Guide To The Types Of Paraneoplastic Syndromes

Paraneoplastic syndromes are rare disorders that can develop in cancer patients. Though the syndromes typically affect the nervous system, they can also affect organ systems including the dermatologic, hematologic, rheumatologic, and endocrine systems. Therefore, they affect an individual's hormones, joints, blood, and skin. Paraneoplastic syndromes happen when the immune system's cancer-fighting agents mistakenly attack portions of the muscle, peripheral nerves, spinal cord, or brain.

The symptoms are wide-ranging because they depend upon which part of the nervous system was attacked. While the injury can sometimes be reversed, it's also possible for the disease to cause rapid and irreversible nervous system damage.

Lambert-Eaton Myasthenic Syndrome

Lambert-Eaton myasthenic syndrome (LEMS) is a paraneoplastic syndrome in which the immune system attacks the connection between the muscles and nerves. This attack interrupts the ability of the nerves to send signals to the muscles. The specific attack is on the calcium channels found on nerve endings. When the calcium channels are broken down, the nerve endings release less acetylcholine. This neurotransmitter acts as a messenger to trigger contraction in the muscles. Since the acetylcholine levels are lowered in LEMS patients, they can't contract their muscles normally. This leads to muscle weakness.

Lambert-Eaton myasthenic syndrome starts by causing weakness in the hips and upper legs, which makes walking difficult. It also causes weakness in the shoulders and upper arms, so day-to-day tasks become difficult. There may also be mild symptoms related to the eye muscles and muscles used when swallowing. The majority of patients with LEMS have mild nervous system dysfunction, most commonly presenting as dry mouth. Lambert-Eaton myasthenic syndrome is particularly associated with small cell lung cancer. The main theory about the disease is the immune system attacks the nerve endings because they share some protein types with the cancer cells.

Peripheral Neuropathy

Peripheral neuropathy is the name given to any condition that causes the peripheral nerves to become diseased or damaged. Peripheral nerves are the nerves throughout the body that transmit messages to the spinal cord and brain. The network connects the central nervous system to the internal organs, skin, and muscles. Peripheral nerves are attached to the spinal cord.

There are a number of different peripheral neuropathies. As a paraneoplastic syndrome, the condition occurs when the immune system attacks the peripheral nerves. In most cases, this results in polyneuropathy. Unlike mononeuropathy, which occurs when only one nerve is affected, polyneuropathy refers to cases where multiple nerves are affected. Cancer patients often have autonomic problems because of long bed rest, chemotherapy, malnutrition, or high-dose analgesics. With that said, this condition should be considered whenever a cancer patient has symptoms of autonomic nervous system dysfunction.

Stiff Person Syndrome

Stiff person syndrome is a rare syndrome that affects an individual's nervous system. The symptoms often include extreme stiffness in the muscles, painful spasms and rigidity in the limbs and trunk, and severe impairment of mobility. The muscle spasms may be forceful enough to cause bone fractures. Stiff person syndrome occurs when the central nervous system's inhibition decreases, leading to an increase in muscle activity. In all cases, the condition is thought to be related to autoimmune diseases. The majority of patients with stiff person syndrome eventually become disabled.

There aren't definitive answers about what causes this condition, though studies have shown the majority of individuals with stiff person syndrome have antibodies that attack the protein GAD. GAD is found in certain neurons that make gamma-aminobutyric acid. This acid, commonly known as GABA, is vital for controlling muscle movements. When the immune system attacks the GAD-producing neurons, this leads to a GABA deficiency. Patients without enough of this acid cannot control their muscle movements. It's also common for paraneoplastic stiff person syndrome to involve antibodies to amphiphysin. This protein helps transmit signals between neurons. When individuals have these antibodies, they also have a higher chance of having or developing colon, lung, or breast cancer.

Cerebellar Degeneration

Paraneoplastic cerebellar degeneration is the most commonly recognized and devastating of the paraneoplastic syndromes. It occurs in fewer than one percent of cancer patients. The condition is associated with a number of different tumors like breast cancer, ovarian cancer, lung cancer, Hodgkin's lymphoma, and some other forms of cancer.

It's believed the condition occurs when the immune system attacks portions of the central nervous system, generally Purkinje cells, which are found in the cerebellum. They are among the largest neurons in a human's brain. It's common for patients to seek treatment for paraneoplastic cerebellar degeneration before their underlying cancer is identified. The neurological symptoms include ataxia, involuntary eye movement, and speech disorders.

Myelopathy

Myelopathy occurs when the spinal cord is severely compressed, the only treatment for which is decompression surgery. There are multiple causes of myelopathy. In paraneoplastic syndrome, the cause is autoimmune. It's rare for myelopathy to be caused by paraneoplastic reasons, but experts stress the importance of considering a paraneoplastic reason for myelopathy. Patients may present with this condition before they show symptoms of cancer, and identification of the paraneoplastic nature may lead to a cancer diagnosis.

Individuals with myelopathy might have pain in their legs, arms, lower back, or neck. They may also experience numbness or weakness. It may be difficult to use fine motor skills for tasks like buttoning a shirt or writing. Walking may also be difficult, and patients may lose their ability to control their bowels.