Chronic Intracranial Pressure Sensor to Assist With Control of Hydrocephalus

Hydrocephalus is a medical condition, where excessive accumulation of CerebroSpinal Fluid leads to an abnormal increase of intracranial pressure (ICP). Early and timely detection of elevated ICP is very important to mitigate symptoms during the entire life of the patient to avoid headaches, mental disability, and death caused by abnormal increased ICP. We describe our fabricated active capacitance pressure for continuous ICP measurement. The active sensor consists of two metal plates, which transduces the pressure change to capacitance change. We introduced a novel special connection method between the inside-bonded metal plates to external sensor electronics. We tested biocompatibility of the sensor materials in a sheep. We developed prototypes, and in vitro measurement results demonstrate that the active capacitive sensor achieves good performance: 550-900 mmHg measurement range, 0.094% accuracy, 0.022 mmHg (0.001 pF) resolution, and from ±0.136 to ±0.5 mmHg three months long-term drift for 10 different capacitive pressure sensors. Here, 0.5 mmHg corresponds to 0.14% full-scale output with a full range of 550 to 900 mmHg.