Gupta Vinod Kumar
Dubai Police Medical Services, Dubai, United Arab Emirates.
Pain Med. 2006 Sep-Oct;7(5):386-94. doi: 10.1111/j.1526-4637.2006.00216.x.
Scalp injection of botulinum toxin type A (BT-A) into the superficial musculature has evoked interest in the management of migraine headache. In clinical trials, prevention of migraine attacks for 3 months or more has been seen in some patients following BT-A scalp injections. In the majority of pain syndromes where BT-A is effective, inhibition of muscle spasms appears to be an important component of its activity. A direct or independent and prolonged analgesic action unrelated to skeletal muscle relaxation is believed to underlie the prophylactic efficacy of BT-A in migraine; peripheral and central modulation of pain impulses by BT-A has also been proposed. A direct peripheral antinociceptive effect was not seen in three controlled studies of BT-A in normal human volunteers. Experimental evidence for BT-A-induced analgesia in rats is suggestive but dose-dependent and lasts only 2 weeks. In migraine patients, a consistent or dose-dependent response to BT-A treatment has not been seen. Peak responses to BT-A in migraine patients are seen at 8-12 weeks, whereas BT-A-affected nerve endings in mice fully recover function between 63 and 91 days; the difference in species limits the interpretation of this dissonance. As BT-A does not normally cross the intact blood-brain barrier, meningeal nociceptors appear unlikely to be influenced by scalp injections of BT-A; the possibility of antidromic transfer of BT-A in the trigeminovascular system should be considered. The extended period for which migraine prophylaxis might be required, the antigenic and headache-provoking potential of BT-A, the inability of BT-A to affect central neuronal processes significantly, including the aura of migraine, the possible placebo effect of needling, and purely subjective outcome measures in headache studies are additional concerns in evaluating this treatment strategy. The clinical utility of BT-A has not been compared against established migraine prophylactic agents. The efficacy of BT-A in preventing migraine headache attacks remains controversial and the underlying scientific rationale is debatable.
向浅表肌肉组织头皮注射A型肉毒杆菌毒素（BT - A）已引起人们对偏头痛治疗的关注。在临床试验中，一些患者在接受BT - A头皮注射后，偏头痛发作得到了3个月或更长时间的预防。在BT - A有效的大多数疼痛综合征中，抑制肌肉痉挛似乎是其作用的一个重要组成部分。据信，与骨骼肌松弛无关的直接或独立且持久的镇痛作用是BT - A预防偏头痛的疗效基础；也有人提出BT - A对疼痛冲动的外周和中枢调节作用。在三项针对正常人类志愿者的BT - A对照研究中，未观察到直接的外周抗伤害感受作用。在大鼠中，BT - A诱导镇痛的实验证据具有提示性，但呈剂量依赖性且仅持续2周。在偏头痛患者中，尚未观察到对BT - A治疗的一致或剂量依赖性反应。偏头痛患者对BT - A的峰值反应出现在8 - 12周，而小鼠中受BT - A影响的神经末梢在63至91天之间完全恢复功能；物种差异限制了对这种不一致性的解释。由于BT - A通常不会穿过完整的血脑屏障，脑膜伤害感受器似乎不太可能受到BT - A头皮注射的影响；应考虑BT - A在三叉神经血管系统中逆行传递的可能性。评估这种治疗策略时，还需考虑偏头痛预防可能需要的较长时间、BT - A的抗原性和引发头痛的可能性、BT - A对包括偏头痛先兆在内的中枢神经元过程的显著影响能力不足、针刺可能产生的安慰剂效应以及头痛研究中纯粹主观的结果测量等问题。BT - A的临床效用尚未与已确立的偏头痛预防药物进行比较。BT - A预防偏头痛发作的疗效仍存在争议，其潜在的科学原理也存在争议。
