Lambert-Eaton syndrome (LEMS) is an autoimmune disorder in cancer patients. It happens when your body makes antibodies that attack voltage-gated calcium channels on presynaptic nerve terminals. This decreases the amount of the neurotransmitter acetylcholine that muscles can receive.
The majority of LEMS cases are associated with malignancy. This is often small-cell lung cancer but can be a non-tumor paraneoplastic form or a lymphoproliferative disorder.
Lambert Eaton Syndrome, also called myasthenic syndrome of Lambert Eaton or LEMS, can happen in people with small-cell lung cancer. It’s unknown why, but the immune system mistakenly attacks the contact point between motor nerves and muscles in these cases. This damage interferes with normal muscle signals, causing weakness. Symptoms usually begin in the legs and arms and may involve muscles of the neck and face, as well as those involved in breathing or swallowing.
These symptoms aren’t as severe as those in myasthenia gravis, but they can still make walking or climbing stairs hard. They can also cause tingling in your hands or feet or dry mouth and eyes (xerostomia). In some people with LEMS, the immune system attacks nerves that control breathing and blood pressure.
Doctors use a variety of tests to diagnose LEMS. They might check your heart rate and blood pressure and look for signs of lung disease, like a chest X-ray or CT scan. They may also order a blood test to check for antibodies that attack neuromuscular junctions. They can also perform electromyography, a test that involves inserting needles into your skin and muscles and sending electrical currents to them. This test measures the speed at which nerve signals travel to the forces. It can help doctors determine if you have Lambert-Eaton syndrome or myasthenia gravis.
Diagnosing Lambert Eaton Syndrome
LEMS can be difficult to diagnose because the symptoms develop gradually over weeks or months. They include fatigue and muscle weakness that affects your legs, arms, and face. The weakness can make it hard to get up from a chair, walk up stairs or a flight of steps, or move your legs when driving a car. You may also need help controlling automatic body functions like blood pressure.
In LEMS, your body’s natural defense system (immune system) mistakenly attacks the contact point between motor nerves and muscles — the neuromuscular junction. This causes problems with the signals that go to your muscles to make them contract.
The antibodies attack the part of nerve endings that release acetylcholine. Less acetylcholine is released, which reduces the strength of the signal sent to your muscles. Your healthcare provider will check your symptoms, do a physical exam, and examine your medical history.
They will also do a chest X-ray or CT scan and ask about your lung function. They may order an electromyography test to check how well your muscles and nerves work together, which shows specific results in people with LEMS.
LEMS can be associated with or without cancer as a paraneoplastic syndrome. Your healthcare provider will check for and treat it if it’s related to cancer. If the cancer is treated, your LEMS will likely improve.
In most people with Lambert-Eaton syndrome, the symptoms come on slowly and get worse over time. The most common symptoms are fatigue and significant muscle weakness. The weakness can be exacerbated by heat, exhaustion, or exercise. People with LEMS may also experience a lack of energy or have difficulty breathing, swallowing, and speaking.
The condition is caused when the body’s natural defenses mistakenly attack the nerves and muscles that control movement. Specifically, the immune system attacks the contact point where motor nerves connect to muscles — the neuromuscular junction. Damage to this area impairs signaling between nerves and muscles, causing weakness. The weakness typically starts in your legs, then affects the muscles of your arms and face. It can also interfere with automatic functions like controlling your blood pressure.
Some people with LEMS have small-cell lung cancer and develop the disorder as a side effect of their treatment (CA-LEMS). Others don’t have any cancer but have a genetic predisposition to autoimmune diseases that can cause the condition.
Your doctor will physically examine you and ask about your symptoms to diagnose the condition. They will also check your medical history. Your doctor may order an electromyography test (EMG). This tests the speed of signals from your nerves to your muscles. It can help rule out other conditions that cause weakness, such as myasthenia gravis.
Prevention of Lambert Eaton Syndrome
In this condition, your body’s immune system mistakenly attacks the part of your nervous system where nerve cells meet muscle fibers. The signal to make muscles work is weaker, and your legs or arms may feel heavy. It affects both voluntary muscles (the ones you control) and autonomic muscles (the ones that help with breathing and blood pressure).
LEMS can be a paraneoplastic disorder in association with cancer, such as small-cell lung cancer (CA-LEMS), or it can occur without cancer, called NC-LEMS. In both types, circulating antibodies against voltage-gated calcium channels interfere with neuromuscular transmission by inhibiting the inward flow of calcium ions into synaptic clefts and the release of the chemical messenger acetylcholine.
If you have a tumor, treating it should improve your Lambert-Eaton Syndrome symptoms. If you don’t have a tumor, your doctor will want to schedule regular checkups to watch for lung cancer and other forms of cancer. They may also prescribe medicines that suppress your immune system or help improve the signals between your nerve and muscle cells.
The first step to prevent LEMS is to stop smoking or avoid it if you have a smoking history. Your healthcare provider will give you tips and advice to quit. Other ways to prevent LEMS include not taking aspirin, ibuprofen, or other medications that can raise your risk of bleeding or cause stomach upset.