Re: 몸통 신경포착 탐구!!

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Abdominal Cutaneous Nerve Entrapment Syndrome 

복부 피신경 포착 증후군

ACNES는

복벽 신경(주로 thoracoabdominal nerves, T6~L1 수준)이 entrapment(압박/포획)되어 발생하는 통증 증후군

복통으로 수술을 하는 오류

복부 통증의 많은 경우가 복강 내 문제로 오진되어

불필요한 검사, 입원, 심지어 수술까지 이어집니다.

https://pmc.ncbi.nlm.nih.gov/articles/PMC6220638/

Abdominal Cutaneous Nerve Entrapment Syndrome (ACNES): A Commonly Overlooked Cause of Abdominal Pain - PMC

Introduction Abdominal cutaneous nerve entrapment syndrome (ACNES) may sound like an esoteric condition rarely seen by clinicians but is a common condition. When a patient is seen for abdominal pain without other clinically significant symptoms, ACNES shou

pmc.ncbi.nlm.nih.gov

Abdominal Cutaneous Nerve Entrapment Syndrome (ACNES)는

흔하지만 자주 간과되는 복부 통증 원인.

이 논문(2002년, William V. Applegate 저)은

ACNES의 진단과 치료를 강조하며,

복부 통증 환자에서 복벽(복부 벽) 문제를 먼저 고려해야 한다고 주장.

주요 내용 요약

1. 배경과 중요성

• ACNES는 복벽 신경(주로 thoracoabdominal nerves, T6~L1 수준)이 entrapment(압박/포획)되어 발생하는 통증 증후군
• 복부 통증의 많은 경우가 복강 내 문제로 오진되어 불필요한 검사, 입원, 심지어 수술까지 이어집니다.
• 과거 연구에서 불필요한 검사 비용이 환자당 수백~수천 달러에 달하며, 많은 환자가 불안/우울증 등 정신과 진단을 받기도 합니다.
• 저자 경험상 1차 진료에서 흔히 볼 수 있는 질환(150명당 1~2명)으로, 특히 저녁 진료나 활동이 많은 봄/여름에 급성 사례가 많습니다.

2. 병태생리 (Pathophysiology)

• 신경이 근육/섬유 조직을 통과하며 방향이 급변하는 지점(특히 rectus abdominis muscle 측면)에서 압박, 견인(traction), 또는 herniation(탈출)이 발생합니다.
• 복압 증가, 복근 사용, 복부 팽만, 수술 흉터 등이 유발 요인입니다.
• 신경 다발(neurovascular bundle)이 fibrous ring을 통해 압박되면 국소 부종과 통증이 생깁니다.

3. 임상 양상 (Clinical Presentation)

• 급성: 국소적, 둔하거나 타는 듯한 통증(한쪽), 움직일 때 방사. 젊은 층에서 흔함. 여성은 “난소 통증”으로 호소하는 경우 많음.
• 만성: 간헐적, 수년간 반복. 불안/우울 증상을 동반하기 쉽습니다.
• 통증 위치: T6~T12/L1 수준의 rectus abdominis 가장자리(배꼽, 서혜부 등).
• 다른 질환(충수염, 담낭염, 요로결석, 탈장, 난소 문제 등)과 감별 필요하나, ACNES 환자는 보통 조용히 누워 손으로 아픈 부위를 누르고 있습니다.

4. 진단

• 병력: 정확한 통증 위치 물어보기 (환자가 한 손가락으로 지시).
• 이학적 검사:
  • Carnett’s sign: 복근을 긴장시켰을 때 통증이 유지되거나 증가하면 복벽 원인 (감소하면 복강 내).
  • 신경 출구(foramen) 촉진: rectus abdominis 가장자리의 aponeurotic opening에서 압통.
  • Hover sign: 환자가 “That’s it!” 하며 반응.
• 국소 마취제 주사로 통증이 완전히 사라지면 확진.

이 논문은

ACNES, LACNES, POCNES라는

세 가지 trunk cutaneous nerve entrapment syndrome를 체계적으로 비교·정리한 narrative review입니다.

기존에 ACNES만 잘 알려져 있었던 상황에서,

lateral과 posterior subtype까지 하나의 spectrum으로 통합하여 이해할 수 있는

중요한 conceptual framework를 제공합니다.

1. 연구 배경 및 목적 (Graduate-level context)

• 하부 흉간신경 (T7–T12 intercostal nerves)의 cutaneous branches가 entrapment되어 발생하는 chronic trunk wall pain의 주요 원인.
• 해부학적 분류 (Fig. 1 참조):
  • Anterior branch → ACNES (복부 전벽)
  • Lateral branch → LACNES (측복부·측흉부)
  • Posterior (dorsal) ramus cutaneous branch → POCNES (등·paravertebral)
• 기존 문헌은 각 subtype을 따로 다루었으나, 비교 분석이 부족. 본 review는 PubMed/Cochrane 검색 (2022년 3월 & 9월)으로 ACNES 62편, LACNES 6편, POCNES 3편 + 추가 16편을 종합하여 similarity vs. difference를 강조.

공통 병태생리: 신경이 근육·근막·결합조직을 관통하는 지점에서 fibrous band, scarring, 또는 mechanical compression → neuropathic pain (sharp, burning, allodynia/hyperalgesia).

