Psychology Unit, College of Science, Health, Engineering and Education, Murdoch University, Perth, Australia.
School of Medicine, University of Notre Dame, Fremantle, Australia.
Pain. 2019 Aug;160(8):1891-1900. doi: 10.1097/j.pain.0000000000001574.
Residual lower-limb pain after low back surgery (postsurgical sciatica) and complex regional pain syndrome (CRPS) involving a lower limb are separate conditions but may share some mechanisms (eg, tissue inflammation, neuroimmune disturbances, and central neuroplasticity). As adrenergically evoked pain contributes, in part, to CRPS, whether an adrenergic mechanism also contributes to postsurgical sciatica was investigated in this study. Immunohistochemistry was used to identify α1-adrenoceptors (α1-AR) on nerve fibres and other targets in the affected and contralateral skin of 25 patients with postsurgical sciatica, and α1-AR expression was investigated in relation to pain and pinprick hyperalgesia after intradermal injection of the α1-AR agonist phenylephrine. In addition, quantitative sensory testing was performed on all 4 limbs and on each side of the forehead. α1-AR expression was greater in keratinocytes (but not blood vessels or nerve fibres) in the symptomatic than contralateral leg, and dermal nerve fibre density was reduced in both legs. However, distal adrenergic involvement in pain in postsurgical sciatica seems unlikely, as neither heightened α1-AR expression in keratinocytes nor reduced dermal nerve fibre density were associated with pain or hyperalgesia to intradermal phenylephrine injection. Sensitivity to pressure-pain, pinprick, and cold-pain was greater in the ipsilateral than contralateral forehead of the entire cohort, but sensory disturbances were most pronounced in patients with additional CRPS-like features. Together, these findings suggest that bilateral distal neuropathy and central neuroplastic changes are involved not only in the pathophysiology of CRPS but also in postsurgical sciatica. This may have treatment implications for patients with postsurgical sciatica.
下腰痛手术后残留的下肢疼痛（手术后坐骨神经痛）和涉及下肢的复杂性区域疼痛综合征（CRPS）是两种不同的疾病，但可能有一些共同的机制（例如组织炎症、神经免疫紊乱和中枢神经可塑性）。由于肾上腺素能诱发的疼痛部分导致了 CRPS，因此本研究旨在探讨肾上腺素能机制是否也与手术后坐骨神经痛有关。采用免疫组织化学方法，在 25 例手术后坐骨神经痛患者的患侧和对侧皮肤中，鉴定神经纤维和其他靶标上的α1-肾上腺素能受体（α1-AR），并研究α1-AR 表达与皮内注射α1-AR 激动剂苯肾上腺素后的疼痛和刺痛性痛觉过敏的关系。此外，还对所有 4 条肢体和前额的每一侧进行了定量感觉测试。与对侧下肢相比，症状性下肢的角质形成细胞（而非血管或神经纤维）中α1-AR 的表达增加，并且两条腿的真皮神经纤维密度均降低。然而，手术后坐骨神经痛中远端肾上腺素能参与疼痛的可能性似乎不大，因为角质形成细胞中α1-AR 表达的增加或真皮神经纤维密度的降低均与皮内注射苯肾上腺素后的疼痛或痛觉过敏无关。整个队列中，同侧前额对压力性疼痛、刺痛和冷痛的敏感性大于对侧前额，但在有类似 CRPS 特征的患者中，感觉障碍更为明显。这些发现表明，双侧远端神经病变和中枢神经可塑性改变不仅与 CRPS 的病理生理学有关，而且与手术后坐骨神经痛有关。这可能对手术后坐骨神经痛患者的治疗有影响。
