Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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February 13, 2012
Aneurysmal Bone Cyst of Temporal Bone
- Aneurysmal bone cysts (ABCs) are uncommon lesions of the bone. Usually they develop in the vertebrae and in the flat bones; only 3% to 6% grow in the bones of the cranium. They occur more frequently in the first three decades of life.
- ABCs are expansile, lytic lesions consisting of multiple thin-walled, blood-containing, nonendothelialized cystic cavities. Although they are classified as benign, malignant trasformation has been reported in 3% of the cases. Their origin remains unknown; the hypothesis is that they may represent a reactive process, secondary to trauma, or a vascular disturbance.
- A skull ABC usually presents as an enlarging mass that can cause symptoms depending on its location including pain, pathological fractures, and neurological deficits like cranial nerve palsies, ptosis, loss of vision, and conductive hearing loss.
- Key Diagnostic Features: Plain radiographs: ABCs appear as single or multiple lytic lesions. CT: demonstrates expansile multiloculated bone lesions that may enhance peripherally after injection of contrast. However, MRI is the investigation of choice and typically shows fluid levels within the multiple cysts.
- DDx: Chondrosarcoma, lymphoma, leukemia, metastases, endolymphatic sac tumor
- Rx: Complete excision is the treatment of choice.
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