Mechanisms of blast induced traumatic brain injury (bTBI), particularly the role of primary pressure wave, are still not fully understood. Recent neuropathological analyses of brain tissue from post-mortem cases of blast TBI indicate that the brain tissue close to ventricles sustains damage. Two possible explanations for this location of injury are CSF cut-off pressure effect and skull flexure effect. Here we investigate whether CSF cut-off pressure and/or skull flexure can produce large strain and strain rate concentrations at the CSF/brain interface. To test this hypothesis, a two-dimensional human head FE model of blast TBI is developed, composed of skin, skull, CSF, brain and ventricles. To model CSF volumetric response under negative pressure, a cut-off pressure was defined in the material model. If the pressure drops below the cut-off value, it is reset to that value. The CSF cut-off pressure effect was investigated by comparing brain deformation of CSF material models with and without cut-off pressure. The effect of skull flexure was studied by increasing skull stiffness. Results shows that CSF cut-off pressure leads to strain discontinuity at the CSF/brain interface and elevated strain levels in brain. Similar effects can be seen for strain rate distribution, though the discontinuity is not as pronounced as for strain distribution. Increasing skull stiffness reduces the strain level within cranium, but it does not have a significant effect on strain distribution. Interestingly, increasing skull stiffness did not have a significant influence on the level and distribution of strain rate. In this study we used a 2D brain model, an approach adopted in previous literature, which is one of the limitations. We will extend the work by using 3D models. Our results suggest that blast pressure wave can cause CSF pressure dropping to cut-off pressure, which leads to strain concentration in the brain near ventricles and that skull flexure increase the level of strain. These results may have implications for novel ways to better prevent bTBI.