Paraneoplastic syndromes of the nervous system are a group of rare disorders that develop in some people with cancer, most commonly in people with lung, breast or ovarian cancer. Some of these disorders are believed to occur when cancer-fighting antibodies mistakenly attack normal cells in the nervous system.

Paraneoplastic syndromes of the nervous system are rare, occurring in less than 1 percent of the people who have cancer.

Symptoms of paraneoplastic syndromes of the nervous system usually appear when cancer is still in its early stages, often before you even know you have cancer. Treatment of the cancer may eliminate the symptoms of a paraneoplastic syndrome. In some cases, your immune system may need to be suppressed.

Features common to neurological paraneoplastic syndromes in general include:

• Difficulty walking
• Difficulty maintaining your balance
• Difficulty swallowing
• Loss of muscle tone
• Loss of fine motor coordination
• Slurred speech
• Memory loss
• Vision problems
• Sleep disturbances
• Dementia
• Seizures
• Numbness and tingling in your arms and legs
• Dizziness
  
  

Disorders that may occur as paraneoplastic syndromes of the nervous system include the following:

• Cerebellar degeneration. This disorder causes the death of nerve cells in the area of your brain that controls muscle functions and balance (cerebellum). The most common sign is a wide-legged, unsteady walk, often accompanied by a tremor in the trunk of your body.
• Encephalomyelitis. This condition involves inflammation of your brain and spinal cord. Symptoms can range from numbness to respiratory failure.
• Lambert-Eaton myasthenic syndrome. Muscle weakness, fatigue, difficulty swallowing and vision changes are the most frequent signs and symptoms of this disorder, which is caused by disrupted communication between your nerves and muscles.
• Limbic encephalitis. In this disorder, portions of your brain swell, which can cause memory loss, drowsiness, confusion, disorientation and seizures, among other signs and symptoms.
• Myasthenia gravis. This disorder is characterized by weakness and rapid fatigue of any of the muscles under your voluntary control, including those in your face, eyes, arms and legs. The muscles involved in chewing, swallowing, talking and breathing may be affected as well. Myasthenia gravis is often associated with a tumor of the thymus gland (thymoma).
• Neuromyotonia. This condition — also known as Isaacs syndrome — is characterized by abnormal nerve impulses from the motor neurons of your peripheral nerves. These impulses cause twitching, progressive stiffness, muscle cramps and slowed movement, among other signs and symptoms.
• Neuropathies. Neuropathy is damage to your nerves. Paraneoplastic syndromes may include autonomic neuropathy (damage to the nerves that regulate the body functions you can't voluntarily control, such as heart rate, blood pressure, perspiration and digestion) and sensory neuropathy (damage to sensory nerves in your peripheral nervous system, which include nerves in your face, arms, legs, torso and some nerves in your skull).
• Opsoclonus-myoclonus. Rapid, irregular eye movements (opsoclonus) coupled with quick involuntary muscle jerks (myoclonus) can result from damage to your nervous system.
• Stiff person syndrome. This disabling neurological disorder is characterized by progressive, severe muscle stiffness or rigidity, mainly in your spine and legs. It may also cause painful muscle spasms.

Paraneoplastic syndromes occur in people who have cancer. In the nervous system, these syndromes are believed to be caused by cancer-fighting antibodies or some white blood cells, known as T cells, that your body activates to combat the cancer. Instead of attacking only the cancer cells, the antibodies attack normal cells in your brain and nervous system as well.

Neurological paraneoplastic syndromes are most common in people who have lung, breast or ovarian cancer. Most often, they're the result of your immune system's response to cancer. But, it's not clear why this response occurs in some people who have cancer and not in others. Doctors have not found any risk factors that increase your chances of developing a neurological paraneoplastic syndrome if you have cancer.

Signs and symptoms of neurological paraneoplastic syndromes may decrease or stop once you have received treatment for your cancer. If, however, you have a paraneoplastic syndrome that has destroyed neurons, such as in cerebellar degeneration, that damage usually cannot be reversed and, in some cases, it may result in permanent disability.

While you might first discuss your symptoms with your family doctor, he or she may refer you to a neurologist for further evaluation.

What you can do
Because appointments can be brief, plan ahead and write a list that includes:

• Detailed descriptions of your symptoms
• All the medications and dietary supplements you take
• Questions you want to ask the doctor

What to expect from your doctor
In addition to a general physical exam, your doctor may also check your neurological health by testing your:

• Reflexes
• Muscle strength
• Muscle tone
• Senses of touch and sight
• Coordination
• Balance

If your doctor suspects you have a neurological paraneoplastic syndrome, he or she may recommend the following tests:

Laboratory tests

• Blood test. A sample of your blood may contain one or more of the antibodies commonly associated with paraneoplastic syndromes. But it's possible to have one of these syndromes and not have the antibodies in your blood.
• Spinal tap (lumbar puncture). During a lumbar puncture, a needle is inserted into your lower spine to extract a small amount of cerebrospinal fluid (CSF) — the fluid that cushions your brain and spinal cord — for laboratory analysis. Sometimes, paraneoplastic antibodies may be present in CSF fluid even if they're not detectable in your blood.

Imaging tests
CT, MRI or positron emission tomography (PET) scans can often reveal the cancerous tumor that has triggered your paraneoplastic syndrome. Some tumors, however, are so small and slow growing, they're difficult to find.

• CT. A CT machine takes X-rays from many different angles and then combines them to make cross-sectional images. The scan takes about 20 minutes.
• MRI. This technique uses a magnetic field and radio waves to create detailed cross-sectional images of your head and body. You lie on a bed that slides into a long tube-shaped machine. The machine makes a loud thumping or banging noise as it operates. The test — which can take as long as an hour — is painless, but some people feel claustrophobic inside MRI machines.
• Positron emission tomography (PET). Using radioactive isotopes injected into your bloodstream, PET scans can show brain activity, blood flow and tumor growth.

Treatment of neurological paraneoplastic syndromes involves treating the cancer and, in some cases, decreasing or stopping the immune response that's causing the neurological signs and symptoms. Your treatment will depend on the specific type of paraneoplastic syndrome you have, but it may include:

Medications
In addition to drugs, such as chemotherapy, that you may need to combat your cancer, your doctor also may suggest one or more of the following drugs to stop your immune system from damaging your nerves.

• Corticosteroids, such as prednisone
• Cyclophosphamide (Cytoxan)
• Cyclosporine (Gengraf)
• Tacrolimus (Prograf)
  

Therapies

• Physical therapy. Specific exercises may help you regain some of the muscle and nerve functions that may have been damaged.
• Speech therapy. If a paraneoplastic syndrome has affected your ability to speak, a speech therapist can help improve your communication skills.

Other procedures

• Plasmapheresis. This process — also known as plasma exchange — removes the fluid part of the blood, called plasma, from your blood cells with a device known as a cell separator. The red and white blood cells, along with your platelets, are returned to your body, while the plasma, which contains unwanted paraneoplastic antibodies, is discarded and replaced with other fluids.
• Intravenous immunoglobulin (IVIg). Immunoglobulin contains healthy antibodies from blood donors. High doses of immunoglobulin can block the damaging antibodies in your blood.

Everyone has his or her own way of coping with cancer. But, you don't have to do it alone. If you have questions or would like guidance, talk with a member of your health care team. The more you know about your condition, the better you're able to participate in decisions about your care.

Support groups can put you in touch with others who have faced the same challenges you're facing. If you can't find an appropriate support group where you live, you might find one on the Internet.