What is the assessment and treatment protocol for Anterior Cutaneous Nerve Entrapment Syndrome?

Assessment and Treatment Protocol for Anterior Cutaneous Nerve Entrapment Syndrome (ACNES)

Anterior Cutaneous Nerve Entrapment Syndrome (ACNES) requires a stepwise diagnostic approach followed by a three-step treatment protocol, beginning with local injections and progressing to surgical neurectomy in refractory cases.

Diagnostic Assessment

Clinical Presentation

• ACNES presents as chronic abdominal pain caused by entrapment of cutaneous branches of lower thoracoabdominal intercostal nerves at the lateral border of the rectus abdominis muscle 1
• Pain is typically severe, localized, and often refractory to standard pain management approaches 1
• ACNES is frequently underdiagnosed despite numerous diagnostic evaluations 2

Physical Examination

• Identify specific trigger points at the lateral border of the rectus abdominis muscle 3
• Perform Carnett's test (increased pain when abdominal muscles are tensed) which is positive in ACNES 4
• Look for sensory disturbances in the affected dermatome 1
• Deep palpation at the trigger point typically reproduces the patient's pain 3

Diagnostic Testing

• Local anesthetic injection at the trigger point serves as both diagnostic and therapeutic - significant pain reduction (>50%) confirms diagnosis 3
• Deep skin biopsy may be considered to exclude other pathologies, similar to the approach recommended for cutaneous PAN 5
• Ultrasound imaging can help identify the affected nerve and surrounding structures 4

Treatment Protocol

Step 1: Conservative Management

• Begin with non-invasive approaches:
  • Osteopathic manipulation techniques 2
  • Active release techniques and instrument-assisted soft tissue mobilization 2
  • Directional cupping and stretching exercises 2
  • Strengthening exercises targeting the abdominal wall 2

Step 2: Injection Therapy

• Trigger point injections with local anesthetic (1% lidocaine) at the identified point of maximal tenderness 3
• Consider adding corticosteroids for subsequent therapeutic injections 3
• Ultrasound-guided transversus abdominis plane (TAP) block can provide more precise delivery of medication 4
• Multiple injections may be required - approximately 33% of patients achieve permanent pain relief with injection therapy alone 3

Step 3: Surgical Intervention

• For patients who fail conservative and injection therapies, anterior neurectomy should be considered 3
• Surgical neurectomy is effective in approximately 71% of injection-refractory patients 3
• The procedure involves localized removal of terminal branches of affected intercostal nerves 6

Pharmacological Management

• Consider adjunctive medications similar to those used for other neuropathic pain conditions:
  • Tricyclic antidepressants (nortriptyline, desipramine) 7
  • Serotonin-norepinephrine reuptake inhibitors (duloxetine) 7
  • α-δ agonists (pregabalin, gabapentin) 7

Follow-up and Monitoring

• Assess pain levels using validated tools such as Visual Analog Scale (VAS) or Verbal Rating Scale (VRS) 3
• Monitor for long-term efficacy and potential recurrence 3
• Provide patients with strategies to prevent recurrence, including specific exercises 2

Common Pitfalls and Caveats

• ACNES is frequently misdiagnosed as visceral pain, leading to unnecessary diagnostic procedures 1
• Failure to perform proper physical examination techniques like Carnett's test often leads to missed diagnosis 4
• Superficial injections may miss the affected nerve, resulting in treatment failure 3
• Patients may require a combination of treatment modalities for optimal outcomes 2

Emerging Techniques

• Radiofrequency ablation may be considered in refractory cases 1
• Neuromodulation techniques show promise for chronic cases 1
• Peripheral nerve stimulation might be beneficial based on evidence from similar neuropathic conditions 8