Foramen magnum decompression without bone removal: C1–C2 posterior fixation for Chiari with congenital atlantoaxial dislocation/basilar invagination

Abstract

Background: Atlantoaxial dislocation (AAD) and basilar invagination (BI) may coexist with Chiari malformations (CM) and a small posterior fossa volume. These are typically treated with craniovertebral junction fusion and foramen magnum decompression (FMD). Here, we evaluated whether C1–C2 posterior reduction and fixation (which possibly opens up the ventral foramen magnum) would effectively treat AAD and CM without additionally performing FMD. Methods: This is a retrospective analysis of 38 patients with BI, AAD, and CM who underwent C1–C2 posterior reduction and fusion without FMD. Baseline and follow-up clinical, demographic, and radiological data were evaluated. Results: The vast majority of patients (91.9%) improved both clinically and radiographically following C1–C2 fixation alone; none later required direct FMD. Notably, AAD was irreducible in 25 (65.8%) patients. Preoperatively, syringomyelia was present in 28 (73.7%) patients and showed resolution. In 3 (8.1%) patients, resolution of syrinxes did not translate into clinical improvement. Of interest, 5 patients who sustained inadvertent dural lacerations exhibited transient postoperative neurological worsening. Conclusions: Posterior C1–C2 distraction and fusion alone effectively treated AAD, BI, accompanied by CM. The procedure sufficiently distracted the dens, reversed dural tenting, and restored the posterior fossa volume while relieving ventral brainstem compression making FMD unnecessary. Surgeons should, however, be aware that inadvertent dural lacerations might contribute to unwanted neurological deterioration.

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

“…PFDD is associated with a larger reduction in syrinx size, but with a higher incidence of CSF leakage and aseptic meningitis. Despite these favorable results, it has to be mentioned that resolution of syringomyelia has been shown after posterior C1-C2 distraction and fusion as well [82].…”

Transoral intraarticular cage distraction and C-JAWS fixation for revision of basilar invagination with irreducible atlantoaxial dislocation

“…It is generally believed that surgical approaches for such patients depend mainly on the reducibility of BI and AAD [ 12 , 13 ]. If the BI and AAD can be reduced after axial cervical traction in hyperextended position, a posterior-only approach is indicated to achieve reduction, decompression, fixation and fusion [ 3 , 14 , 15 ]; If the BI or AAD cannot be reduced by cervical traction, a transoral anterior release and posterior reduction, decompression, fixation and fusion is often necessary [ 4 , 16 – 18 ]. But, the high risks of catastrophic complications and technique demanding of anterior procedure make the posterior-only approach preferred for BI with IAAD in clinical practice.…”

“…Reduction of atlantoaxial joint, descent of the dens, fixation and fusion were common treatment for BI with AAD. Because of more technical difficulty of anterior approach, in clinical practice, a posterior-only occipitocervical fusion (OCF) procedure is frequently used to address BI with AAD regardless of the reducibility [ 3 , 4 ]. Once a satisfactory reduction was failed after OCF, a subsequent revision surgery, which is usually requisite for the residual compression of the spinal cord, will be more difficult to perform because the posterior structure of the craniocervical level has been destroyed in previous OCF procedure [ 5 , 6 ].…”

Response to “Questionable Supremacy of C1-C2 Fusion for Chiari Without Apparent Instability: Comments on ‘Surgical Outcomes of C1-2 Posterior Stabilization in Patients With Chiari Malformation Type 1' by Arslan et al”

“…There are no postoperative X-rays in any of the radiological images in neither publication of Salunke et al 1,2 At the same time, they did not verify atlantoaxial instability in any preoperative and postoperative CT. We probably attribute their lower success rate to their inadequate reduction and fusion. In our manuscript, 3 adequate reduction and fixation can be clearly observed in our postoperative X-rays and CTs (E, F, G, H sections in the Figures 2, 3, and 4)…”

“…Ali Arslan, MD 1 We thank Salunke et al for their criticism of our manuscript. Obtaining certainty on the path of science is of course a long and tiring process.…”