The present invention relates to an apparatus for monitoring the intracranial pressure of a patient. The apparatus includes an implantable sensor implanted in the skull of a patient. The implantable sensor senses pressure and outputs a signal indicative of the pressure in the patient's skull. The apparatus further includes a probe receiving the signal output by the implantable sensor when the probe is positioned near the implantable sensor. The probe outputs a signal indicative of the pressure sensed by the implantable sensor. An interrogation circuit is provided for receiving the signal output by the probe and automatically outputting a digital signal proportional to the pressure sensed by the implantable sensor.