2. 주요 비교 (Table & Figure 기반)

항목ACNES (Anterior)LACNES (Lateral)POCNES (Posterior)

침범 신경	Anterior cutaneous branch (T7–T12)	Lateral cutaneous branch	Posterior rami cutaneous branch
통증 위치	복부 전벽 (rectus sheath 관통 부위)	측복부·flank (lateral abdomen/chest)	Paravertebral (척추에서 3–5 cm lateral)
빈도	가장 흔함 (복벽 통증의 2–5% 이상)	중간	가장 드물지만 under-recognized
진단 검사	Carnett’s test (+) Pinch test	Pinch test lateral-specific maneuver	Pinch test paravertebral tenderness
Trigger	수술, 임신, 운동, endoscopy	운동, trauma	Trauma, posture
치료 1st line	Trigger Point Injection (TPI)	TPI (ultrasound-guided)	TPI
Refractory	Neurectomy (success 60–70%)	Neurectomy	Neurectomy

• ACNES: Th10–11 level이 가장 흔함. 여성 > 남성 (2:1), median age ~42세. Right side가 약간 더 많음 (right-handed bias?).
• LACNES: Flank pain으로 요로결석, 근육통과 자주 오진.
• POCNES: Back pain으로 척추 질환, facet joint pain과 감별 어려움. 젊은 여성에서 상대적으로 보고 많음.

공통 진단 특징:

• History: 국소적, position/movement-dependent pain.
• Physical: Pinch test (통증 부위를 살짝 꼬집어 당길 때 통증/이상감각 증가) — 매우 유용.
• Imaging: 대부분 normal (MRI/CT negative). US로 indirect finding (nerve swelling) 가능.
• Diagnostic confirmation: US-guided TPI (lidocaine ± steroid) — 진단 + 치료 동시에, >75% positive response.

한 줄 요약:

이 review는

ACNES·LACNES·POCNES를 해부학·임상·치료 측면에서 통합적으로 정리하여,

trunk wall pain의 treatable neuropathic cause로 인식하게 만드는 중요한 bridging paper입니다.

복부·측복부·등 국소 통증 환자에서

Carnett’s/Pinch test를 routine으로 시행할 것을 강력히 권고

나머지는 천천히!!!

ACNES는 복벽통증(abdominal wall pain)의 가장 대표적인 원인으로, 만성 국소 복부통증에서 자주 간과되지만, 대부분의 최신 리뷰에서는 visceral(내장성) 원인이나 functional/disorders of gut-brain interaction(DGBI)과 구분하여 다룹니다. ACNES는 Carnett’s sign 양성 등으로 쉽게 감별되므로, 아래 논문들은 ACNES를 “복벽통증” 카테고리로 언급하면서 그 외 흔한 원인을 체계적으로 정리하고 있습니다.

1. 급성 복부통증(Acute Abdominal Pain, <7일) – 가장 실용적인 최신 리뷰

Yew KS et al. Acute Abdominal Pain in Adults: Eval‎‎uation and Diagnosis. Am Fam Physician. 2023 Jun;107(6):585-595.

• ED에서 가장 흔한 원인 (대형 연구 기반, 20가지 원인이 전체 70% 차지):
  • 급성 위장염 (10.8%)
  • 비특이적 복부통증 (nonspecific abdominal pain, 10.4%)
  • 담석증/cholelithiasis (4.5%)
  • 요로결석/urolithiasis (4.3%)
  • 게실염/diverticulitis & 충수염/appendicitis (각 3.8%)
• 기타 흔한 extra-abdominal 원인: 호흡기 감염, 요로계 문제 (약 10%), 65세 이상에서는 호흡기 원인이 10% 정도.
• 복벽통증(abdominal wall pain, ACNES 포함)은 “less common”으로 별도 언급되며, Carnett’s sign으로 감별.
• 위치별 감별진단 표가 매우 상세 (epigastric, RUQ, RLQ 등).

이 논문은 급성 복부통증의 실제 진료 현장에서 가장 많이 인용되는 실용적 가이드입니다.

2. 만성 복부통증(Chronic Abdominal Pain, ≥3개월) – ACNES 외 원인을 가장 잘 정리한 최신 자료

Paine P. Chronic Abdominal Pain: Practical Approaches. Br J Hosp Med. 2025 Oct 9. (2025년 최신 실용적 리뷰)

• 진단 알고리즘을 제시하면서 ACNES(국소적, Carnett 양성, pinpoint tenderness)와 명확히 구분.
• ACNES 외 가장 흔한 원인:
  • Disorders of gut-brain interaction (DGBI): IBS (가장 흔함, 배변 변화와 연관), functional dyspepsia (상복부, 식사 관련), centrally mediated abdominal pain syndrome (CAPS, 지속적·전신적 통증).
  • Organic visceral 원인 (약 10%): GERD, 소화성궤양, 만성 췌장염, IBD, 담석/담관계 문제, mesenteric ischemia 등.
  • 기타: narcotic bowel syndrome, post-surgical pain, gynecologic/endometriosis (여성), referred pain.
• Brain-gut axis, biopsychosocial 접근 강조. 불필요한 검사·수술·opioid 피하기를 권고.

Merck Manual Professional – Chronic Abdominal Pain and Recurrent Abdominal Pain (2024~2026 업데이트)

• 약 90%가 DGBI (IBS, CAPS).
• 10% 정도가 occult structural/inflammatory/metabolic (adhesions, endometriosis, ovarian cyst 등).
• Carnett’s sign으로 abdominal wall pain(ACNES) 감별 명시.

BMJ Best Practice – Eval‎‎uation of chronic abdominal pain (2026년 2월 업데이트)

• Common differentials (ACNES/복벽통증 포함하지만, 그 외 다수):
  • GERD, 소화성궤양, lactose intolerance, chronic cholecystitis/cholelithiasis, nephrolithiasis, IBS, gastroparesis, functional dyspepsia, CAPS, referred pain.
• Uncommon: Crohn’s, UC, celiac, chronic pancreatitis, 각종 암, porphyria 등.

