The effectiveness of optic nerve sheath diameter in surgical decision-making for type I Chiari malformations

Introduction: This study evaluates the relationship between optic nerve sheath diameter (ONSD), measured through magnetic resonance imaging (MRI), and increased intracranial pressure (ICP) in patients with Type I Chiari malformation (CM). Methods: This retrospective study includes 61 patients who underwent surgery for type I CM between January 2011 and January 2025. Patient data, including age, sex, presenting symptoms, presence of syringomyelia, comorbidities, type of dural opening technique, postoperative complications, and ONSD measured preoperatively and postoperatively through MRI, were analyzed. All MRIs were performed using a 1.5 Tesla scanner. ONSD measurements were made manually on axial T2-weighted sequences, 3 mm posterior to the optic disc in the mediolateral direction. The data were evaluated by two independent researchers. P