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

Abstract

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.

Pulsatile Tinnitus Caused by a Dilated Mastoid Emissary Vein

“…More recently, Chauhan et al (9) presented multiple emissary veins of the posterior fossa and unusual origin of the left petrosquamosal sinus from a dilated mastoid emissary vein. Thus, our case report is probably the third account of MEV-related pulsatile tinnitus.…”

“…Bilateral osseous canals in the lateral petrous temporal bones had originated from the enlarged mastoid emissary canal and from the transverse sinus, respectively. In addition, HRCT suggested an enlarged MEV orifice and the presence of condyloid and occipital emissary foramina (9). …”

Extraordinary cerebral venous drainage pathway with mastoid emissary and posterior external jugular veins detected by contrast-enhanced neck computed tomography

“…Incidence of MEV was reported in a large range between 60 and 90 %. MEV diameter is variable and occasionally wide up to 7.5 mm [3,7]. Dilated MEV may cause symptoms like pulsatile tinnitus or may be asymptomatic.…”

Why should we report posterior fossa emissary veins?

“…During growth of the jugular sinuses, most of them disappear, but some persist and enlarge. The cause may be related to failure of normal maturation of the sigmoid-jugular complexes (6).…”