The BNAC uses phase contrast imaging to quantify cerebral spinal fluid (CSF) drainage through the Aqueduct of Sylvius.  CSF is primarily formed in the choroid plexus in the lateral, third and fourth ventricles, and it flows in a to-and-from movement with a caudal (also referred to as “antegrade” or “negative”) net flow through the cerebral aqueduct and foramina of Luschka and Magendie into the spinal subarachnoidal space.  In the aqueduct of Sylvius, using cine MR techniques, it has been shown that the CSF flow is due to systolic expansion of the cerebral hemispheres, which cause antegrade flow (toward the forth ventricle) during systole and retrograde flow (toward third ventricle, also referred to as “cephalic” or “positive”) during diastole.  Using semi-automated quantitative analysis of these images, it has been shown that the net flow of CSF through the Aqueduct of Sylvius is significantly reduced in multiple sclerosis patients when compared with normal controls.

Image A shows the prescription on a sagittal scan.  The Aqueduct of Sylvius is the thin white strip under the middle dot on the prescription.  Image B shows the axial scan of the Aqueduct of Sylvius, with the semi-automated ROI outlining the edges of the Aqueduct.