Background and Aims Anterior cutaneous nerve entrapment syndrome (ACNES) is often overlooked as a cause of chronic abdominal pain. Its classical diagnosis requires clinical observation of the Carnett’s sign. However, treatments’ efficacy remains fairly variable, underlining the need for additional defining criteria. Herein, we suggest that blockade of the rectus sheath may contribute to improve the diagnosis of this syndrome.

Methods A convenience sample of 9 patients presenting the Carnett’s sign were enrolled at the Pain Center (CHU de Strasbourg, France) between November 2020 and November 2021. Patients underwent a blockade of the rectus sheath (5 mL, 1% lidocaine). The procedure was considered successful when patients displayed an immediate ≥70% pain reduction on the visual analogic scale (VAS). Regardless of the efficiency of the anesthetic block, we performed pulsed radiofrequency (PRF) on the anterior cutaneous branch. The nerve was located by ultrasound guidance and sensitive neurostimulation (50Hz, 0.3–0.5V) prior to the treatment (3x2 min, 45V, 42°C). Successful response was considered as a ≥50% pain reduction on the VAS at 6 months.

Results 6 patients responded positively to the rectus sheath block. For each of these patients, the effects of PRF were effective for up to 6 months. Conversely, the rectus sheath block failed for 3 patients. Additionally, PRF was ineffective for each of those 3 patients.

Conclusions These results suggest that rectus sheath block is a promising avenue for the diagnosis of ACNES. Confirmation of these results in larger cohorts may lead to improved guidelines for the clinical care of patients with ACNES.