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Lambert Eaton Syndrome Diagnosis – What You Need to Know

    Lambert Eaton Syndrome

    Lambert Eaton syndrome, or LEMS, is a neuromuscular autoimmunity associated with cancer. In half of the cases (CA-LEMS), the tumor is small cell lung carcinoma that expresses functional voltage-gated calcium channels (VGCC).

    Circulating antibodies target VGCC on presynaptic nerve terminals, inhibiting inward calcium current and the release of acetylcholine. Weakness develops gradually, typically in the proximal muscles of the legs and arms. Autonomic dysfunction and absent deep tendon reflexes are also common.


    LEMS is an autoimmune disease that affects the neuromuscular junctions, the sites where nerves connect to muscles. This makes it difficult for your brain to send the signals that tell your muscles what to do. This condition usually develops as a paraneoplastic disorder associated with cancer (CA-LEMS), often small-cell lung cancer. Still, it may also happen without cancer as part of a general autoimmune state (NCA-LEMS).

    Symptoms of LEMS include muscle weakness and fatigue that get worse over time. It typically starts in your legs, then spreads to your arms, hands, and feet. It can also cause problems with your breathing and swallowing.

    A healthcare provider can diagnose LES by taking a medical history and doing a physical exam. Your doctor will ask about any previous cancers you’ve had and may perform a chest X-ray, computed tomography (CT) scan, or magnetic resonance imaging (MRI) of your chest. These tests can check for signs of lung cancer, which may help find the cause of your symptoms.

    If there is an underlying cancer, your healthcare provider will treat the cancer, and you may improve from this treatment. Your healthcare provider may also prescribe medicines to suppress your immune system or to help strengthen the signaling between your nerve and muscle cells. Other treatments may include plasmapheresis, which replaces the blood in your body and removes harmful immune system proteins that can worsen symptoms.


    What is Lambert Eaton Syndrome? Lambert-Eaton syndrome (LEMS) is caused by your body’s immune system attacking the connection between motor nerves and muscles — the neuromuscular junction. This damages the neuromuscular junction and impairs signaling, leading to weakness that usually starts in your upper legs. It can later affect other muscle groups, such as your arms, shoulders, and those that help you swallow and speak. The weakness can also cause tingling sensations in your hands and feet and fatigue.

    LEMS is often a paraneoplastic disorder that develops due to cancer, particularly small-cell lung cancer, but it can also occur in people without cancer. If your healthcare provider suspects you have this condition, they will check for the presence of cancer and other causes of the disease. Your doctor will use a series of tests to assess your strength, muscle tone, reflexes, and balance. They may order blood tests for antibodies against voltage-gated calcium channels on presynaptic nerve terminals. They will also perform repetitive-nerve stimulation on your muscles, looking for a decrease in the size of the muscle action potential after the electrical stimulus.

    Other signs of this condition include poor reflexes that improve after repeated muscle contraction and dry mouth. You may also have symptoms of autonomic dysfunction, such as erectile dysfunction in men and constipation, dizziness, and altered perspiration.


    In LEMS, antibodies destroy nerve endings that normally trigger the release of a chemical called acetylcholine. Without enough acetylcholine, muscles cannot contract, which causes the symptoms of fatigue and muscle weakness that characterize the condition.

    A doctor will review your medical history and do a physical exam to see if you have the symptoms of Lambert-Eaton syndrome. They may order a blood test to check for the presence of antibodies that attack neuromuscular junctions. They will also do a test called repetitive nerve stimulation, which sends electrical currents through your muscles and checks for lack of response.

    If your doctor suspects you have LEMS, they will probably perform a CT scan of your lungs. This will help them see if your illness is related to cancer. Suppose your doctor doesn’t find cancer in your lungs. In that case, they will probably give you a treatment called plasmapheresis, which involves replacing the plasma in your body with fresh plasma that does not contain harmful immune system proteins.

    LEMS is sometimes a paraneoplastic disorder associated with underlying cancer (CA-LEMS). However, it can occur without cancer and as part of a general autoimmune state (NCA-LEMS). Symptoms typically begin slowly and get worse over time. They are usually confined to proximal muscles such as the hip girdle and thigh muscles. Proximal weakness is accompanied by absent or reduced tendon reflexes that fail to facilitate after brief exercise and a dry mouth. Serum P/Q-type voltage-gated calcium channel antibodies are often present.


    Lambert-Eaton syndrome (LEMS) is a condition that weakens muscles. It is caused by the body’s immune system attacking the area where nerve cells connect to muscle fibers. This area is called the neuromuscular junction. In LEMS, antibodies attack the part of the nerve cell where calcium channels are located, reducing the amount of the released chemical messenger acetylcholine. Without enough acetylcholine, muscle fibers cannot contract and move the legs, arms, chest, and other body parts.

    People with LEMS often develop the condition after a cancer diagnosis, especially small-cell lung cancer (SCLC). The tumor may have caused the body to make the antibodies that cause the condition. Other types of cancers also can cause LEMS, including prostate cancer, thymoma, and lymphoproliferative disorders. People with LEMS can also develop the disease even if they don’t have cancer.

    In some cases, the symptoms of this condition improve with treatment for the underlying cancer. This can include surgery, radiation, and chemotherapy. Medicines to suppress the immune system and drugs that will enhance the signals between nerve cells and muscles can also help treat the condition.

    To help diagnose LEMS, your healthcare provider will review your symptoms and do a physical exam. You will have a blood test to check for the antibodies that can cause this condition. You will also have a breathing test or X-ray of your lungs and an electromyography test, which shows how well your muscles work.

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