CASE REPORT Incidental Giant Arachnoid Granulation

SUMMARY: Arachnoid granulations may expand the dural sinuses or inner table of the skull. Although usually incidental, giant arachnoid granulations that are of sufficient size to fill the lumen of a dural sinus and cause local dilation or filling defects can rarely cause symptoms due to sinus obstruction leading to venous hypertension. This 31-year-old man presented with a 3-month history of progressive bifrontal headaches and a giant arachnoid granulation at the posterior superior sagittal sinus. Intrasinus pressure measurements showed no significant pressure difference across the lesion to explain the headaches, which were then treated medically. Dural sinus pressure measurement, in certain cases of giant arachnoid granulations, can be used to exclude the lesion as the cause of the patient’s symptoms. Arachnoid granulations are growths of arachnoid mem-brane into the dural sinuses through which CSF enters the venous system.1 They normally measure a few millime-ters but may grow to fill and dilate the dural sinuses or expand the inner table of the skull.1-3 They are often dis-covered as incidental findings in the transverse and poste-rior superior sagittal sinus,1-3 though they have rarely bee