Purpose or Case Report: Chondroblastomas (CBs) are rare benign bone tumors that usually present within the first two decades of life, are more common in males, and originate within the epiphysis of long bones. In this same age group, Aneurysmal Bone Cysts (ABCs) commonly occur. ABCs are benign expansile osteolytic lesions which can be primary, occurring in isolation, or they can occur alongside other bone tumors such as CBs. CBs are one of the most common tumors to present with associated ABC-like changes. CBs and ABCs are often difficult to treat because of their locations. To minimize operative morbidity, especially in hard-to-reach lesions, percutaneous approaches for both lesions have been individually described. We present a skull base CB with associated ABC-like changes treated by combining two different previously described percutaneous modalities.

A 17-year-old healthy male presented with neck and shoulder pain. Imaging revealed an expansile lytic bone tumor replacing the clivus and left occipital condyle. The lesion was predominantly cystic with blood-fluid levels on T2W images but also had a 1 cm diameter dark nodular area in the left side of the clivus that was initially felt to be blood products rather than a solid tumor nodule. Pathology later revealed that this nodular area was a CB and the adjacent cystic portions were ABC-like changes. The CB was treated with Radiofrequency Ablation (RFA) and the adjacent ABC areas with doxycycline sclerotherapy. After 3 years of follow-up, there has been no clinical or radiological evidence of recurrence. RFA was complicated by a hypoglossal nerve injury. Otherwise, he had complete resolution of all symptoms and has returned to all activities including collegiate athletics.
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Conclusions: CBs rarely occur in the skull base and, as elsewhere in the body, can be associated with ABC-like changes. Successful percutaneous treatment of such a CB with ABC-like changes is possible by combining previously described techniques of RFA and doxycycline sclerotherapy.