Abscess-a rare fourth ventricular mass.

Midline posterior fossa mass lesions in young adults are usually medulloblastomas, pilocytic astrocytomas, haemangioblastomas or ependymomas. We present clinical, imaging and intraoperative findings of an abscess occurring within the fourth ventricle which was associated with right chronic suppurative otitis media and right transverse sinus thrombosis. The possible pathogenesis is discussed.