Schott G D
National Hospital for Neurology and Neurosurgery, London, UK.
Brain. 1994 Apr;117 ( Pt 2):397-413. doi: 10.1093/brain/117.2.397.
For 80 years the sympathetic nervous system has been implicated in certain human pains, notably causalgia and reflex sympathetic dystrophy. This assumption has led to the accepted concept of 'sympathetic dependent' pain. In this critical review, the evidence for this assumption is assessed. It is found that the clinical phenomena suggesting sympathetic nerve involvement may be more satisfactorily attributed to effects of neuropeptides released from afferent C-fibres. The evidence also demonstrates that the effects resembling sympathetic dysfunction relate neither to the pain nor to pain relief following sympathetic blockade. The techniques and results of sympathetic blockade have rarely been adequately evaluated, and the apparent efficacy, specificity and mode of action of peripheral sympatholytic drugs are questioned. An alternative explanation is proposed: that visceral afferents subserve a number of human pains, including those that have been considered sympathetically mediated. Problems of terminology are discussed; use of the term 'visceral afferent' is clarified and broadened to include afferents, particularly those related to blood vessels, which travel within autonomic nerves, in addition to the classical visceral afferent innervation of the organs of the great body cavities. The clinico-anatomical evidence reviewed here indicates that this general and widespread system of afferents could subserve certain pains. The relationship between visceral afferents, somatic afferents and autonomic efferents is outlined, and support is found for the unitary nature of the sensory system envisaged by Langley. Conflicting results from experiments on animals and clinical studies in man on the pain-subserving properties of visceral afferents are summarized; these confirm that visceral afferents can, at least on occasions in man, mediate pain not considered typically 'visceral'. This conclusion receives support from a number of clinical observations: not only are diseases of the autonomic nervous system painless, but damage to previously painless autonomic nerves can generate pain, as illustrated by several different conditions; pain from diseases other than of the viscera of the great cavities and which involves the widespread visceral afferents may be alleviated by sympathetic blockade, presumably since afferents travelling within autonomic fibres are simultaneously blocked; and diseases which impair the function of autonomic nerves may be unexpectedly painless. The central nervous system sequelae following involvement of visceral afferents are outlined and found to be relevant to phenomena sometimes seen with causalgia and related conditions: spread of pain; mirror involvement; associated features such as involuntary movements; and referred pain. Visceral afferents are generally clinically silent unless damage occurs.(ABSTRACT TRUNCATED AT 400 WORDS)
80年来，交感神经系统一直被认为与某些人类疼痛有关，尤其是灼性神经痛和反射性交感神经营养不良。这一假设导致了“交感神经依赖性”疼痛这一被广泛接受的概念。在这篇批判性综述中，对这一假设的证据进行了评估。结果发现，提示交感神经受累的临床现象可能更令人满意地归因于传入C纤维释放的神经肽的作用。证据还表明，类似于交感神经功能障碍的效应既与疼痛无关，也与交感神经阻滞后的疼痛缓解无关。交感神经阻滞的技术和结果很少得到充分评估，外周抗交感神经药物的明显疗效、特异性和作用方式也受到质疑。本文提出了另一种解释：内脏传入神经参与了多种人类疼痛，包括那些被认为是由交感神经介导的疼痛。文中讨论了术语问题；明确并扩展了“内脏传入神经”一词的用法，以包括除大腔体器官的经典内脏传入神经支配外，在自主神经内走行的传入神经，特别是与血管相关的传入神经。本文综述的临床解剖学证据表明，这种广泛分布的传入神经系统可能参与了某些疼痛。文中概述了内脏传入神经、躯体传入神经和自主神经传出神经之间的关系，并为兰利设想的感觉系统的统一性找到了支持。总结了动物实验和人体临床研究中关于内脏传入神经的疼痛传导特性的相互矛盾的结果；这些结果证实，内脏传入神经至少在某些情况下可以介导通常不被认为是“内脏性”的疼痛。这一结论得到了一些临床观察结果的支持：不仅自主神经系统疾病无痛，而且如几种不同情况所示，对以前无痛的自主神经的损伤会产生疼痛；除大腔体内脏疾病外，涉及广泛内脏传入神经的其他疾病引起的疼痛可能会通过交感神经阻滞得到缓解，大概是因为自主神经纤维内走行的传入神经同时被阻断；以及损害自主神经功能的疾病可能意外无痛。文中概述了内脏传入神经受累后的中枢神经系统后遗症，并发现其与灼性神经痛及相关病症中有时出现的现象有关：疼痛扩散；镜像受累；诸如不自主运动等相关特征；以及牵涉痛。除非发生损伤，内脏传入神经在临床上通常是无感觉的。（摘要截选至400字）
