief — the "flick sign"
- Aggravated by wrist flexion and by activities such as holding a phone or newspaper
Clinical Tests
| Test | Method | Positive result |
|---|---|---|
| Tinel sign | Percussion over the flexor retinaculum | Tingling in the median distribution |
| Phalen test | Wrist held fully flexed for 60 seconds | Reproduction of paraesthesiae |
| Reverse Phalen | Wrist held extended | Same |
| Durkan test | Direct pressure over the tunnel for 30 seconds | Symptoms reproduced; the most sensitive |
| Nerve conduction study | Distal motor and sensory latency | Confirmatory |
Applied Aspects
- Treatment — night splints holding the wrist neutral, NSAIDs, local corticosteroid injection; surgical division of the flexor retinaculum if severe or if there is wasting
All questions in Upper Limb
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- SN1Write a short note on Erb–Duchenne palsy. ★
- SN2Describe the course of the radial nerve and the effects of its injury at different levels. ★
- SN3Describe the carpal tunnel with its contents. Discuss carpal tunnel syndrome. ★
- SN4Describe the course of the ulnar nerve and the features of its injury. Explain the ulnar paradox. ★
- SN5Describe the anatomical snuffbox with its boundaries and contents. Add a note on scaphoid fracture. ★
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- SN7Describe the cutaneous innervation and dermatomes of the upper limb.