요약: ACNES 외 가장 흔한 복부통증 원인 (만성 기준)

카테고리흔한 원인특징

DGBI (가장 흔함)	IBS, functional dyspepsia, CAPS	배변 변화·식사 관련, brain-gut axis
위식도·소화기	GERD, peptic ulcer, gastroparesis	상복부, 식후 악화
담·신·췌장	Cholelithiasis, urolithiasis, chronic pancreatitis	위치별 통증 (RUQ, flank 등)
염증·기타	Diverticulitis, IBD, endometriosis (여성)	반복적·염증 징후
Acute overlap	Gastroenteritis, nonspecific pain	급성 악화 시

추천: 만성 통증이라면 Paine 2025 리뷰를 먼저 보시는 걸 권합니다. ACNES 감별 후 DGBI나 visceral 원인을 체계적으로 접근하는 데 가장 실용적입니다. 실제 진료에서는 Carnett’s sign + history + minimal imaging으로 ACNES를 먼저 배제한 뒤 위 원인들을 평가합니다.

1. Lumbar Sympathetic Chain Injury (주로 iatrogenic, OLIF/ALIF 수술 중 압박·traction)

• 위치: L2~L4 vertebral body anterolateral (psoas major 앞, retroperitoneal).
• 최신 논문 (2024): Singhatanadgige W et al. “Incidence and Risk Factors for Lumbar Sympathetic Chain Injury After Oblique Lumbar Interbody Fusion” (Neurospine 2024; PMC11456933).
  • 발생률: 17.5% (255명 OLIF 환자 중).
  • 독립적 위험인자: retraction time >31.5분 (prolonged retraction → traction/compression).
  • 증상: ipsilateral lower limb warmth, edema, sweating abnormality (sympathetic dysfunction), 대부분 transient (3개월 내 회복)하나 영구적일 수도 있음.
  • 임상적 함의: Anterior/lateral lumbar fusion 시 sympathetic trunk가 surgical corridor에 직접 노출되므로 retraction technique 개선과 neuromonitoring 필요.
• 관련 2023 논문: Pan Q et al. “Lumbar Sympathetic Trunk Injury: An Underestimated Complication of Oblique Lateral Interbody Fusion” (Orthop Surg 2023; PMC10102305) — ALIF/OLIF 후 sympathetic dysfunction을 under-reported complication으로 강조.

2. Thoracic Osteophyte (골극)에 의한 Sympathetic Trunk / Greater Splanchnic Nerve 압박

• 위치: Thoracic vertebral body anterolateral (T8–T10 가장 흔함).
• 고전적 근거 (Cadaver study): Nathan H (1987, Spine) — 1,000개 cadaver 중 65.5%에서 osteophyte가 sympathetic trunk/splanchnic nerves 압박 (right side 우세, greater splanchnic nerve 가장 빈번).
• 최신 증례 (2022, 최초 symptomatic clinical report): Jankowski J et al. “Thoracic osteophyte as a cause of symptomatic greater splanchnic nerve compression” (Neurochirurgie 2022).
  • 39세 남성, 2년간 thoracic + upper abdominal pain.
  • T8-9 right anterolateral osteophyte가 greater splanchnic nerve 직접 압박.
  • 치료: Transthoracic osteophytectomy → 수술 후 6개월·2년 follow-up에서 완전 증상 소실, MRI상 완전 제거 확인.
  • 의의: Cadaver 연구는 많았으나 임상적으로 증상 유발 사례는 극히 드물었음. DISH (diffuse idiopathic skeletal hyperostosis)나 심한 spondylophyte에서도 유사 기전 가능.

3. Thoracic Osteoporotic Vertebral Compression Fracture (OVCF)에서의 Sympathetic Nerve Stimulation/Compression

• 기전: Vertebral body collapse → peripheral bulging → anterior longitudinal ligament, vertebral periosteum, paravertebral autonomic plexus (sympathetic afferent fibers) 자극/압박 → referred costal (늑간) pain.
• 최신 논문 (2025): Chen R et al. “Risk factors of costal pain of thoracic osteoporotic vertebral compression fractures: a multicenter retrospective analysis” (Scientific Reports 2025).
  • 425명 OVCF 환자 분석.
  • 독립적 위험인자: middle thoracic level, injured vertebral width ratio 증가 (bulging 정도), foraminal area reduction.
  • 기전 강조: “referred pain due to sympathetic nerve stimulation caused by peripheral bulging of the vertebral body” — 통증이 fracture level과 일치하지 않고 diffuse하며 poorly localized함.

4. Prevertebral Ganglia (Celiac Ganglion) 압박 — Median Arcuate Ligament Syndrome (MALS)

• 위치: Celiac plexus/ganglion (T12-L1 추체 앞, aorta 앞).
• Median arcuate ligament (diaphragm)이 celiac artery + celiac ganglion/plxus를 동시에 압박 → vascular ischemia + neurogenic (neuropathic) pain.
• 최근 trend: neurogenic etiology (ganglion entrapment)가 주요 증상 원인으로 재평가.
• 최신 evidence: 2024–2026 series (Kirk et al. 72 patients 등) — MAL release + celiac plexus neurolysis/ganglionectomy 병행 시 long-term outcome 우수. Diagnostic celiac plexus block 후 효과적인 경우 surgical decompression 권고.

