Subdural or intraparenchymal placement of long-term telemetric intracranial pressure measurement devices?

We established a CE-certified telemetric device to measure intracranial pressure (ICP) noninvasively. To evaluate whether subdural or intraparenchymal insertion of such devices should be preferred, we implanted these telemetric ICP measurement devices (Raumedic, Rautel) in both locations. The study was performed in nine minipigs. The telemetric data were validated every 3 months using conventional intraparenchymal ICP measurement probes.The intraparenchymal telemetric device failed in one animal 12 months after insertion. Computed tomography (CT) revealed first hints for failure: Despite the implantation in adult animals, the skull dimensions seemingly increased after implantation, and the sensor tip was dislocated on the tabula interna level. This finding could also be verified by histopathological examination which would explain the reason for mismeasurement. The subdural catheter failed after 9 months. CT and histopathological examination revealed a bony encapsulation of a large catheter part, which had been located correctly initially. We propose that chronic pulsatile stress on the device was the underlying reason for this phenomenon, comparable to that in meningeal arteries.In some of the other animals, failure of subdural catheters could be detected. Histopathological examinations in these cases are still pending. Nevertheless, we assume similar underlying reasons for failure in these subdural probes.In conclusion, we favour intraparenchymal placement of telemetric ICP measurement devices.