Lambert-Eaton Syndrome Explained

Lambert-Eaton syndrome, or Lambert-Eaton myasthenic syndrome (LEMS), is a rare disorder that interferes with signals between the nerves and muscles. This interference causes muscle weakness and motor difficulties, among other symptoms. Doctors typically diagnose LEMS through blood tests, nerve studies, and imaging tests. Treatment for LEMS may seek to address underlying conditions, improve nerve signal function, or boost the immune system.

Read on to learn more about the types, symptoms, treatments, and outlook for people with Lambert-Eaton syndrome.

Experts generally split LEMS into two types.

LEMS that occurs alongside cancer (CA-LEMS) is a paraneoplastic disorder. Paraneoplastic disorders result from an atypical immune response to a neoplasm, which is a type of cancerous tumor.

The body’s immune reaction to the tumor affects the nerves and disrupts their signals to the muscles. Many cases of CA-LEMS are associated with small cell lung cancer.

LEMS that occurs without cancer (NCA-LEMS) is a general autoimmune condition. As with CA-LEMS, the immune system overreacts and interferes with the signals to the muscles.

The exact trigger for this autoimmune reaction is currently unknown.

The signal disruption between nerves and muscles leads to gradual muscle weakness. This weakness is characteristic of LEMS and can develop over weeks or months.

LEMS can particularly affect the arms and legs, causing motor difficulties. Climbing stairs or walking up an incline may become difficult for individuals with LEMS. Over time, the condition may begin to affect other muscles, including:

• shoulder muscles
• foot muscles
• hand muscles
• muscles involved in speech and swallowing
• eye muscles

LEMS can also cause other symptoms, including:

• dry mouth and eyes
• constipation
• weight loss
• decreased sweating
• reduced tendon reflexes
• sexual dysfunction, such as erectile dysfunction for males and reduced sex drive for females

To diagnose LEMS, your doctor will first assess your medical history and perform a physical examination. If they suspect nerve issues, they may refer you to a neurologist for further testing.

Tests that can aid in confirming a diagnosis may include:

• Blood tests: These tests can determine the presence of certain antibodies. The immune system produces these antibodies when it overreacts to the body’s nerves.
• Nerve studies: Nerve studies can help doctors assess if nerve signals are reaching the muscles.
• Imaging tests: CT scans and PET scans may show lung cancer that could indicate CA-LEMS.

Research indicates that LEMS may precede a lung cancer diagnosis by several years. Even if initial testing doesn’t show cancer, frequent follow-up visits may be necessary to monitor any cancer development.

Because there is no cure for LEMS, treatment focuses on symptom relief and quality of life improvements.

For CA-LEMS, addressing the cancer is the primary treatment. Sometimes, this may be all that’s necessary to relieve LEMS symptoms. Depending on the type of cancer, treatment may include:

• chemotherapy
• radiation therapy
• surgery
• combined treatments

Medications are available to facilitate signaling between nerves and muscles. These drugs may include pyridostigmine (Mestinon, Regonol) and amifampridine (Firdapse). Immunosuppressants can also relieve symptoms by reducing the immune system’s response.

Medications are the main treatment. However, doctors may also use short-term treatments for severe weakness or if other treatments have been ineffective.

Immunoglobulin therapy involves injecting antibodies from donated blood into an affected individual. These antibodies temporarily halt the immune system’s reaction to the nerves.

Plasmapheresis may also provide short-term relief. This process removes, filters, and replaces blood plasma to remove antibodies that interfere with nerves.

The outlook for people with LEMS depends on the type of LEMS. People with CA-LEMS can experience rapidly progressing symptoms and a poorer outlook.

People with NCA-LEMS typically have a near-average survival rate, compared with the general population. However, many people experience long-term disability resulting from muscle weakness.

LEMS can cause complications related to gradual muscle weakness. Reduced strength and coordination may cause more frequent falls and lead to injury.

In addition, some people may experience difficulty swallowing. Although it is rare, advanced LEMS may also cause respiratory failure.

Not all cases of LEMS are preventable. However, reducing some of the risk factors for lung cancer may help lower your risk of developing LEMS.

The American Cancer Society provides the following tips to reduce lung cancer risk:

• Stop smoking and avoid exposure to secondhand smoke.
• Avoid exposure to radon.
• Reduce your exposure to cancer-causing agents, such as asbestos or diesel exhaust.
• Eat a balanced diet with lots of fruits and vegetables.

These are a few other common questions people may ask about LEMS. These answers have been reviewed by Dr. Meredith Goodwin.

LEMS and myasthenia gravis (MG) can cause similar symptoms, such as muscle weakness and rapid fatigue. Typically, LEMS initially causes weakness in the arms and legs before progressing to other areas. MG usually causes more pronounced muscle weakness in the eyes and respiratory muscles.

People with LEMS are also more likely to experience dry mouth and constipation.

LEMS is most commonly associated with small cell lung cancer. However, it can also occur with non-small cell lung cancer, prostate cancer, and thymoma.

People with NCA-LEMS typically have average life expectancies. However, people with CA-LEMS may have shorter life expectancies due to delayed diagnoses, which can complicate treatment.

There is currently no known cure for LEMS. Treatment focuses on addressing any underlying cancer and improving symptoms.

LEMS is an autoimmune condition that affects the nerves’ ability to communicate with the muscles. It may occur with or without cancer.

The main symptom of LEMS is progressive muscle weakness. Other symptoms can include dry mouth, sexual dysfunction, decreased sweating, and reduced tendon reflexes.

Doctors typically diagnose LEMS with blood tests, nerve studies, and imaging tests.

If LEMS occurs with cancer, addressing the cancer may be sufficient to provide symptom relief. In other cases, medications can help improve signal function and suppress the immune system.

Contact your doctor to discuss ways to manage LEMS.