ICP curve morphology and intracranial flow-volume changes: a simultaneous ICP and cine phase contrast MRI study in humans.
BACKGROUND
The intracranial pressure (ICP) curve with its different peaks has been extensively studied, but the exact physiological mechanisms behind its morphology are still not fully understood. Both intracranial volume change (ΔICV) and transmission of the arterial blood pressure have been proposed to shape the ICP curve. This study tested the hypothesis that the ICP curve correlates to intracranial volume changes.


METHODS
Cine phase contrast magnetic resonance imaging (MRI) examinations were performed in neuro-intensive care patients with simultaneous ICP monitoring. The MRI was set to examine cerebral arterial inflow and venous cerebral outflow as well as flow of cerebrospinal fluid over the foramen magnum. The difference in total flow into and out from the cranial cavity (Flowtot) over time provides the ΔICV. The ICP curve was compared to the Flowtot and the ΔICV. Correlations were calculated through linear and logarithmic regression. Student's t test was used to test the null hypothesis between paired samples.


RESULTS
Excluding the initial ICP wave, P1, the mean R 2 for the correlation between the ΔICV and the ICP was 0.75 for the exponential expression, which had a higher correlation than the linear (p = 0.005). The first ICP peaks correlated to the initial peaks of Flowtot with a mean R 2 = 0.88.


CONCLUSION
The first part, or the P1, of the ICP curve seems to be created by the first rapid net inflow seen in Flowtot while the rest of the ICP curve seem to correlate to the ΔICV.
['Unnerbäck|Mårten|M|0000-0001-6483-7190', 'Ottesen|Johnny T|JT|', 'Reinstrup|Peter|P|']
D000328:Adult D062186:Arterial Pressure D001921:Brain D002560:Cerebrovascular Circulation D005260:Female D005539:Foramen Magnum D006801:Humans D007427:Intracranial Pressure D008279:Magnetic Resonance Imaging D019028:Magnetic Resonance Imaging, Cine D008297:Male D008875:Middle Aged D008991:Monitoring, Physiologic D012886:Skull D014057:Tomography, X-Ray Computed
Intracranial pressure Magnetic resonance imaging Cerebral blood flow Intracranial compliance