[Evaluation of the reserve spaces of the cerebrospinal system by using noninvasive methods].

This paper presents a theory according to which fluid volumes and pressures in the cerebrospinal system should be related nonlinearly rather than exponentially. The curve describing elasticity E as a function of pressure P should have two almost linear segments separated by an intercept. This concept is based on experimental and model data suggesting that the cerebrospinal system can be viewed as an elastic cavity which can, at normal and low pressures, trap an additional volume of any CSF component and shift other components; as a result, this leads to a linear increase in pressure within the cavity. The theoretical concepts found support in comparative invasive-noninvasive studies of the intracranial fluid with the aid of ultrasonic examination and in postural tests to which patients with cerebral lesions were exposed. A noninvasive technique for measuring fluid volumes and pressures in the cerebrospinal cavity was developed. The technique can be used as a diagnostic tool in the case of intracranial distension.