Epidural pressures have been reported as being systematically higher than ventricular fluid pressures. These discrepancies have been attributed both to the characteristics of the sensor and to the particular anatomy of the epidural space. To determine which of these two possible causes better explains higher epidural readings, the authors compared pressure values obtained during simultaneous epidural and lumbar pressure monitoring in 53 patients and during simultaneous subdural and lumbar pressure monitoring in 22 patients. The same nonfluid coupled sensor device was used in all compartments.
All 75 patients had normal craniospinal communication. Simultaneous intracranial and lumbar readings were performed every 30 seconds. The epidural–lumbar and subdural–lumbar pressure values were compared using correlation analysis and the Bland–Altman method.
The median differences in initial epidural–lumbar and subdural–lumbar pressure values were 11 mm Hg (interquartile range 2–24 mm Hg) and 0 mm Hg (interquartile range −2 to 1 mm Hg), respectively. The correlation coefficients of the mean epidural–lumbar and subdural–lumbar intracranial pressure (ICP) values were ρ = 0.48 (p < 0.001) and ρ = 0.88 (p < 0.001), respectively. Using the Bland–Altman analysis, epidural–lumbar methods showed a mean difference of −20.93 mm Hg; epidural pressure values were systematically higher than lumbar values, and these discrepancies were greater with higher ICP values. Subdural–lumbar methods showed a mean difference of 0.35 mm Hg and both were equally valid with all mean ICP values.
Epidural ICP monitoring produces artifactually high values. These values are not related to the type of sensor used but to the specific characteristics of the epidural intracranial space.
Abbreviations used in this paper:CSF = cerebrospinal fluid; ICP = intracranial pressure; SD = standard deviation.
Anonymous: The Brain Trauma Foundation. The American Association of Neurological Surgeons The Joint Section on Neuro-trauma and Critical Care Recommendations for intracranial pressure monitoring technology. J Neurotrauma17:497–5062000
CoroneosNJTurnerJMGibsonRMMcDowallDGPickerodtVWKeaneyNPComparison of extradural with intraventricular pressure in patients after head injury. BrockMDietzH: Intracranial Pressure. Experimental and Clinical AspectsBerlinSpinger-Verlag1972. 51–58
EsparzaJManriqueALobatoRDLamasESimultaneous epidural and intraventricular pressure measurement during the occurrence of supratentorial expanding lesions. ShulmanKMarmarouAMillerJDBeckerDPHochwaldGMBrockM: Intracranial Pressure IVBerlinSpringer-Verlag1980. 377–380
MartinGT: Reliability of epidural pressure measurement in clinical practice: behavior of three modern sensors during simultaneous ipsilateral intraventricular or intraparenchymal pressure measurement. Neurosurgery44:9201999. (Letter)
PickardJDTeasdaleGMathesonMLindsayKGalbraithSWyperD: Intraventricular pressure waves: the best predictive test for shunting in normal pressure hydrocephalus. ShulmanKMarmarouAMillerJD: Intracranial Pressure IVBerlinSpringer-Verlag1980. 498–500
PoonWSouthJRPoonCThe human factor in the accuracy of intracranial pressure (ICP) monitoring using extradurally placed microtransducers. HoffJTBetzAL: Intracranial Pressure VIIBerlinSpringer-Verlag1989. 95–100
RaabeATotzauerRMeyerOStockelRHohreinDSchocheJ: Reliability of epidural pressure measurement in clinical practice: behavior of three modern sensors during simultaneous ipsilateral intraventricular or intraparenchymal pressure measurement. Neurosurgery43:306–3111998
RosnerMJ: Comment in Raabe A, Totzauer R, Meyer O, Stockel R, Hohrein D, Schoche J: Reliability of epidural pressure measurement in clinical practice: behavior of three modern sensors during simultaneous ipsilateral intraventricular or intraparenchymal pressure measurement. Neurosurgery43:3111998
SahuquilloJRubioECodinaAMolinsAGuitartJMPocaMA: Reappraisal of the intracranial pressure and cerebrospinal fluid dynamics in patients with the so-called “normal pressure hydrocephalus” syndrome. Acta Neurochir (Wien)112:50–611991
SymonLDorschNWStephensRJLong term measurement of extradural pressure in “low pressure” hydrocephalus. BrockMDietzH: Intracranial Pressure. Experimental and Clinical AspectsBerlingSpringer-Verlag1972. 280–285
TakizawaHGabra-SandersTMillerJDVariations in pressure volume index and CSF outflow resistance measured at different places in the craniospinal axis. MillerJDTeasdaleGMRowanJOGalbraithSLMendelowD: Intracranial Pressure VIBerlinSpringer-Verlag1986. 43–47