Remote Monitoring of Intracranial Pressure

Abstract

During various pathological states, it is important for the neurosurgeon to know the magnitude of intracranial pressure. It is desirable to have a device small enough to be implanted and left in a trephine hole on a chronic basis, with associated circuitry that would lie beneath the skin surface. An appropriate device is described. The heart of the device is a strain gage bridge that is used to sense differential pressure. The bridge is driven by a 5kHz astable multivibrator, and bridge unbalance frequency-modulates a 100kIlz oscillator. The latter signal is telemetered through the skin via a double-tuned transformer. Power to drive the implant is fed in through a second transformer at 2MHz.