Clinical and surgical implications of emissary venous anatomy.

PURPOSE: To review the anatomy and clinical significance of the cranial emissary veins (CEVs) with an emphasis on the posterior fossa pathways, their relevance to neuroradiologic interpretation, and implications for surgical planning. METHODS: A narrative, imaging-focused review was performed while discussing anatomic descriptions and clinically relevant patterns of CEV appearance on cross-sectional imaging. RESULTS: CEVs are valveless veins that pass through cranial apertures and connect the intracranial venous sinuses and extracranial veins. CEVs play a crucial role in normal cerebral venous drainage, brain thermoregulation, and various pathological states, particularly in high-flow vascular malformations, fistulas, and venous thrombosis. CEVs must be identified and reported before surgeries involving the posterior fossa and mastoid region to avoid complications. CEVs, specifically of the posterior fossa, are a source of complications that may include uncontrollable bleeding and air embolism, venous thrombosis, and venous ischemic and hemorrhagic infarcts. CEVs may also be therapeutically beneficial, as a large mastoid emissary vein (MEV) may provide endovascular access for treating lesions involving the transverse or sigmoid sinus. CONCLUSION: Knowledge of the key CEV anatomy is important for the neuroradiologist to inform preoperative planning and promptly identify their pathologic variations. Beyond neurosurgical procedures, understanding the anatomy of the emissary veins is crucial for reconstructive surgeons operating in the scalp and craniofacial region. Misidentification of this anatomy and injury to these structures can lead to intra-operative and post-operative complications, including bleeding, flap congestion, and even intracranial complications.