Radial Nerve Injury (Wrist Drop)

Definition

Radial nerve injury, commonly known as wrist drop, occurs when the radial nerve, which controls movement and sensation in the arm and hand, is damaged. This injury results in an inability to extend the wrist and fingers, leading to a characteristic "wrist drop" appearance.

Aetiology

Radial nerve injury can be caused by various factors, including:

• Trauma: Fractures of the humerus, dislocations, or penetrating injuries
• Compression: Prolonged pressure on the nerve (e.g., from crutches, tourniquets, or tight casts)
• Infections: Herpes zoster (shingles)
• Systemic diseases: Diabetes, rheumatoid arthritis
• Intoxication: Alcoholism or drug overdose leading to prolonged pressure on the nerve

Pathophysiology

The radial nerve controls the muscles that extend the wrist and fingers. Damage to this nerve disrupts the transmission of signals from the brain to these muscles, resulting in weakness or paralysis and sensory loss in the back of the hand and forearm.

Risk Factors

• Trauma or injury to the arm
• Use of crutches or other devices that apply pressure to the axilla
• Prolonged immobility or improper positioning during sleep or surgery
• Systemic conditions like diabetes or rheumatoid arthritis
• Alcoholism or substance abuse

Signs and Symptoms

• Inability to extend the wrist and fingers (wrist drop)
• Weakness in the forearm and hand
• Numbness or tingling in the back of the hand and forearm
• Loss of sensation in the radial nerve distribution area

Investigations

• Clinical history and physical examination
• Nerve conduction studies to assess the function of the radial nerve
• Electromyography (EMG) to evaluate muscle activity and nerve conduction
• Imaging studies (e.g., X-ray, MRI) to identify fractures or other structural causes
• Blood tests to rule out systemic conditions

Management

Primary Care Management

• Initial assessment and diagnosis based on clinical history and physical examination
• Immobilisation of the affected limb to prevent further injury
• Pain management with analgesics
• Referral to a specialist for further evaluation and treatment

Specialist Management

• Advanced diagnostic testing (e.g., nerve conduction studies, EMG)
• Physical therapy to maintain muscle strength and prevent contractures
• Occupational therapy to improve hand function and adapt daily activities
• Surgical intervention in severe cases (e.g., nerve decompression, repair, or grafting)
• Management of underlying conditions (e.g., diabetes, rheumatoid arthritis)

Example Management for Radial Nerve Injury (Wrist Drop)

A patient presenting with wrist drop due to a radial nerve injury following a humerus fracture should initially be managed with immobilisation of the arm in a splint and pain relief with NSAIDs. Referral to a specialist for nerve conduction studies and EMG should be arranged to assess the extent of the injury. Physical therapy should be initiated to maintain muscle strength and prevent contractures. If there is no improvement after conservative management, surgical intervention may be considered.

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References

1. NICE. (2024). Peripheral Neuropathy: Diagnosis and Management. Retrieved from NICE
2. NHS. (2023). Peripheral Nerve Injury. Retrieved from NHS
3. Campbell, W. W. (2013). Evaluation and Management of Peripheral Nerve Injury. Clinical Neurophysiology.
4. Watson, J. C., & Dyck, P. J. (2015). Peripheral Neuropathy: A Practical Approach to Diagnosis and Management. Mayo Clinic Proceedings.
5. Preston, D. C., & Shapiro, B. E. (2012). Electromyography and Neuromuscular Disorders: Clinical-Electrophysiologic-Ultrasound Correlations. Elsevier.