A 71-year-old man with long-standing polyostotic Paget's disease involving the skull develops occipital headaches, difficulty swallowing, and intermittent diplopia. Lateral skull radiographs show flattening of the skull base with upward migration of the cervical spine into the posterior fossa. What is the responsible complication?

• A Communicating hydrocephalus from CSF malabsorption
• B Sarcomatous transformation of the clivus
• C Platybasia with basilar invagination ✓
• D Compression of the optic chiasm by enlarged frontal sinuses

Explanation

Pagetic bone of the calvarium and skull base softens under weight bearing, flattening the base (platybasia) and allowing the odontoid process to protrude into the foramen magnum (basilar invagination). This compresses the medulla, cerebellum and lower cranial nerves, producing headache, dysphagia and diplopia. Hydrocephalus can occur in Paget disease but causes gait disturbance and dementia rather than lower cranial nerve palsies, and sarcomatous change would present as a destructive mass with escalating pain.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.