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Introduction/Purpose Idiopathic normal pressure hydrocephalus (iNPH) is a potentially reversible syndrome treated primarily with ventriculoperitoneal (VP) shunting, which carries significant procedural and long-term hardware morbidity. The eShunt® Implant is a novel endovascular cerebrospinal fluid (CSF) diversion device implanted transvenously without craniotomy. Objective neuroimaging evidence of ventricular decompression following endovascular CSF diversion has not been systematically characterized. We report neuroimaging outcomes from a prospective multicenter pilot study of the eShunt System.Materials and Methods Neuroimaging data were prospectively collected from 64 patients with iNPH across 13 international centers (April 2022-January 2025). Three validated radiographic biomarkers were assessed at baseline, immediate post-procedure, and at 7, 30, and 90 days: Evans index (EI), bicaudate index (BCI), and callosal angle (CA). Matched-pair analysis using two-tailed paired t-tests was performed versus baseline at each timepoint. Effect sizes were calculated using Cohen’s d. Twelve Patients with 180-day timepoint (n=12) were also included.Results Mean baseline values confirmed established iNPH: CA 71.7±16.5°, EI 0.375±0.042, BCI 0.192±0.023. The CA demonstrated statistically significant improvement at all post-procedural timepoints: immediate post-procedure (+1.87°, 95%CI [0.16,3.59], p=0.033, d=0.30, n=52), 7 days (+2.83°, 95%CI [1.42,4.24], p=0.0002, d=0.57, n=50), 30 days (+6.16°, 95%CI [3.00,9.33], p=0.0005, d=0.84, n=23), 90 days (+4.27°, 95%CI [2.72,5.83], p<0.001, d=0.74, n=55), and 180 days (+5.47°, 95%CI [1.71,9.23], p=0.009, d=0.92, n=12). Effect sizes progressed from small-medium at immediate post-procedure to large by 30 days. The BCI showed a borderline trend toward reduction at 30 days (Δ=−0.005, p=0.057, d=−0.40) and 90 days (Δ=−0.003, p=0.057, d=−0.26). EI did not change significantly at any timepoint, consistent with the known insensitivity of this metric within 6 months.Conclusion Endovascular CSF diversion using the eShunt Implant produces early, progressive, and sustained callosal angle improvement from immediately post-procedure through 180 days, with large effect sizes. The CA was found to be the most sensitive neuroimaging biomarker following endovascular shunting. These data provide objective neuroimaging evidence for ventricular decompression via the minimally invasive eShunt treatment and support continued investigation of this imaging response with clinical outcome.Disclosures M. Abdalkader: None. P. Lylyk: None. C. Matouk: 4; C; CereVasc. R. Hanel: None. J. Reavey-Cantwell: None. H. Riina: None. D. Altschul: None. A. Siddiqui: None. J. Fraser: None. K. Ebersole: None. T. Bhalla: None. M. Bender: None. C. Ogilvy: None. P. Taussky: None. A. Baker: None. M. Jayaraman: None. C. Heilman: 2; C; CereVasc. 4; C; CereVasc. A. Malek: 2; C; CereVasc. 4; C; CereVasc.Abstract O-054 Figure 1