A Retrospective Study of the Prevalence of Maxillary Sinus Cysts Incidentally Detected on MRI Among Non-Symptomatic Caucasian Population

Maxillary sinus abnormalities, including retention cysts and mucosal thickening, are often incidental findings and may be present in up to 35.6%, depending on imaging modality and population characteristics. To date, few studies have explored the appearance of maxillary sinus retention cysts using MRI. <b>Aim:</b> This study provides the first large-scale MRI-based assessment of these lesions, with the aim of evaluating the prevalence and characteristics of maxillary sinus abnormalities detected incidentally on head MRI scans, particularly focusing on retention cysts and mucosal changes. <b>Materials and Methods:</b> A retrospective analysis of 3092 head MRI scans obtained between 2023 and 2024 was conducted to assess the prevalence and characteristics of maxillary sinus abnormalities. The mean patient age was 54.5 ± 18.6 years (median 56; range 18-99 years), with 1,825 women (59%). Statistical power exceeded 83% to detect differences of at least 10% in the prevalence of cysts between age groups (α = 0.05). A simplified MRI-based sinus assessment scale was used to categorize findings. <b>Results:</b> Out of 3092 scans, 1995 (64.5%) showed normal sinuses, 817 (26.4%) had mucosal thickening < 5 mm, 116 (3.8%) presented with retention cysts without other pathology, 100 (3.2%) exhibited moderate changes, and 64 (2.1%) had severe changes. Cysts were significantly more frequent in men (7.5%) than in women (4.4%) (<i>p</i> < 0.001). Additionally, maxillary sinus involvement differed significantly between sexes, with a higher prevalence in men. <b>Conclusions:</b> Incidental maxillary sinus findings are common and often benign. A comprehensive diagnostic approach is essential, especially for unilateral lesions near tooth roots. Conservative management remains appropriate for asymptomatic patients, but ongoing monitoring and patient education are key to preventing complications.