August 8, 2019
A 19-year-old man with a painful swelling on the top of his skull that has been growing rapidly in the last few weeks.
Skull Anuerysmal Bone Cyst
- Background
- Aneurysmal bone cysts are uncommon benign bone lesions usually affecting teenagers and young adults. They tend to occur in long bones and vertebrae, very rarely involving the skull and facial bones. These lesions may be either primary or secondary, these ones developing in pre-existing bone lesions, including fibrous dysplasia.
- Clinical Presentation
- They usually present with a rapidly painless growing mass.
- Key Diagnostic Features
- MRI reveals an expansile bone, with multiple fluid-fluid levels, hemorrhagic foci and heterogeneous enhancement due to internal septae, surrounded by a thin hypointense rim.
- Differential Diagnosis
- The hallmark of an ABC is the blood-fluid level; however, this is not a specific finding and be also found in:
- Telangiectatic osteosarcoma — A highly vascular sarcoma with similar appearance, usually has a more aggressive cortical destruction, infiltrating into the surrounding soft tissue soft (which normally enhance);
- Giant cell tumors — Most common in the mandible and maxilla but has been reported in the skull base, including the temporal bone; usually have solid components that enhance;
- Fibrous dysplasia — Usually has a ground-glass pattern or a homogeneously dense pattern on CT;
- Hemangioma — Thin borders and a characteristic sunburst pattern of trabecular thickening radiating from a common center.
- The hallmark of an ABC is the blood-fluid level; however, this is not a specific finding and be also found in:
- Treatment
- Total resection of the aneurysmal bone cyst is recommmend. When possible, embolization of the feeding arteries may reduce bleeding during surgery, enabling maximal resection. However, these lesions tend to recur in ~1/5 of cases, so close follow up is mandatory.
