Hyperostosis frontalis interna is characterised by benign overgrowth of the inner table of the frontal bone. It is seen most commonly seen in older females. The aetiology is unknown. The condition is generally of no clinical significance and an incidental finding. It is typically bilateral and symmetrical, and may extend to involve the parietal bones. It may also diffusely involve the skull, a variant known as hyperostosis calvariae diffusa. The skull thickening may be sessile or nodular, and may affect the bone in a focal or diffuse manner. Other differential diagnoses for focal skull thickening include Paget’s disease, fibrous dysplasia, metastases and meningioma.
Credit: Dr Donna D’Souza