Long-term Survival Rates in U.S. Veterans Shunted for iNPH: A Focused Analysis of Radiological Predictors.

Abstract

Long-term survival following idiopathic normal pressure hydrocephalus (iNPH) shunting in the U.S. is underreported, and the prognostic value of ventriculomegaly markers for overall survival (OS) remains unestablished. We leveraged a national veteran cohort to address these gaps. Kaplan-Meier analysis compared 10-year OS of a shunted iNPH cohort (n=154) and a non-shunted, suspected iNPH cohort (n=45) against age- and sex-matched controls (≤5 per patient). Survival comparisons between the two iNPH groups were limited to an imaged shunted subset (n=94) and the non-shunted cohort. OS was modeled using eight preoperative CT-derived ventriculomegaly markers. The estimated 10-year survival rate for U.S. veterans shunted for iNPH was 39% (95%CI:[27%,51%]), compared to an international estimate of ∼42%. OS did not significantly differ between shunted patients and controls (hazard ratio (HR)=1.24, CI:[0.93,1.66], p=0.14), whereas non-shunted patients experienced worse OS than controls (HR=1.82, CI:[1.1,3.0], p=0.020). In the imaged shunted subset, Callosal angles (CAs) > 74° (high-CA) indicated longer 10-year OS (21 mos.,CI:[2.5,40], p=0.030) compared to CAs ≤ 74° (low-CA). The shunted high-CA subgroup additionally demonstrated a 10-year survival advantage over non-shunted patients (20 mos., CI:[2,40], p=0.030). OS in U.S. veterans shunted for iNPH was comparable with international iNPH cohorts and matched U.S. veteran controls, whereas non-shunted patients with suspected iNPH had higher mortality. Additionally, higher preoperative CAs predicted a 10-year survival advantage post-shunting over lower-CA, and non-shunted patients. These findings call for targeted postoperative management in severe iNPH (low-CA) and suggest that improved surgical selection strategies when surgery is contraindicated may normalize long-term survival in suspected iNPH.