Anterior Cutaneous Nerve Entrapment Syndrome in ...

Journal of Pediatric Surgery xxx (2015) xxx–xxx

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Anterior Cutaneous Nerve Entrapment Syndrome in Children☆,☆☆ Sigrid Bairdain a,⁎, Pradeep Dinakar b, David P. Mooney a a b

Department of Pediatric Surgery, Boston Children’s Hospital, Boston, MA, USA Department of Anesthesia, Boston Children’s Hospital, Boston, MA, USA

a r t i c l e

i n f o

Article history: Received 29 June 2014 Received in revised form 14 January 2015 Accepted 14 January 2015 Available online xxxx Key words: Chronic abdominal pain Nerve blocks

a b s t r a c t Purpose: The purpose of this manuscript is to report on an entity known as Anterior Cutaneous Nerve Entrapment Syndrome (ACNES) and its relevance to chronic abdominal pain encountered in children. Methods: Following institutional review board approval, we retrospectively reviewed patients who underwent operation for presumed ACNES from 2011-2014. Variables reviewed included age, gender, age at surgery, time from onset of pain to surgery, additional medical treatments, and surgery performed. The main outcome measure was amelioration of pain. Results: Nine patients met the study criteria whereby 7 were female and 2 were male patients. Median age at time of surgery was 14 years (range: 10-19 years) and time from onset of symptoms to surgery was 10 months (range: 0.5-60 months). Eight reported complete resolution of the original symptoms in follow-up appointments. One patient reported new, yet similar symptoms on her opposite trunk. Conclusion: ACNES is a reported cause of chronic abdominal pain that can be managed surgically in the pediatric patient once medical management has been optimized. Close collaboration between surgeons and pain specialists helps identify patients who will benefit from surgical interventions and consideration of this condition could result in more timely pain relief in children. Further studies on a larger scale are needed to determine the long-term outcomes of this procedure. © 2015 Elsevier Inc. All rights reserved.

Anterior cutaneous nerve entrapment syndrome (ACNES) is an entity that has gained more awareness in children; yet there is still a paucity of data surrounding its exact etiology, overall incidence, and long-term outcomes. ACNES is often encompassed by the umbrella term, chronic abdominal pain (CAP), and may often be mistaken for other etiologies of chronic abdominal pain [1,2]. Even though there is debate on the utility and sensitivity of physical examinations versus more invasive tests to distinguish ACNES from more common entities, what is known is that there is often a delay in definitive diagnosis and initiation of treatment for this relatively rare condition [2,3]. A recent, double-blinded randomized control trial, showed that surgery for chronic abdominal pain caused by ACNES was both effective and safe in adults [4]. Preliminary results in the pediatric population have also demonstrated similar results to their adult counterparts with respect to local, targeted medical management, as well as for those patients requiring surgery [1,5]. Therefore, the purpose of this report is to thus to detail Anterior Cutaneous Nerve

☆ Funding/Disclosure: None of the authors have commercial associations to disclose. ☆☆ Author Contributions: SB, PD and DPM contributed to the study design, data collection, analysis and the drafting of this manuscript. SB contributed to the editing and proofreading of the initial manuscript. PD and DPM approved the final manuscript. ⁎ Corresponding author at: Pediatric Surgery Research Fellow and Critical Care Fellow, Boston Children’s Hospital and Harvard Medical School, Department of Pediatric Surgery, Fegan 3, 300 Longwood Avenue, Boston, MA 02115. E-mail address: [email protected] (S. Bairdain).

