Abdominal Cutaneous Nerve Entrapment Syndrome: A Treatable Cause of Chronic Groin Pain

Sir, Abdominal cutaneous nerve entrapment syndrome (ACNES) remains a frequently underdiagnosed yet treatable cause of chronic abdominal wall pain. On average, over a year may pass before a definitive diagnosis is reached, often resulting in unnecessary referrals and investigations.[1] The syndrome arises from entrapment of anterior branches of thoracoabdominal nerves, most commonly T11–T12, as they traverse a fibrous neurovascular channel within the rectus abdominis muscle. This anatomical bottleneck predisposes them to ischemic irritation and neuropathic pain, particularly under conditions of repetitive strain, scarring, or myofascial inflammation.[2,3] We report the case of a 46-year-old man with several years of localized, nonradiating lower abdominal pain, prominently over the pubic crest and pubic symphysis. The pain was dull and persistent, with intermittent sharp, electric-shock-like sensations triggered by abdominal wall contraction. Clinical examination revealed Grade II tenderness at the rectus abdominis insertion and a positive Carnett's sign, test is considered to be positive when localized abdominal tenderness remains unchanged or worsens upon tensing of the abdominal muscles (e.g. during a leg-raising maneuver) supporting a myofascial rather than visceral origin, Differential diagnoses such as ilioinguinal neuralgia, Spigelian hernia, and inguinal hernia were considered. Unlike ACNES, Ilioinguinal neuralgia typically radiates to the groin or upper medial thigh; there was no swelling in the inguinal region or lower abdominal wall, even with increased intra-abdominal pressure, making a hernia less likely. Given the clinical suspicion of ACNES, an ultrasound-guided hydrodissection was performed. Using a high-frequency linear probe in the transverse plane, the rectus muscle and its lateral margin (linea semilunaris) were identified. While the cutaneous nerve was not directly visualized, a 22G needle was advanced in-plane beneath the rectus sheath at the site of maximal tenderness. A mixture of 15 mL 1% lignocaine with 40 mg triamcinolone was injected to achieve fascial plane separation, ensuring spread without peritoneal breach [Figure 1].Figure 1: Ultrasound-guided hydrodissection for ACNES: needle placement and spread at the posterior rectus sheathThe patient experienced prompt and substantial relief, with the Numeric Rating Scale (NRS) score decreasing from 8/10 to 3/10. This diagnostic-therapeutic response confirmed the diagnosis of ACNES. He was subsequently prescribed Tolperisone 150 mg daily for 5 days and a 15-day magnesium supplementation course. The patient was followed up monthly for 3 months and remained pain-free with no recurrence of symptoms. Continued outpatient monitoring was advised, with further interventions such as repeat hydrodissection or pulsed radiofrequency (PRF) therapy reserved for recurrence. ACNES typically manifests with localized neuropathic pain aggravated by trunk flexion, Valsalva, or exertion.[4] It is essential to distinguish it from mimics such as ilioinguinal neuralgia, Spigelian hernia, and pelvic pathology, which often present with radiating or visceral pain patterns.[5] While diagnosis remains primarily clinical, high-resolution ultrasound improves accuracy by identifying fascial entrapments and guiding targeted interventions.[6] Treatment begins with local anesthetic and steroid injections. In refractory cases, PRF has shown efficacy, and surgical neurectomy is a last resort.[7] Timely diagnosis is critical to prevent central sensitization and ensure optimal recovery. Raising clinical awareness and integrating imaging-based techniques can minimize diagnostic delays and enhance patient outcomes. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given consent for clinical information and images to be reported in the journal. The patient understands that names and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.