A new method of attaching a solid‐state pressure sensor for measurement of chronic intracranial pressure in freely moving rats using biotelemetry

Abstract

Precise and long-term measurements of intracranial pressure (ICP) in freely moving small animals is essential when investigating pathologies involving raised ICP, such as stroke and traumatic brain injury. The current method of measuring chronic ICP in small animals such as rats, is based on using a commercially available fluid filled pressure catheter telemetry system from Data Sciences International. The telemetry implant is secured on top of the animal's head in a cut 3cc syringe body along with tubing to interface with the fluid filled catheter. This provides useful data but it requires extensive assembly of various tubing and external implant housing. In addition, the most serious drawback for this method is the fluid filled pressure sensor which is prone to artifacts associated with motion due to catheter bending and barostatic effects. We have developed a new method to measure ICP which is based on a biotelemetry system that uses a Millar based solid-state pressure sensor (EG2-V0S1T, Endosomatic Systems Inc, Davis, CA). The sensor is secured on the skull as shown on the diagram and the complete assembly of pressure catheter, implant and battery is tunneled subcutaneously. The ICP probe consists of a specially designed absolute pressure Millar 3F catheter that is only 15mm long with a very flexible cable leading to the implant. This ensures that head movements do not cause motion artifacts due to catheter stiffness.