Anatomy of abdominal anterior cutaneous intercostal nerves with respect to the pathophysiology of anterior cutaneous nerve entrapment syndrome (ACNES): A case study

Introduction: Anterior Cutaneous Nerve Entrapment Syndrome is allegedly caused by entrapment of an intercostal nerve in a fibrous ring in the rectus abdominis muscle leading to neuropathic pain. Surgical release of the strained nerve (neurectomy) obtains adequate pain relief in 70% of patients. Standard anatomy texts and previous research however might underestimate the complex network of nerve branches in the abdominal wall, leading to suboptimal treatment results and misguided pathophysiology. Material and methods: One fresh frozen cadaver with no gross previous pathology was dissected to map the course of intercostal nerves from the lateral abdominal wall to their nerve terminals in the subcutis of the anterior abdominal wall. Histology was performed to differentiate between nerve tissue and fascia. Special attention was payed to fibrous ring like structures. Results: Five major neurovascular bundles were identified (T8-T12). Fibrous rings were not found intramuscularly but in the posterior rectus sheath, if present. Multiple neural interconnections at the lateral border of the posterior rectus sheath were found. Per dermatome several small branches perforated the rectus abdominis muscle. Conclusions: The trajectory of nerves in the abdominal wall appears to be more complex than previously suggested, which should be addressed when for instance a neurectomy is performed. : The trajectory of nerves in the abdominal wall is more complex than previously suggested, which should be addressed when a neurectomy is performed in patients with Anterior Cutaneous Nerve Entrapment Syndrome (ACNES). Keywords: Intercostal nerve, Abdominal wall, Pain, ACNES, Entrapment, Neurectomy