Abstract: PURPOSE: To study the relationship between the stylomastoid foramen and surrounding bony structures, enrich anatomical data and provide reference for clinical surgery. METHODS: A total of 62 intact and dry adult skulls were selected. The shape of the stylomastoid foramen was observed, the diameter of the stylomastoid foramen, the distances from the posterolateral point and the anterior medial point to the surrounding bony structures were measured with a vernier caliper. SPSS 25.0 software package was used to analyze the data. RESULTS: There were four shapes of stylomastoid foramen, i.e., circular (61.29%), oval (29.84%), irregular (8.06%) and triangular (0.81%). The circular diameter was (2.80±0.61) mm, the oval long and short diameters were (4.43±0.96) and (2.79±0.60) mm. Distances from the posterolateral and anterior medial points of the stylomastoid foramen to the posterolateral point of the external opening of the carotid canal, the anterior medial point of the jugular foramen, the midline, the most anterior point of the foramen magnum, the posterior point of the great palatine foramen, the posterolateral point of the foramen lacerated, the foramen ovale, the posterolateral point of the foramen spinosum, the anterior point of the styloid process root, the outermost point of the tympanomastoid fissure and the tip of the mastoid process were (16.10±2.81), (24.01±2.65), (44.95±3.24), (45.10±2.71), (61.66±4.14), (35.56±4.35), (32.26±2.85), (29.12±3.40), (10.39±3.25), (9.49±2.24) and (12.01±2.79) mm; (12.80±2.41), (21.56±2.51), (42.96±3.97), (42.91±2.76), (58.97±3.97), (32.98±4.14), (29.20±2.77), (25.80±2.87), (7.37±2.33), (11.42±2.00) and (15.41±2.57) mm, respectively. Statistical analysis showed that there was no significant difference in the apertures and distances between the left and right side(P>0.05). CONCLUSIONS: Most of the stylomastoid foramen are round and oval, understanding the distance between the foramen and surrounding bony structures is helpful for guiding clinical operations and enriching anatomical knowledge.

Key words: Stylomastoid foramen, External opening of carotid canal, Jugular foramen, Foramen lacerated