Entrapment Syndrome (ACNES) and its relevance to chronic abdominal pain encountered in a single pediatric surgical population. 1. Patients and methods 1.1. General Methodology Following approval from our Institutional Review Board (IRB# P00009259), a retrospective review was undertaken of the medical records of all patients for whom ACNES was treated operatively from 2011 to 2014 at Boston Children’s Hospital. Those who had other wallrelated pain syndromes were excluded. The international classification of disease code (ICD-9) that was utilized to detect cases of ACNES was 355.9 and the current procedural terminology code (CPT) that was utilized to detect operative cases was 64772. The data points collected included: date of birth, weight at surgery, gender, presence of other medical conditions, injuries, medications, number of previous operations and/or number of other treatments, age and time to operation, perioperative complications, and time to last follow-up. The main outcome measure was the presence of pain symptoms following surgery. No standardized pain scale was utilized for this study but record of utilization of analgesic and narcotic medications were evaluated pre and postoperatively. Adjunctive tests, including ultrasounds (US) and/or contrast studies were at the discretion of the local provider. Physical examination entailed examination of the affected

http://dx.doi.org/10.1016/j.jpedsurg.2015.01.006 0022-3468/© 2015 Elsevier Inc. All rights reserved.

Please cite this article as: Bairdain S, et al, Anterior Cutaneous Nerve Entrapment Syndrome in Children, J Pediatr Surg (2015), http://dx.doi.org/ 10.1016/j.jpedsurg.2015.01.006

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S. Bairdain et al. / Journal of Pediatric Surgery xxx (2015) xxx–xxx Table 1 Demographics of the Study Cohort.

Adipose tissue

External oblique Internal oblique Transversus abdominus

Rectus muscle

Peritoneum

Patient Sex Age (y)

Weight Number of (kg) TAP Blocks

Months to surgery

Follow- Symptoms up still present

1 2 3 4 5 6 7 8 9

34 59.1 62.3 50.5 62.5 42.5 49.2 44.5 51.2

10 12 19 7 2 60 0.5 0.5 30

Y Y Y Y Y Y Y Y Y

M F F F M F F F F

10 14 14 11 17 11 16 19 14

3 2 2 3 1 2 1 3 4

N N N N N N N N N

TAP: Transversus abdominus plane; kg: kilograms; y: years

Figure 1. Under US guidance, a needle was passed along the anteromedial and posteriorolateral direction with deposition of local anesthetic and/or local steroids between the aponeuroses of the internal oblique and transversus abdominis muscles in the affected area as seen in Figure 1.

area paying close attention to trigger points, sensibility over the affected area, dermatomes affected, and referral of pain posteriorly or laterally. 1.2. Transversus Abdominis Plane (TAP) Block Technique Patients identified as having persistent, localized abdominal wall pain and tenderness were considered candidates for TAP blocks as seen in Figure 1. The number of TAP blocks and average length of its affects were recorded. 1.3. Operative Technique Patients who continued to have persistent pain following TAP blocks were referred for surgical intervention. All outpatient procedures were performed under general anesthesia in the supine position. Preoperatively, the area of maximal point tenderness was marked. A small incision was cosmetically placed if possible; if not possible it was made directly over the marked area, dissecting down to the surface of the anterior rectus sheath. A cutaneous branch of the intercostal nerve supplying that dermatome was typically identified coursing through an opening in the fascia at the location of maximal tenderness. Utilizing blunt dissection, the nerve of interest was then freed from the fascial opening so that it was freed from any attachments to the fascia and then divided. The nerve was divided using sharp electrocauterization. A segment of the nerve was sent to pathology to confirm histopathology. A small vessel accompanying the nerve was also usually cauterized. The base of the nerve of interest was allowed to retract back and the fascia was not closed subsequently. Exploration was made for any similar cutaneous nerves within 2 to 3 cm of the maximally tender location and these were similarly freed and divided. The area was then infiltrated with ¼% -Marcaine™ and closed.

