A tumor is an abnormal growth, whether noncancerous (benign) or cancerous (malignant). In many parts of the body, a noncancerous tumor causes few or no problems. However, if any growth or mass in the brain (brain tumor) or spinal cord (spinal cord tumor) is getting larger, it can cause considerable damage because the structures that contain the brain (the skull) and spinal cord (the spine) cannot expand to make room for any increase in their contents.
Tumors, whether cancerous or not, can develop from nerve tissue in the brain or spinal cord. Cancerous tumors can spread (metastasize) to the brain or spinal cord from elsewhere in the body.
Some cancers elsewhere in the body cause symptoms of nervous system dysfunction even though there is no evidence that nerve tissue has been invaded. These disorders are called paraneoplastic syndromes. They can cause dementia, mood swings, seizures, incoordination, dizziness, double vision, and abnormal eye movements. The most common effect of paraneoplastic syndromes is dysfunction of peripheral nerves (polyneuropathy), resulting in muscle weakness, numbness, and tingling.
Tumors of the nervous system may be treated with surgery, radiation therapy, chemotherapy, or, most often, a combination. Radiation therapy sometimes damages the nervous system, despite the best efforts to prevent this effect. Chemotherapy can affect brain function, so doctors choose chemotherapy drugs carefully to avoid causing undue harm.