Primary intraosseous osteoblastic meningioma

This paper discusses how best to manage a patient with primary intraosseous meningioma, with particular consideration given to the merits of cranioplasty and dural biopsy. Rarely, meningiomas may arise from arachnoid cells within the diploe of the skull. The latter are usually destroyed in the process and there is increased vascularity of the tumour. Bony destruction results in the tumour lying subcutaneously with or without an intracranial component. These patients usually present with symptoms and signs of a painless gradually expanding mass. If associated with a significant intracranial component, they may present with headache, seizures and focal neurological signs, such as limb weakness or dysphasia depending on the location of the lesion. Under the microscope, the characteristic appearance is that of a spindle cell tumour composed of lobules and whorls of bland cells often with scattered psammoma bodies; there are, however, rarer subtypes showing different morphological features. Meningiomas account for 15–20% of primary intracranial neoplasms with the incidence peaking in the fourth and fifth decades and a female:male ratio of almost 2:1. Osteomas of the skull typically present as a slowly growing, expansile mass. Often this is a painless process. However, there may be headaches or localized pain over the swelling. The pain is classically worse at night and relieved by administration of salicylates. They are the most common primary tumours of the calvaria. The outer table is the most frequently involved with a well-demarcated homogenous and dense projection. Unlike in meningiomas, the diploe are preserved and the vascular channels not increased. Osteomas present as hot lesions on nuclear bone scans. Histologically, they are composed of dense, mature and predominantly lamellar bone. Fibrous dysplasia involving the skull high on the calvaria is of the cystic type with a higher incidence below 30 years of age. It may present as an incidental finding or with local pain, swelling and cranial nerve involvement if it affects the cranial nerve foramina. Widening of the diploe with thinning of the outer and inner tables and a ground glass appearance on X-ray is typical but not characteristic. Microscopically, the typical appearance is of narrow, curved and misshaped bony trabeculae, so called ‘Chinese letters’, which are interspersed with fibrous tissue of variable cellularity. Other pathologies causing focal or localized increase in bone density include the en-plaque variety of meningiomas which often involve the sphenoid bone and are associated with hyperostosis. Osteoblastic metastases such as those originating from prostatic carcinoma are also recognized. Rarer causes include the early stages of Paget’s disease, hyperostosis frontalis interna, osteosarcomas and ossifying fibromas. The symptoms, signs and radiological appearances may be of little help in distinguishing one DECLARATIONS