Prevalence and radiographic features of Haller cells: A systematic review

Purpose: Haller cells (HCs) represent an anatomical variation in the maxillofacial region, frequently linked to sino-nasal pathologies. Numerous regional studies have reported the prevalence of HCs using various imaging modalities. This systematic review aims to evaluate the prevalence of HCs as reported in the existing literature. Materials and Methods: A comprehensive literature search was carried out across multiple databases, including ScienceDirect, PubMed, Scopus, Dentistry and Oral Sciences (EBSCO), Ovid, and LILACS. Different keyword combinations employing Boolean logic were used to identify relevant studies. Data extraction procedures adhered closely to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The quality of studies was assessed using the Critical Appraisal Skills Program (CASP) checklist for cross-sectional studies. Results: After data extraction, 9 studies qualified for critical analysis. The highest reported prevalence of HCs was 66.84%, whereas the lowest was 16%. Across these 9 studies, the average prevalence was 32.40%. Unilateral HCs predominated in most reported studies. Four studies provided details regarding the shapes of HCs, while size information was available in three studies. Eight of the 9 included studies demonstrated strong evidence quality according to the CASP checklist. Conclusion: Approximately one-third of radiographic scans analyzed in published studies revealed the presence of HCs. Unilateral HCs were found to be more common than bilateral HCs. The most frequently reported shapes were round, ovoid, and teardrop, with the majority measuring between 2 and 4 mm.