Introduction of a Novel Concept to Decompress Foramen Magnum in Chiari 1/2 Malformation without Affecting Stability

Objective: Chiari 1 malformation has crowding at CVJ, treated by FMD but is associated with high failure rates. Recently introduced concept of central instability explains this; so, we propose a newer concept to relieve the crowding without affecting stability.

To derive a threshold for coring out of internal surface of C1 posterior arch, instead of complete laminectomy accompanying FMD.

Methods: We prospectively included nine patients with a mean age of 25.33 ± 7.97 years, diagnosed with ACM-1 without AAD, who were operated with FMD with lax duraplasty and C1 laminectomy. The preoperative dural diameter and area covered under dura at the level of C1 were measured and compared from the postoperative state. Results were analyzed to derive a cut-off threshold, which can be drilled from the inner aspect of c1 arch.

Results: The postoperative AP diameter of Dura increased statistically significantly from pre-op; however, the AP extension was less than preoperative diameter with posterior arch included. Likewise, area spanned by Dura increased statistically significantly from pre-op but was less than the cumulative area of Dura with c1 arch included in pre-op. Analyzing all, a mean cut-off of 50.58% was achieved.

Conclusion: The authors would suggest FMD with partial coring (~50%) of the inner part of arch of C1, instead of full-thickness laminectomy with a wider length of coring as the target, and this will serve the purpose intended, without increasing mobility.

Publication History

Article published online:
15 February 2022