Anterior cutaneous nerve entrapment syndrome, more commonly known as ACNES, is a condition that causes chronic pain of the abdominal wall. Around 20% of patients with chronic abdominal pain have abdominal wall pain, which is often caused by ACNES.
ACNES is characterized by a sharp stabbing pain, always in the same area, which typically increases with the use of abdominal muscles. The condition most commonly affects young women, but it can occur at any age. History of trauma, pregnancy and delivery, or abdominal surgery is sometimes present. A substantial number of patients report previous visits to the ER with acute pain.
Diagnosing ACNES is very difficult and it usually involves imaging and lab tests, as well as the injection of local anesthetic. Although the injection serves as a tool for diagnosis, it will sometimes reduce the patient’s pain. Physical examination will reveal altered skin sensibility in the affected area, with one specific painful spot, and reproducibility of pain by pinching the affected skin area.
ACNES often produces misleading diagnoses, like hernia, tumors, tears and endometriosis of abdominal wall, radiculopathy, and herniated discs.
Treating ACNES isn’t easy, as most pain killers have no effect on this type of neuropathic pain. Treatment is typically by injection of the anterior cutaneous nerve with a local anesthetic at the point at which it pierces the fascia by free hand or under ultrasound guidance. Neuropathic pain killers like pregabaline or amitryptilline may be helpful.
In patients whose pain persists after several injections, surgical exploration and neurectomy is recommended. This strategy of injections followed by neurectomy is curative in about 80% of patients.