Abdominal Cutaneous Nerve Entrapment Syndrome

Overview

Nerve entrapment as a cause of chronic abdominal pain is frequently overlooked. A series of nerves pass through the muscles of the abdomen before reaching the skin to carry sensations. They can get trapped within the muscles leading to severe pain resulting in a condition known as Abdominal Cutaneous Nerve Entrapment Syndrome (ACNES). ACNES affects between 10-30% of patients with chronic abdominal wall pain. A definitive diagnosis of ACNES is obtained by anaesthetising these nerves. Initial management includes education and avoidance of known triggers. It is common practice to inject steroid with local anaesthetic during the diagnostic injections itself to prolong pain relief. Like other nerve entrapment conditions, this is also refractory to medical treatment. Hence repeated injections and nerve entrapment release surgery are commonly carried out. In Aberdeen, a number of patients have been treated for this condition. A cohort of patients have benefitted with injection alone while recurrence has been noted in patients who have undergone surgery. This project aims to gain more understanding about the clinical course of patients with suspected ACNES by evaluation of the clinic progress.

This is a cross-sectional survey, best suited to evaluate the effect of treatments. Potential participants will be identified from a list of patients who have attended the pain clinic at Aberdeen Royal Infirmary for chronic abdominal wall pain. These patients will be invited to participate in the study via posted letter. The letter will include a participant information sheet detailing who is running the study, what the purpose of the study is, what participating in the study requires of a patient and how their information will be used. Patients who wish to participate will return a note of interest, included within the participant information pack, and will then be invited to attend an outpatient clinic in the Aberdeen Health Care and Community Village. Informed consent will be obtained. The questionnaire will be distributed. It is estimated that the questionnaire will take approximately 15 minutes to complete. Each completed questionnaire will be reviewed immediately by a member of the research team to ensure all relevant sections have been completed. Following completion of the questionnaire, patients will be allowed to leave. It is not anticipated that participants will need to be contacted after submitting their completed questionnaire. Participants who explicit express the need for further pain management will be referred to NHS Grampian pain clinic. A response from potential participants will be awaited for 4 weeks. In the event of no response, a maximum of 2 written reminders 4 weeks apart will be sent along with participant information pack. The questionnaires have previously been validated for use in neuropathic pain, and the outcomes of the questionnaire are consistent with those recommended by the 2008 Initiative on Methods, Measurement and Pain Assessment in Clinical Trials (IMMPACT) publication. 17 The questionnaire will consist of four main sections: baseline demographic details, a detailed pain history prior to surgery, including questions from the Brief Pain Inventory, 18 open-ended questions to explore the patient's opinions of both the operation and their health status since and, finally, an overall picture of health using the European Quality of Life-5 Dimensions (EQ-5D) Score 19 and patient global impression of change scale. 20 In order to compare pain both before and after surgery, participants will be asked to complete these sections twice, focusing on their previous health state and their current health. Since pain scores are not routinely collected and all patients will be seen after surgery, pre-operative pain scores will be retrospective.