Paraneoplastic syndromes of the nervous system are a group of rare disorders that develop in some people who have cancer. Paraneoplastic syndromes of the nervous system are the most commonly reported paraneoplastic syndromes, but these syndromes can also affect other organ systems including hormone (endocrine), skin (dermatologic), blood (hematologic) and joints (rheumatologic). Paraneoplastic events may also in part explain some of the most common symptoms of cancer, such as fatigue, loss of appetite for food (anorexia) and weight loss. Paraneoplastic syndromes of the nervous system occur when cancer-fighting agents of the immune system also attack parts of the brain, spinal cord, peripheral nerves or muscle.
About 3–5 % of patients with small-cell lung cancer and 15– 20 % of patients with thymoma develop paraneoplastic neurological syndromes . Less than 1 % of patients with other types of tumours develop paraneoplastic neurological symptoms
Common paraneoplastic syndromes of the nervous system include:
1. Cerebellar degeneration. This is the loss of nerve cells in the area of the brain that controls muscle functions and balance (cerebellum).
2. Limbic encephalitis. This is inflammation affecting a region of the brain known as the limbic system, which controls emotions, behaviors and certain memory functions.
3. Encephalomyelitis. Opsoclonus-myoclonus. This syndrome is due to dysfunction of the cerebellum or its connections. It can cause rapid, irregular eye movements (opsoclonus) and involuntary, chaotic muscle jerks (myoclonus) in your limbs and trunk.
4. Stiff person syndrome. Previously called stiff man syndrome, this syndrome is characterized by progressive, severe muscle stiffness or rigidity, mainly affecting your spine and legs.
5. Myelopathy. This term refers to a syndrome of injury limited to the spinal cord. It sometimes is called transverse myelitis.