Mastoid foramen: morphometric study in dry skulls of Colombian population

Abstract

Introduction: The mastoid foramen is an anatomically inconstant opening that transmits the mastoid emissary vein. It is located either near the occipitomastoid suture or at the posterior margin of the mastoid process of the temporal bone. Knowledge of the anatomic and morphologic variations of this foramen is essential to prevent complications during surgical procedures. Objective: To describe the anatomical and morphometric characteristics of the mastoid foramen in a sample of skulls of Colombian population. Materials and methods: A cross-sectional descriptive study was carried out in 103 dry skulls (206 hemiskulls) of adults (35-55 years old) owned by the human skeletal repositories of three universities in Manizales, Colombia. The mastoid part of the temporal bone and the occipitomastoid suture were observed macroscopically to determine the prevalence and number of mastoid foramina. The morphometric characteristics of the foramina were determined using a digital caliper and each foramen was probed using 0.35mm diameter nylon. In addition, a 100mL syringe was used to filter water through the foramina in order to verify the intracranial connection of each foramen. Results: The prevalence of mastoid foramen was 94.17% (right half: 95.15%; left half: 93.20%). Moreover, 10.82%, 42.78% and 37.63% of the left and right skull halves had three, two, and one foramen, respectively. Most of the foramina (55.87%) communicated with the groove for sigmoid sinus. Conclusions: In the Colombian population, the mastoid foramen is variable in size, may be absent or have one or more foramina in each skull half, and usually communicates with the groove for sigmoid sinus, although it may communicate with other parts of the endocranium.