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

Background and Objectives: 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. Materials and Methods: Ninety-three consecutive adult CM-I underwent DP- (n = 54) or DP+ (n = 39) between 2014 and 2022. Pre- and post-operative 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 improved functional outcomes (p > 0.05). Cerebellar slump occurred more often after DP+ (30.8% vs. 9.3%; p < 0.05). Complication rates, particularly CSF-related events, were significantly higher with DP+ (17.9% vs. 3.7%, p = 0.032). Morphometric expansion of the foramen magnum did not correlate with functional outcomes. Conclusions: 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.