MR imaging of CSF pulsatory flow and its relation to intracranial pressure

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Abstract
In a retrospective study of magnetic resonance (MR) images obtained in 289 neurosurgical patients, loss of signal intensity (signal-void phenomenon, SVP) of the cerebrospinal fluid (CSF) in the mesencephalic aqueduct was observed in 77 patients. This SVP was noted in the MR studies of 12 of 14 patients with communicating hydrocephalus who showed a normal mean intracranial pressure (ICP) and normal pulse pressure, but in only seven of 50 patients with high mean ICP and high pulse pressure (such as those with a supratentorial tumor). The difference in the incidence of SVP between these two disease groups was statistically significant by Fisher's direct probability test. Based on MR images triggered by electrocardiography (EKG) waves, graphs were plotted to show the signal intensity of ventricular CSF versus time after the EKG R-wave. These graphs showed six distinct patterns which changed after the ICP was lowered by the withdrawal of CSF via a lumbar puncture. It is known that CSF in the cranial cavity flows toward the spinal space in a to-and-fro manner in response to the pulsations of the brain. The SVP reflects the capacity of the craniospinal cavity to buffer pressure changes within it. It may be possible to differentiate normal from increased ICP by the MR signal intensity of the CSF in the ventricular system.