Letter to the Editor. Chiari formation

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TO THE EDITOR: I read with interest the article on Chiari I “formation” by McClugage and Oakes10 (McClugage SG III, Oakes WJ: The Chiari I malformation. JNSPG 75th Anniversary Invited Review Article. J Neurosurg Pediatr 24:217–226, September 2019). The title indicates that it is a review article and the authors claim that they discuss the evolution in the understanding of the subject. It is rather troublesome to notice that the authors have preferred to entirely omit our contributions to the subject in which it is proposed that atlantoaxial instability is the nodal point of pathogenesis of Chiari I formation and atlantoaxial stabilization is the treatment.

In 2015, our article in the Journal of Neurosurgery: Spine proposed that atlantoaxial instability is the primary point of pathogenesis and Chiari formation and a host of other musculoskeletal and neural alterations are secondary and nature’s protective responses.2 Accordingly, we preferred the term Chiari “formation” to Chiari “malformation” and craniovertebral “alterations” to craniovertebral “anomalies.”3 It was proposed that tonsillar herniation forms a protective cushion, or is “nature’s airbag,” which protects neural structures from compression between the bones in the event of potential or manifest atlantoaxial instability.2

We proposed an alternative method of assessment of atlantoaxial instability based on the alignment of the facets on lateral profile imaging and evidence of instability during manual manipulation of bones. We introduced a novel concept of “central” or “axial” atlantoaxial instability, wherein the atlantoaxial joint is unstable despite the traditionally accepted and validated parameter of alteration of the atlantodental interval on dynamic imaging being within normal range, and compression of the dura or neural structures opposite the odontoid process is not present.4 Chiari formation is more often associated with central or axial atlantoaxial instability. This form of instability is usually chronic or longstanding in nature. A host of musculoskeletal alterations that include basilar invagination, assimilation of the atlas, platybasia, Klippel-Feil abnormality, bifid arch of the atlas, and C2–3 fusion, and neural alterations that include Chiari formation, syringomyelia, syringobulbia, external syringomyelia, and external syringobulbia are secondary outcomes of chronic atlantoaxial instability. More importantly, all these secondary musculoskeletal and neural abnormalities are reversible following atlantoaxial fixation.8,9,11

In response to our article in 2015,2 a number of pediatric neurosurgeons based in North America argued that our concept is valid more for adult cases with Chiari I formation and in those patients in whom there are complex craniovertebral junction bone malformations.1 We have subsequently published our results of surgical treatment of Chiari I formation by atlantoaxial fixation in pediatric age-group patients5 and in cases with Chiari I formation wherein there is no bone deformity.6

The authors have identified the more common symptoms of occipital headache, speech disturbance, and sleep apnea in cases with Chiari formation. We have recently shown that all these symptoms are entirely resolved in the immediate postoperative phase following atlantoaxial stabilization.7 We also demonstrated reversal of kyphoscoliosis following atlantoaxial fixation.9

I wish to take this opportunity to convey to the readers of this esteemed journal that the concept of atlantoaxial instability as a cause of Chiari I formation is here to stay. Any kind of foramen magnum decompression is not necessary for the treatment of Chiari formation.

Disclosures

The author reports no conflict of interest.

References

  • 1

    Brockmeyer DLOakes WJRozzelle CJohnston JRocque BGAnderson RC: Chiari malformation Type 1 and atlantoaxial instability: a letter from the Pediatric Craniocervical Society. J Neurosurg Spine 23:8208212015 (Letter)

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  • 2

    Goel A: Chiari malformation—is atlantoaxial instability the cause? Outcome analysis of 65 patients with Chiari malformation treated by atlantoaxial fixation. J Neurosurg Spine 22:1161272015

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  • 3

    Goel A: Is Chiari a “formation” or a “malformation.” J Craniovertebr Junction Spine 8:122017

  • 4

    Goel ADhar AShah AJadhav DBakale NVaja T: Central or axial atlantoaxial dislocation as a cause of cervical myelopathy: a report of outcome of 5 cases treated by atlantoaxial stabilization. World Neurosurg 121:e908e9162019

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  • 5

    Goel AGore SShah ADharurkar PVutha RPatil A: Atlantoaxial fixation for Chiari 1 formation in pediatric age-group patients: report of treatment in 33 patients. World Neurosurg 111:e668e6772018

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    • Export Citation
  • 6

    Goel AKaswa AShah A: Atlantoaxial fixation for treatment of Chiari formation and syringomyelia with no craniovertebral bone anomaly: report of an experience with 57 cases. Acta Neurochir Suppl 125:1011102019

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    • Export Citation
  • 7

    Goel APrasad AShah AGore SDharurkar P: Voice quality affection as a symptom of Chiari formation. World Neurosurg 121:e296e3012019

    • Search Google Scholar
    • Export Citation
  • 8

    Goel ASathe PShah A: Atlantoaxial fixation for basilar invagination without obvious atlantoaxial instability (Group B basilar invagination): outcome analysis of 63 surgically treated cases. World Neurosurg 99:1641702017

