Analytical model of normal pressure hydrocephalus
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The driving force that causes the enlargement of the ventricles is still mysteriousremains unclear in case of normal pressure hydrocephalus (NPH). The present paper proposes an analytical model for aof normal healthy and NPH brain using the fundamental equations of conservation and further on carry out sensitivity analysis for different ses over the biomechanical parameters of the brain parenchyma. CTo this aim, cerebrospinal fluid pressure and brain tissue displacement are simulated in steady state. The brain geometry is simplified into aas a hollow sphere with an internal and external radius. The role of blood vessels in the interstitial fluid absorption is incorporated into the model using the Starling’s law. A proportion of cerebrospinal fluid seeping through the ventricle walls towards the brain is applied as a constant entering flux. An analytical expression for the pressure difference between the pia and ventricles is derived assuming permeable pia and ventricle membranes. The stability condition for the normal healthy brain is obtained assuming that this condition consists in exists with a net zero displacement of ventricle wall and low ventriculosubarachnoidintracranial pressure variation gradient as observed experimentally from [0 to -1] mm Hg. The NPH equilibrium position of the ventricle wall is dependent on the rate of cerebrospinal fluid flux and the efficiency of vascular absorption from the parenchyma. The results indicate that CSF flux and level of fluid absorption within the parenchyma both play an important role to help maintain mechanical equilibrium of the healthy and NPH brain.
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