Persistence of multiple emissary veins of posterior fossa with unusual origin of left petrosquamosal sinus from mastoid emissary.

Emissary veins are valveless veins which pass through the cranial apertures and connect the dural venous sinuses and the extracranial veins. The clinical importance of emissary veins is increasingly being appreciated. Some emissary veins like the petrosquamosal sinus and mastoid emissary vein may cause significant bleeding during middle ear and skull base surgeries. A dilated mastoid emissary vein or condylar emissary vein can sometimes be a rare cause of tinnitus. Radiological identification of these venous channels has been described in recent years and assumes significance in light of their clinical importance. We describe the CT and MRI findings of a rare case that had persistence of multiple emissary veins and presented clinically with tinnitus. The radiological findings included a dilated left mastoid emissary vein, bilateral petrosquamosal sinuses, posterior condylar veins, occipital emissary veins and an intrapetrous venule. The left petrosquamosal sinus had an unusual origin from the dilated mastoid emissary vein. The patient also had major anomalies of posterior fossa venous sinuses which are discussed. A relevant review of literature is included.