MR imaging of lytic changes in Paget disease of the calvarium

The authors present two patients with Paget disease, both showing lytic changes in the calvarium. On T1 contrast sequences, the first patient demonstrated an extraaxial soft tissue mass in the temporooccipital region. This abnormality was hypointense to the adjacent normal diploic tissue. The second patient demonstrated a hypointense frontal abnormality on the T1-weighted sequence. Intracranial extension of this lesion was associated with lysis in otherwise mixed signal pagetoid bone. The first patient had osteoclastic Paget disease or osteoporosis circumscripta. The second patient had sarcomatous degeneration.