Radial Nerve Lesions

Common causes include:

• Trauma
• Compartment syndromes
• Sustained pressure to the axilla

Investigation and management depend on the cause, onset, and severity.

Anatomy

Course of the radial nerve

• Origin: C5–T1, from the posterior cord of the brachial plexus
• Travels between the long and medial heads of triceps, through the spiral groove with the profunda brachii artery
• Pierces the lateral fascial septum above the elbow, enters the cubital fossa
• Divides at lateral epicondyle into:
  • Superficial branch: sensory
  • Deep branch (posterior interosseous nerve): motor

Radial nerve innervations

In axilla:

• Triceps (long and medial heads)
• Posterior cutaneous brachial nerve

In spiral groove:

• Lateral and medial heads of triceps, anconeus
• Lower lateral brachial cutaneous nerve
• Posterior cutaneous nerve of forearm

At cubital fossa:

• Lateral part of brachialis
• Supinator
• Brachioradialis
• Extensor carpi radialis longus

Superficial branch:

• Sensation to lateral 2/3 of dorsum of hand, lateral 2½ fingers

Deep branch:

• Extensor muscles of the posterior forearm

Actions of Radial Nerve-Innervated Muscles

Muscle	Action
Triceps	Elbow extension
Lateral part of brachialis	Elbow flexion
Supinator	Forearm supination
Brachioradialis	Elbow flexion, brings forearm to mid-prone
Extensors of forearm	Extend wrist, MCP, PIP and DIP joints; thumb abduction/extension

Pathology

Causes of radial nerve lesions

1. Trauma:
   • Blunt or penetrating trauma
   • Fractures:
     • Humeral shaft (esp. middle third)
     • Monteggia fracture
   • Shoulder/elbow dislocations
2. Neuropraxia:
   • Commonly due to axillary compression
   • “Saturday night palsy” or “honeymooners palsy”
3. Mass lesions:
   • Tumours, abscesses
4. Neuropathies:
   • Diabetes mellitus
   • Malignancy (compression, paraneoplastic)
   • Infection: leprosy, HIV
   • CTDs: RA, SLE, PAN, scleroderma, sarcoidosis
   • Others: amyloidosis, Lyme disease, heavy metals

Clinical Assessment

Radial Nerve Deficits

Axilla lesions:

• Paralysis: triceps, anconeus, extensors
• Wrist drop, inability to grip
• Sensory loss: posterior arm/forearm, dorsum of lateral hand and fingers

Spiral groove lesions:

• Paralysis: wrist/finger extensors
• Triceps and cutaneous branches spared
• Wrist drop, ± small dorsal sensory deficit

Deep branch injury:

• Motor loss to posterior forearm extensors (except supinator, ECRL)
• No wrist drop
• No sensory loss

Superficial branch injury:

• Pure sensory deficit over dorsum of hand and lateral fingers

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Investigations

• Nerve conduction studies: diagnosis, rule out generalised disease, predict prognosis
• Blood tests: FBC, U&Es, glucose, CRP, ESR, heavy metals if indicated
• CT/MRI: delineate compressive lesions, visualise nerve pathology
• Biopsy: rarely indicated for mononeuritis, suspected leprosy

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Management

1. Treat the underlying cause
2. Compartment syndrome:
   • Fasciotomy if indicated
3. Occupational therapy:
   • Splinting, functional supports
4. Physiotherapy:
   • Rehabilitation and prevention of complications

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Disposition

Depends on:

• Cause of lesion
• Severity
• Onset

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Appendix 1

Median Nerve Anatomy

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Appendix 2

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References

Publications

• Brazis PW, Masdeu JC, Biller J. Localization in Clinical Neurology. 8e 2021
• Fuller G. Neurological Examination Made Easy. 6e 2019
• O’Brien M. Aids to the Examination of the Peripheral Nervous System. 6e 2023

FOAMed

• Cadogan M. Sir Henry Head (1861-1940). LITFL
• Cadogan M. Holstein–Lewis fracture. LITFL
• Coni R. Neuro 101: Peripheral Nervous System. LITFL
• Nickson C. Myotomes and Differentiating Nerve Lesions. LITFL