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    • Export Citation
  • 9

    Goel AVutha RShah ADharurkar PJadhav NJadhav D: Spinal kyphoscoliosis associated with Chiari formation and syringomyelia ‘recovery’ following atlantoaxial fixation: a preliminary report and early results based on experience with 11 surgically treated cases. World Neurosurg 125:e937e9462019

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    • Export Citation
  • 10

    McClugage SG IIIOakes WJ: The Chiari I malformation. JNSPG 75th Anniversary Invited Review Article. J Neurosurg Pediatr 24:2172262019

    • Search Google Scholar
    • Export Citation
  • 11

    Shah ASathe PPatil MGoel A: Treatment of “idiopathic” syrinx by atlantoaxial fixation: report of an experience with nine cases. J Craniovertebr Junction Spine 8:15212017

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    • Export Citation
Keywords:

Response

We appreciate Dr. Goel’s letter and response to our invited review. Much of the discussion and reasoning concerning his approach was outlined in the letter to the editor1 following Dr. Goel’s 2015 article and will not simply be repeated here. While a limited number of patients may benefit from fusion of the atlantoaxial joint, we have restricted this procedure to patients with demonstrable pathological movement of that area. To state that “all these [common] symptoms are entirely resolved in the immediate postoperative phase” with stabilization is a very fortunate outcome.

Time will tell if atlantoaxial fusion is the universal answer to this condition or if a more limited application of this technique to those with demonstrable instability is appropriate.

References

1

Brockmeyer DLOakes WJRozzelle CJohnston JRocque BGAnderson RC: Chiari malformation Type 1 and atlantoaxial instability: a letter from the Pediatric Craniocervical Society. J Neurosurg Spine 23:8208212015 (Letter)

  • Search Google Scholar
  • Export Citation

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Article Information

Contributor Notes

Correspondence Atul Goel: atulgoel62@hotmail.com.INCLUDE WHEN CITING Published online November 29, 2019; DOI: 10.3171/2019.9.PEDS19511.Disclosures The author reports no conflict of interest.
Headings
References
  • 1

    Brockmeyer DLOakes WJRozzelle CJohnston JRocque BGAnderson RC: Chiari malformation Type 1 and atlantoaxial instability: a letter from the Pediatric Craniocervical Society. J Neurosurg Spine 23:8208212015 (Letter)

    • Search Google Scholar
    • Export Citation
  • 2

    Goel A: Chiari malformation—is atlantoaxial instability the cause? Outcome analysis of 65 patients with Chiari malformation treated by atlantoaxial fixation. J Neurosurg Spine 22:1161272015

    • Search Google Scholar
    • Export Citation
  • 3

    Goel A: Is Chiari a “formation” or a “malformation.” J Craniovertebr Junction Spine 8:122017

  • 4

    Goel ADhar AShah AJadhav DBakale NVaja T: Central or axial atlantoaxial dislocation as a cause of cervical myelopathy: a report of outcome of 5 cases treated by atlantoaxial stabilization. World Neurosurg 121:e908e9162019

    • Search Google Scholar
    • Export Citation
  • 5

    Goel AGore SShah ADharurkar PVutha RPatil A: Atlantoaxial fixation for Chiari 1 formation in pediatric age-group patients: report of treatment in 33 patients. World Neurosurg 111:e668e6772018

    • Search Google Scholar
    • Export Citation
  • 6

    Goel AKaswa AShah A: Atlantoaxial fixation for treatment of Chiari formation and syringomyelia with no craniovertebral bone anomaly: report of an experience with 57 cases. Acta Neurochir Suppl 125:1011102019

    • Search Google Scholar
    • Export Citation
  • 7

    Goel APrasad AShah AGore SDharurkar P: Voice quality affection as a symptom of Chiari formation. World Neurosurg 121:e296e3012019

    • Search Google Scholar
    • Export Citation
  • 8

    Goel ASathe PShah A: Atlantoaxial fixation for basilar invagination without obvious atlantoaxial instability (Group B basilar invagination): outcome analysis of 63 surgically treated cases. World Neurosurg 99:1641702017

    • Search Google Scholar
    • Export Citation
  • 9

    Goel AVutha RShah ADharurkar PJadhav NJadhav D: Spinal kyphoscoliosis associated with Chiari formation and syringomyelia ‘recovery’ following atlantoaxial fixation: a preliminary report and early results based on experience with 11 surgically treated cases. World Neurosurg 125:e937e9462019

    • Search Google Scholar
    • Export Citation
  • 10

    McClugage SG IIIOakes WJ: The Chiari I malformation. JNSPG 75th Anniversary Invited Review Article. J Neurosurg Pediatr 24:2172262019

    • Search Google Scholar
    • Export Citation
  • 11

    Shah ASathe PPatil MGoel A: Treatment of “idiopathic” syrinx by atlantoaxial fixation: report of an experience with nine cases. J Craniovertebr Junction Spine 8:15212017

    • Search Google Scholar
    • Export Citation
  • 1

    Brockmeyer DLOakes WJRozzelle CJohnston JRocque BGAnderson RC: Chiari malformation Type 1 and atlantoaxial instability: a letter from the Pediatric Craniocervical Society. J Neurosurg Spine 23:8208212015 (Letter)

    • Search Google Scholar
    • Export Citation
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