Chiari I Malformation: Is It the Result of an instability, and Should We Perform a Fusion Surgery?

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Neurospine. 2019;16(2):221-222
Publication date (electronic) : 2019 June 30
doi : https://doi.org/10.14245/ns.19edi.009
Department of Neurosurgery, Ege University, Izmir, Turkey
Corresponding Author Mehmet Zileli E-mail: zilelim@gmail.com

The paper by Deora et al. [1] is a good review of the current knowledge about treatment options for Chiari I malformation. We are not too far from the theories trying to explain the reasons of Chiari I malformation and syringomyelia. However, we realized that the obstruction of the cerebrospinal fluid pathways was the main reason of the symptoms created by these disorders. Additional basilar invagination, and atlantoaxial dislocation were making the management more complex. We used to do combined transoral decompression and posterior fixation which were full of many tricks and high complication rates [2]. We then learned a revolutionary surgical technique presented by Goel [3] that was simplifying the management of basilar invagination by a posterior only reduction and fixation of C1 and C2 joint. This surgical technique improved the outcomes, had lower complication rates, and the need of transoral surgeries have significantly decreased.

The concept of central atlantoaxial instability has recently been introduced by Goel [4] to answer the etiology of Chiari I malformation. If that concept is true, the immobilization by C1 and C2 fixation should be the surgical technique for Chiari I.

That concept was well discussed by Goel [5] and Deora et al. [1] in this issue of the Neurospine by defending contradictory views. I congratulate the editorial team for creating such a nice discussion area.

The question arises if we should perform a stabilization surgery in simple Chiari I malformations. The manuscript of Goel [5] urges that it is the best solution for Chiari I. However, literature is full with papers evidencing that a simple foramen magnum decompression is successful in more than 70% of the cases. There is no literature yet comparing a decompressive surgery with fixation surgery.

Even if it is an unstable condition, the necessity of doing a stabilization surgery is not obvious. Deora et al. [1] have done a nice analogy with lumbar spinal stenosis. Lumbar spinal stenosis may also be considered as a result of instability of a motion segment. The degeneration process starts from the intervertebral disc, then facets degenerate and an unstable condition occurs. Disc bulging, ligament hypertrophy and osteophytes are secondary to that unstable condition. Should we always consider a fusion surgery in lumbar spinal stenosis? Simply no. Even if there is degenerative listhesis, necessity of pedicle screw fixation or other fusion techniques is not hundred percent.

Central atlantoaxial instability may be the reason of Chiari malformation. However, we need biomechanical and clinical studies to investigate this theory. We also need high class clinical studies comparing the outcomes of simple decompressive surgeries and fixation surgeries.

References

1. Deora H, Behari S, Sardhara J, et al. Is cervical stabilization for all cases of Chiari-I malformation an overkill? Evidence speaks louder than words! Neurospine 2019;16:195–206.
2. Zileli M, Cagli S. Combined anterior and posterior approach for managing basilar invagination associated with type I Chiari malformation. J Spinal Disord Tech 2002;15:284–9.
3. Goel A. Treatment of basilar invagination by atlantoaxial joint distraction and direct lateral mass fixation. J Neurosurg Spine 2004;1:281–6.
4. Goel A. Is atlantoaxial instability the cause of Chiari malformation? Outcome analysis of 65 patients treated by atlantoaxial fixation. J Neurosurg Spine 2015;22:116–27.
5. Goel A. A review of a new clinical entity of ‘central atlantoaxial instability’: expanding horizons of craniovertebral junction surgery. Neurospine 2019;16:186–94.

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