Paraneoplastic syndromes of the nervous system

Overview

Paraneoplastic syndromes of the nervous system are a group of rare conditions that develop in some people who have cancer. In addition to the nervous system, paraneoplastic syndromes also can affect other organ systems including hormones, skin, blood and joints.

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.

Depending on where the nervous system is affected, paraneoplastic syndromes can affect muscle movement, coordination, sensory perception, memory, thinking skills or even sleep.

Sometimes the injury to the nervous system can be reversed with therapy directed toward the cancer and the immune system. But sometimes paraneoplastic syndromes can result in permanent damage to the nervous system.

Treating the cancer and other therapies may prevent further damage and improve symptoms and quality of life.

Symptoms

Symptoms of paraneoplastic syndromes of the nervous system can develop relatively quickly, often over days to weeks. They often begin even before a cancer is diagnosed.

Symptoms vary depending on the body part being injured, and may include:

• Trouble walking.
• Trouble with balance.
• Loss of muscle coordination.
• Loss of muscle tone or weakness.
• Loss of fine motor skills, such as picking up objects.
• Trouble swallowing.
• Slurred speech or stuttering.
• Memory loss and other thinking impairment.
• Vision changes.
• Trouble sleeping.
• Seizures.
• Hallucinations.
• Movements that can't be controlled.

Types of paraneoplastic syndromes

Examples of paraneoplastic syndromes of the nervous system include:

• Cerebellar degeneration, also known as cerebellar ataxia. In this syndrome, loss of nerve cells occurs in the area of the brain called the cerebellum that controls muscle functions and balance. Symptoms may include trouble walking, lack of coordination in the arms and legs, trouble maintaining posture, and dizziness. They also may include nausea, eye movements that can't be controlled, double vision, trouble speaking or trouble swallowing.
• Limbic encephalitis. This syndrome involves swelling, known as inflammation, of an area of the brain known as the limbic system. The limbic system controls emotions, behaviors and certain memory functions. People with this condition may experience personality changes or mood changes, memory loss, seizures, hallucinations, or drowsiness.
• Encephalomyelitis. This syndrome refers to inflammation of the brain and spinal cord. There may be a wide variety of symptoms depending on the area affected.
• Opsoclonus-myoclonus. This syndrome occurs when the cerebellum or its connections don't work properly. It can cause rapid, irregular eye movements and muscle jerks in the arms, legs and trunk.
• Stiff person syndrome. Previously called stiff man syndrome, this syndrome leads to serious muscle stiffness, known as rigidity, that gets worse over time. Stiffness mainly affects the spine and legs. It also may cause painful muscle spasms.
• Myelopathy. This term refers to a syndrome that involves injury to the spinal cord. Symptoms depend on the level of spinal cord injury. Symptoms may include changes in bowel and bladder function, and weakness and numbness up to a certain level in the body. If the level of injury includes the neck, it can cause a serious disability that affects the arms and legs.

• Lambert-Eaton myasthenic syndrome. This syndrome is caused by disrupted communication between nerves and muscles. Symptoms include muscle weakness in the pelvis and legs, and fatigue. It also may cause trouble swallowing and speaking, irregular eye movement, and double vision. Other symptoms may include dry mouth and erectile dysfunction.

  When it occurs as a paraneoplastic syndrome, Lambert-Eaton myasthenic syndrome is typically associated with lung cancer.

• Myasthenia gravis. Myasthenia gravis also is related to disrupted communication between nerves and muscles. People with myasthenia gravis have weakness and rapid fatigue of any of the muscles that are under voluntary control. These include muscles in the face, eyes, arms and legs. The muscles involved in chewing, swallowing, talking and breathing may be affected as well.

  When myasthenia gravis occurs as a paraneoplastic syndrome, it is typically associated with cancer of the thymus gland, known as thymoma.

• Neuromyotonia, also known as Isaacs' syndrome. Neuromyotonia occurs when there are an excess number of nerve impulses that control muscle movement. This is known as peripheral nerve hyperexcitability. These impulses can cause twitching, muscle rippling that looks like a "bag of worms" and stiffness that gets worse over time. It also may cause muscle cramps, slowed movement and other issues with the muscles.
• Peripheral neuropathy. In this condition, nerves that transmit messages from the brain or spinal column to the rest of the body are damaged. These nerves are known as peripheral nerves. When damage involves only the sensory nerves, it causes pain and changes in sensation anywhere in the body.
• Dysautonomia. Dysautonomia refers to a wide range of symptoms that result from injury to the nerves that regulate involuntary body functions. Known as the autonomic nervous system, these nerves control heart rate, blood pressure, sweating, and bowel and bladder functions. Symptoms may include low blood pressure, irregular heartbeats and trouble breathing.

When to see a doctor

Symptoms of paraneoplastic syndromes of the nervous system are similar to those of many conditions, including cancer, cancer complications and some cancer treatments.

But if you have any symptoms suggesting a paraneoplastic syndrome, see your healthcare professional as soon as possible. Early diagnosis and appropriate care are important for treating the cancer and preventing further damage of the nervous system.

Causes

Paraneoplastic syndromes of the nervous system are not caused by cancer cells directly or by the cancer spreading, known as metastasis. They're also not caused by other complications, such as infections or treatment side effects. Instead, the syndromes occur alongside the cancer as a result of the activation of your immune system.

Researchers believe that paraneoplastic syndromes of the nervous system are caused by cancer-fighting abilities of the immune system. In particular, antibodies and certain white blood cells, known as T cells, are thought to be involved. Instead of attacking only the cancer cells, these immune system agents also attack the healthy cells of the nervous system.

Risk factors

Any cancer may be associated with a paraneoplastic syndrome of the nervous system. However, it occurs more often in people with cancers of the lung, ovary, breast, testis or lymphatic system.