Arachnoid Granulations – Arachnoid Villi- Pacchionian Granulations
The Common Vein Copyright 2010
Definition
The arachnoid granulations are protrusions of arachnoid through the dura into the venous sinuses that enable the CSF to empty into the venous system.
Functionally the CSF drains from the higher pressure of the subarachnoid space into the lower pressure venous system via one way direction system.
 Arachnoid Granulation
Penetration of the Arachnoid through the Dura into the Dural Sinus |
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This diagram shows the morphology of the arachnoid granulation which is formed by the protrusion of the arachnoid membrane through the dura into the sinus. As it extends into the sinus it draws the subarachnoid space with it. The communication of the subarachnoid space and the arachnoid with the dural venous sinus allows the CSF to move from the subarachnoid space into the venous system. Also shown is the bone (white), dura (green), subdural space (black) arachnoid (pink) subarachnoid space (light blue) piamater (maroon) and the brain (cream colored) . Courtesy Ashley Davidoff MD Copyright 2010 98482b06.9 |
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 Osteolytic Changes in the Bone From the Arachnoid Granulations |
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The CT of the vertex of the skull shows characteristic lobular (a) and linear changes (c,d) on the inner table of the skull reminiscent of osteolytic effects of arachnoid granulations. Courtesy Ashley Davidoff MD 71164c01 |