진단·치료 공통점 (Graduate level)

• 진단: CT/MRI (osteophyte/bulging-nerve relationship), diagnostic sympathetic ganglion block (lidocaine ± steroid, US/fluoro-guided).
• 치료: Conservative → Pulsed RF / neurolysis → Surgical decompression (osteophytectomy, MAL release, neurectomy).
• Sympathetic Nerve Entrapment Point Injection (SNEPI, 한국 pain clinic 기법): 2023 Seong JW et al. (PMC10817430) — paravertebral sympathetic entrapment point에 대한 intramuscular injection으로 migraine/cluster headache 등에 사용. Entrapment 가설 기반 치료.

요약 및 임상적 함의 추체 앞 교감신경절 압박·포착은 수술 후 합병증 (OLIF/ALIF), 퇴행성 골극, 압박골절 bulging, MALS (celiac ganglion) 등에서 주로 발생합니다

Intern Med

. 2024 Jan 13;63(16):2231–2239. doi: 10.2169/internalmedicine.2927-23

Three Subtypes of Cutaneous Nerve Entrapment Syndrome: A Narrative Review

Yuki Otsuka 1, Kosuke Ishizuka 2, Yukinori Harada 3, Taku Harada 4, Kiyoshi Shikino 5, Yoshihiko Shiraishi 6, Takashi Watari 6,7,8

• Author information
• Article notes
• Copyright and License information

PMCID: PMC11414353  PMID: 38220195

Abstract

Anterior, lateral, and posterior cutaneous nerve entrapment syndromes have been proposed as etiologies of trunk pain. However, while these syndromes are analogous, comprehensive reports contrasting the three subtypes are lacking. We therefore reviewed the literature on anterior, lateral, and posterior cutaneous nerve entrapment syndrome. We searched the PubMed and Cochrane Library databases twice for relevant articles published between March and September 2022. In addition to 16 letters, technical reports, and review articles, a further 62, 6, and 3 articles concerning anterior, lateral, and posterior cutaneous nerve entrapment syndromes, respectively, were included. These syndromes are usually diagnosed based solely on unique history and examination findings; however, the diagnostic process may be prolonged, and multiple re-eval‎uations are required. The most common first-line treatment is trigger point injection; however, the management of refractory cases remains unclear. Awareness of this disease should be expanded to medical departments other than general medicine.

Keywords: anterior cutaneous nerve entrapment syndrome, lateral cutaneous nerve entrapment syndrome, posterior cutaneous nerve entrapment syndrome, trigger point injection, trunk pain

Introduction

Lower thoracic cutaneous nerve entrapment syndrome, which causes acute or chronic trunk pain, is considered an entrapment neuropathy of the cutaneous branches, mainly the 7th-12th intercostal nerves (1). Trauma or unidentified events can cause entrapment of the terminal parts of these branches, leading to pain (1,2). Anterior cutaneous nerve entrapment syndrome (ACNES), the most common manifestation of this syndrome, was first described approximately half a century ago and has an incidence of 1 in 2,000. However, it is frequently overlooked in clinical practice (3,4).

In addition to ACNES, there are two other types of lower thoracic cutaneous nerve entrapment syndromes: lateral cutaneous nerve entrapment syndrome (LACNES) and posterior cutaneous nerve entrapment syndrome (POCNES) (Fig. 1) (5). LACNES, caused by entrapment of the lateral branches of the lower intercostal nerves, can cause spontaneous lateral chest or flank pain (6). However, POCNES, caused by entrapment of the dorsal branches of the lower intercostal nerves, can cause paravertebral back pain located laterally (3-5 cm) to the spinal process (7).

Figure 1.

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Anatomical image of the cutaneous nerve (horizontal view). Every intercostal nerve separates from the spinal cord through the nerve root segments into dorsal, lateral, and ventral branches to the back muscles, lateral abdomen, and anterior abdominal wall. Each of these can be affected, leading to three subtypes of cutaneous nerve entrapment syndrome.

ACNES, LACNES, and POCNES share a similar pathophysiology, which involves the compression or irritation of peripheral nerves in the abdominal, lateral, and back regions. However, they are often misdiagnosed and treated as cases of unexplained abdominal or flank pain in general internal medicine. A comprehensive analysis and comparison of the three syndromes are essential for improving the diagnosis and management. However, despite the importance of such an analysis, to our knowledge, there are no comprehensive reports contrasting the characteristics of LACNES and POCNES with those of ACNES.

Therefore, we conducted a narrative review of ACNES, LACNES, and POCNES to emphasize the similarities and differences among them and highlight their specific clinical features.

Materials and MethodsStudy design

This narrative review was conducted in accordance with the preferred reporting criteria for systematic reviews and meta-analyses (PRISMA).

Search strategy

We searched for relevant articles on ACNES, LACNES, and POCNES in the PubMed and Cochrane Library databases. Searches were performed on March 3 and September 23, 2022. No filters were used for study design, publication date, or language. Relevant keywords were employed including “anterior,” “lateral,” “posterior,” and “cutaneous nerve entrapment.” See Supplementary material 1 for detailed search formulae. Two authors (YO and KI) performed additional manual searches of the references in the included articles. We used the online systematic review software program Rayyan (https://www.rayyan.ai/) to organize article information.

Selection process

After deleting duplicate records, we employed a two-stage study-selection process. The titles and abstracts were screened for potential relevance, followed by full-text screening. Both screenings were performed independently by two authors (YO and KI). Conflicts were resolved through discussions. We used the following eligibility criteria for the selection process: articles written in English that described ACNES, LACNES, or POCNES, regardless of the study type and design, excluding conference abstracts (Fig. 2).

Figure 2.

