The effect of filum terminale sectioning for Chiari 1 malformation treatment: systematic review.

Purpose: Symptomatic Chiari type I malformation (CM) is treated with posterior fossa decompression with/ without duroplasty. Few authors suggested cerebellar tonsil caudal migration due to a supposed "caudal traction" of cranial nerve structures in a so-called occult tethered cord syndrome. For these authors, filum terminale (FT) sectioning may improve CM symptoms. The objective of this review is to evaluate the effect of FT sectioning on the treatment of CM.

Methods: Using the PRISMA guidelines for systematic reviews, we reviewed studies to evaluate patient's outcomes with CM who underwent FT sectioning. The MINORS instrument was used for methodological quality assessment. The included studies' levels of evidence (LOE) were classified according to the Oxford Centre of Evidence-Based Medicine.

Results: Two studies from the same group of authors were included. We cannot assure if the cited cases in the first study were also included in their latter published study. The described results suggest that outcomes were not collected in a standardized fashion. Outcomes are described vaguely as a percentage of improvement. Case series samples were small and included not only patients with CM but also patients with scoliosis and syringomyelia. The MINORS score reported that both studies had low methodological quality. Both included studies were classified as level 4 of evidence.

Conclusion: There is no scientific support for filum terminale sectioning in patients with CM without evidence of tethered cord. This procedure may be considered experimental and should be validated in a strict criterion of inclusion clinical trial comparing outcomes in posterior fossa decompression.