Introduction

Recently, a novel hypothesis has been proposed concerning the origin of craniovertebral junction (CVJ) abnormalities. Commonly found in patients with these entities, atlantoaxial instability has been suspected to cause both Chiari malformation type I and basilar invagination, which renders the tried and tested surgical decompression strategy ineffective. In turn, C1-2 fusion is proposed as a single solution for all CVJ abnormalities, and a revised definition of atlantoaxial instability sees patients both with and without radiographic evidence of instability undergo fusion, instead relying on the intraoperative assessment of the atlantoaxial joints to confirm instability.

Methods

The authors conducted a comprehensive narrative review of literature and evidence covering this recently emerged hypothesis. The proposed pathomechanisms are discussed and contextualized with published literature.

Conclusion

The existing evidence is evaluated for supporting or opposing sole posterior C1-2 fusion in patients with CVJ abnormalities and compared with reported outcomes for conventional surgical strategies such as posterior fossa decompression, occipitocervical fusion, and anterior decompression. At present, there is insufficient evidence supporting the hypothesis of atlantoaxial instability being the common progenitor for CVJ abnormalities. Abolishing tried and tested surgical procedures in favor of a single universal approach would thus be unwarranted.

中文翻译：

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I型Chiari畸形和源自寰枢椎不稳的基底内陷：文献复习和关键分析。

介绍

近来，已经提出了关于颅上椎关节（CVJ）异常的起源的新假设。通常在患有这些疾病的患者中发现，寰枢椎不稳被怀疑同时引起I型Chiari畸形和基底内陷，这使得经过实践检验的手术减压策略无效。反过来，C1-2融合被提议作为所有CVJ异常的单一解决方案，修订后的寰枢椎不稳定义使有或没有影像学证据显示不稳定的患者均接受融合，而不是依靠术中对寰枢关节的评估来确定不稳定。

方法

作者对文献进行了全面的叙述性回顾，并涵盖了这一新近出现的假设的证据。所提出的病理机制已通过出版的文献进行了讨论和情境化。

结论

对现有证据进行评估，以支持或反对CVJ异常患者的单一后C1-2融合，并将其与常规外科手术策略（如后颅窝减压，枕颈融合和前路减压）的报道结果进行比较。目前，没有足够的证据支持寰枢椎不稳假说是CVJ异常的常见原因。因此，没有必要采用单一的通用方法来废除经过实践检验的手术程序。