Mastoid Emissary Foramina in Dry Skulls: Its Morphometry, Topography, and Associated Clinical Implications

Mastoid emissary foramen transmitting mastoid emissary vein connects the posterior auricular vein with the sigmoid sinus. This foramen and so the mastoid emissary vein varies in prevalence, number, size and location, knowledge of which is essential for carrying out uneventful surgeries, especially retrosigmoid, mastoidectomy, and skull base surgeries. There is a paucity of literature on this foramen in the Indian context, so the study was done. The purpose of the study is to elaborate on the prevalence, number, size, and location of mastoid foramen in dry adult skulls. The study was conducted in the Department of Anatomy using 90 dry skulls of unknown age and sex, and prevalence, number, size, and location in these skulls were noted. The mastoid foramen was detected in 27.8% of skulls, with an incidence of 31.1% and 12.2% on right and left sides of skulls, respectively. The number of foramina ranged between 1 and 4. The mean diameter of this foramen was 0.9 mm, and the most frequent location was mastoid process. The detailed morphology and morphometry of mastoid foramen are of utmost use to neurosurgeons, ENT surgeons, radiologists, and vascular surgeons as it transmits mastoid emissary vein and meningeal branch of the occipital artery, which may be injured during various surgical procedures involving mastoid region and skull base causing catastrophic hemorrhage. In addition to this, mastoid emissary vein may be the source of thrombus, causing thrombus of sigmoid sinus creating helm of neurological complications.