Duraplasty Versus Bony Decompression in Adult Chiari I: Comparative Clinical and Morphometric Analysis

Background The optimal surgical technique for Chiari type I malformation (CM-I) remains debated, particularly in patients without syringomyelia. While duraplasty (DP+) may enhance radiological outcomes, it can carry higher complication risks. We compared clinical, radiological, and morphometric outcomes after suboccipital decompression with DP + and without duraplasty (DP–), with prespecified subgroup analyses by syringomyelia status. Methods Ninety-three consecutive adult CM-I underwent DP– (n = 54) or DP+ (n = 39) between 2014 and 2022. Pre- and postoperative MRI and neurological evaluations were obtained at 1 year. Functional recovery was assessed using the Chicago Chiari Outcome Scale (CCOS). Clinical and radiological outcomes, complication rates, and subgroup results (with vs without syringomyelia) were compared. Results Overall clinical improvement was observed in 92.5% of patients (DP–: 94.4%; DP+: 89.7%; p > 0.05). Among patients without syringomyelia, clinical improvement remained high with DP–. Radiological benefit—including syrinx regression and mega cisterna magna formation—was greater with DP+ (64.1% vs 24.1%; p < 0.001), but this did not translate into higher CCOS scores (p > 0.05). Cerebellar slump occurred more often after DP+ (30.8% vs 9.3%; p < 0.05). Complication rates, including CSF-related events, were higher with DP+. Morphometric expansion of the foramen magnum did not correlate with functional outcomes. Conclusion At 1-year follow-up, suboccipital decompression without duraplasty appears to provide comparable clinical improvement to DP+, with fewer complications, in selected CM-I patients without syringomyelia. Duraplasty offers radiological advantages, especially for syringomyelia, but at the cost of increased risk. Longer follow-up is necessary to determine the durability of these findings.