Giant intradiploic calvarial abscess of posterior fossa behaving progressive mass lesion.

A unique case of a large intradiploic abscess involving posterior fossa osseous structures is reported. A 16-year-old boy presented with a hard mass in the calvarium of posterior fossa region, fever and confusion. Radiological examination revealed an intradiploic collection with compression to cerebellum, fourth ventricle and brain stem, resulting in syringomyelia in cervical and thoracic spinal cord. After drainage and resection of the abscess wall, closure of a round dural defect was performed. The medical history of the patient and the intraoperative observations support the contention that the abscess in the reported case was a result of chronic and subclinical process of an intraosseous infection. The features concerned with diagnosis, differential diagnosis and pathogenesis of this rare entity are discussed.