Paget's disease with tumefactive soft tissue extension mimicking a chronic subdural hematoma

Paget's disease, the leading cause of skull sclerosis, is often under-diagnosed on imaging with tumefactive soft issue extension being mistaken for other intracranial findings. A 71-year-old female with past medical history of hypertension, chronic obstructive pulmonary disease, transient ischemic attack, 7 pack year smoke history, and alcohol abuse experienced an episode of bilateral upper extremity weakness, left arm numbness, left hand clumsiness, and word deficits that resolved within 20 minutes. Head computed tomography showed a right convexity mass measuring 6 mm with slight mass effect on the right cerebral hemisphere but no midline shift. She also had a sclerotic calvarium with focal erosions, periosteal reaction and scalp edema with no evidence of acute infarct, significant stenosis, occlusion, and aneurysm of the major intracranial arteries. Additional magnetic resonance imaging was ordered. The pattern of sclerosis of the right hemicalvarium extending into the left hemicalvarium and areas of abnormal bony texture and enhancement where sclerosis had not occurred suggested this to be the sclerotic phase of Paget's Disease. Additionally, the enhancing soft tissues on either side of the right hemicalvarium and overlying the posterior left parietal bone were thought to represent benign tumefactive soft tissue or pseudotumor. Tumefactive lesions often present a differential dilemma that is best resolved through a multi-disciplinary approach with extensive review on clinical and imaging findings. Tumefactive soft tissue extension related to Paget's disease of the skull has not been described in the literature and our case study highlights the importance of considering this entity on one's differential for patients presenting with an extra-axial lesion.