Radiological Classification of Anterior Skull Base Anatomy Prior to Performing Medial Orbital Wall Decompression

Purpose: To study a radiological classification, originally described by Keros in 1965, which provides an objective assessment of anterior skull base anatomy relevant in patients undergoing external medial orbital decompression. Materials and methods: The classification is based on anatomical landmarks measured via coronal CT-scan. The patients are divided into 3 Keros categories based on their olfactory fossa depth; Keros 1 (1-3 mm), Keros 2 (4-7 mm) and Keros 3 (8-16 mm). A cross-sectional group of 32 consecutive patients on the hospital radiology database with coronal CT scans were classified according to the Keros system. Results: All the patients fell into one of the three Keros categories. Anatomical associations of the Keros classification suggest that Keros 1 patients have the least risk of intracranial entry whilst Keros 3 patients carry the greatest risk. Conclusion: Keros classification provides an objective assessment of anterior skull base anatomy and can therefore guide the surgeon on the superior extent of medial wall bone removal during orbital decompression. This may help improve the safety profile of the procedure.