Primary hydatid disease of the occipital bone presenting as space occupying cystic mass of the posterior fossa

Brain involvement of hydatid disease accounts for 1 to 4% of all cases. extra-dural, intra-calvarial location is even less. we report, a 24 years old woman with primary intracalvarial hydatid cyst that presented as an extradural cystic mass lesion of the posterior fossa. in the case presented, removal of the pathology without rupture could not be achieved. as same with the other locations, hydatid cysts of calvaria must be tried to be removed without rupture when possible. however, this exceptional host, the calvaria, seems to ease the pre-mature rupture of the cyst due to the neighboring sharp edges of the bone. in such situations, excessive irrigation with hyper-tonic solutions, %3 nacl for example, is known to be effective for preventing dissemination. pre-operative diagnosis is very important for surgical planning. extra-dural locations of cystic lesions must remind the surgeon hydatid cysts especially in the countries where the disease is more common.