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Literature inclusion flow chart. After the initial screening and manual review of titles and abstracts, 100 articles on the 3 subtypes of cutaneous nerve entrapment syndrome underwent full-text screening.

Data extraction

Standardized data collection was independently performed by three authors (YO, KI, and TH) according to the PRISMA and Cochrane Collaboration Guidelines for Systematic Reviews. Before data collection, the authors thoroughly discussed, tested, and revised the data collection form. The following information was obtained from each study: article title, year of publication, author names, journal name, country of origin, study type and design, and participants' ages, sex, body mass index (BMI), symptom characteristics, examinations, interventions, prognosis, and physical limitations.

Synthesis of results

For reports with detailed and concrete descriptions per case, regardless of whether they were original articles or case reports, the characteristics of each participant were extracted and summarized. The number of cases was determined according to sex, impairment level, laterality, and onset triggers per category; the median age was also calculated.

ResultsSearch results

Initial screening of the PubMed and Cochrane Library databases yielded 312 and 19 articles, respectively. Twenty-three duplicate articles were removed, and 208 articles were eliminated based on manual screening of titles and abstracts. Subsequently, full-text screening of the remaining 100 patients was performed, excluding 15 who did not meet the eligibility criteria. Eighty-five articles were included, as follows: 38 case reports, 31 original articles, 9 review articles, and 7 technical reports or letters. Sixteen review articles, technical reports, and letters were excluded from the quantitative review (Fig. 2).

ACNES•Study selection

Sixty articles described ACNES, including 21 single case reports, 10 case series, and 29 original articles (21 descriptive observational studies, 3 comparative observational studies, 4 randomized controlled trials [RCTs], and 1 cross-sectional study). Detailed case descriptions were identified in 61 cases from 31 articles.

•Epidemiology

In 2013, van Assen et al. reported that the preval‎ence of ACNES among patients with abdominal pain who visited their primary care physician was 3.6% in the Netherlands (8). Furthermore, based on a large-scale observational study of 1,116 ACNES cases, Mol et al. reported a median age of 42 (range, 7-81) years old (9). ACNES may occur in children or adults but is more common in younger patients than in older ones. The proportion of women was more than twice that of men in all observational studies, and the same trend was observed in the case reports (19 men and 42 women). No racial differences were observed between the groups. Most observational studies were conducted in Western countries, whereas most of the case reports were from Japan (10 articles, 32%). This does not necessarily indicate regional differences in incidence but rather that the disease may be unrecognized in some countries.

•Symptom triggers

Abdominal surgery (n=10), gastrointestinal endoscopy (n=7), pregnancy (n=4), and exercise/sports (n=2) were reported triggers of ACNES. ACNES reportedly occurs in open abdominal and minimally invasive laparoscopic surgery. Both upper and lower endoscopies have been reported (10). Notably, some cases were reported after kiteboarding or were apparently triggered by the use of low-dose estrogen progestin (11,12). However, idiopathic cases were the most common, accounting for ＞50% of cases (9,13-20).

•Symptom characteristics

Patients with ACNES typically complained of pain localized to areas of a single anterior cutaneous nerve distribution, such as Th7-12 and the anterior part of the abdomen from the pericardium to the inguinal region (Fig. 3). Cases involving Th10 and 11 were particularly common (Table 1), although lumbar cutaneous nerve entrapment may also cause the disease in rare cases (21). Furthermore, some cases involved multiple anterior cutaneous nerve areas.

Figure 3.

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Course of the anterior cutaneous nerves. The abdominal wall is innervated by the cutaneous branches of six paired lower intercostal nerves (Th7-12) penetrating the rectus abdominus sheath.

Table 1.

Distribution of the Levels of Impaired Anterior Cutaneous Nerves.

Th5Th6Th7Th8Th9Th10Th11Th12L1L2

(22)		n=9	11%	11%	11%		33%	44%	22%	22%	11%	11%
(10)		n=1,116			2%	9%	13%	27%	34%	14%
(19)	Bilateral	n=142			3%	10%	15%	29%	27%	16%
	Unilateral	n=970			2%	9%	13%	28%	34%	14%
(18)		n=495			1%	8%	11%	24%	37%	18%
(23)		n=38				11%		89%
(24)		n=30				3%	17%	7%	40%	3%
(36)		n=6					17%	17%	67%
Case reports*		n=23			9%	4%	22%	26%	26%	7%		4%

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Some cases involved multiple levels; two cases in Th8+9, one in Th8+9+10, one in Th8+11, one in Th9+10, one in Th10+12, one in Th10+11+12, and two in Th11+12.

*: list of the included literature is provided in Supplementary material 2

Pain was often rated ≥7/10 on a numerical scale. Pain is usually described as sharp, although descriptions vary, and occurs predominantly on the right side (61%, 62%, 63%, 68%, and 74%, respectively) (4,15,19,22,23); however, many left-sided bilateral cases have been reported (12,24). The reason for the higher preval‎ence of right-sided ACNES than left-sided remains unclear; however, it could be inferred that it is more common on the right side because of the global preval‎ence of right-handed individuals and the fact that many people exert more effort on their right side. The pain may be persistent or intermittent and may be induced by supine positioning or repositioning. Exercise can be an exacerbating or triggering factor (25). Therefore, daily school activities are impaired in most pediatric cases (26).

•Time to the diagnosis

The median time from symptom onset to the ACNES diagnosis ranged from 6 months to 2 years; however, 31% of patients experienced pain for ＞1 year, and 1 in 8 patients experienced it for ＞5 years (13). The time to the diagnosis was much longer in bilateral cases (18 vs. 23 months) than in unilateral cases (18). Notably, some cases are reportedly challenging to diagnose, with some taking as long as 13 years from the onset to the diagnosis (27).

