A system for measuring and converting to an observer intelligible form an internal physiological parameter of a medical patient. The invention allows transcutaneous telemetry of the measured information intracranial pressure via a system which includes a patient implanted sensor module and a processing and display module which is external of the patient and optically coupled to the sensor module via an external coupling module. A sensor within the implanted module transduces the measured information and a near infrared (NIR) emitter transmits this telemetry information when interrogated by the complementary external coupling module. Power for the sensor module is derived inductively through rectification of a transcutaneously-applied high-frequency alternating electromagnetic field which is generated by a power source within the external coupling module, in concept much like a conventional electrical transformer. A computer within the processing and display module calculates the parameter value from the NIR telemetry signal and represents this data either in numerical, graphical, or analog format.