Cerebrospinal Fluid-Skull Interaction Analysis for a Non-Invasive Intracranial Monitoring Technique

Intracranial pressure (ICP) monitoring methods can be categorized into invasive and non-invasive. Invasive methods increase the risks of bleeding and infection and need professional personnel; therefore, non-invasive methods are investigated more often. One non-invasive method is based on monitoring transcranial signals, which can be captured and processed from the skull. For this reason, the effects of cerebrospinal fluid (CSF) pressure increment on the natural frequencies of the skull have been investigated. In this paper, we model the human skull as a hemispherical shell employing skull bone mechanical
characteristics. CSF will be considered as an incompressible and inviscid fluid with a pressure increase less than 2 kPa. Employing Finite Element (FE) numerical techniques, the fluid-solid interaction (FSI) of CSF-skull is discretized, and the eigenvalue problem is solved to obtain the first 50 natural frequencies and the associated skull vibrational mode-shapes. The results illustrate that rising in CSF pressure causes slightly decrement in the unsymmetrical and symmetrical vibration frequency modes. Moreover, the modes of skull vibration sensitivity with respect to CSF pressure variation are calculated. The sensitivity graph demonstrates that the skull vibration in higher frequencies modes is sensitive to ICP variation in comparison with the lower vibration modes.