Lambert-Eaton myasthenic syndrome

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at December 5, 2016
StartDiseasesLambert-Eaton myasthenic syndrome

Lambert-Eaton myasthenic syndrome is a degenerative disease in which the body attacks its own neuromuscular junctions. Neuromuscular junctions allow signals from the brain to pass through nerves into muscle cells. People with Lambert-Eaton myasthenic syndrome find it difficult to move some muscles as they normally would.

Contents

Definition & Facts

Edward Lambert and Lee Eaton first described Lambert-Eaton myasthenic syndrome at the Mayo Clinic in Minnesota during the 1950's and 60's. Lambert-Eaton myasthenic syndrome is an autoimmune disease where the body's own immune system attacks otherwise healthy parts of the body.

With Lambert-Eaton myasthenic syndrome, the immune system attacks something called neuromuscular junctions, where the nerve endings meet up with muscle tissue. In a healthy neuromuscular junction, signals from the brain relay through the nerve into the muscle to command movement. Patients with Lambert-Eaton myasthenic syndrome find moving some muscles difficult due to signal disruption caused by a damaged neuromuscular junction.

Lambert-Eaton myasthenic syndrome is very similar to another autoimmune disorder known as myasthenia gravis. In each disease, the immune system attacks different parts of the neuromuscular junction, causing similar symptoms. Lambert-Eaton myasthenic syndrome can affect the muscles of the face. This can interfere with the ability to speak, swallow, and breathe.

Symptoms & Complaints

The main symptom of those suffering from Lambert-Eaton myasthenic syndrome is weakness in the leg muscles. This weakness tends to dissipate temporarily with a little bit of exercise or exertion.

Other symptoms may or may not be experienced by a patient with Lambert-Eaton myasthenic syndrome. These symptoms include:

Causes

Lambert-Eaton myasthenic syndrome often affects those with a certain type of lung cancer known as small-cell lung cancer. The onset of Lambert-Eaton myasthenic syndrome is thought to be a side effect of the body's effort to fight the cancer. The body's immune system is activated to fight the cancer.

This hyperactivity of the immune system has the unintended consequence of damaging the neuromuscular junction, disrupting the signal relay of the nerves into muscle tissue. In other patients, Lambert-Eaton myasthenic syndrome follows the onset of other autoimmune disorders. In a rare few, the cause is simply unknown or idiopathic.

Autoimmune disorders happen when the immune system, normally tasked with defending the body against disease, begins to attack otherwise healthy cells. Arthritis and type 1 diabetes are examples of common autoimmune diseases.

In Lambert-Eaton myasthenic syndrome, an army of white blood cells disrupts the release of ACh, a chemical released by the nerve that helps tell the muscle to contract. The vast majority of those with Lambert-Eaton myasthenic syndrome test positive for an antibody for a protein known as VCGG. This protein is essential for the release of ACh. Small-cell lung cancer cells produce VGCC which forces small-cell lung cancer patients to make anti-VGCC which disrupts the transmission of ACh.

Diagnosis & Tests

Doctors give a special blood test for Lambert-Eaton myasthenic syndrome. The blood test is looking for the anti-VGCC antibody that interrupts the transmission of ACh which causes the autoimmune disorder's symptoms. Doctors must also be very careful when examining the symptoms because myasthenia gravis, which also attacks ACh receptors in the muscles, is incredibly similar.

An electromyograph is a machine that evaluates how well muscles and nerves are working. It can help identify the affected muscles to help doctors make a diagnosis. Since about 60 percent of Lambert-Eaton myasthenic syndrome are associated with small-cell lung cancer, doctors are likely to test for cancers, including lymphoma, as well. If no cancer is found right away, regular checkups for the development of cancer will be recommended.

Treatment & Therapy

For most patients with Lambert-Eaton myasthenic syndrome, cancer is the disease treated first. Small-cell lung cancer and other cancers that cause Lambert-Eaton myasthenic syndrome can be life threatening and must be effectively treated before considering the autoimmune condition. These treatments include surgery, radiation, and chemotherapy. Once the cancer is treated effectively and the patient is responding well to treatment, the Lambert-Eaton myasthenic syndrome can be addressed. In most cases, however, effective cancer treatment also improves the symptoms of Lambert-Eaton myasthenic syndrome.

Doctors can prescribe medications that suppress the immune system in hopes the immune system stops attacking the neuromuscular junction. This can put the patient at risk for other illnesses as the immune system is suppressed. A treatment called plasmapheresis can also help patients with Lambert-Eaton myasthenic syndrome. Blood plasma is replaced in order to remove the proteins that destroy normal neuromuscular junction, such as anti-VGCC.

Prevention & Prophylaxis

Nobody knows exactly how Lambert-Eaton myasthenic syndrome works or how to prevent it. There is consensus that the autoimmune disorder cam be caused by small-cell lung cancer. The best way to avoid Lambert-Eaton myasthenic syndrome is to reduce the risk of lung cancer.

The very best way to reduce chances of lung cancer is to not begin smoking, to quit smoking if one is a smoker, and to avoid secondhand smoke altogether. Other ways to lower cancer risk is to eat a diet full of fresh fruits and vegetables, and to exercise regularly. The house can also be inspected for radon, an airborne chemical known to cause lung cancer.