Revision surgery for patients with persistent, recurrent, or progressive syringomyelia following foramen magnum decompression (FMD) for Chiari malformation I-syringomyelia (CM-SM) is not uncommon and presents both strategic and technical challenges.We conducted a retrospective study including all patients who underwent revision Cerebellar Tonsillectomy (CTL) for CM-SM between 2003 and 2023. Additionally, we performed uni- and multivariate analyses to identify possible factors contributing to failed CTL outcomes.Sixty-three consecutive patients (13 males; average age 45.86±11.18 years) underwent surgical treatment for persistent (n=29), progressive (n=21), or recurrent (n=13) syringomyelia, with an average interval of 65.57±73.33 months (range: 3-480 months) between the two surgeries. Factors significantly associated with the effectiveness of the revision CTL included dural incision and tonsil manipulation during the first surgery, severe intradural adhesions during the revision CTL, and spinal cord atrophy before the revision CTL. Multivariate logistic regression revealed that dural incision (P=0.031, OR=6.779, 95%CI (1.187∼38.719)), tonsillar manipulation (P=0.037, OR=7.432, 95%CI (1.131∼48.835)), and severe intradural adhesions (P=0.030, OR=11.465, 95%CI (1.264∼103.967)) constituted risk factors significantly statistical associated with prognosis outcomes. Long-term follow-up (average 18.75±6.86 months, range: 12-72 months) of revision CTL demonstrated clinical stabilization in 55.6% of cases for at least 1.5 years. The complication rate for revision CTL was 14.3% (n=9).Dural incision and tonsillar manipulation during the first surgery, spinal cord atrophy prior to revision CTL, and severe intradural adhesions during revision CTL are significant risk factors associated with poor prognosis in revision surgery for CM-SM.Copyright © 2025 The Author(s). Published by Elsevier Inc. All rights reserved.