Working Diagnosis:
Anterior cutaneous nerve entrapment syndrome

Treatment:
Patient returned for a diagnostic and therapeutic ultrasound guided anterior cutaneous nerve perineural corticosteroid injection. Two days post-injection, she returned to clinic with concern for post-injection steroid reaction and completed a course of oral steroids with resolution of reaction and significant improvement of symptoms. The patient had recurrence of symptom after one month and was referred to pediatric neurosurgery for planned surgical release and neurectomy procedure with pediatric plastic surgery. Photos below demonstrate the pre and post perineural injection visualization, respectively.
Case Photo #3 , Case Photo #4

Outcome:
The patient had successful surgical release and neurectomy of two anterior cutaneous nerves that were entrapped within the abdominal rectus sheath. At her 3-week post-operative visit, she had resolution of her neuropathic pain and could contract her abdominal muscles without recurrence of symptoms. Patient continued with activity restrictions for an additional 4 to 6 weeks before starting a gradual return-to-play program. She was cleared for full return to sport without restrictions at 3-month follow-up.

Author's Comments:
Anterior cutaneous nerve entrapment syndrome (ACNES) is a rare nerve entrapment condition that can cause unilateral abdominal pain and sensation changes in a well-defined region. The nerve itself starts as the lower intercostal nerves of T8-T12 and runs just deep to the internal obliques until it traverses in a fibrous band through the rectus abdominus to innervate the skin at that level. It is thought that the main cause of entrapment is the sudden turn of the course of nerve through the rectus, although entrapment at the linea semilunaris is a possibility as well. Photo 5 demonstrates the illustrated course of the anterior abdominal cutaneous nerve as it traverses the rectus abdominis.
Case Photo #5
It may be difficult to differentiate abdominal wall pain from visceral abdominal pain. It was apparent in our patient with discrete sensation changes with light touch outlining the distribution of the nerve, but in patients with less clear presentation, other clinical signs such as a positive skin pinch test (hyperesthesia to skin pinch) or Carnett’s sign (increased tenderness to palpation while tensing abdominal muscles and lifting legs and head off bed while supine) can be useful. Ultrasound evaluation can also be helpful in making the diagnosis and would show increased size of the nerve and loss of echotexture distal to the site entrapment as well as possible scar/fibrous tissue attached to an hourglass narrowing of the nerve directly at the site of entrapment. Greater than 50% relief with injection of anesthetic to the nerve is diagnostic as well.
The most conservative treatment options include anesthetic injection and hydrodissection, preferably under ultrasound guidance, with corticosteroids. In resistant cases, chemical neurolysis with alcohol or phenol have been described, as well as radiofrequency ablation. Surgical neurectomy is the definitive treatment in refractory cases.

Editor's Comments:
This is an important case that highlights the recurrent presentations of a patient, challenging diagnosis, and successful management of anterior cutaneous nerve entrapment syndrome (ACNES) in a competitive youth athlete. It is thought to account for approximately 2% all patients presenting to the ED with acute abdominal pain, and although less common, is one providers of multiple disciplines must be familiar with due to its ability to mimic other acute and life-threatening cases of abdominal pain. This often leads to extensive, unnecessary work-ups, repeat visits, prolonged pain and often delayed return to play as discussed in this case (5). Although little literature exists on return-to-play, initial return should focus limit strenuous activities involving the abdominal wall musculature with gradual re-introduction into strength training and sports specific exercises.
This team did an excellent job in weighing previous diagnostic testing, with close re-examination to confirm and treat this rare diagnosis. Their utilization of bedside ultrasound allowed for both the confirmation of ACNES and its subsequent treatment, pointing to its utility and importance in both diagnostic and therapeutic intervention. In the case of ACNES injection has been noted to have a wide range of success in studies from 38% to 87%, with a follow-up duration ranging from 4 weeks to 39 months in pediatric patients (6). Although this patient eventually required surgical intervention, she had an excellent prognosis and successful return-to-play!

References:
1. Chrona E, Kostopanagiotou G, Damigos D, Batistaki C. Anterior cutaneous nerve entrapment syndrome: management challenges. J Pain Res. 2017 Jan 13;10:145-156. doi: 10.2147/JPR.S99337. PMID: 28144159; PMCID: PMC5245914.
2. Pedersen KF, Roumen R, Scheltinga M, Bisgaard T. [Anterior cutaneous nerve entrapment syndrome]. Ugeskr Laeger. 2019 Aug 26;181(35):V02190133. Danish. PMID: 31495364.
3. Schwabl C, Schmidle G, Kaiser P, Drakonaki E, Taljanovic MS, Klauser AS. Nerve entrapment syndromes: detection by ultrasound. Ultrasonography. 2023 Jul;42(3):376-387. doi: 10.14366/usg.22186. Epub 2023 Feb 2. PMID: 37343936; PMCID: PMC10331057.
4. Waldman SD. Pain management. Philadelphia: WB Saunders; 2007
5. Van Assen T, Brouns JA, Scheltinga MR, Roumen RM. Incidence of abdominal pain due to the anterior cutaneous nerve entrapment syndrome in an emergency department. Scand J Trauma Resusc Emerg Med. 2015 Feb 8;23:19. doi: 10.1186/s13049-015-0096-0. PMID: 25887961; PMCID: PMC4327965.
6. Markus J, Sibbing IC, Ket JCF, de Jong JR, de Beer SA, Gorter RR. Treatment strategies for anterior cutaneous nerve entrapment syndrome in children: A systematic review. J Pediatr Surg. 2021 Mar;56(3):605-613. doi: 10.1016/j.jpedsurg.2020.05.014. Epub 2020 May 16. PMID: 32553455.

Return To The Case Studies List.