A pearl of wisdom

An 8-year-old girl presented with progressive unsteadiness on her feet over a 2-year period. She was otherwise fit and well. No neurological deficit was found on examination, but movements of the lumbar spine were reduced. Conventional radiographs of the lumbar spine, myelogram and computed tomography (CT) myelographic findings are demonstrated in Figs 1–3, respectively. What is your differential diagnosis? What further information would you seek to clarify the diagnosis? The plain radiographs of the lumbar spine show a scoliosis concave to the right and subtle scalloping of the posterior aspects of the lumbar vertebral bodies 3–5. On the anteroposterior view there is some flattening of the medial side of both L4 pedicles. There is no evidence of bone destruction, disc space narrowing or expansion of the exit foramina.