Apart from irregular flow rate, hydrocephalus can also occur due to flow obstructions of cerebral spinal fluid (CSF) flow from the ventricles to the subarachoid space such as stenosis that builds up at the aqueduct. Since the size of the stenosis can affect the seriousness of hydrocephalus, simulation study can be used as cheaper and more detailed method to provide internal flow pattern inside the aqueduct. In this study, three dimensional models of the third ventricle and the aqueduct of Sylvius derived from MRI scans were constructed and the flow patterns were modeled by using MIMICS and CFD software. The constructed region of interest (ROI) was regarded as rigid wall and steady state flows were assumed. Different flow rates were simulated at the Foramen of Monro and several stenosis of various sizes were modeled at the middle of the aqueduct of Sylvius at a fixed location. These were made corresponding to normal patients with variation of CSF flow rates physiologically, and abnormal patients with tumor causing obstruction to or within the aqueduct of Sylvius, respectively. The results shows that the small difference of stenose sizes (1.2 times) is outweighed the difference of the flow rate (2 times) for contributions to abnormal and hydrocephalus. Unlike normal flow rates, there are flow recirculation appeared in the region of interest (ROI) in hydrocephalus cases. The flow recirculation might cause the pressure increase for abnormal flow rates to stay around at 50% - 60% of range for 10% of increment in stenose size. The analysis of the CSF flow patterns can provide a possible potential risk indicator of stenosis severity to the patients
