Anterior cutaneous nerve entrapment syndrome (ACNES)

What is anterior cutaneous nerve entrapment syndrome (ACNES)?

Anterior cutaneous nerve entrapment syndrome (ACNES) is one of the most frequent causes of abdominal pain in adults and children. The condition occurs when nerves within the abdominal wall— the anterior cutaneous abdominal nerves — become pinched or entrapped within the abdominal wall muscle.

What are the symptoms of anterior cutaneous nerve entrapment syndrome (ACNES)?

Abdominal pain is a common complaint in children, but ACNES has some unique symptoms. These include chronic abdominal pain and tenderness over the same very small area, typically less than 2 centimeters in diameter.

Abdominal nerve pain from ACNES tends to be sharp. Activities that tighten the abdominal muscles can make it worse. You may notice that your child’s pain is worse when they are sitting or lying on their side and less intense when they lie on their back.

What causes anterior cutaneous nerve entrapment syndrome (ACNES)?

Several factors can cause nerves to become entrapped, including:

  • muscle tears from injuries that healed with an internal scar
  • abdominal wall scars from prior operations
  • overly flexible cartilage

What causes pain in children with anterior cutaneous nerve entrapment syndrome (ACNES)?

  • clothing or belts around the abdomen that rub on the spot
  • tightening the abdominal wall muscles by laughing, sneezing, and exercising
  • oral contraceptive use may also increase the risk of ACNES

How is anterior cutaneous nerve entrapment syndrome (ACNES) diagnosed?

ACNES can be difficult to diagnose and can be confused with other conditions that cause abdominal wall pain, such as hernias, appendicitis, or cholecystitis.

There are no tests to diagnose ACNES. It can only be diagnosed by physical examination. Your child’s clinician will look for specific things:

  • a consistent spot in the skin that is sensitive to light touch or cold temperatures
  • pain with pinching the skin in that spot, but not in other places
  • pain and tenderness with tapping and pressing on that spot but not in other places
  • a positive Carnett’s sign, which is tenderness to pressing that worsens when your child tenses their abdomen by either lifting their head and shoulders or legs
  • pain relief following injections of a local anesthetic drug or steroids where the pain is most intense

How is anterior cutaneous nerve entrapment syndrome (ACNES) treated?

ACNES treatments are intended provide immediate and long-lasting pain relief; some may also release the pinched nerves. They include:

Trigger point injections. Your child’s clinician may first start with injections of local anesthetics like lidocaine and/or steroids at the site of the abdominal pain. Known as trigger point injections, they can relieve the pain after one injection, but a series of injections may be needed if the pain does not go away or returns later.

If the pain returns after multiple trigger point injections, your child’s physician may consider other options, such as:

Chemical neurolysis, which involves injecting alcohol to dull nerve pain

Pulsed radio frequency (PRF), which involves applying a small electrical current to the painful site to disrupt the nerve

Surgery. A surgical neurectomy — which involves removing specific nerve branches within the abdominal wall at the point of the pain — can provide permanent pain relief. About one in three times there is loss of skin sensation over the spot. Surgeons look into the abdominal wall underneath the painful spot and divide any cutaneous nerve branches they find. They do not cut into the abdomen itself. Our research shows that at Boston Children’s, around 80 percent of patients who undergo surgical neurectomy for ACNES are pain-free after treatment.

How we care for ACNES at Boston Children’s Hospital

We know each child’s pain is unique and deserves personalized care. Our patients with ACNES are seen within the hospital’s Pediatric Interventional Pain Program within the Department of Anesthesiology, Critical Care and Pain Medicine. Your child will be cared for by a team of anesthesiologists, neurologists, pediatricians, nurses, surgeons, physical therapists, and psychologists, all experienced in diagnosing, effectively treating, and supporting children with ACNES.