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Radial nerve
Related Subjects: |Radial Nerve |Median Nerve |Ulnar Nerve |Musculocutaneous nerve |Axillary nerve |Brachial plexus |Dermatomes
💤 Saturday night palsy: weakness of wrist & finger extensors on waking after alcohol-induced sleep due to prolonged radial nerve compression.
🧩 Origin and Course
- Origin:
- Posterior cord of brachial plexus (C5–T1).
- Carries all posterior division fibres → major motor to extensors.
- Course:
- Descends posterior to axillary artery → radial groove of humerus.
- Winds laterally → anterior to lateral epicondyle.
- Divides in proximal forearm into:
- Deep branch (posterior interosseous nerve).
- Superficial sensory branch.
🌿 Branches of the Radial Nerve
- Muscular branches: triceps, anconeus, brachioradialis, extensor carpi radialis longus.
- Cutaneous branches:
- Posterior cutaneous of arm.
- Inferior lateral cutaneous of arm.
- Posterior cutaneous of forearm.
- Deep branch (Posterior interosseous nerve) → all forearm extensors.
- Superficial branch → sensory to dorsum of hand (thumb, index, middle, radial half of ring finger; NOT fingertips).
⚙️ Functions
- Motor: elbow extension (triceps), wrist/finger extension, supination (supinator).
- Sensory: posterior arm & forearm, dorsum of hand (radial side).
🚨 Clinical
- Radial nerve palsy ("Saturday night palsy", "honeymoon palsy"):
- Wrist drop ✋ (cannot extend wrist/fingers).
- Sensory loss over dorsal hand.
- Usually temporary (resolves over weeks).
- Humeral shaft fracture:
- High risk of nerve injury in radial groove.
- Motor/sensory loss pattern as above.
- Compression injuries:
- Axilla: “crutch palsy”.
- Forearm: posterior interosseous entrapment (pure motor weakness).
🧪 Investigations
- Clinical exam: test wrist/finger extension, check sensory dorsum of hand.
- Electrophysiology: EMG, nerve conduction studies → localise lesion.
- Imaging: X-ray for humeral fracture; MRI/US for entrapment or soft tissue mass.
📋 Causes
- Pressure palsy (sleep, crutches, prolonged positioning).
- Mononeuropathy: diabetes, alcohol, B12 deficiency.
- Trauma: humeral fracture, dislocation.
💊 Management
- Remove/avoid cause (e.g. avoid alcohol sleep posture, replace B12).
- Splint wrist to prevent contractures + OT/PT for recovery.
- Neuropathic pain management if present.
- Most palsies recover in weeks–months; poor prognosis if severe axonal loss on EMG.
🔑 Exam tip: Wrist drop + humeral fracture = radial nerve injury. Posterior interosseous branch → pure motor deficit without sensory loss.
| The content on this website is provided for educational and informational purposes only to support exam preparation (e.g., MLA, MRCP, USMLE) and learning. This is NOT medical advice, diagnosis, treatment, or professional guidance. It does not replace consultation with a qualified healthcare professional, official guidelines (e.g., NICE, GMC, BNF), or supervised clinical practice. Always verify information with current, authoritative sources. Makindo and its contributors accept no liability for any reliance on this content, including errors, omissions, or any resulting harm, loss, or consequences. By using this site, you agree to these terms. |
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