Persistent petrosquamosal sinus: Underlying cause of otitic hydrocephalus with lateral sinus thrombosis

Lateral sinus thrombosis (LST) occurs when a middle ear infection disseminates directly via bone erosion or disseminates indirectly through the venous networks. The petrosquamosal sinus (PSS) is the residual accessory dural sinus connecting intracranial to extracranial drainage. This report describes a case of a patient with persistent PSS running through the mastoid in context of otitic hydrocephalus with LST. To identify PSS, enhanced CT and reconstructed image from CT venography were more useful than MRI. The possibility of persistent PSS running through the mastoid should be considered if LST without marked inflammation and bone erosion is noted.