Introduction: iNPH is one of the few causes of dementia that can be reversed when diagnosed opportunely and treated with CSF diversion. Although shunting has shown benefits, it also has well-documented and important rates of complications. New prognostic markers for shunt response are needed to estimate benefit/risk when deciding treatment. Phase-contrast-MRI looking at CSF-flow through the cerebral aqueduct CAQ is a promising prognostic factor; yet, there is a lack of understanding regarding its dynamics during the early stages and throughout the progression of the disease. iNPH identification before symptoms presentation is very challenging, we propose a Phase-contrast-MRI for CSF exploration in the CAQ in a novel rodent model of chronic communicating hydrocephalus.

Methods: Kaolin was injected over the cerebral convexities bilaterally into the subarachnoid space in Sprague-Dawley Adult Rats. An 11.7T-Bruker MRI was used to acquire Phase Contrast MR with retrospect cardiac gated images, perpendicular to the direction of CSF at the aqueduct. Aqueductal Stroke Volume ASV results were compared with the ventricular volume VV at 15,60,90,120 days.

Results: Significant ventricular enlargement was found in Kaolin injected animals at 15(p=0.002),60(p=0.001),90(p=<0.001), and 120(p=<0.001) days when compared with control/shams. ASV differed between cases and controls/shams at every time point, (p=0.004,0.001,0.001,and<0.001 at 15,60,90 and 120 days, respectively). After correlation between the ASV and the VV, there was a significant correlation between both measurements at 15(p=0.015),60(p=0.001),90(p<0.001) and 120 days(p<0.001). There was a significant positive linear correlation between the change in ASV and the change in VV for the first period(15-60days).

Conclusions: This study demonstrates the feasibility of a rodent ASV flow measurement in a controlled fashion at specific time points. There is a high correlation between the ASV and the ventricular volume with a special linear association during the first 60 days. Previous studies from our group have shown symptom onset after 68 days with this model.

Patient Care: With this work, we aim to identify conditions, values, times and thresholds to predict shunting response in animals; hoping to one day correlate these findings in the iNPH human population, for them to receive a timely treatment with a higher rate of benefit than the known complications.

Learning Objectives: To elucidate the aqueductal CSF flow dynamics during the early stages and throughout the progression of communicating chronic hydrocephalus.

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