Surgical Treatment of Chiari 1 Malformation: A ‘one fits all’ approach?

Abstract OBJECTIVES To assesses the postoperative outcome and the applicability of current Chiari 1 malformation (CM1) scores in a tailored surgical treatment approach in patients with CM1. METHODS This retrospective single center study analyzed 81 surgically treated patients between 2000 and 2020. Based on our institutional policy, four types of approaches were performed in that period based on a case by case decision: 1) Foramen magnum decompression (FMD) with dura splitting (FMDds), 2) FMD with duraplasty (FMDdp), 3) FMD with duraplasty and tonsillar manipulation (FMDao) and 4) tonsillar resection/reduction (TR). Patient characteristics, the Chicago Chiari Outcome Scale (CCOS), Chiari Severity Index (CSI), and the fourth ventricular roof angle (FVRA) were compared among the four groups to establish a treatment algorithm. RESULTS FMDds, FMDdp, FMDao and TR was performed in 11 (14%), 24 (30%), 21 (26%) and 25 (31%) patients, respectively. After a mean follow-up time of 6.6 years, 8/11 (73%), 19/24 (79%), 19/21 (90%) and 24/24 (100%) patients had a CCOS of 13–16 points after FMDds, FMDdp, FMDao and TR, respectively. Overall, 6/11 (55%), 4/17 (24%), 3/18 (17%) and 7/24 (29%) patients had a CSI grade 1 before FMDds, FMDdp, FMDao and TR. A weak negative and statistically not significant correlation between CCOS and CSI was observed (p = 0.07, n = 69). The preoperative FVRA was < 65° in 9/11 (82%), 13/15 (87%), 7/14 (50%) and 13/22 (59%) patients after FMDds, FMDdp, FMDao and TR, respectively. Despite the proportion of patients with a FVRA of < 65° decreasing with a more invasive surgical technique, differences between the surgical groups were statistically not significant (p = 0.45). CONCLUSIONS An individualized surgical approach in patients with CM1 is safe and effective. Currently available scores, such as the CSI and FVRA, may be used to determine the appropriate surgical approach for patients with CM1.