Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 7, 9220 Aalborg Øst, Denmark.
Pain. 2013 Aug;154(8):1318-24. doi: 10.1016/j.pain.2013.04.013. Epub 2013 Apr 9.
Pain hypersensitivity has been consistently detected in chronic pain conditions, but the underlying mechanisms are difficult to investigate in humans and thus poorly understood. Patients with endometriosis pain display enlarged reflex receptive fields (RRF), providing a new perspective in the identification of possible mechanisms behind hypersensitivity states in humans. The primary hypothesis of this study was that RRF are enlarged in patients with musculoskeletal pain. Secondary study end points were subjective pain thresholds and nociceptive withdrawal reflex (NWR) thresholds after single and repeated (temporal summation) electrical stimulation. Forty chronic neck pain patients, 40 chronic low back pain patients, and 24 acute low back pain patients were tested. Electrical stimuli were applied to 10 sites on the sole of the foot to quantify the RRF, defined as the area of the foot from where a reflex was evoked. For the secondary end points, electrical stimuli were applied to the cutaneous innervation area of the sural nerve. All patient groups presented enlarged RRF areas compared to pain-free volunteers (P<.001). Moreover, they also displayed lower NWR and pain thresholds to single and repeated electrical stimulation (P<.001). These results demonstrate that musculoskeletal pain conditions are characterized by enlarged RRF, lowered NWR and pain thresholds, and facilitated temporal summation, most likely caused by widespread spinal hyperexcitability. This study contributes to a better understanding of the mechanisms underlying these pain conditions, and it supports the use of the RRF and NWR as objective biomarkers for pain hypersensitivity in clinical and experimental pain research.
痛觉过敏在慢性疼痛病症中一直被检测到，但由于难以在人体中进行研究，因此其潜在机制尚未被完全了解。患有子宫内膜异位症疼痛的患者表现出扩大的反射感受野（RRF），为在人类中确定过敏状态背后可能的机制提供了新的视角。本研究的主要假设是，肌肉骨骼疼痛患者的 RRF 扩大。次要研究终点是单次和重复（时间总和）电刺激后的主观疼痛阈值和伤害性撤回反射（NWR）阈值。对 40 名慢性颈痛患者、40 名慢性腰痛患者和 24 名急性腰痛患者进行了测试。在足底的 10 个部位施加电刺激以量化 RRF，定义为可以引发反射的足部区域。对于次要终点，在腓肠神经的皮肤神经支配区施加电刺激。与无症状志愿者相比，所有患者组的 RRF 区域均扩大（P<.001）。此外，他们还显示出对单次和重复电刺激的 NWR 和疼痛阈值降低（P<.001）。这些结果表明，肌肉骨骼疼痛病症的特征是 RRF 扩大、NWR 和疼痛阈值降低以及时间总和增加，这很可能是由于广泛的脊髓过度兴奋所致。本研究有助于更好地理解这些疼痛病症的潜在机制，并支持将 RRF 和 NWR 用作临床和实验性疼痛研究中疼痛过敏的客观生物标志物。
