Gated magnetic resonance imaging of the intracranial cerebrospinal fluid spaces.

The pulsatile nature CSF flow in the cerebral aqueduct has been demonstrated by du Boulay using air cineventriculography, a technique which disturbs normal CSF dynamics. To investigate this phenomenon non-invasively, we studied 35 normal volunteers using high-resolution, cardiac-gated magnetic resonance imaging (MRI). Specifically, we wished to document changes in size, configuration and signal intensity of the CSF spaces as they related to time in the cardiac cycle. Results show that changes in size and configuration were measurable in the third ventricle only (size increased during systole in 7 of the 35 volunteers). Except for the lateral ventricles, some loss in signal intensity was seen in all CSF spaces at least during systole, in all 35 volunteers-findings consistent with du Boulay's. However, contrary to du Boulay's observations, asymmetric loss of signal, consistent with pulsatile CSF flow, was demonstrated in the foramen of Monro in 15 of the 35 volunteers. Based on the pattern of signal void at the level of the foramen of Monro and on the expansion of the third ventricle during systole we propose a theory of synchronous CSF flow at the foramen of Monro and aqueduct, which unifies our MRI findings with du Boulay's cineventriculographic observations.