Cranial chordomas.

The clinical and radiological features of 44 cranial chordomas are recorded. Classical features of a mid-line partially calcified tumour, destroying the clivus and causing a soft tissue mass in the sphenoid sinus or nasopharynx were present in about half of the cases. The high incidence of unilateral bone erosion which occurred in nearly a third of the cases, the diagnosti1c significance of erosion of the tip of the clivus and odontoid peg and the not infrequent sclerotic bone reaction to the tumour, are stressed. Increased uptake of 99Tcm occurred in the five cases in which gamma encephalography was performed. Computed transmission tomography was valuable not only in showing the intracranial extension of the tumours and changes in the ventricular system, but also in outlining the extent of the mass within the skull base. Chordomas tend to displace the dura before transgressing it so that the subarachnoid space is usually patent adjacent to quite large tumours allowing the margins of any intracranial or spinal extension to be outlined at encephalography or myelography. Displacements of basal vessels are helpful in confirmation of the site and extent of the tumour. Narrowing of arteries by compression is not frequent but encasement is rare. Pathological circulation which has not been considered to be a feature of chordomas was shown in six cases.