The invention relates to a device for determining a parameter for the diagnostics of hydrocephalus and other disorders of intracranial pressure, wherein information about the volume elasticity is obtained from a pressure signal or another characteristic signal which contains information about the pressure or the volume composition in the skull.The characteristic parameter determined according to the invention is the ratio of the amplitude of a modulating wave in the processed characteristic signal to the amplitude of the modulated wave in the course of the pulse amplitude of the modulated wave of the processed characteristic signal.