Pneumatisation patterns surrounding the internal acoustic meatus

This study aimed to investigate the prevalence and anatomical patterns of temporal bone pneumatisation surrounding the internal acoustic meatus (IAM), specifically across its three anatomical regions: the porus acusticus internus (medial opening), the proper IAM (tubular midportion), and the fundus (lateral end). A secondary objective was to evaluate the association between pneumatisation and the thickness of the overlying tegmen in each region.

A total of 160 IAMs (80 patients, bilateral assessment) were analyzed using cone-beam computed tomography (CBCT). The IAM was anatomically subdivided into the porus, proper IAM, and fundus. Pneumatisation was assessed separately for each region's superior (tegmen), inferior, anterior, and posterior bony walls. Linear measurements of tegmen thickness were obtained and compared between pneumatised and non-pneumatised regions. Statistical analyses included Shapiro-Wilk normality tests, Levene's variance equality test, and independent samples t-tests.

Complete superior wall pneumatisation was observed in 23.8 % of right sides and 22.5 % of left sides. Inferior wall pneumatisation was absent bilaterally in 52.5 % of cases, while anterior wall involvement was noted in fewer than 17 % of cases. Posterior wall pneumatisation was absent in 80.0 % (right) and 75.0 % (left) sides. Pneumatised regions demonstrated significantly greater tegmen thickness across all areas (p < 0.001 in most cases). Gender-based analyses were conducted.

IAM-adjacent pneumatisation most often involves the superior wall and correlates with greater tegmen thickness, supporting targeted imaging for safer skull-base surgery and updating clinicians' understanding of this region.