Chiari malformation type I and basilar invagination originating from atlantoaxial instability: a literature review and critical analysis

Abstract

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.

Occipital condyle screw fixation after posterior decompression for Chiari malformation: Technical report and application

“…[16] OCJ instability is often found in patients with CM-1 but is not always symptomatic nor requires OCJ fusion. [26] is association is thought to result from morphometric differences in the ligaments located in the OCJ among patients with CM-1. [11] Posterior fossa decompression is the standard surgical treatment in patients with CM-1, and its use has been shown to improve outcomes.…”

“…[ 16 ] OCJ instability is often found in patients with CM-1 but is not always symptomatic nor requires OCJ fusion. [ 26 ] This association is thought to result from morphometric differences in the ligaments located in the OCJ among patients with CM-1. [ 11 ]…”

MRI brain findings in Rheumatoid Arthritis: a review of the literature

“…This could potentially increase the risk for thrombosis, lead to vertebral artery occlusion and posterior circulation infarction [5,21]. In advanced stages, tonsillar herniation or syringomyelia may appear [22,23]. We did not find definitive data in literature, regarding the incidence of the described types of complications in RA patients with proven atlanto-axial instability or AAS.…”

Medical genomic approach to early-onset scoliosis

“…Chiari malformation type I is one of the etiologies of EOS. Chiari malformation type I is a caudal displacement of the cerebellar tonsils through the foramen magnum, and descent of the cerebellar tonsil to at least 5 mm into the upper cervical canal [33]. The prevalence of Chiari malformation type I is 0.56% to 1% of the population [34].…”