A Pilot Study to Explore the Use of Skin Biopsy as Diagnostic Tool in Anterior Cutaneous Nerve Entrapment Syndrome (ACNES)

Study Overview
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Brief Summary
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ACNES is a neuropathic pain condition of the abdominal wall. It is a clinical diagnosis based on patient's history and physical examination. No diagnostic test is available to confirm the diagnosis. This pilot study will determine if skin biopsies can be used as diagnostic test. Two 3mm biopsies will be taken and used to count the small nerve fibres in the skin. The number of small nerve fibres of the painful skin will be compared to non-painful skin. Skin biopsy and small fibre nerve count is already used as diagnostic test in patients with small-fibre neuropathy. The investigators hypothesize that patients with ACNES will have a reduced number of small nerve fibres in the affected skin, compared to the non-affected skin.

Official Title
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Skin Biopsy as Diagnostic Tool in Anterior Cutaneous Nerve Entrapment Syndrome (ACNES): A Pilot Study

Conditions
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Anterior Cutaneous Nerve Entrapment Syndrome, Nerve Entrapment Syndrome, Chronic Pain Syndrome, Diagnosis

Intervention / Treatment
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* Procedure: Skin biopsy


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Duration of pain >3 months Newly diagnosed unilateral ACNES Fully completed intake questionnaire Obtained written informed consent Exclusion Criteria: Inability to understand Dutch language Bilateral ACNES Previously administered injections with corticosteroids at trigger point (injection with a local anaesthetic is allowed) Previous Pulsed Radiofrequency (PRF)-treatment at trigger point History of open abdominal surgery History of neurectomy Known neuromuscular or neurodegenerative disease Antiplatelet or anticoagulants use or known coagulation disorders Disorder known to cause a reduced IENFD; Diabetes Hypothyroidism Renal failure Vitamin B12 deficiency Monoclonal gammopathy Alcohol abuse (>5 IU a day) Malignancies Medication that cause neuropathy (for example chemotherapy)

Ages Eligible for Study
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Minimum Age: 21 Years
Maximum Age: 50 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Diagnostic
Intervention Model: Single Group Assignment
Interventional Model Description: Skin biopsies will be performed on patients with an unilateral ACNES. Biopsies will be taken at the triggerpoint (affected side) and contralateral, non-affected side of the abdominal wall. Affected vs non-affected will be compared. The non-affected side serves as control.
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Patients with unilateral ACNES<br> | Procedure: Skin biopsy<br>* Two 3mm skin biopsies from the abdominal wall will be taken. One at the triggerpoint of the pain, the second one at the contralateral, non-affected side of the abdominal wall. Lidocaine will be used for local anaesthesia of the skin, before the biopsies will be taken.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Intraepidermal Nerve Fibre density (IENFD) | Difference in IENFD (measured in IENF/mm) from both affected and non-affected side of the abdominal wall. | Both biopsies will be taken at the same time, as their difference will be studied. The biopsies will be taken at the second outpatient visit, 2 or 3 weeks after the first visit, just after the second triggger point injection (standard of care). | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Pain score | Average pain score, assessed using the Numeric Rating Scale (NRS) 0-10 before start of treatment. 0 no pain, 10 worst possible pain. | Assessed at first outpatient visit, used as baseline data. | 
| Duration of pain | Duration of pain in months before diagnosis | Assessed at first outpatient visit, used as baseline data. | 
| Treatment response | Patients will receive standard of care treatment for ACNES. Treatment is unsuccessful if <50% pain reduction or when patients are not satisfied with their pain relief and want additional treatment. | Treatment response will be assessed 2 to 6 weeks after each treatment (trigger point injections, PRF and neurectomy), as standard of care. | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Diagnostic test for ACNES, Intraepidermal nerve fibre density (IENFD)