Chondrosarcomas of the base of skull are rare compared with other base of skull tumours, but are an important differential diagnosis as surgical resection and management are affected by the preoperative diagnosis.
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 7%). They are an even smaller proportion of intracranial neoplasms (making up only ~ 0.2% of all intracranial neoplasms in one series).
The vast majority of chondrosarcomas of the base of skull are sporadic, however some predisposing conditions are reported, and include:
Patients usually present due to mass effect, either on adjacent brain, brainstem, cranial nerves or (if extension inferiorly) structures of the superior neck.
They are thought to arise from embryonal rest cells (remember that the base of skull forms via endochondral ossification).
- petro-occipital synchondrosis (most common)
- sphenoethmoidal junction
- sella turcica
- other rare sites that have been reported (presumably from metaplasia) include:
Chondrosarcomas of the base of skull follow the same general imaging characteristics of chondrosarcomas elsewhere. (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: high signal
- GE: calcifications typically in rings and arcs
- usually heterogeneous enhancement
- fat saturation should be employed to better delineate inferior component
Treatment and prognosis
They are relatively slow growing but locally aggressive. Metastatic disease is uncommon. Local resection is often the treatment of choice. Radiotherapy may sometimes be employed although sensitivity is thought to be minimal.
Imaging differential considerations include :
- 1. Morimoto T, Sasaki T, Takakura K et-al. Chondrosarcoma of the skull base: report of six cases. Skull Base Surg. 1992;2 (4): 177-85. - Free text at pubmed - Pubmed citation
- 2. Meyers SP, Hirsch WL, Curtin HD et-al. Chondrosarcomas of the skull base: MR imaging features. Radiology. 1992;184 (1): 103-8. Radiology (abstract) - Pubmed citation
- 3. Oot RF, Melville GE, New PF et-al. The role of MR and CT in evaluating clival chordomas and chondrosarcomas. AJR Am J Roentgenol. 1988;151 (3): 567-75. AJR Am J Roentgenol (abstract) - Pubmed citation
- 4. Brackmann DE, Teufert KB. Chondrosarcoma of the skull base: long-term follow-up. Otol. Neurotol. 2006;27 (7): 981-91. doi:10.1097/01.mao.0000233812.48800.b4 - Pubmed citation