Recent studies have revealed a strong coupling and tightly synchronized pulsations between electrical activity (EEG), hemodynamic responses (BOLD fMRI) and cerebrospinal fluid (CSF) flow in the brain. However, our understanding of the extent of these interactions and their underlying mechanisms is far from complete. To address this, we present a computational framework for studying multiphysics brain waves. In this framework, the brain parenchyma is modelled as a linear poroelastic medium permeated by a single fluid network, based on Biot's equations. Cerebrospinal fluid flow in the subarachnoid space and ventricular system is governed by viscous fluid dynamics through the Stokes equations. The primary driver of motion in the model is a prescribed blood inflow source term within the parenchyma. We explore the use of BOLD fMRI data to inform this source term, establishing a connection between vascular signals and CSF dynamics. A three-field finite element formulation is used to perform simulations on a detailed, three-dimensional geometry reconstructed from magnetic resonance imaging. This framework offers a flexible tool for studying the relationships between hemodynamics, cerebrospinal fluid flow, and brain tissue mechanics.