Sympathetic control of cutaneous blood flow and blood pressure in human spinal cord injury

虽然脊髓损伤会导致神经系统的毁灭性变化，瘫痪和感觉丧失，但人们对交感神经系统的变化知之甚少。交感神经系统与血压、血流和体温的持续控制密切相关。脊髓损伤后可发生交感神经控制丧失。下行通路中断可导致部分或完全丧失胸腰椎节段的交感神经流出。完全分散可导致自主神经反射障碍（自主神经反射亢进），在这种情况下，来自病变下方的感觉刺激引起交感神经驱动血管的反射增加，导致血管收缩。因此，血压可能会突然升高并保持在如此高的水平，从而可能发生中风和（偶尔）心脏骤停。这种现象，自主神经反射障碍，被认为是一种医学紧急情况。自主神经反射障碍的典型主观征象包括抽动性头痛、头部刺痛或鼻塞；病变上方出汗和潮红是促使医务人员测量血压和定位感觉刺激来源的临床症状（通常是膀胱肿胀或结肠受压，有时是压疮或趾甲向内生长）。然而，通常情况下，亚临床发作未被发现，这种无声反射障碍现象越来越受到关注。该项目将开发评估脊髓损伤患者病变下方交感神经系统完整性和状态的方法，并表征反射激活的交感神经元的放电特性。

While spinal cord injury can cause devastating changes in the nervous system paralysis and loss of sensation relatively little is known about changes to the sympathetic nervous system. The sympathetic nervous system is intimately involved in the ongoing control of blood pressure, blood flow and temperature control. Loss of sympathetic control can occur following spinal cord injury. Interruption of descending pathways can result in partial or complete loss of sympathetic outflow from the thoracolumbar segments. Complete decentralization can result in autonomic dysreflexia (autonomic hyperreflexia), in which sensory stimuli originating below the lesion evoke a reflex increase in sympathetic drive to the blood vessels, causing them to constrict. Because of this, blood pressure may rise suddenly and remain at such high levels that stroke and (occassionally) cardiac arrest may occur. This phenomenon, autonomic dysreflexia, is considered a medical emergency. The typical subjective signs of autonomic dysreflexia include a throbbing headache, tingling in the head or nasal congestion; sweating and flushing above the lesion are clinical signs that prompt medical staff to measure blood pressure and to locate the source of sensory irritation (usually a distended bladder or impacted colon, sometimes a pressure sore or ingrown toenail). Commonly, however, subclinical episodes go undetected, and this phenomenon of silent dysreflexia is of increasing concern. This project will develop means of assessing the integrity and state of the sympathetic nervous system below a lesion in patients with spinal cord injury and characterize the firing properties of reflexly activated sympathetic neurones.