Head Growth and Fundoscopy as Proxies for Intracranial Pressure in Metopic Synostosis Treated Surgically vs Conservatively.

Importance: The risk of increased intracranial pressure (ICP) in metopic synostosis remains poorly defined, leading to uncertainty about the need for routine surgical intervention vs conservative management. Objective: To compare head growth trajectories and the prevalence of signs of increased ICP among patients with metopic synostosis managed surgically or conservatively. Design, Setting, and Participants: This prospective cohort study included all 209 new patients with single-suture metopic synostosis presenting to Erasmus Medical Center, Rotterdam, the Netherlands, from January 1, 2017, to December 31, 2024. The current analysis included data collection up to July 31, 2025. Patients underwent annual follow-up with head circumference measurement and fundoscopy. Intervention: Surgical or conservative management of metopic synostosis determined through shared decision-making between clinicians and parents. Main Outcome and Measures: The primary outcome was longitudinal head circumference standard deviation (SD), analyzed using linear mixed models. Secondary outcomes were head growth deflection and papilledema, understood as signs of increased ICP, detected on fundoscopy. Results: Among 209 patients (78 surgical and 131 conservative; median age at presentation, 4 months [IQR, 2-7 months]; 154 boys [74%]), the median age at last follow-up was 40 months (IQR, 24-61 months). Head circumference SD increased significantly with age in a nonlinear pattern (age spline df = 1; β = 0.87; 95% CI, 0.54-1.21; P < .001; and age spline df = 2; β = 0.73; 95% CI, 0.29-1.16; P < .001). Female sex was associated with higher SD (β = 0.31; 95% CI, 0.03-0.60; P = .03). Surgical treatment was associated with higher initial SD but a significantly flatter growth trajectory over time compared with conservative treatment (β = -1.02; 95% CI, -1.52 to -0.52; P < .001 for interaction age spline and treatment). Severe deformity phenotype was associated with lower SD values compared with mild deformity phenotype (β = -0.39; 95% CI, -0.75 to -0.04; P = .03). Among 158 patients with 2 or more years of follow-up, head growth deflection occurred among 3 patients (1.9%): 2 of 65 (3.1%) in the surgical group and 1 of 93 (1.1%) in the conservative group (P = .57). Papilledema was observed in 3 patients (1.4%): 2 of 78 (2.6%) in the surgical group and 1 of 131 (0.8%) in the conservative group (P = .56). None of these patients required additional surgery. Conclusions and Relevance: In this prospective cohort of patients with metopic synostosis, signs of elevated ICP were rare and did not differ between surgical and conservative groups. Although surgery altered head growth trajectories, the low prevalence of ICP-related findings supports close monitoring and selective surgical intervention as safe alternatives to routine surgery.