Chronic intracranial pressure monitoring by telemetry: Clinical experience

Intracranial pressure (ICP) monitoring is a critical measure for avoiding severe brain dysfunction or brain death by directing supportive therapy so as to prevent ICP increase severe enough to reduce cerebral blood perfusion. Such situations occur with brain swelling, increased cerebral vascular volume, and increase in cerebrospinal fluid (CSF) volume. Causes include ischemic stroke, subarachnoid bleeding, brain contusion, encephalitis (as in Reye's syndrome), and hydrocephalus from meningitis or neoplasm. When several days of ICP monitoring can direct resolution of the pressure crisis, the invasive direct connection of an intracranial sensor with external recording device carries only minimal infection risk. Prolonged ICP monitoring for weeks or months demands telemetry and becomes desirable in a number of chronic disease problems including both congenital and acquired hydrocephalus where enlarged and pressurized cerebral ventricles develop with reduced absorption of continuously secreted CSF. Although the primary disturbance in CSF circulation can remain incurable, its palliation by valve-regulated CSF diversions or shunting can restore normal brain function and in infants permit normal brain development. Missing this goal can result from failure to maintain a sufficiently normal pattern of CSF dynamics and ICP. Monitoring of the CSF pressure fluctuations transmitted through an intraventricular catheter provides the most accurate record of ICP pulsations. Therefore, a pressure sensing module can be “T'd” into an existing shunt system in continuity with the already placed ventricular tube. The capacity to monitor ICP accurately by telemetry was first established in dogs made hydrocephalic to assure free CSF pulse through a ventricular catheter (1,2,3, 4,5). The subsequent use of ICP monitoring by telemetry in three patients will be described.