van Rijckevorsel Dagmar C, Boelens Oliver B, Roumen Rudi M, Wilder-Smith Oliver H, van Goor Harry
Pain and Nociception Neuroscience Research Group, Department of Surgery, Radboud university medical center, Nijmegen, The Netherlands.
Pain and Nociception Neuroscience Research Group, Department of Surgery, Maasziekenhuis Pantein, Boxmeer, Boxmeer, The Netherlands.
Scand J Pain. 2017 Jan;14:53-59. doi: 10.1016/j.sjpain.2016.09.014. Epub 2016 Nov 4.
10-30% of chronic abdominal pain originates in the abdominal wall. A common cause for chronic abdominal wall pain is the Anterior Cutaneous Nerve Entrapment Syndrome (ACNES), in which an intercostal nerve branch is entrapped in the abdominal rectus sheath. Treatment consists of local anaesthetics and neurectomy, and is ineffective in 25% of cases for yet unknown reasons. In some conditions, chronic pain is the result of altered pain processing. This so-called sensitization can manifest as segmental or even generalized hyperalgesia, and is generally difficult to treat.
The aim of this study was to assess pain processing in ACNES patients responsive and refractory to treatment by using Quantitative Sensory Testing, in order to explore whether signs of altered central pain processing are present in ACNES and are a possible explanation for poor treatment outcomes.
50 patients treated for ACNES with locally orientated treatment were included. They were allocated to a responsive or refractory group based on their response to treatment. Patients showing an improvement of the Visual Analogue Scale (VAS) pain score combined with a current absolute VAS of <40mm were scored as responsive. Sensation and pain thresholds to pressure and electric skin stimulation were determined in the paravertebral bilateral ACNES dermatomes and at four control areas on the non-dominant side of the body, i.e. the musculus trapezius pars medialis, musculus rectus femoris, musculus abductor hallucis and the thenar. The ACNES dermatomes were chosen to signal segmental hyperalgesia and the sum of the control areas together as a reflection of generalized hyperalgesia. Lower thresholds were interpreted as signs of sensitized pain processing. To test for alterations in endogenous pain inhibition, a conditioned pain modulation (CPM) response to a cold pressor task was determined. Also, patients filled in three pain-related questionnaires, to evaluate possible influence of psychological characteristics on the experienced pain.
Patients refractory to treatment showed significantly lower pressure pain thresholds in the ACNES dermatomes and for the sum of as well as in two individual control areas. No differences were found between groups for electric thresholds or CPM response. Duration of complaints before diagnosis and treatment was significantly longer in the refractory compared to the responsive group, and refractory patients scored higher on the pain-related psychological surveys.
In this hypothesis-generating exploratory study, ACNES patients refractory to treatment showed more signs of sensitized segmental and central pain processing. A longer duration of complaints before diagnosis and treatment may be related to these alterations in pain processing, and both findings could be associated with less effective locally orientated treatment. In order to validate these hypotheses further research is needed.
NCT01920880 (Clinical Trials Register; http://www.clinicaltrials.gov).
10% - 30%的慢性腹痛源于腹壁。慢性腹壁疼痛的一个常见原因是前皮神经卡压综合征（ACNES），即肋间神经分支在腹直肌鞘内被卡压。治疗方法包括局部麻醉和神经切除术，但25%的病例因不明原因治疗无效。在某些情况下，慢性疼痛是疼痛处理改变的结果。这种所谓的敏化可表现为节段性甚至全身性痛觉过敏，通常难以治疗。
本研究旨在通过定量感觉测试评估对治疗有反应和难治的ACNES患者的疼痛处理情况，以探讨ACNES患者是否存在中枢性疼痛处理改变的迹象，以及这是否是治疗效果不佳的可能原因。
纳入50例接受局部针对性治疗的ACNES患者。根据他们对治疗的反应将其分为反应性或难治性组。视觉模拟量表（VAS）疼痛评分改善且当前绝对VAS <40mm的患者被评为反应性。在双侧椎旁ACNES皮节以及身体非优势侧的四个对照区域（即斜方肌内侧部、股直肌、拇展肌和鱼际）测定对压力和皮肤电刺激的感觉和疼痛阈值。选择ACNES皮节以显示节段性痛觉过敏，将对照区域的总和作为全身性痛觉过敏的反映。较低的阈值被解释为疼痛处理敏化的迹象。为了测试内源性疼痛抑制的改变，确定了对冷加压任务的条件性疼痛调制（CPM）反应。此外，患者填写了三份与疼痛相关的问卷，以评估心理特征对所经历疼痛的可能影响。
难治性患者在ACNES皮节以及对照区域总和及两个单独对照区域的压力疼痛阈值显著更低。两组在电刺激阈值或CPM反应方面未发现差异。与反应性组相比，难治性组在诊断和治疗前的主诉持续时间显著更长，且难治性患者在疼痛相关心理调查中的得分更高。
在这项产生假设的探索性研究中，难治性ACNES患者表现出更多节段性和中枢性疼痛处理敏化的迹象。诊断和治疗前更长的主诉持续时间可能与这些疼痛处理改变有关，这两个发现都可能与局部针对性治疗效果较差有关。为了验证这些假设，需要进一步研究。
NCT01920880（临床试验注册；http://www.clinicaltrials.gov）