ACNES. The remaining 37 patients had other abdominal or other wallrelated pain syndromes. Of the 48 patients diagnosed with ACNES, 9 patients ultimately needed surgery. Their characteristics were described in Table 1. None of the patients had other, associated major anomalies. Seven patients were female and 2 patients were males. Seven out of the nine patients reported that the pain onset was as sudden, following a sporting event, but they denied any overt injuries. On physical examination, the pain was primarily localized to the affected nerve distribution or dermatome and these patients denied lateral (flank) or posterior manifestations. Exquisite, point tenderness, in one particular spot, was often replicated on exam in each patient. The majority of the patients (7 patients) did report pain on the right side, and in the lower abdominal quadrant. Two patients reported pain bilaterally. The patients had received, on average, 2-3 previous ultrasoundguided injections of local anesthetic and/or steroids; full range of 1-5 TAP blocks. The patients tolerated the TAP blocks quite well and there were no complications from those procedures; each one lasting approximately 3 months in each patient. In this cohort, median number of analgesic or narcotic medications prior to surgery were 2 medications (ranging from 1-4 medications). The average time from onset of pain to operation was 10 months (range: 0.5-60 months). Median age at the time of operation was 14 years (range: 10-19 years). One patient had undergone one other surgical intervention for a related pain, whereas the remaining patients had no previous operations for this condition. There were no perioperative complications and patients were discharged the day of the operation. All patients were followed postoperatively for an average of 9 months (range: 1-30 months). Follow-up was performed in both the general surgery clinic and pain service clinics at the discretion of the provider. All nine patients reported improvement in pain and all had returned to activities of daily living. Following surgery, only one patient was still being prescribed a narcotic medication. The site was evaluated for continued point tenderness as well as altered sensibility. Two out of the 9 patients reported altered sensibility (numbness) following the procedure but with gradual improvement over time; this was tested with a swab and was primarily limited to the associated dermatome. One of those patients also reported similar pain on the other side and is continuing to be evaluated by both the general surgeons and the anesthiologists.

1.4. Follow-up Evaluation 3. Discussion Patients were allowed a full activity level afterward. Patients had routine follow-up with both the general surgeon and the pain-care specialist. Number and timing of postoperative visits were at the discretion of the providers. Patients were assessed for pain and medications being utilized, sensibility over the affected area, the presence of other dermatomes being affected, and referral of pain posteriorly or laterally. 2. Results During the study time-period, 85 patients underwent a TAP. Of the 85 patients who underwent a TAP, 48 patients were diagnosed with

This study describes our short-term experience with ACNES at a single children’s hospital. Out of the 85 patients that underwent TAP blocks, 48 patients were ultimately diagnosed with ACNES, and 9 progressed to requiring surgery. Similar to Boelens et al study (2013), we have also shown similar results indicating the resolution of pain in our neurectomy group with minimal complications following failure of one or more conservative treatments [4]. Our study employed the same algorithm of optimizing medical management with TAP blocks and then progressing to surgery only when other options had failed given similar positive results seen in other small series [1,6,7].


S. Bairdain et al. / Journal of Pediatric Surgery xxx (2015) xxx–xxx

The advent and refinement of ultrasound (US)-guided nerve blocks has helped identify the etiology of pain in these children and provided adequate relief in most of the patients seen. One other contemporary study reported full resolution of symptoms with local anesthesia alone [8]. In a smaller subset of patients, these blocks may have a limited longevity, even with the addition of steroid infusion [9]. Thus, this approach requires close coordination between pain clinic personnel and surgeons to best determine which patients are candidates for the operation. We have made it our practice to perform at least 2 to 3 anesthetic injections; if these injections resulted in only temporary pain relief, or no pain relief, we often proceeded to an operation. However, given that most previously reported series are small and long-term outcomes are not know, it remains to be seen if this is the best technique or if it will be supplanted by a technique that is less invasive and/or does not require a general anesthetic. Given that ACNES is still a relatively unknown entity in the pediatric realm, we expect that there are many more children with ACNES that have actually been encountered. Previous studies have suggested that the cause of this pain is nerve entrapment, specifically where the nerve courses through the abdominal wall fascia, and may be irritated secondary to trauma or previous operations [1,10,11]. In our series, only one child had a previous operation in the vicinity of their nerve impingement. A majority of our patients were involved in sporting events antecedent to the reports of pain beginning; however, it did not appear that a specific traumatic incident caused the irritation, but rather repetitive irritation of the abdominal wall fascia. Examining the history of our small number of patients and their results, we believe that the underlying etiology is likely multifactorial, may not have the same etiology as other entrapment syndromes, and that each patient should have an individualized treatment plan from a multidisciplinary team. Given the multidisciplinary management of these children, all of the patients have resumed activities of daily living, have returned to sporting activities, and have seen a decrease in the number of prescribed narcotic medications. Fortunately, no child has suffered a complication of either the TAP block or the surgical procedure in and of itself. There have been a minority of patients (n = 2) that have reported somewhat altered sensation at the specific dermatome; yet all report improvement in sensation over time. This study had important strengths and weaknesses. The main weaknesses are its small sample size and retrospective nature at a single institution. However, we have continued to work quite closely with our anesthesiologists and “acute pain service” counterparts to create a strong collaborative front for this diagnosis and multidisciplinary treatment of these patients. In concordance with contemporary literature, the long-term effects and results of this procedure are not known; thus, data acquisition continues to be in progress. Our hope is that this serves as a clear call to pediatric pain clinics and surgeons in other locations to encourage them to consider this diagnosis when faced with a child with chronic abdominal wall pain.

