Mastoid emissary vein, mastoid emissary foramen, and mastoid emissary canal: anatomy, variability, imaging, and clinical implications.

PURPOSE: The mastoid emissary vein (MEV), mastoid emissary canal (MEC), and mastoid emissary foramen (MEF) are common but variably reported structures of the mastoid-posterior fossa region. Existing literature is fragmented across osteological, imaging-based, and clinical studies, with inconsistent prevalence and morphometric estimates, and with limited integration of anatomical variation into surgical and radiological decision-making. This SANRA-guided narrative review aimed to synthesise the anatomy, variability, imaging assessment, and clinical implications of MEV/MEC/MEF.

METHODS

This SANRA-guided narrative review synthesised anatomical, imaging, and clinical studies identified through PubMed/MEDLINE, Scopus, and Google Scholar from database inception through March 2026. Eligible studies included dry-skull, cadaveric, CBCT, MDCT/HRCT, and case-based reports addressing morphology, morphometrics, prevalence, or clinical relevance. Owing to methodological heterogeneity, findings were synthesised narratively.

RESULTS

Across osteological and imaging studies, MEF/MEC prevalence was generally high but heterogeneous, with frequent unilateral or bilateral multiplicity. Most canals/foramina were small, whereas a minority were markedly enlarged and potentially relevant to surgical bleeding, collateral venous drainage, or venous pulsatile tinnitus. Enlarged MEVs have been implicated in selected cases of venous pulsatile tinnitus, with reported treatments including conservative management, surgical clipping/ligation, and endovascular or percutaneous occlusion. In mastoid and posterior fossa surgery, prominent MEVs have been reported as potential sources of difficult venous bleeding. In paediatric Osia implantation, larger preoperative MEV calibre correlated with intraoperative bleeding.

CONCLUSIONS

MEV/MEC/MEF should be assessed systematically on preoperative imaging, including presence, number, calibre, and relationships to surgical landmarks. Consistent reporting may reduce avoidable haemorrhagic and diagnostic complications.