Foramen magnum meningioma and arachnoid cyst coinciding in the lateral cerebellomedullary cistern--case report.

An extremely rare foramen magnum meningioma associated with an arachnoid cyst in the lateral cerebellomedullary cistern occurred in a 65-year-old female presenting with dizziness. Neuroimaging revealed a meningioma at the left lateral edge of the foramen magnum and an arachnoid cyst mainly located in the right lateral cerebellomedullary cistern, compressing the medulla oblongata bilaterally. After fenestration of the cyst wall and tumor removal, the clinical symptoms ameliorated. We recommend that where a foramen magnum tumor coexists with an arachnoid cyst of the posterior fossa, the tumor should be removed after shrinking the cyst to obviate the need for brainstem retraction.