Variant anatomy of the external surface of the mastoid bone in a Kenyan population

Abstract

Background: The external surface of the mastoid part of the temporal bone is crucial for localising the mastoid antrum and avoiding facial nerve injury during middle ear surgeries. Its morphology varies by sex, ethnicity, and side, but there's a dearth of information specific to Kenyans. Objective: The study aimed to document the variant anatomy of the mastoid part of the temporal bone in a Kenyan population. Materials and Methods: A cross-sectional study was conducted on 105 dry sexed skulls from the National Museums of Kenya. The study examined the suprameatal spines and depressions, and the presence of mastoid grooves and canals on the mastoid process's external surface. Using a digital Vernier caliper, distances and lengths were measured and statistically analyzed. Results: The crest type suprameatal spine was the most common (75.2%), while the triangular type was present in 15.8% of skulls. Suprameatal depressions were shallow in 67.1% and deep in 24.3% of the sides. Mastoid grooves and canals were present in 30.5% and 16.2% of sides, respectively, with both being present on the same side in 24.3% of cases. Distance measurements between structures varied slightly between the left and right sides. Conclusion: Suprameatal spines and depressions were found in the majority of skulls studied, providing surgeons with reliable landmarks for localizing the deeply seated mastoid antrum. Surgeons should also be aware of the high prevalence of mastoid grooves to prevent iatrogenic vascular injuries.