•Physical findings

Abdominal tenderness localized to a pinpoint area within a few square centimeters is a characteristic finding in ACNES. Furthermore, a positive Carnett's sign at the point of tenderness is helpful because it indicates that pain originates from the abdominal wall. However, Carnett's sign was negative in approximately 10% of cases (9,13,18). Other physical findings associated with this disease include hypoesthesia, hyperalgesia, allodynia, and positive pinch test (using the thumb and index finger to “pinch” and lift the skin around the tender point, eliciting a painful response compared to the contralateral side) around the tender areas, with a positive result being found in approximately 80% of cases (9,18). Although there are still no consensus diagnostic criteria for ACNES, the following 7 items were included in the diagnostic criteria in several randomized controlled trials: 1) at least 1-3 months of locoregional abdominal pain; 2) unilateral single tender spot in the abdominal area (tender point); 3) constant site of abdominal tenderness with a small (＜2 cm) area of maximal intensity (tender point/trigger point) situated within the lateral boundaries of the rectus abdominis muscle; 4) tenderness increased by abdominal muscle tensing using Carnett's test; 5) the presence of somatosensory skin disturbances, such as altered cool sensation, hypoesthesia, or hyperesthesia covering the tender point; 6) normal laboratory findings (e.g. C-reactive protein, leukocyte count, and urine sedimentation); and 7) no abnormal abdominal imaging findings (if previously performed) (19,20,28,29). However, the sensitivity and specificity of these findings remain unclear.

•Examinations

Numerous patients were accurately diagnosed within a short timeframe, thereby avoiding superfluous tests, when the physicians possessed sufficient expertise in the symptomatic manifestations of ACNES. However, during a prolonged disease course, patients are often subjected to various examinations, including blood tests, abdominal ultrasound, computed tomography (sometimes with contrast), magnetic resonance imaging or angiography, upper and lower endoscopies, gynecological examinations, and, in some cases, even more invasive tests, such as surgical procedures (28,30). ACNES is a disease that does not show any abnormal findings on these examinations; therefore, there have been several cases in which patients were suspected of having a somatic symptom disorder or were referred to a psychiatrist during the long course of their illness (Table 2) (31-33). Despite the patients experiencing abdominal pain, only 3 cases each were diagnosed in the gastrointestinal and surgical departments, whereas 6 were diagnosed in the general department among the 19 cases for which information on the diagnosing department was clearly stated.

Table 2.

Differential Diagnoses of the Three Subtypes of Cutaneous Nerve Entrapment Syndrome.

ACNES (31-33)LACNES (44)POCNES (49)

• Hernias	• Somatic symptom disorder	• Thoracic wall abnormality (hematoma, endometriosis, tumor, tear)
• Tumors	• Abdominal myofascial pain syndrome	• Radiculopathy (traumatic, diabetic)
• Tears	• Abdominal wall abnormality (hematoma, endometriosis, tumor, tear)	• Slipping rib syndrome
• Endometriosis of the abdominal wall	• Radiculopathy (diabetic, traumatic)	• Scar tissue
• Radiculopathy (diabetic, traumatic, herpetic)	• Scar tissue	• Myofascial pain syndrome
• Herniated vertebral disc	• Slipping rib syndrome	• Rib abnormalities
• Rib and vertebral column abnormalities	• Rib abnormalities	• Postherpetic neuralgia
	• Postherpetic neuralgia	• Neurofibroma
	• Neurofibroma	• Schwannoma
	• Schwannoma	• Herniated disc
	• Herniated disk	• Epidemic pleurodynia (Bornholm disease)
	• Epidemic pleurodynia (Bornholm disease)

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•Treatment

Trigger point injection (TPI) is the most commonly performed treatment, as reducing pain to ＜50% by injection is considered helpful in diagnosing ACNES. In the reviewed cases, the effect was confirmed within 15 min of injection, and the temporary response rate was 97% (26,34). However, the percentage of patients who become pain-free or are in remission ranges from 20% to 60% (9,15,18,23); therefore, TPI is usually repeated. Furthermore, several RCTs revealed no significant difference in response rates based on whether the injections were performed freehand or under ultrasound guidance (20). These RCTs also indicated that the subcutaneous fatty tissue thickness did not affect the response rate. Local anesthetics, such as lidocaine, xylocaine, bupivacaine, and ropivacaine, can be used as injectable agents. Notably, some patients responded by adding steroids (methylprednisolone or betamethasone) to anesthetics (25,26). However, studies that directly compared the addition of steroids to local anesthetics alone showed no significant differences in response rates (16). Pulsed radiofrequency (PRF) has been reported to have a higher success rate than TPI (24% vs. 42%) (9); however, one study reported that PRF was ineffective in the long term in 80% of cases (15).

Neurectomy was considered when TPI and/or PRF were ineffective. In an outlier report, all patients responded to neurectomy; however, the sample size was small, with only a few cases (35), and approximately 60-80% of patients responded to neurectomy. However, only patients for whom other treatments had failed were included (17,36,37). Furthermore, approximately 60% of patients require reoperation (38). The posterior approach may be an option in the event of unsuccessful initial neurectomy, in addition to repetition of the same surgery. There has been a report of a patient successfully treated after three surgeries (32). An RCT of 44 patients comparing neurectomy and sham surgery demonstrated the benefits of neurectomy (16 vs. 4 patients) (29).

Relatively rare treatments include chiropractic care (39), peripheral nerve stimulation, (40,41) dorsal root ganglion stimulation (21), and botulinum toxin injections (42).

