Hyperostosis frontalis interna

Hyperostosis frontalis interna (HFI) is a benign irregular nodular thickening of the inner table of the frontal bone that is almost always bilateral. The midline is spared at the insertion of the falx. Unilateral cases have been reported, and in these cases, one must R/O other etiologies such as meningioma, calcified epidural hematoma, osteoma, fibrous dysplasia, an epidural fibrous tumor, or Paget’s disease.

Tumor-associated hyperostosis is usually restricted to a small area immediately over the tumor, while the latter condition, HFI, can affect the inner table of the entire frontal region. HFI is a condition defined by bone deposition and thickening, usually limited to the inner table of the frontal bone, often sparing the midline. It has a prevalence of 5%-12%, more often affects women than men, and appears to be associated with elderly postmenopausal women in particular, with an incidence of 40%-60% ¹⁾