Chordomas are tumours of notochordal tissue which usually arise from remnants of embryonic notochord tissue within the skull base, spinal vertebrae, or sacrum. Chordomas arising from these remnants begin within bone and cause extensive bone destruction as they enlarge. More rarely chordomas can arise from small ectopias of notochord known as ecchordoses. Such an origin is the likely explanation for the rare intradural extraosseous basilar chordomas.

Cranial chordomas are uncommon, representing approximately 0.2 per cent of all primary brain tumours. Cranial chordomas are more common in men than in women (2:1) and are diagnosed most commonly in the fourth or fifth decade of life. Although nearly all cranial chordomas have some relationship to the clivus, the clinical presentation depends on the precise growth pattern of the tumour. The most common presenting symptom is a lateral rectus palsy, since the VIth cranial nerve has a long course within the dura of the clivus. Chordomas that remain within the clivus can produce multiple cranial nerve palsies,brain-stem dysfunction, hydrocephalus from pressure against the brain-stem, or a mass in the nasopharynx. When a chordoma expands rostrally into the sella or parasellar regions, symptoms of hypopituitarism, visual loss, diplopia, and facial numbness are possible. Expansion of a chordoma caudally along the inferior clivus can cause lower cranial nerve palsies, compress the medulla or upper cervical spinal cord, or may lead to upper cervical pain or occipitocervical instability.

Within the spine chordomas occur most commonly in the sacrococcygeal region, although they have been observed at all levels. The symptoms and signs of spinal chordoma depend upon the level of the spine involved by the tumour and on the growth pattern of the tumour. Back pain is a common early symptom and may be present for up to a year prior to diagnosis. Sacrococcygeal chordomas can grow into the presacral space and exert direct pressure against the rectum: such tumours can present with altered bowel habits, tenesmus, or bleeding, and misdiagnosis is common. Chordomas arising within vertebral bodies present initially with local back pain, followed by radicular pain, and later, symptoms and signs of spinal cord compression.

The radiographic hall mark of the chordoma is an expansible, destructive lesion within bone, often associated with an extraosseus soft tissue mass. High resolution CT scans are the best means of evaluating the extent of bony destruction caused by the tumour. A sclerotic rim is often present at the tumour–bone interface. Calcifications, particularly of an amorphous nature and located at the periphery of the tumour, can be found in up to 90 per cent of chordomas. MRI scans are the best means to evaluate the extent of neural tissue distortion created by the tumour.

Regardless of the location of the chordoma the treatment of choice is extensive surgical resection followed by radiation therapy. For chordoma of the clivus the newer, more radical, surgical approaches to the base of the skull are often used. Chordomas in the sacrococcygeal region often require sacral resection and a combined surgical approach from the back and through the abdomen. It is particularly important that presacral masses are not biopsied transrectally for diagnostic purposes: tumour cells will seed the rectum, and rectal resection will then be required if one is to attempt curative surgery.

Although chordomas do not usually metastasize they have a high rate of local recurrence. Many adjunctive therapies have been tried, including high-dose gamma-irradiation, local radiation implants, proton beam therapy, and chemotherapy. Chemotherapy has not been successful in most hands. Radiation therapy will clearly prolong the disease-free interval after surgical resection and may lead to cure. The author's preferred method of radiation therapy is proton beam therapy, which delivers a high dose of radiation to the tumour, while avoiding important adjacent neural structures.