LACNES•Study selection and epidemiology

Six articles, including four single case reports, one case series, and one descriptive observational study describing LACNES, were identified. Seven cases (including 1 complicated by ACNES) were described in 5 case reports, whereas 30 were reported in a descriptive observational study (43). Among the 37 reported cases, the median age was 51.0 (range: 32.0-59.0) years old, and 27 patients were women (73.0%). Two of these five case reports were published in the 1990s. The remaining 3, reported 20 years later in 2021, were from Japan (44-46), suggesting that the preval‎ence or awareness of the disease in Japan may be rapidly increasing.

•Time to the diagnosis

The average onset-to-referral time was 18 (range: 3-360) months (43). Cases reported in the 1990s required months to years before a diagnosis was made, whereas those reported in 2021 required only a few days (45,46).

•Triggers of symptoms

Similar to ACNES, triggers for LACNES often remain unspecified. However, spontaneous movements, such as trying to pick up objects (6,44), compression fractures, or pregnancy, have been considered (6,46).

•Pain characteristics

Patients often described their symptomatology as sudden-onset, sharp, and severe flank pain. The pain associated with LACNES is sometimes intermittent, aggravated by trunk movements, such as rotation and lateral bending, and relieved in the supine position (47). Of the 37 reported LACNES cases, 12 were left-sided and 25 right-sided. The impairment levels were as follows: Th7 in four cases; Th8, in five cases; Th9, in nine cases; Th10, in four cases; Th11, in seven cases; Th12, in one case, and Th10+Th11 in one case (Table 3).

Table 3.

Distribution of the Levels of Impaired Lateral and Posterior Cutaneous Nerves.

Th5Th6Th7Th8Th9Th10Th11Th12L1L2

LACNES *	n=37			11%	14%	24%	11%	19%	3%
POCNES	n=16			6%	19%		6%	19%	50%

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*: One case involved in multiple levels (Th10+11).

•Physical findings

The diagnostic criteria for LACNES proposed in 2017 require three of the following four criteria (43): 1) a three-month-or-longer history of locoregional pain; 2) a constant area of tenderness in the flank covering a small fingertip point of maximal pain in the midaxillary line; 3) a larger area of altered skin sensation, such as hypoesthesia, hyperesthesia, or altered cool perception, covering this maximal pain point, but not necessarily corresponding to a specific complete dermatome; and 4) a positive pinch test.

•Differential diagnoses and examinations

Abdominal myofascial pain syndrome, abdominal wall pain (hematoma, endometriosis, tumor, and tear), radiculopathy (diabetic and traumatic), scar tissue, slipping rib syndrome, rib abnormalities, postherpetic neuralgia, neurofibroma, schwannoma, and herniated disk have been proposed as differential diagnoses of LACNES (Table 2) (44). Patients were usually investigated through imaging and laboratory tests before the diagnosis was made; these were not required for a diagnosis but were performed in all 30 cases. Reports from the 1990s were from family medicine physicians, and all reports from 2021 were from general medicine departments.

•Treatment

Classically, a mixture of bupivacaine and betamethasone has been used (6,47); however, recently, a local injection of approximately 5-10 mL of 1% lidocaine has been commonly utilized. The pain improved quickly, usually within 10 minutes. If ineffective, a combination of 40 mg methylprednisolone was reportedly successful in the long term in 53% of cases (43). The low efficacy of additional steroids in LACNES patients was consistent with that in ACNES patients.

POCNES•Study selection and epidemiology

Only 3 studies, including 2 case reports and a descriptive observational study with 14 patients, concerning POCNES were available (7,48,49). Of the 16 total patients, 14 were women (87.5%), and the median age was 26 years (range: 20.5-44.5 years). Notably, 6 patients (37.5%) had a history of ACNES. This observational study was conducted in the departments of general surgery of two hospitals in the Netherlands, where surgeons from both centers had a special interest in the management of chronic pain syndromes of the abdominal wall and groin (48). One patient from the Netherlands was referred to the abdominal wall pain research group (7), and the other patient from Japan was referred to the general medicine department (49).

•Time to the diagnosis

The median onset-to-diagnosis time was 22 (range: 5-48) months in an observational study (48). In contrast, in the most recent case report, the diagnosis was made within only two weeks from the onset (49), underscoring the importance of raising awareness of POCNES for its timely diagnosis.

•Triggers of symptoms

Unfortunately, there is no description of the triggers of symptoms in POCNES in the current published articles.

•Pain characteristics

Patients with POCNES complained of neuropathic pain, such as severe, sharp back pain (7,48,49). The pain was exacerbated by standing or trunk movements and attenuated by lying down (7,49). Regarding the involved nerve levels, most cases were at the Th11 and Th12 vertebral levels; indeed, 11 of 16 patients (68.9%) had impaired Th11 or Th12 (Table 3) (7,48,49). There was no significant laterality; however, there were two bilateral cases (48).

•Physical findings

Localized tenderness of a 2×2-cm2 area with positive pinching, allodynia, or hypoesthesia appears to be a characteristic physical finding of POCNES (7,49). An observational study defined POCNES using the following five inclusion criteria: 1) a three-month-or-longer history of locoregional back pain; 2) a localized circumscriptive area of tenderness lateral to the spinous process covering a small and predictable point of maximal pain; 3) a large area of skin somatosensory abnormalities (such as hypoesthesia, hyperesthesia, and/or altered cool perception) overlying this maximal pain point; 4) local pressure on the tender point resulting in a predictable, severe pain response; and 5) normal laboratory and imaging findings (48). The pinch test results were positive in 13 patients (48).

