Teaching Case

History of fall with no loss of consciousness.

The patient presented with a history of a fall with no loss of consciousness. Plain radiographs of the skull and a CT scan of the head were performed.

No fracture was seen. However, sclerosis of the frontal bone was noted. On CT the bone windows showed nodularity of the inner table of the frontal bones and also the extent of the process. The findings were in keeping with hyperosteosis frontalis interna. Also, the presence of an osteoma at the left parietal region was noted incidentally.

Hyperosteosis frontalis interna (endostosis crani, hyperostosis calvariae interna), involving the skull vault, is a condition of unknown aetiology seen almost exclusively in postmenopausal women. Men are very rarely affected. It may be hormone related. Some authors claim that it is seen in up to 12% of postmenopausal women. Inconsistent features associated with this condition include obesity, hirsutism, hypertension, headache, diabetes insipidus and psychological disorders. Increased serum alkaline phosphatase and elevated serum calcium may occur.

Radiologically, it is seen as an irregular nodular thickening of the inner table of the skull vault, the frontal bones being the most commonly involved. The outer table is not affected. The thickening can be 1cm or more in depth. The overlying superficial veins are unaffected. The lesions are bilaterally symmetrical and tend to spare the midline. Occasionally they are more extensive and involve the parietal bones. The occipital bone is rarely involved. CT shows the thickening and nodularity better and also the extent of the lesion. Isotope studies show an increased uptake, especially during the early stage of the process.

Radiological findings are virtually diagnostic. However, meningoma (en plaque), Paget's disease, metastastic lesions and acromegaly can give a similar picture. In such cases other features and CT will exclude the diagnosis.