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4. Conclusion ACNES is a reported cause of chronic abdominal pain that can be managed surgically in a subset of pediatric patients. Close collaboration between surgeons and pain specialists helps identify those patients who will benefit from surgical interventions. Consideration of this rare condition could result in more timely pain relief in children who initially present with chronic abdominal pain. Further studies on a larger scale are needed to determine the long-term outcomes of this procedure but has proven to be safe and effective at our institution. Acknowledgements The authors wish to thank the Anesthesiologists who have provided superb care and have continued to treat these patients. The authors would also like to thank Mr. Christopher Currier for his assistance in data collection and organization. Funding disclosure and conflicts of interest No external funding was secured for this study. The authors have no financial relationships to disclose, as well as no other conflicts of interest to disclose. References [1] Žganjer M, Bojić D, Bumči I. Surgery for Abdominal Wall Pain Caused by Cutaneous Nerve Entrapment in Children-A Single Institution Experience in the Last 5 Years. Iran Red Crescent Med J 2013;15(2):157–60. http://dx.doi.org/10.5812/ircmj.8422 [Published online 2013 February 5]. [2] Towfigh S, Anderson S, Walker A. When it is not a Spigelian hernia: abdominal cutaneous nerve entrapment syndrome. Am Surg 2013;79(10):1111–4. [3] Peleg R. Abdominal wall pain caused by cutaneous nerve entrapment in an adolescent girl taking oral contraceptive pills. J Adolesc Health 1999;24(1):45–7. [4] Boelens OB, van Assen T, Houterman S, et al. A doubleblind, randomized, controlled trial on surgery for chronic abdominal pain due to anterior cutaneous nerve entrapment syndrome. Ann Surg 2013;257(5):845–9. http://dx.doi.org/10.1097/SLA. 0b013e318285f930. [5] Scheltinga MR, Boelens OB, Ten WE Tjon A, et al. Surgery for refractory anterior cutaneous nerve entrapment syndrome (ACNES) in children. J Pediatr Surg 2011; 46(4):699–703. http://dx.doi.org/10.1016/j.jpedsurg.2010.08.054. [6] Ahmed I, Singh S, Rawat JD. Chronic Abdominal Pain in the Child. Saudi J Gastroenterol 2011;17(4):295–6. [7] Goddard JM. Chronic pain in children and young people. Curr Opin Support Palliat Care 2011;5(2):158–63. [8] Akhnikh S, de Korte N, de Winter P. Anterior Cutaneous Entrapment Syndrome (ACNES)-a forgotten diagnosis. Eur J Pediatr 2013. http://dx.doi.org/10.1007/ s00431-013-2140-2. [9] Marhofer P, Harrop-Griffiths P, Willschke H, et al. Fifteen years of ultrasound guidance in regional anesthesia: Part 2—Recent developments in block techniques. Br J Anesth 2010;104(6):673–83. [10] Koppell HP, Thompson WA. Peripheral entrapment neuropathies. Robert Kreiger Publishing companies; 1976. [11] Lindsetmo RO, Stulberg J. Chronic Abdominal wall pain-a diagnostic challenge for the surgeon. Am J Surg 2009;198(1):129–34.
