Abstract
Entrapment of the anterior cutaneous branch of the intercostal nerve is an uncommon and a frequently overlooked cause of anterior abdominal wall pain. The most common site of entrapment is the lateral border of the rectus abdominus muscle. Entrapment of the anterior cutaneous nerve by the lateral border of the rectus abdominus muscle produces a constellation of symptoms consisting of severe knife-like pain emanating from the anterior abdominal wall and associated with the physical finding of point tenderness over the affected anterior cutaneous nerve. The pain radiates medially to the linea alba, but in almost all cases does not cross the midline. This nerve entrapment syndrome occurs most commonly in young women. The patient can often localize the source of pain accurately by pointing to the spot at which the anterior cutaneous branch of the affected intercostal nerve pierces the fascia of the abdominal wall at the lateral border of the rectus abdominus muscle. At this point, the anterior cutaneous branch of the intercostal nerve turns sharply in an anterior direction to provide innervation to the anterior wall. The nerve passes through a firm fibrous ring as it pierces the fascia, and at this point the nerve becomes subject to entrapment. The nerve is accompanied through the fascia by an epigastric artery and vein. There is the potential for small amounts of abdominal fat to herniate through this fascial ring and become incarcerated, which results in further entrapment of the nerve. The pain of anterior cutaneous nerve entrapment is moderate to severe in intensity.
Keywords
anterior cutaneous nerve entrapment, intercostal nerve, abdominal pain, rectus abdominus muscle, nerve entrapment, diagnostic ultrasonography, ultrasound guided nerve block, Carnett’s test, slipping rib syndrome, intercostal nerve
ICD-10 CODE G58.9
Keywords
anterior cutaneous nerve entrapment, intercostal nerve, abdominal pain, rectus abdominus muscle, nerve entrapment, diagnostic ultrasonography, ultrasound guided nerve block, Carnett’s test, slipping rib syndrome, intercostal nerve
ICD-10 CODE G58.9
Clinical Syndrome
Entrapment of the anterior cutaneous branch of the intercostal nerve is an uncommon and a frequently overlooked cause of anterior abdominal wall pain. The most common site of entrapment is the lateral border of the rectus abdominus muscle. Entrapment of the anterior cutaneous nerve by the lateral border of the rectus abdominus muscle produces a constellation of symptoms consisting of severe knife-like pain emanating from the anterior abdominal wall and associated with the physical finding of point tenderness over the affected anterior cutaneous nerve. The pain radiates medially to the linea alba, but in almost all cases does not cross the midline. This nerve entrapment syndrome occurs most commonly in young women. The patient can often localize the source of pain accurately by pointing to the spot at which the anterior cutaneous branch of the affected intercostal nerve pierces the fascia of the abdominal wall at the lateral border of the rectus abdominus muscle ( Fig. 77.1 ). At this point, the anterior cutaneous branch of the intercostal nerve turns sharply in an anterior direction to provide innervation to the anterior wall. The nerve passes through a firm fibrous ring as it pierces the fascia, and at this point the nerve becomes subject to entrapment ( Fig. 77.2 ). The nerve is accompanied through the fascia by an epigastric artery and vein. There is the potential for small amounts of abdominal fat to herniate through this fascial ring and become incarcerated, which results in further entrapment of the nerve. The pain of anterior cutaneous nerve entrapment is moderate to severe in intensity.
Signs and Symptoms
As mentioned earlier, the patient often can point to the exact spot that the anterior cutaneous nerve is entrapped. Palpation of this point often elicits sudden, sharp, lancinating pain in the distribution of the affected anterior cutaneous nerve. Voluntary contraction of the abdominal muscles puts additional pressure on the nerve and may elicit the pain. The patient attempts to splint the affected nerve by keeping the thoracolumbar spine slightly flexed to avoid increasing tension on the abdominal musculature. Having the patient do a sit-up often reproduces the pain, as does a Valsalva maneuver. Patients suffering from anterior cutaneous nerve entrapment will also exhibit a positive Carnett’s test when the patient is asked to tense his or her abdominal musculature which is indicative of abdominal wall pain rather than pain with an intraabdominal nidus ( Fig. 77.3A and B ).
