Arachnoid Granulations of Pacchioni

Arachnoid granulations of Pacchioni play a major role in the resorption of cerebrospinal fluid. They are most commonly found within the lacunae laterales of the superior sagittal sinus, producing calvarial impressions between 13 and 15 mm lateral to midline in the region.

Arachnoid granulations can also protrude directly into the sinus lumen, adjacent to venous entrance sites, and should not be mistaken for sinus thrombosis. Arachnoid granulations are present in the superior sagittal sinus, transverse sinus, cavernous sinus, superior petrosal sinus, and straight sinus in decreasing order of frequency.


Arachnoid granulations of Pacchioni in the venous sinuses. Sagittal 2D MIP image from CT venography show arachnoid granulations (arrows) in the superior sagittal sinus and straight sinus.

Arachnoid granulations of Pacchioni in the venous sinuses. Axial contrast-enhanced CT image shows a well-limited lobulated defect (arrow) in the right transverse sinus.
 
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