Walsh & Hoyt: Meningeal Carcinomatosis

Diffuse infiltration of the meninges by metastatic tumor cells was first described histopathologically by Eberth in 1870. Knierim subsequently called this condition meningeal carcinomatosis. This disorder may result from extension of a parenchymal metastasis to the leptomeninges at the base of the brain or from direct hematogenous dissemination of tumor to the subarachnoid space. It can also develop when a cerebral metastasis impinges on the ventricular system, at which time the tumor cells destroy the ependymal cells and gain entry to the circulating CSF. Other proposed routes include perivenous spread from bone marrow metastases, and Batsons plexus. There is evidence that surgical removal of a solitary metastasis lead to a substantial reduction in the incidence of meningeal spread. Regardless of the mechanism by which meningeal carcinomatosis occurs, the result is low-grade meningitis that is often characterized by symptoms and signs of damage to the cranial nerves at the base of the brain or spinal cord. About 5% of patients with cancer develop meningeal disease. It is estimated that 5% of breast cancer patients, 23% of melanoma patients, and 923% of small-cell lung cancer patients will develop meningeal carcinomatosis.