Spinal drop metastasis from grade I skull base chondrosarcoma.

Chondrosarcoma of the skull base is a rare tumour with a good prognosis following surgical resection. We describe a patient with low-grade chondrosarcoma of the skull base with intradural extramedullary spinal metastases. A 31-year-old female with grade 1 chondrosarcoma involving the cavernous sinus, sphenoid wing and clivus presented at age 19. The tumour was subtotally excised at initial surgery and over the following 4 years, 3 subsequent resections were undertaken for tumour progression followed by proton beam radiotherapy to the residual tumour. The patient re-presented with cervical radiculopathy 7 years later. MRI showed multiple, intradural extramedullary spinal drop metastases. Following surgical excision of the symptomatic lesion, histological diagnosis was confirmed as a mixed hyaline/myxoid grade 1 chondrosarcoma. Patients with skull base chondrosarcoma with intradural extension should have whole spine imaging as part of long-term monitoring to exclude drop metastases, particularly after intradural surgery.