Long-term testing of an intracranial pressure monitoring device.
OBJECTIVE
Long-term monitoring of intracranial pressure (ICP) is limited by the lack of an implantable sensor with low drift. The goal of this study was to demonstrate that a new capacitive transducer system will produce accurate and stable ICP records over extended periods.


METHODS
Intracranial pressure sensors were implanted into the frontal white matter of four dogs. In addition, a fluid-filled catheter was placed in the cisterna magna (CM) to measure cerebrospinal fluid (CSF) pressure. The animals were tested using standard physiological maneuvers such as jugular vein compression, head elevation, and CSF withdrawal from and saline injection into the CM to verify that the ICP sensor precisely matched CSF pressure changes. The mean ICP pressure and CM pressure were compared for months to demonstrate that the transducer system produced minimal drift over time. The change in the ICP sensor record closely duplicated that of the CSF waveform in the CM in response to well-known physiological stimuli. More important, mean ICP pressure remained within 3 mm Hg of CM pressure for months, with a mean difference of less than 0.3 mm Hg. Histological examination of the dog brains revealed only minimal tissue reaction to the presence of the sensor.


CONCLUSIONS
The authors demonstrate a new implantable solid-state sensor that reliably measures ICP for months, with minimal drift. The clinical application of this sensor and its telemetry is for long-term monitoring of patients with head injury, mass lesions, and hydrocephalus.
Kroin
J S
JS
Department of Neurosurgery, Rush Medical College, Chicago, Illinois 60612, USA. jkroin@rush.edu
McCarthy
R J
RJ
Stylos
L
L
Miesel
K
K
Ivankovich
A D
AD
Penn
R D
RD
D000818:Animals; D001930:Brain Injuries / Q000134:cerebrospinal fluid / Q000175:diagnosis*; D002946:Cisterna Magna; D004285:Dogs; D005260:Female; D006849:Hydrocephalus / Q000134:cerebrospinal fluid / Q000175:diagnosis*; D007427:Intracranial Pressure; D008991:Monitoring, Physiologic / Q000295:instrumentation* / Q000379:methods / Q000592:standards; D015203:Reproducibility of Results; D013686:Telemetry / Q000295:instrumentation / Q000592:standards; D013997:Time Factors