The brain and spinal cord together are known as the central nervous system (CNS). Three layers of membranes (the meninges) and bone (the skull and vertebrae) surround the CNS.
The three layers of the meninges are:
Between the pia and the arachnoid layers of the meninges, there is fluid. This fluid is known as spinal fluid or cerebrospinal fluid (CSF). CSF is a clear fluid produced in the brain that flows in and around the spaces of the brain and around the spine in the spinal column.
The pia mater, arachnoid mater and the CSF together are called the leptomeninges.
Leptomeningeal cancer (LMC), leptomeningeal disease (LMD) or leptomeningeal metastasis (LM) is cancer that has spread to the leptomeninges.
Note: Over time, many different terms have been used to describe cancer growing in the leptomeninges. Leptomeningeal cancer, leptomeningeal disease, leptomeningeal metastases, carcinomatous meningitis, leptomeningeal carcinomatosis, LC, LM, LMD, LMC – many different names but all referring to the same disease.
Cancer can enter the leptomeninges in many ways, such as through:
Often, we do not know how cancer has entered into the leptomeninges. Some cancers spread from other parts of the body and some cancers grow first in the leptomeninges and do not need to spread into the space.
Once in the leptomeninges, cancer can settle onto the surfaces of the CNS, or it can float in the CSF. Often, the cancer does both of these things. As the cancer cells multiply and grow, they stick on the nerves and irritate the tissue, causing symptoms. They also can cause the CSF to flow more slowly or build up, leading to symptoms.
Brain Metastases vs. Leptomeningeal Cancer
Some doctors include leptomeningeal metastasis in the same category as brain metastases. They are a little different. Brain metastases describes cancer spread into the brain tissue itself.
Leptomeningeal cancer travels to the leptomeninges. You may have one or the other or both. Having one of these does not mean that you will develop the other.
