Chordoma

Chordomas arise from remnants of the notochord along the axial skeleton. In the United States they occur at about 0.08 per 100,000 people per year, with skull-base, mobile-spine and sacral tumours each making up roughly one third; skull-base chordomas present at a younger age than sacral ones^[1]. They are slow-growing but locally destructive, infiltrate bone well beyond the visible margin and recur repeatedly. Nuclear expression of the transcription factor brachyury is the diagnostic marker that separates chordoma from chondrosarcoma, an important distinction because chondrosarcoma has a much better prognosis.

Clival chordomas cause headache and cranial-nerve palsies, most typically diplopia from abducens palsy at Dorello's canal. Upper clival tumours compress the optic apparatus and pituitary; lower clival tumours cause lower cranial-nerve deficits and may extend to the craniocervical junction, with brainstem compression in advanced cases. Nasal obstruction occurs with ventral extension.

CT shows a destructive, midline lytic lesion of the clivus, often with intratumoural bone fragments. MRI shows marked T2 hyperintensity with heterogeneous, “honeycomb” enhancement. Imaging defines the relationship to the basilar artery, the paraclival and petrous carotid arteries, the brainstem and the occipital condyles, which determines resectability and the need for fusion. Ecchordosis physaliphora, a small non-enhancing notochordal remnant behind the clivus, should not be mistaken for chordoma. Staging of the spine is advised, and biopsy, if done, should be performed along a corridor that will be removed at the definitive operation to avoid seeding.

International consensus recommends that patients be treated at experienced centres and that the first treatment aim for the greatest safe resection, followed by high-dose radiotherapy, usually with protons or other particles, because local control falls sharply after incomplete surgery and recurrence is difficult to salvage^[2,3]. En bloc resection is the aim in the sacrum and mobile spine; at the skull base, where en bloc removal is rarely possible, the goal is gross-total piecemeal resection with removal of the involved bone.

The endoscopic endonasal transclival approach has become the main route for midline clival chordomas, with lateral or posterolateral approaches (transpetrosal, far lateral, transcondylar) added for tumour lateral to the carotid artery or hypoglossal canal. Staged combined approaches are common for large tumours.

• Plan the bony removal to include infiltrated clival bone; drill until normal-looking, bleeding bone is reached.
• Identify the paraclival carotid arteries early with Doppler and navigation; the abducens nerve lies just behind the clival dura at the gulfar segment.
• Intradural extension requires dissection off the basilar artery and its perforators and the brainstem.
• Reconstruct with a vascularised nasoseptal flap after any dural opening^[4].
• Assess craniocervical stability after condylar or C1–C2 resection; occipitocervical fusion may be needed.

Overall survival in the population-based series was a median of about six years, with long survival possible after aggressive initial treatment^[1]. Extent of resection and adequate radiation dose are the most consistent predictors of local control. Recurrences are treated by repeat surgery, re-irradiation or clinical trials; conventional chemotherapy has little effect.