Metastases of a spinal glioblastoma multiforme into an intracranial arachnoid cyst.

Spread of spinal cord glioblastoma multiforme to the intracranial compartment is uncommon. This report documents a case of metastatic spread of glioblastoma multiforme from the spinal cord to an intracranial arachnoid cyst. Seeding of the cyst cavity could have occurred by direct permeation of the cyst wall by the neoplastic glial cells spreading via the cerebrospinal fluid or by direct access of the cells through a defect in the arachnoid cyst wall and their subsequent entrapment by a ball valve type mechanism, leading to multiple implants.