What is the recommended maneuver test to diagnose anterior cutaneous nerve entrapment syndrome?

Diagnostic Maneuver for Anterior Cutaneous Nerve Entrapment Syndrome

The Carnett sign is the primary diagnostic maneuver for ACNES, performed by palpating the point of maximal abdominal tenderness while the patient tenses their abdominal muscles (by lifting their head or legs); pain that persists or worsens indicates a positive test and suggests abdominal wall origin rather than intra-abdominal pathology. 1, 2

Clinical Examination Technique

Carnett Sign Performance

• Locate the trigger point at the lateral border of the rectus abdominis muscle where maximal tenderness is present 2
• Have the patient lie supine and identify the most painful spot through palpation 3
• Ask the patient to tense their abdominal muscles by either lifting their head off the examination table or performing a partial sit-up while you maintain pressure on the tender point 1
• A positive Carnett sign occurs when pain persists or increases with muscle contraction, indicating the pain originates from the abdominal wall rather than intra-abdominal structures 1

Additional Diagnostic Findings

• Altered skin sensation (hyperesthesia or hypoesthesia) is present in approximately 92% of ACNES patients and should be assessed in the area surrounding the trigger point 2
• The trigger point is typically small and well-localized (less than 2.5 cm in diameter) and located at the lateral edge of the rectus abdominis muscle 3
• Pain is often unilateral and can be precisely reproduced with fingertip palpation 3

Confirmatory Testing

Diagnostic Injection Test

• A diagnostic injection of 10 mL of 1% lidocaine into the trigger point just beneath the anterior fascia of the rectus abdominis muscle serves as the definitive diagnostic test 4
• Pain reduction of at least 50% on visual analog scale (VAS) or 2 points on verbal rating scale (VRS) within 15-20 minutes confirms the diagnosis 4
• This response is based on an anesthetic mechanism rather than placebo effect, as demonstrated in randomized trials where lidocaine was significantly more effective than saline injection (54% vs 17% success rate, P = 0.007) 4
• Approximately 81% of patients with suspected ACNES demonstrate significant pain reduction after the first diagnostic injection 3

Common Diagnostic Pitfalls

Critical Considerations

• ACNES is frequently overlooked in the differential diagnosis of chronic abdominal pain, leading to unnecessary invasive testing and procedures 5, 3
• The condition affects approximately 1 in 8 adolescents presenting with chronic abdominal pain to pediatric outpatient departments, making it more common than typically recognized 2
• Do not rely on imaging studies for diagnosis—ACNES is a clinical diagnosis confirmed by physical examination and response to local anesthetic injection 5
• Failure to perform the Carnett sign or assess for altered skin sensation can result in missed diagnosis and prolonged patient suffering 1, 2

Age-Specific Considerations

• In pediatric populations (ages 10-18 years), the Carnett sign was positive in 100% of confirmed ACNES cases 2
• The diagnostic approach and physical examination findings are consistent across age groups, making the Carnett sign reliable in both adults and children 3, 2