Basilar Impression

53-year-old female with a history of chronic neck pain and headaches. There is upward displacement of the anterior arch of the atlas and dens into an otherwise normal appearing foramen magnum. There is effacement and crowding of the foramen magnum with prominent kinking of the cervicomedullary junction. In this patient without underlying osseous abnormality, this is a case of basilar impression. Basilar impression may be either congenital or acquired. There is upward displacement of vertebral elements into a normal foramen magnum. The upward migration results in stenosis of the foramen magnum with compression of the medulla. Syringomyelia may be seen.