MRI demonstrates a large intraosseous lesion involving most of the right frontal bone. The lesion is markedly hypointense on T1 and T2 and has a small amount of patchy internal enhancement. Mild irregularity of the inner table of the skull but no intracranial component. Large extracranial component beyond the outer table of the frontal bone. Appearances are most suggestive of a primary intraosseous meningioma or en plaque meningioma.