Central or axial atlantoaxial dislocation and craniovertebral junction alterations: a review of 393 patients treated over 12 years

Abstract

OBJECTIVE The authors reviewed their scientific publications and updated their clinical material obtained over the last 12 years for cases of central or axial atlantoaxial dislocation (CAAD) identified in the presence of craniovertebral musculoskeletal and/or neural alteration(s). The management implications of diagnosing and treating CAAD are highlighted. METHODS During a 12-year period, CAAD was diagnosed in 393 patients with craniovertebral junction–related musculoskeletal and neural alterations who underwent atlantoaxial fixation. No bone decompression was done. All CAAD-related craniovertebral junction structural changes were identified to have a naturally protective role. Hence, in this paper the term "craniovertebral alterations" is used for "craniovertebral junction anomalies" and the term "Chiari formation" is used instead of the commonly used term "Chiari malformation." RESULTS The major radiological diagnosis was determined either singly or in cohort with one or more of other so-called pathological entities that included Chiari formation (367 cases), syringomyelia with Chiari (306 cases), idiopathic syringomyelia (12 cases), type B basilar invagination (147 cases), bifid arch of the atlas (9 cases), assimilation of the atlas (119 cases), C2–3 fusion (65 cases), Klippel-Feil alteration (4 cases), and dorsal kyphoscoliosis (15 cases). The follow-up period ranged from 6 to 155 months. Clinical improvement was observed in all patients. CONCLUSIONS Understanding and treating CAAD may have significant implications in the surgical treatment of a number of clinical entities. The gratifying clinical outcomes obtained in patients after atlantoaxial fixation, without any type of decompression involving bone or soft-tissue resection, consolidate the concept that atlantoaxial instability has a defining role in the pathogenesis.

Letter: Congenitally Fused Cervical Spine is Associated With Adjacent-Level Degeneration in the Absence of Cervical Spine Surgery

“…Atlantoaxial stabilization in these cases can result in remarkable resolution of symptoms. 9 Considering that most patients in the series were "elderly" (average age 51 years and maximum age 73 years), it is obvious that in atleast a number of these patients bone fusion is related to longstanding spinal degeneration. Our related articles mention that vertical spinal instability that leads to clinical and radiological manifestations of spinal degeneration is more often multisegmental rather than unisegmental.…”

“…5 In chronic situations, atlantoaxial instability can be of central or axial variety (CAAD). 6-9 Our articles discuss that it is not the disk space reduction or loss of disk substance, but it is vertical spinal instability that is the point of genesis of spinal spondylotic disease. 10-13 Both vertical spinal instability and CAAD might not be diagnosed on dynamic imaging with validated radiological parameters because of the lateral location of the facets, often subtleness of instability and frequently related to the absence of evidences of neural or dural compression.…”

Letter: Congress of Neurological Surgeons Systematic Review and Evidence-Based Guidelines for Patients With Chiari Malformation: Surgical Interventions

“…I find it difficult to understand the reasons for ignoring my "multiple" articles published in major neurosurgery journals over the past 3 decades that analyze probably the largest patient cohort on the subject of Chiari malformation. [2][3][4][5][6][7] The concept proposed in my articles is that chronic or longstanding atlantoaxial instability forms the nodal point of pathogenesis of Chiari malformation. We, and recently others, have reported remarkable or "magical" clinical recovery from symptoms after atlantoaxial stabilization.…”

“…We, and recently others, have reported remarkable or “magical” clinical recovery from symptoms after atlantoaxial stabilization. 2-9…”

“…I believe that it was responsibility of the authors to identify from the "published literature" the altered views on pathogenesis and changing paradigm of management of Chiari malformation. [2][3][4][5][6][7] In this respect, I believe that the authors have done injustice to the readers of Neurosurgery in entirely ignoring the concept that atlantoaxial instability can be the basis of Chiari formation and atlantoaxial stabilization can be the treatment. The authors might not agree with this concept, but to put it under the carpet and selectively ignoring it, might not be in the spirit of scientific evaluation of an important clinical issue, such as Chiari malformation.…”