Anatomical variants of the temporal bone as depicted by HRCTS of patients evaluated in two radiology centers in Nairobi.

Abstract

Background: The temporal bone is the centre of otology practice thus understanding its anatomy and variations is important for diagnosis, treatment and surgical planning in ear pathology. Aim: To determine the patterns and prevalence of anatomical variations in temporal bone anatomy as depicted on high resolution computed tomography (HRCT) scans. Methodology Study Sites: The Kenyatta National Hospital and Plaza Imaging Solutions. Study duration: 12 months Study Sample Size: 100 participants were recruited where 82 paired temporal bones (TBs) and 18 unpaired TBs totaling 182 TBs were assessed. Study Design and Procedure: This was a descriptive cross-sectional study. The study population included patients who had undergone HRCT of the temporal bone at the two radiology centres. Their demographic data was collected and their scans were evaluated by the principal researcher in conjunction with a consultant radiologist in the respective study site. Variations of the temporal bone were recorded in a data collection sheet. Data analysis and Results: Data analysis was done using SPSS version 22. The age range was 2-74 years with a mean of 31.6±16.5 years and a male to female ratio of 1:1.1. Anatomical variations were observed in 99% of participants. The most prevalent variants were type B sinus tympani (73.1%), prominent sigmoid sinus (70.3%), Korner’s septum (57.1%), petrous pneumatization (56.5%) and Hans type 4 mastoid pneumatization (47.8%). The least prevalent variants included large cochlea aqueduct (0.6%), enlarged vestibular aqueduct (1.1%), petrosquamous sinus (1.1%) and sclerosed petrous (3.3%). Correlation by Fisher’s exact test showed significant correspondence between mastoid and petrous pneumatization patterns (p <0.001), male preponderance to large internal auditory canal (p=0.03) and Hans 1 mastoid pneumatization (p=0.003), and female preponderance to low lying tegmen (p=0.02). Paediatric petrous pneumatization pattern was predominantly diploe (80%) compared to adults’ aerated petrous in 62.4% (p <0.003). No observations of aberrant internal carotid artery, persistent stapedial artery or jugular diverticulum were made. Conclusion and Recommendation: There is a high prevalence rate of temporal bone anatomical variants in this study, with significant disparity between gender, age groups and individuals. These variants must thus be actively sought on case to case basis.