Revision 9 for 'Chondrosarcoma of the base of skull'
Chondrosarcoma of the base of skull
Chondrosarcomas of the base of skull make up only a small fraction of all chondrosarcomas (head and neck chondrosarcomas in one series making up only 6.7%). They are an even smaller proportion of intracranial neoplasms (making up only 0.16% of all intracranial neoplasms in one series). They are thought to arise from embryonal rest cells (remember that the base of skull forms via enchondral ossification).
- petrooccipital synchondrosis (most common)
- sphenoethmoidal junction
- sella turcica
- other rare sites that have been reported (presumably from metaplasia) include:
Metastatic disease is uncommon.
The vast majority of chondrosarcomas of the base of skull are sporadic, however some predisposing conditions are reported, and include:
Chondrosarcomas of the base of skull follow the same general imaging characteristics of chondrosarcomas else where. (see generic chondrosarcoma article)
As a historical note, skull x-rays were important in the diagnosis of these lesions, and demonstrated lytic lesions in 50% and calcifications in approximately 60%. The differentiation of chondrosarcomas from other skull base tumours was very difficult prior to cross-sectional imaging.
Useful sequences include:
- T2: to demonstrate high T2 signal, useful in distinguishing from meningiomas (although some meningiomas may have high T2 signal) - axial +/- coronal
- gradient echo: to demonstrate calcifications, or haemorrhage - axial
- T1 post contrast with fat saturation: as extension below base of skull is common, fat saturation should be employed to better deliniate inferior component.- axial, coronal +/- sagittal.
Local resection and radiotherapy employed.