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Emissary Veins

venae emissariae

Emissary veins are valveless communications between the extracranial venous system of the scalp and the intracranial dural venous sinuses, passing through small foramina in the skull. The principal emissary veins include the parietal emissary (through the parietal foramen, connecting scalp veins to the superior sagittal sinus), the mastoid emissary (through the mastoid foramen, connecting posterior auricular or occipital veins to the sigmoid sinus), the condylar emissary, and the occipital emissary.

Region: Head & Skull

Clinical Relevance

Clinical Notes

Emissary veins are valveless bidirectional conduits that allow infection to spread from scalp cellulitis to intracranial sinuses, causing dural sinus thrombosis and meningitis. Scalp infections draining through parietal emissary veins into the superior sagittal sinus can cause septic sinus thrombosis. The mastoid emissary vein is encountered during mastoid surgery and posterior fossa craniotomy; inadvertent entry causes venous bleeding that is controlled by wax. Emissary veins dilate in sinus thrombosis and in arteriovenous malformations as alternative drainage routes, visible on MR venography.

Pathology

Common Injuries & Conditions

Scalp Infection Spreading via Emissary Veins to Dural Sinuses

Scalp cellulitis or abscess draining through parietal or mastoid emissary veins produces septic thrombosis of the superior sagittal or sigmoid sinus, presenting with headache, fever, and papilloedema; anticoagulation and IV antibiotics are required along with treatment of the primary scalp infection.