Aim:Some meta-analyses have focused on foramen magnum decompression with duraplasty (PFDD) and without duraplasty (PFD) in paediatric or mixed populations. Nevertheless, no meta-analysis has evaluated adults only. This study aimed to include new relevant findings in a systematic review to provide the first comparison of PFDD and PFD in adult CM-I.Material and Methods:We retrospectively searched Web of Science, PubMed, Embase and ClinicalTrials.gov to summarize all relevant published papers on adults. A systemic review was adopted to evaluate clinical or radiological improvement, surgical complications, and reoperation rates between the PFD and PFDD groups.Results:Nine papers containing information on 497 adult participants met the criteria. PFDD was related to a lower revision rate (RR=2.96, 95% CI: 1.34-6.51, P=0.007) but a higher complication rate (RR=0.35, 95% CI: 0.22-0.55, P< 0.00001). No significant difference was noted between PFD and PFDD in terms of overall symptom improvement (RR=0.93, 95% CI: 0.84-1.03, P = 0.17) or syringomyelia reduction (RR=0.84, 95% CI: 0.63-1.12, P = 0.24). No significant difference in symptom improvement was observed between patients with syringomyelia (RR=0.86, 95% CI: 0.69-1.08, P = 0.20) and patients without syringomyelia (RR=0.94, 95% CI: 0.68-1.30, P = 0.73).Conclusion:This systematic review of observational studies reveals that PFDD may provide lower revision rates but pose a higher risk than PFD in the management of CM-I in adults. However, PFD is similar to PFDD in clinical and radiological improvements.