The Treatment of Subdural Collections in Patients With Shunted Normal Pressure Hydrocephalus: A Single-Center Experience

BACKGROUND AND OBJECTIVES: Normal pressure hydrocephalus (NPH) affects approximately 0.2% to 2.9% of adults older than 65 years and is characterized by progressive gait impairment, cognitive decline, and urinary incontinence. Cerebrospinal fluid shunting is the mainstay of treatment but carries a risk of overdrainage, leading to subdural collections. Evidence guiding the management of these collections in patients with shunted NPH remains limited. We aimed to characterize treatment strategies and outcomes for subdural collections in patients with shunted NPH and to propose a practical management framework for nonemergent presentations. METHODS: We performed a retrospective cohort study of patients with shunted NPH who developed subdural collections requiring treatment between January 2014 and September 2025. Interventions included valve pressure adjustment, middle meningeal artery (MMA) embolization, and surgical evacuation. Clinical, radiographic, and treatment data were extracted from the electronic health record. Time-to-resolution and recurrence were assessed using Kaplan-Meier analysis. Receiver operating characteristic analysis determined the predictive value of baseline collection volume for failure of valve adjustment. RESULTS: Sixty patients with 96 total collections underwent 91 valve pressure increases, 8 craniotomies for 8 collections, 23 MMA embolization procedures for 32 collections, and 15 subdural evacuating port system procedures for 16 collections. The median time to resolution for collections that underwent valve adjustment only, MMA embolization without evacuation, evacuation without MMA embolization, and both MMA embolization and evacuation was 1.91, 3.99, 1.77, and 5.17 months, respectively. Using pretreatment volume to predict valve adjustment failure demonstrated an area under the curve of 0.75 with an optimal cutoff of 40.05 cm3, corresponding to a sensitivity of 75.0% and a specificity of 71.4%. CONCLUSION: Baseline hematoma volume may help identify which shunted NPH patients with subdural hematomas are at higher risk of failing valve adjustment alone. We propose a volume-informed management framework in which larger hematomas (approximately >40 cm3) prompt earlier consideration of treatment escalation.