Individualized Functional Decompression Options for Adult Chiari Malformation With Syringomyelia and A Novel Scale for Syringomyelia Resolution: A Single-Center Experience

Abstract

Objective: To compare outcomes of posterior fossa bony decompression alone (PFD) versus PFD with duraplasty (PFDD) versus PFDD with additional obex exploration (PFDDO) in patients with Chiari malformation type I (CMI) combining syringomyelia.

Methods: Clinical records of adult patients who underwent decompressions from 2014 to 2022 were retrospectively analyzed. The decompression procedure was individualized based on the cerebrospinal fluid pulse in the surgical field. The Chicago Chiari Outcome Scale (CCOS) was used to assess the prognosis of the patients and a novel syringomyelia resolution scale, based on 3-dimensional volume, was introduced. The percentage change in the cervical syrinx volume was classified as follows by resolution: ≥ 70%, 30%-70%, and < 30%.

Results: Seventy-eight individuals were enrolled, of which 22, 20, and 36 underwent PFD, PFDD, and PFDDO, respectively. The three decompression groups had no significant difference in the preoperative characteristics and postoperative prognosis. Multivariate analyses revealed that better CCOS was significantly correlated with younger age at surgery (p = 0.018), syrinx originated from lower cervical levels (p = 0.037), narrower preoperative cerebral aqueduct (p = 0.005), and better syrinx volume resolution (p = 0.004). Additionally, a better cervical syrinx volume resolution was significantly correlated with higher CCOS (p = 0.017), narrower cerebral aqueduct (p = 0.035), and better tonsillar descent resolution (p = 0.007).

Conclusion: Individualized functional decompression induced an equal effect on CCOS and syrinx volume resolution for all CMI patients with syringomyelia. Our syringomyelia resolution scale facilitates communication and prediction of CMI prognosis.

Keywords: Chiari malformation type I; Chicago Chiari Outcome Scale; Individualized functional surgery; Posterior fossa decompression; Syringomyelia.

Fig. 1.

Measurements of Sagittal magnetic resonance imaging. Line ab (red) indicates the distance of tonsillar herniation, while line ac (green) indicates the distance of tonsillar descent. Line mn indicates the cerebral aqueduct diameter. Line ef indicates the pB–C2.

Fig. 2.

Measurements of the cervical syrinx volume. (A) The cervical syrinx volume was measured above the C7 level (green dotted line). (B) Three-dimensional reconstruction of the cervical syrinx volume.

Fig. 3.

ROC curve of diagnostic efficiency of tonsillar descent. The area under the ROC achieved 0.909. ROC, receiver operating characteristic.