We report the case of a 47-year-old woman who underwent a mastoidectomy. Preoperative computed tomography demonstrated an unusually distended bony canal that passed through the superolateral portion of the right petrous bone. Intraoperatively, we identified the anomaly as a petrosquamosal sinus (PSS). This unusually dilated venous channel had arisen from the adjacent sigmoid sinus. A PSS is an emissary vein of the posterior fossa that courses along the petrosquamosal junction, connecting the sigmoid or transverse sinus with the extracranial venous system. While it usually regresses during fetal life, a dilated PSS occasionally persists into adulthood. Its anatomic course may lead to problematic bleeding during mastoidectomy.
A petrosquamosal sinus (PSS) is a rare emissary vein of the posterior fossa that drains into the external jugular vein to connect the sigmoid or transverse sinus with the extracranial venous system. Only a few radiologically detected and surgically confirmed cases of PSS have been reported in the literature.1-5
We report a new case of radiologically detected PSS. We suggest that detection of PSS on imaging prior to surgery is important in order to prevent certain surgical complications.