Department of Anatomy and Histology and.
Faculty of Dentistry, University of Sydney, Sydney 2006, New South Wales, Australia.
J Neurosci. 2018 Jan 10;38(2):465-473. doi: 10.1523/JNEUROSCI.1647-17.2017. Epub 2017 Nov 24.
Preclinical investigations have suggested that altered functioning of brainstem pain-modulation circuits may be crucial for the maintenance of some chronic pain conditions. While some human psychophysical studies show that patients with chronic pain display altered pain-modulation efficacy, it remains unknown whether brainstem pain-modulation circuits are altered in individuals with chronic pain. The aim of the present investigation was to determine whether, in humans, chronic pain following nerve injury is associated with altered ongoing functioning of the brainstem descending modulation systems. Using resting-state functional magnetic resonance imaging, we found that male and female patients with chronic neuropathic orofacial pain show increased functional connectivity between the rostral ventromedial medulla (RVM) and other brainstem pain-modulatory regions, including the ventrolateral periaqueductal gray (vlPAG) and locus ceruleus (LC). We also identified an increase in RVM functional connectivity with the region that receives orofacial nociceptor afferents, the spinal trigeminal nucleus. In addition, the vlPAG and LC displayed increased functional connectivity strengths with higher brain regions, including the hippocampus, nucleus accumbens, and anterior cingulate cortex, in individuals with chronic pain. These data reveal that chronic pain is associated with altered ongoing functioning within the endogenous pain-modulation network. These changes may underlie enhanced descending facilitation of processing at the primary synapse, resulting in increased nociceptive transmission to higher brain centers. Further, our findings show that higher brain regions interact with the brainstem modulation system differently in chronic pain, possibly reflecting top-down engagement of the circuitry alongside altered reward processing in pain conditions. Experimental animal models and human psychophysical studies suggest that altered functioning of brainstem pain-modulation systems contributes to the maintenance of chronic pain. However, the function of this circuitry has not yet been explored in humans with chronic pain. In this study, we report that individuals with orofacial neuropathic pain show altered functional connectivity between regions within the brainstem pain-modulation network. We suggest that these changes reflect largely central mechanisms that feed back onto the primary nociceptive synapse and enhance the transfer of noxious information to higher brain regions, thus contributing to the constant perception of pain. Identifying the mechanisms responsible for the maintenance of neuropathic pain is imperative for the development of more efficacious therapies.
临床前研究表明,脑干疼痛调节回路功能改变可能是维持某些慢性疼痛状态的关键。虽然一些人类心理物理学研究表明,慢性疼痛患者的疼痛调节效能发生改变,但尚不清楚慢性疼痛患者的脑干疼痛调节回路是否发生改变。本研究旨在确定神经损伤后慢性疼痛是否与脑干下行调制系统的持续功能改变有关。使用静息态功能磁共振成像,我们发现,患有慢性神经性口面痛的男性和女性患者,其脑干疼痛调节区域(包括腹外侧导水管周围灰质和蓝斑)与延髓头端腹内侧区(RVM)之间的功能连接增加。我们还发现,RVM 与接收口面伤害感受器传入的区域(三叉神经脊束核)之间的功能连接增加。此外,在慢性疼痛患者中,vlPAG 和 LC 与大脑更高区域(包括海马、伏隔核和前扣带回皮质)的功能连接强度增加。这些数据表明,慢性疼痛与内源性疼痛调节网络内的持续功能改变有关。这些变化可能是初级突触下行易化加工增强的基础,导致伤害性传入信号向大脑更高区域传递增加。此外,我们的发现表明,在慢性疼痛中,大脑更高区域与脑干调制系统的相互作用不同,这可能反映了疼痛状态下电路的自上而下参与以及改变的奖赏处理。实验动物模型和人类心理物理学研究表明,脑干疼痛调节系统功能改变有助于慢性疼痛的维持。然而,这种电路的功能尚未在慢性疼痛患者中进行探索。在这项研究中,我们报告称,患有口面神经性疼痛的患者在脑干疼痛调节网络内的区域之间存在功能连接改变。我们认为,这些变化反映了主要反馈到初级伤害感受突触并增强有害信息向大脑更高区域传递的中枢机制,从而导致持续的疼痛感知。确定维持神经性疼痛的机制对于开发更有效的治疗方法至关重要。
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