New telemetric system safe and effective for ICP measurement

A new implantable sensor device provides a less-invasive alternative for monitoring pressure within the skull (intracranial pressure, or ICP), suggests a pilot study in Operative Neurosurgery, a quarterly supplement to Neurosurgery, official journal of the Congress of Neurological Surgeons. Neurosurgery is published by Lippincott Williams & Wilkins, a part of Wolters Kluwer Health.

"This new telemetric system was safe and effective for ICP measurement over a long period, including home monitoring," according to the study by Dr. Stefan Welschehold of University Medicine Mainz, Germany.

Initial Experience Supports Use of Telemetric ICP Monitor
The researchers evaluated the telemetric ICP monitoring system in ten patients with previous brain surgery. (Telemetry means "measurement over a distance.") The patients—including children as young as three—had conditions such as hydrocephalus (fluid buildup inside the skull) placing them at risk of increased ICP. Abnormally high ICP is a serious medical problem, with the potential to cause brain damage and death.

The telemetric ICP monitoring device consists of a miniature probe—about one inch long—attached to a disk-shaped transducer. A simple surgical procedure is performed to insert the probe tip into the brain through a small hole in the skull, and to place to transducer under the scalp.

To obtain ICP values, a recording device is simply held over the implanted sensor and transducer. Because the recording device is battery powered, the patients are completely mobile. Values can be measured even through bandages.

Eight patients continued ICP monitoring at home after being discharged from the hospital. Monitoring continued for up to six months. The main limitation was that the recording device had to be connected to a computer at least once every three weeks to clear space for data storage.

In seven out of ten patients, monitoring showed no abnormal increases in ICP and thus no need for further surgery. In these patients, the monitoring probe was eventually removed. In some cases, monitoring detected normal and temporary increases in ICP related to factors like position changes, exercise, or crying in children.

In the remaining three patients, monitoring showed persistent or recurrent increases in pressure inside the skull. This alerted doctors that further surgery was required to correct the cause of increased ICP.

Controlling ICP is a critical factor in the management of patients with hydrocephalus and certain other conditions. Current approaches to ICP monitoring have important disadvantages. The most accurate technique involves readings taken directly from a catheter inserted into the spaces within the brain. Catheter monitoring is an invasive procedure, with a significant of risk infections and other complications.

The preliminary results support the usefulness of the new system for less-invasive, fully mobile ICP monitoring. "The main advantage of this new telemetric ICP-monitoring system is the possibility of long-term measurement under daily life conditions," Dr. Welschehold and coauthors write.

Because the system is easily managed by patients and families, it may be especially valuable for ICP monitoring in children, the researchers believe. With further study—including comparison with established techniques—the new telemetric system could enable 24-hour monitoring, identifying patients with potentially serious increases in ICP while reducing the need for hospitalization and invasive tests.