What are the recommendations for evaluation and treatment of axillary nerve injury following a Tdap (tetanus, diphtheria, and pertussis) vaccination?

Evaluation and Treatment of Axillary Nerve Injury Following Tdap Vaccination

Initial Recognition and Clinical Assessment

Axillary nerve injury following Tdap vaccination represents a rare but recognized complication of brachial neuritis, which is self-limited and does not preclude future tetanus toxoid-containing vaccines. 1

Key Clinical Features to Identify

• Brachial neuritis (also called neuralgic amyotrophy) is the most likely mechanism of axillary nerve injury post-Tdap, characterized by severe shoulder pain followed by weakness and atrophy of the deltoid and teres minor muscles 1
• The Institute of Medicine concluded that evidence favors a causal relationship between tetanus toxoid-containing vaccines and brachial neuritis, though it remains exceedingly rare 1
• Symptoms typically develop within days to weeks after vaccination, with severe pain preceding motor deficits 1
• Critical distinction: Brachial neuritis symptoms develop 4-12 hours to several days post-vaccination, whereas anaphylaxis occurs within minutes 1

Diagnostic Evaluation Algorithm

Baseline Assessment (Within 4 Weeks of Injury)

• Obtain baseline electromyography (EMG) and nerve conduction studies within 4 weeks of symptom onset to document the extent of nerve injury 2
• Perform a focused neurological examination documenting deltoid strength, sensation over the lateral shoulder (axillary nerve distribution), and range of motion 2
• Document the timeline: vaccination date, symptom onset, and progression of weakness 1

Follow-up Evaluation (12 Weeks Post-Injury)

• Repeat EMG and nerve conduction studies at 12 weeks to assess for clinical or electromyographic improvement 2
• The vast majority of patients with brachial neuritis recover with non-operative treatment, making this follow-up assessment critical for determining need for surgical intervention 2

Treatment Recommendations

Conservative Management (First-Line)

• Initiate conservative management immediately, as brachial neuritis is usually self-limited with spontaneous recovery expected in most cases 1
• Provide symptomatic pain control during the acute phase (typically lasting weeks to months) 1
• Institute physical therapy to maintain range of motion and prevent shoulder stiffness during the recovery period 2
• Reassure the patient that this is a recognized, compensable event through the National Vaccine Injury Compensation Program 1

Surgical Intervention Criteria

• Consider surgery only if no clinical or electromyographic improvement is noted at the 12-week follow-up evaluation 2
• Optimal surgical timing is within 3 to 6 months from injury for best outcomes 2
• Surgical options include neurolysis (if nerve is in continuity), nerve grafting (for transections), or neurotization 2, 3
• The axillary nerve has relatively good surgical outcomes compared to other peripheral nerve injuries due to its monofascicular composition and short distance to motor end-plates 2

Critical Clinical Pitfalls to Avoid

Common Mismanagement Issues

• Do not withhold future tetanus toxoid-containing vaccines: ACIP explicitly states that brachial neuritis is NOT a contraindication or precaution for subsequent Tdap or Td administration 1
• Do not confuse brachial neuritis with Arthus reaction: Arthus reactions present with severe pain, swelling, induration, and edema at the injection site 4-12 hours post-vaccination, whereas brachial neuritis involves neurologic deficits 1
• Do not rush to surgery: The vast majority recover without operative intervention; premature surgical exploration is unnecessary 2
• Do not delay baseline EMG beyond 4 weeks: Early documentation is essential for tracking recovery and surgical decision-making 2

Documentation Requirements

• Document this as a vaccine adverse event and consider reporting to the Vaccine Adverse Event Reporting System (VAERS) 1
• Clearly document that this is brachial neuritis, not a contraindication to future vaccination, to prevent unnecessary withholding of tetanus prophylaxis 1

Prognosis and Patient Counseling

• Reassure patients that brachial neuritis is self-limited with expected recovery in the majority of cases, though recovery may take months 1
• Recovery of axillary nerve function following surgical repair (when needed) has good outcomes compared to other peripheral nerve lesions 2, 3
• Future tetanus toxoid-containing vaccines can and should be administered when indicated (e.g., wound management, routine boosters) without increased risk 1