天坛小儿神外| 专访宫剑：儿童Chiari畸形的天坛小儿神外诊疗策略(上)-手术指征
天坛小儿神外
第4期
神外前沿讯，很多儿童因各种原因偶然发现小脑扁桃体下疝，到医院咨询时经常听到医生提起Chiari畸形。究竟小脑扁桃体下疝与Chiari畸形是什么关系？什么情况下才需要手术？
北京天坛医院小儿神经外科主任宫剑教授认为，先天性小脑扁桃体下疝，多数不需要手术治疗；继发性小脑扁桃体下疝，需要治疗原发病而解除下疝。
访谈内容如下：
神外前沿：儿童小脑扁桃体下疝常见吗？它与Chiari畸形是什么关系？与颅底凹陷、扁平颅底又如何区别呢？
宫剑：颅内小脑扁桃体下疝是指小脑扁桃体疝入枕骨大孔甚至椎管，分为先天性和继发性。先天性小脑扁桃体下疝人群发生率为0.5-3.5%，好发于0-10岁儿童，多数不需要手术治疗1。继发性小脑扁桃体下疝是因颅内原发病灶，如肿瘤、出血、挫裂伤等致使颅压增高，将小脑扁桃体推挤进入枕骨大孔，需要治疗原发病而解除下疝。
Chiari畸形是一组累及后颅窝颅骨、小脑、脑干及颈髓的颅颈交界区病变。1891年由奥地利病理学家Hans Chiari首先提出2，他对一名死于伤寒的17岁女性进行解剖，发现“小脑扁桃体成圆锥体样下疝至枕骨大孔及椎管内”，将其定义为“Chiari畸形”并沿用至今3。
因此，Chiari畸形既往又称为“先天性小脑扁桃体下疝”4、“小脑扁桃体异位”等5；而小脑扁桃体下疝并不都属于Chiari畸形，还可能是其它颅内疾患导致代偿性生理改变，即“继发性小脑扁桃体下疝”。
其它易混淆的概念还包括：
颅底凹陷症（Basilar Invagination），是指颈椎相对位置偏高、偏后，枢椎齿状突侵入枕骨大孔内，超过硬腭后缘-枕骨大孔后缘连线（Chamberlain线）大于5mm6(图1)，向后方压迫延颈髓，堵塞脑脊液循环通道。可见于先天性颅、椎骨发育不良、风湿性关节炎等疾病7，33%合并Chiari畸形8。
扁平颅底（Platybasia），是指鼻根-鞍结节连线与鞍结节-枕大孔前沿连线的夹角（Welcher-Basal角）过大（超过130°-140°9,10），导致后颅窝的容积减少。据报道，Chiari Ⅰ型中60%可发现扁平颅底9。
图1 颅颈交界区畸形测量方法
由于概念繁多，极易混淆，与Chiari畸形相关的其它常见疾病列表如下(表1)
神外前沿：儿童Chiari畸形形成的原因？
宫剑：国内外有大量针对Chiari畸形的病理学研究，但迄今为止，没有一种理论能够清晰阐述。常见的观点包括：
（1）颅腔内容物与容积不匹配假说：先天发育或颅腔容积过小、或内容物过多，导致后颅窝拥挤，小脑扁桃体疝入枕骨大孔22。
（2）压力锤效应假说：胎儿发生脑积水后，脑室系统顺应性降低，一旦失代偿，后颅窝内容物下疝，形成Chiari畸形23。
（3）脊髓腔低压效应假说（suck and slosh effect）：正常情况，脑/脊蛛网膜下腔相通且压力平衡，当脊膜膨出或腰大池-腹腔引流后，脊髓腔压力降低，后颅窝内容物会被“吸入”枕骨大孔，导致小脑扁桃体下疝24。
神外前沿：Chiari畸形的临床分型很复杂，能简单描述一下吗？哪种最常见？具体临床表现？
宫剑：根据影像学的不同表现，Chiari畸形具体分为0型，Ⅰ型，1.5型，Ⅱ型、Ⅲ型、Ⅳ型、Ⅴ型（详见表2）。Chiari Ⅰ型临床最为常见，诊断标准是小脑扁桃体疝出的部分低于McRae线（枕大孔前后点连线）超出5mm25。此标准于1986年由美国影像学家Barkovich提出并沿用至今。Chiari Ⅰ型人群发病率0.5-3.6%26-28，约占Chiari 畸形的85-90%。好发于0-10岁儿童，平均诊断年龄7.6岁，男女比例基本相当26,29。93%的Chiari Ⅰ型患儿无临床症状，不合并脊髓空洞和脑积水，又称为“良性Chiari Ⅰ型”1，不需要手术治疗，定期随访即可5,30。其余7 %需要手术的Chiari Ⅰ型患儿，9.6%31合并脑积水；23%-57%28合并脊髓空洞（其中86%位于颈段28）；14%-22.4%患儿合并脊柱侧弯28。
