The lucent (CT) and enhancing (MR) rim, a sign of Paget's disease of the skull: case report.

Osteoporosis circumscripta is sometimes observed at the skull vault and corresponds to the initial stage of Paget's disease of the bone. Differentiating osteoporosis circumscripta from other reasons for osteolytic images of the vault may be difficult. We report a case of osteoporosis circumscripta of the frontal bone. A lucent rim seen on CT scan, which was enhanced on gadolinium-enhanced MRI, delineated the abnormal bone. The patient was a 50-year-old woman who had CT scans of the skull for chronic sinusitis. Pathology examination showed typical bone changes of Paget's disease. The lucent and enhancing rim sign may help in differentiating Paget's disease from other conditions.