The ICP-dependency of resistance to cerebrospinal fluid outflow: a new mathematical method for CSF-parameter calculation in a model with H-Tx rats.

The international accepted calculation methods concerning the cerebrospinal fluid dynamics proceed from a pressure independent resistance to cerebrospinal fluid outflow. In a new model we focus our attention on the pressure dependency of resistance. In our calculation model we are monitoring the complete pressure course p(t) over the time t during and after the infusion. The comparison of the pressure rise On(p) during the infusion and the descent Off(p) after the infusion in the same pressure level allows to construct all formulas for the compliance C(p) and resistance R(p). The simultaneous measurement of the resistance and complications during a single investigation allows minimizing the patient's exertion. In contrast to the classical methods it is not necessary that the ICP reach a plateau. Our mathematical method diverges with the description of a pressure dependent slope of the function for the resistance from the static examination models. We proved our mathematical method by the use of a dynamic infusion test in ten H-Tx rats without hydrocephalus and five hydrocephalic H-Tx rats. For that we are able to take the non-linearity of the CSF resorption into consideration.