Value of CT and NMR imaging in diagnosing of chordomas.

Chordomas usually occur in the axial skeleton and they arise from the remnants of notochord. Their growth is slow and they often give metastases. Such cases are mainly observed among people above 40 years of age. Most frequently chordomas are situated in sacral bone (50%), in spheno-occipital region of the skull base (35%), and in the cervical, dorsal and lumbar spine (15%). Very rarely chordomas are found within sella, paranasal sinuses and nasopharynx, and in the forms of ectopic foci in the pons and spinal canal. Such tumour situated within spine destroys vertebral bodies and arches and can bulge into subdural space causing impression of the dural sac. Despite osteolytic destruction, chordomas cause visible reactive sclerotization and characteristic granular calcifications or ossifications. Intracranial chordomas destroy bony base of skull, specially clivus, pyramids and sphenoid sinuses.