Abdominal Cutaneous Nerve Entrapment Syndrome – “ACNES”

What is A.C.N.E.S.?

ACNES is chronic abdominal pain caused by a “pinched” nerve – specifically the intercostal nerves.  Like carpal tunnel or cubital tunnel syndromes, a small nerve in the layers of muscles in the abdominal wall becomes compressed, leading to sharp, stabbing, burning pain in one specific area.  Patients can typically point to the exact spot of maximal pain, and pressure in this are makes the pain worse.  Activities that work the abdominal muscles often worsen the pain.  Sitting or bending over can also increase the pain due to wrinkling of the skin and muscles of the abdomen.

How does someone develop A.C.N.E.S.?

Many times, there is no real cause that can be identified that cause the nerve(s) to become compressed and cause pain.  In some cases, patients will describe a fall, a car accident, or a ‘pulled muscle’ in their side, sometimes accompanied by bruising, that sets the process in motion.  One or more nerves that travel between and through the thin muscles under the skin become squeezed as a result, and send continuous pain signals to the brain.

Some people may develop a form of ACNES following surgery.  The same nerves that get compressed in ACNES can be stretched, cut, burned, or caught up in scar as a result of any operation on the abdomen or chest.  Examples include gallbladder removal, hernia repair, kidney or bowel surgery, and mastectomy.  The pain, diagnosis and treatment in these situations is the same as with ACNES.

How is A.C.N.E.S. diagnosed?

ACNES is the great masquerader – patients will often undergo medical work-up by several different physicians, often getting many diagnostic tests that all come up negative.  Because ACNES is not usually on the list of possibilities by medical providers, it often escapes diagnosis.  (It has not been a commonly taught reason for abdominal pain.)  There are many causes of pain INSIDE of the abdomen, and they are usually the main focus of investigation.  However, the pinched nerve(s) of ACNES lie OUTSIDE of the abdominal cavity, WITHIN THE MUSCLES that hold everything in.

ACNES can usually be diagnosed by a simple physical examination alone!  Just including it in the thought process – the “differential” – can lead to it being discovered before obtaining specialist consultations or invasive testing.  Focal pain, reproduced with pressure in one primary spot, is characteristic of ACNES.  Confirmation of the diagnosis and identification of the exact nerve(s) responsible can be obtained with a nerve block – a small shot of numbing medicine that relieves the pain temporarily.  ACNES will not show up on xrays, blood work, or other testing.

Surgery for A.C.N.E.S. Pain

If the physical exam and nerve block are highly suggestive of ACNES, surgery can be highly successful in permanently eliminating the pain.  The surgeon will make an incision over the nerve at the site of pain, find the nerve(s) involved, and either decompress it or remove it.  The success rate is greater than 80% in dramatically reducing or eliminating the pain.  The following day, patients will usually describe that the ’nerve pain’ is better, and has been replaced with ‘surgery pain’, which goes away in a few weeks.  The operation is relatively straightforward, is performed as an outpatient (you go home the same day), and results in very little downtime or recovery.