•Differential diagnoses and examinations

Thoracic radicular pain, thoracic facet pain, and thoracolumbar syndrome (Maigne syndrome) were included as differential diagnoses (Table 2). Furthermore, thoracic wall abnormalities (hematoma, endometriosis, tumor, and tear), radiculopathy (traumatic or diabetic), slipping rib syndrome, scar tissue, myofascial pain syndrome, rib abnormalities, postherpetic neuralgia, neurofibroma/schwannoma, herniated disc, and epidemic pleurodynia (Bornholm disease) have been proposed as differential diagnoses (Table 2) (49).

•Treatment

Similar to the treatment for ACNES and LACNES, 2-5 mL of 1% lidocaine injection to the tender point has been reported as the preferred first-line treatment for POCNES. Lidocaine injection at the tender point was effective in 75% of patients (49). In some patients, pain relief lasted for several weeks. Eleven of the 14 patients underwent neurectomy; however, some pain persisted.

Discussion

In the present study, we reviewed all existing reports on the three subtypes of lower thoracic cutaneous nerve entrapment syndrome. The concept of ACNES was first established, and LACNES and POCNES were later proposed based on this concept. Each syndrome is characterized by pain-in the anterior, lateral, and posterior lower trunk for ACNES, LACNES, and POCNES, respectively-due to the corresponding intercostal nerve branch entrapment (Fig. 1). Concordantly, the other branches are likely to produce referred pain, which might explain why the three subtypes occasionally complicate each other.

The pain characteristics and physical findings of the three subtypes may be similar, because they share the same pathophysiology. Of the physical findings, only Carnett's sign, which determines whether the pain originates from the abdominal wall, is specific to ACNES, because only the anterior aspect of the abdomen can be intentionally stiffened or softened. The three subtypes are similar in that the lower thoracic spine is more likely to be affected and all three conditions are more common in women for unclear reasons.

The most substantial challenge associated with these three subtypes is the lack of a specific objective diagnostic method. Patients misdiagnosed with visceral pain are at risk of undergoing various unnecessary examinations. If the test results are inconclusive, patients may be treated for medically unexplained symptoms or indefinite complaints. Therefore, visceral and organic diseases and other painful disorders must be excluded (Table 2); however, a careful examination of the patient will quickly reveal that the pain is localized to the skin or just below it rather than in the viscera.

A successful differential diagnosis can only be made by determining the characteristics of symptoms. Imaging studies are valuable in ruling out other diseases. Non-contrast abdominal computed tomography or spinal magnetic resonance imaging may be of particular priority in differentiating other diseases that may cause abdominal wall pain. Clinicians, however, must exercise greater diligence in documenting a patient's pain history and conducting abdominal physical examinations. Any trunk pain with a positive Carnett's sign, hypoesthesia, hyperalgesia, allodynia, or positive pinch test around the tender areas may be ACNES, LACNES, or POCNES.

These syndromes are often diagnosed in general medicine departments, and physicians continue to play an important role in treating these syndromes. The awareness of ACNES, LACNES, and POCNES among clinicians is likely not substantially high, and the number of undiagnosed cases should be reduced by increasing the awareness of these syndromes and the diagnostic skills of physicians, especially those in gastroenterology and/or orthopedic departments, who are likely to consult patients with trunk pain. The risk of disease occurrence based on ethnicity has not been specifically reported; however, the regional differences in the origin of previous reports may be attributed to inequalities in region-based disease awareness. These diagnoses remain heavily reliant on the competencies of physicians performing the physical examination; hence, they cannot be fully replicated with technological tools.

Among the three subtypes, evidence concerning the treatment of ACNES is gradually increasing, whereas our knowledge regarding LACNES and POCNES remains limited. Neurectomy has been indicated for LACNES and POCNES when TPI is ineffective. However, several aspects, including the optimal solution and appropriate response to refractory cases, remain unexplored. Surgical treatment is burdensome for patients; therefore, less invasive treatment strategies may be sought based on this disease concept. Furthermore, owing to the limited number of prospective studies on all three syndromes, guidelines for the diagnosis and treatment must be developed by including a larger number of cases in the future. Concerted efforts should be undertaken to increase the exposure of clinicians and students to this medically explainable and treatable but still elusive disease.

Several limitations associated with the present study warrant mention. First, the search formula was designed to be sufficiently broad to collect as much literature as possible without missing references; however, the calls for the three subtypes were indefinite and might have been omitted. Second, references may have been missed during collection because English was the only target language. Despite these limitations, this study provides novel insights.

Conclusions

We comprehensively reviewed previous reports on the three subtypes of lower thoracic cutaneous nerve entrapment syndrome. All three subtypes have a well-established disease basis for pain caused by impairment of a branch of the intercostal nerve; however, the diagnosis can be problematic and protracted owing to the lack of laboratory and imaging abnormalities. Conversely, characteristic physical findings are helpful for the diagnosis. Therefore, these syndromes must be considered during differential diagnoses; a thorough collection of the medical history and a targeted physical examination is necessary to facilitate the early diagnosis and treatment.

The authors state that they have no Conflict of Interest (COI).

Acknowledgement

We thank Dr. Ashwin Gupta for his advice on this study. We also thank the Japanese Non-surgical Orthopedics Society Academic Support (https://academic.jnos.or.jp/) for illustrating Figure 1, 2.

References

• 1. Kamboj AK, Hoversten P, Oxentenko AS. Chronic abdominal wall pain: a common yet overlooked etiology of chronic abdominal pain. Mayo Clin Proc 94: 139-144, 2019. [DOI] [PubMed] [Google Scholar]