1. A method for determining intracranial pressure (ICP) of a subject, comprising: (a) applying transcranial Doppler (TCD) to determine the middle cerebral artery (MCA) velocity of said subject and estimating changes in said ICP continuously based on a functional mapping that relates arterial blood pressure (ABP) and cerebral blood flow velocity (CBFV) to ICP, resulting in an estimated ICP trend; (b) generating a flash visual evoked potential (FVEP) on said subject, processing a detected FVEP signal, and obtaining an estimated ICP; and (c) combining said estimated ICP trend from TCD CBFV and ABP with said estimated ICP obtained by signal processing of said detected FVEP signal to periodically correct said trend and obtain a non-invasive measure of ICP.