What are the next steps for a patient who develops wrist drop and loss of motor function in the 3rd and middle fingers after an intramuscular (IM) injection near the antecubital fossa, with intact sensory function?

Immediate Management of Post-Injection Radial Nerve Injury

This is an iatrogenic radial nerve injury from intramuscular injection near the antecubital fossa, and you must immediately stop any further injections, document the injury thoroughly, obtain urgent neurology consultation, and arrange electrodiagnostic studies within 2-3 weeks to assess the extent of nerve damage. 1

Clinical Assessment and Documentation

Confirm the radial nerve injury pattern:

• Wrist drop with loss of wrist extension indicates posterior interosseous nerve involvement 2
• Loss of motor function in the 3rd and middle fingers (finger extensors) confirms radial nerve distribution 3, 2
• Intact sensation is unusual but can occur with selective motor fascicle injury or early presentation before sensory manifestations develop 1
• Check for brachioradialis reflex—diminished or absent reflex supports radial nerve injury 4

Document the exact injection site and technique immediately:

• Injections near the antecubital fossa can directly traumatize the radial nerve as it courses through the spiral groove and around the humerus 3
• The radial nerve is particularly vulnerable to compression and direct trauma in this anatomical region 4

Urgent Diagnostic Workup

Electrodiagnostic studies are essential but timing matters:

• Do NOT perform EMG/NCS immediately—studies done within the first week are normal in 30-34% of patients even with active nerve injury 1
• Schedule electrodiagnostic testing at 2-3 weeks post-injury to allow Wallerian degeneration to manifest 1, 5
• Expected findings will include prolonged distal latency, reduced amplitude, and slowed motor conduction velocity of the radial nerve 3, 4
• EMG may show fibrillation potentials at rest, polyphasic motor units, and incomplete interference pattern in affected muscles 4

Obtain neurology consultation urgently:

• Neurological consultation is recommended when there is uncertainty in clinical presentation or to guide management 6
• The neurologist can help determine if this is a neurapraxia (best prognosis), axonotmesis, or neurotmesis based on clinical progression 5

Immediate Symptomatic Management

Initiate multimodal treatment immediately:

• Start corticosteroids (methylprednisolone 2-4 mg/kg/day) to reduce inflammation and nerve edema 6
• Provide neuropathic pain management with gabapentin, duloxetine, or tricyclic antidepressants as first-line agents 1
• Consider NSAIDs for anti-inflammatory effects 5
• Provide psychological counseling and reassurance—most injection-related nerve injuries recover spontaneously 5, 3

Implement immediate protective measures:

• Splint the wrist in neutral position to prevent contractures while awaiting recovery 2
• Refer to occupational therapy for hand function preservation 5
• Begin passive range-of-motion exercises immediately to prevent joint stiffness 2

Prognosis and Follow-Up Timeline

Most injection-related radial nerve injuries recover spontaneously:

• In compression-type radial nerve injuries, 90% of patients recover completely within 9-12 weeks 4
• Sensation typically recovers faster than motor function 4
• Independent wrist extension to M4+ strength is achievable in most cases with conservative management 2

Poor prognostic indicators to monitor:

• Longer duration of nerve compression correlates with worse outcomes 4
• Sustained decreased muscle power with signs of active denervation on EMG at 3 months suggests poor prognosis 4
• Complete motor loss (0/5 strength) that persists beyond 3 months may indicate need for surgical intervention 2, 4

Decision Points for Surgical Intervention

Conservative management is appropriate initially:

• Most iatrogenic injection injuries are neurapraxia or mild axonotmesis and recover spontaneously 3, 4
• Continue conservative management with physical therapy, splinting, and symptomatic treatment for at least 3-6 months 2

Consider nerve transfer surgery if:

• No clinical improvement by 3-6 months post-injury 2
• EMG shows complete denervation without reinnervation potentials at 3 months 4
• Median to radial nerve transfer (flexor carpi radialis and flexor digitorum superficialis branches to posterior interosseous nerve) is the surgical option with best outcomes when performed within 6 months of injury 2

Critical Pitfalls to Avoid

Do not perform EMG/NCS too early:

• Testing within the first week will be falsely normal in 30-34% of cases, leading to false reassurance 1
• Wait 2-3 weeks minimum, and repeat if initial studies are equivocal but clinical suspicion remains high 1

Do not delay corticosteroids:

• Early steroid administration may reduce inflammation and improve outcomes, though evidence is limited 6
• The window for maximal benefit is likely within the first few days post-injury 5

Do not assume complete recovery is guaranteed:

• While most recover, approximately 10% may have persistent deficits requiring surgical intervention 2, 4
• Close follow-up every 2-4 weeks is essential to identify patients who need escalation to surgery 2