Abdominal cutaneous nerve entrapment syndrome (ACNES) is not an uncommon condition. When a patient is seen for abdominal pain without other clinically significant symptoms, ACNES should be high on the list of likely diagnoses.
The condition was first described by J P Frank in 1792, who coined the term “peritonitis muscularis.” Abdominal wall pain can often be wrongly attributed to intra-abdominal disorders. This misdirected diagnosis can lead to unnecessary consultation, testing, and even abdominal surgery. All of these can be avoided if the initial examination points to the right diagnosis.
Carnett in the early 20th century, called this syndrome “intercostal neuralgia” and claimed to have seen three patients per week with this diagnosis, including as many as three per day in consultation sessions.
PATHOPHYSIOLOGY
The most common cause of abdominal wall pain is nerve entrapment at the lateral border of the rectus abdominis muscle. Kopell and Thompson stated that peripheral nerve entrapment occurs at anatomic sites where the nerve changes direction to enter a fibrous or osseofibrous tunnel. It may also occur where the nerve passes over a fibrous or muscular band. This entrapment can be at these sites because mechanically induced irritation is most likely to occur at these locations.
INJECTION OF LOCAL ANAESTHETIC AND STEROID
As ACNES is a peripheral nerve entrapment syndrome, it is mainly diagnosed after the response to local anesthetic infiltration. Ultrasound-guided blockade of the abdominal cutaneous nerve serves as a precision diagnostic tool with potential therapeutic efficacy. Ultrasound guidance is useful to localize the nerve, and to spread the injectate around it. This results in hydro dissection, thereby releasing any entrapment. The ability to visualize the needle’s course and the spread of injectate imparts safety to the procedure.
Local injections can be therapeutic. Kuan et al. report 95% of patients experiencing pain relief after one or two injections. Mcgrady and Marks used a peripheral nerve stimulator to localize the nerve and used 1 ml of 6%
phenol for treatment. They reported that 59% of their patients diagnosed as ACNES got complete pain relief and 36% had a few symptoms but did not require further treatment.
PULSED RADIOFREQUENCY LESIONING OF ABDOMINAL CUTANEOUS NERVE
Pulsed radiofrequency treatment can be applied to the abdominal cutaneous nerves for patients who get a positive response to local anaesthetic blocks. Pulsed radiofrequency can provide sustained pain relief in patients with chronic abdominal wall pain or abdominal cutaneous nerve entrapment syndrome (ACNES).
FOR FURTHER INFO: http://www.painspa.co.uk/conditions/abdominal-cutaneous-nerve-entrapment-syndrome-acnes/