Chronic headaches are not uncommon in middle aged women and noncontrast Computed Tomography or Magnetic Resonance imaging is often the initial preferred neuroradiological investigation. A finding often recorded in the report is ‘hyperostosis frontalis interna.’
In the MRT2W image shown above a symmetrical thickening of the inner table of the skull known as Hyperostosis Frontalis Interna (HFI) is seen.
HFI is a disease characterized by excess bone growth on the internal lamina of the frontal bone and, occasionally, other cranial bones. HFI has been reported in 5-12% of the general population The frequency of HFI in cadavers and dry skull materials is identical at 12.5% and 12.3%, respectively.
It is relatively common in postmenopausal women but very rare in men. In cadavers, 87.5% of severe HFI cases are found in females over 65 years-old. Interestingly, the hyperostotic lesions may spread onto adjacent tissues such as the dura and falx cerebri. Men affected by this pathology suffer from diseases, syndromes or treatments causing androgen deficiency.
Moore (1944) classified HFI under the broad category of Metabolic craniopathy, which also included, Nebula frontalis, Hyperostosis calvaria diffusa, and Hyperostosis frontoparietalis, named according to the location of the lesion. Histopathology reveals an organized trabecular pattern with overall thickening of the cancellous bone. The periosteum and cortical bone are unaffected.
HFI should be recognized as a benign entity and distinguished from other disorders that involve the frontal skull bone, such as Paget’s disease, Acromegaly and malignancy.
The etiology of HFI is unknown, but current hypotheses implicate hormonal stimulation.