The Usefulness of Lumbar Epidural Pressure as an Index of Intracranial Pressure

Abstract

The reliability of lumbar intraspinal epidural pressure (ISEDP) as an index of intracranial pressure was investigated in seven patients with high intracranial pressure following neurosurgery. ISEDP and intracranial epidural pressure (ICEDP) were measured simultaneously, the latter by the conventional method. ISEDP was measured with a Gaeltec catheter-tip pressure transducer placed percutaneously in the lumbar epidural space via Touhy's needle. In five of seven patients, the ISEDP value was consistently 70 to 100% of the ICEDP value. In all patients, ISEDP always fluctuated in parallel with ICEDP, and the time courses of both were quite similar in response not only to normal cardiac pulsation but also to various manipulations, such as neck compression, coughing, breath holding, mannitol administration, and compression at the cranial defect. In one patient with communicating hydrocephalus following subarachnoid hemorrhage, the relationship between ISEDP and cerebrospinal fluid (CSF) pressure was studied. Upon gradual withdrawal of CSF, ISEDP decreased in parallel with CSF pressure until the latter reached 8 mmHg. Below 8 mmHg CSF pressure, ISEDP did not correlate with CSF pressure. This phenomenon was attributed to slackness of the dural sac due to lowering of CSF pressure, which severed contact between the spinal dural theca and the sensor. Although the discrepancy between ISEDP and ICEDP was prominent in some patients, especially those with low intracranial pressure or blockage of the subarachnoid space, in this study ISEDP reliably reflected ICEDP. The results suggest that ISEDP measurement is useful in monitoring intracranial pressure in patients with increased intracranial pressure. Also, the procedure is simple and relatively noninvasive.