Large occipital aneurysmal bone cyst causing obstructive hydrocephalus in a pediatric patient

Aneurysmal bone cyst (ABC) is an uncommon benign, tumorlike lesion of bone that is usually located in the long bones and spine. On rare occasions, ABCs are found in the bones of the cranial vault and skull base, occasionally causing mass effect and cranial nerve findings. In this report the authors detail the case of a patient who presented with incidentally discovered hydrocephalus due to a large ABC of the occipital bone that produced mass effect and obstruction of CSF. The diagnosis, imaging findings, and surgical management of this interesting and rare case are discussed.