Chiari Ⅰ型的临床症状体征可分为5种类型32：（1）Chiari头痛：此特征性头痛包括三大特征：①疼痛位于颈枕部；②疼痛可被Valsalva动作（屏气、提重物时）诱发；③呈发作性短时间疼痛，常为数秒或数分钟；（2）颅神经受累症状：如复视、三叉神经痛、听力下降、吞咽困难等（3）脑干受累症状：如呼吸节律变化、眼球震颤等；（4）小脑受累症状：头晕，行走不稳，共济失调；（5）脊髓受累症状：分离性感觉障碍、鱼际肌萎缩。这些临床症状与体征对于手术的选择及预后的评估有重要价值。
表2：详述Chiari畸形各种临床分型及治疗手段
神外前沿：Chiari Ⅰ型国际公认的手术指征是什么？是否应该早发现早治疗？
宫剑：针对Chiari Ⅰ型国际上并没有公认的手术指征。综合各主要医学中心治疗方案，与手术指征相关的因素主要包括：1.是否符合Chiari Ⅰ型，即疝出的小脑扁桃体超出McRae线5mm；2. 是否有典型的Chiari头痛及其它相关症状体征；3.是否合并脊髓空洞。
需要指出，儿童与成人不同，Chiari Ⅰ型的表现往往十分隐匿，特别是3岁以下的幼儿，不具备任何主诉，仅表现为易激惹，需要小儿神经外科医生综合症状体征、影像学改变，精准把控手术指征。
儿童脑部的黄金发育期是0-6岁，6岁以后发育已极为有限。对于有症状的Chiari Ⅰ型患儿，国际公认越早接受治疗，效果越好。芝加哥儿童纪念医院对96名Chiari Ⅰ型儿童患者进行回顾性分析，发现8岁以前手术的患者症状缓解率较8岁以后的患者高出3倍35。美国俄克拉荷马州健康科学中心大学发现，0-8岁的儿童较8-17岁的儿童术后恢复速度更快，住院的时间明显较短36。纽约大学朗格尼医学中心对美国KID数据库13812例Chiari Ⅰ型患者进行了回顾性分析发现，越早手术的患者术后手术并发症越少37。
研究表明，Chiari畸形患者症状持续时间越长（>2年），术后缓解率越低38。部分合并脊髓空洞的成人患者，术后脊髓空洞即便消失了，临床症状仍不缓解甚至加重39。儿童有良好的神经自修复能力，术后症状体征的改善率明显优于成人5,40。因此我们建议，儿童Chiari Ⅰ型患者只要满足手术指征，应早发现早治疗，以免因拖延治疗造成难以修复的神经功能损伤。
表3：世界部分医疗机构针对Chiari I型设定的手术指征：
神外前沿：针对儿童Chiari Ⅰ型，北京天坛医院小儿神经外科诊疗规范是什么？
宫剑：北京天坛医院小儿神经外科是国内主要儿童Chiari畸形诊疗中心，针对儿童Chiari Ⅰ型，综合国际主要医学中心的诊疗规范，结合我们自身大量临床病例总结，制定诊疗规范如下：
1.小脑扁桃体下疝超出McRae线5mm，Chiari Ⅰ型诊断明确者；
2.出现特征性Chiari头痛；
3.出现与Chiari畸形明确相关的其它症状和体征；
4.合并脊髓空洞者。
在第1项基础上，满足2、3、4任何一项即建议手术；满足两项以上者，强烈建议手术。
作者简介
宫剑，教授，主任医师，博士研究生导师，北京天坛医院小儿神经外科病区副主任（主持工作），全面负责病区医疗，科研，教学工作。主要研究方向：1.儿童颅内肿瘤；2.儿童先天性疾患。目前主持科技部十三五、国家自然科学基金等多项课题，国内外专业杂志发表医学论著30余篇。目前担任中国医师协会神经外科医师分会小儿专家委员会副主任委员，中国医药教育协会小儿神经外科分会副主任委员。
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