Paget's disease (also known as osteitis deformans) is a primary systemic bone disease in which there is both resorption of normal bone and abnormal formation of new bone. It is of unknown cause. Diagnosis is established on the basis of characteristic radiographic findings, supplemented by an elevated serum alkaline phosphatase. Neurological symptoms result from bony overgrowth in the skull and vertebral column, leading to compression of adjacent neural structures.
Sarcomatous change may occasionally occur. The highly vascular abnormal bone may also reduce blood supply to adjacent neural structures. Spinal cord or cauda equina compression can occur at any level but is most common in the upper thoracic region. Pain may also be prominent.
Atlantoaxial fractures and dislocations may occur, leading to neurological problems. Myelopathic features have sometimes been seen without compression where the deficit is thought to be due to a vascular steal phenomenon. When there is cord compression, medical treatment with agents including calcitonin, mithramycin, and diphosphonates have sometimes reduced pain and improved neurological function. Surgical decompression may be indicated in some circumstances.