Several conditions can cause muscle weakness. These include myasthenia gravis, multiple sclerosis, and other autoimmune disorders. In about 60% of LEMS cases, the disease is associated with an underlying malignancy. The cancer is usually small-cell lung cancer (SCLC), but lymphoma, malignant thymoma, and neuroblastoma have also been reported.
LEMS (Lambert-Eaton myasthenic syndrome) happens when an area called the neuromuscular junction isn’t working correctly. This is where a nerve signal from the spinal cord meets up with muscle cells. If there are problems in the junction, a standard signal isn’t sent to muscle cells to tighten up and move.
This causes weakness that can affect many parts of the body. But usually, it starts in the proximal muscles of the legs and arms. They can become weaker, making it harder to rise from a chair or climb stairs. It can also cause a feeling that your muscles are stiff and heavy.
Other common LEMS symptoms often happen to the eye muscles, including double-vision and drooping eyelids (ptosis). Weakness in the tongue and jaw can also make it hard to speak clearly. It’s essential to get checked out by a doctor if you experience muscle weakness.
It could be a sign of cancer, especially small-cell lung cancer. Treatment can also help ease the LEMS symptoms if the cancer is found. If there isn’t cancer, you might need a CT scan or other imaging tests to determine what else is causing the symptoms.
In LEMS, muscle weakness usually affects the muscles used for walking first. You might need help getting up from a chair, climbing stairs, or walking up a steep walkway. Then, the weakness spreads from your legs to your arms. It can also affect your eye muscles, causing drooping eyes or double vision.
On a medical exam, you may have poor tendon reflexes (the kind your healthcare provider checks by tapping the knee). A blood test can show you have high levels of anti-calcium channel antibodies. These antibodies block calcium channels at the end of nerve cells, interfering with nerve signals controlling muscle movement.
If the problem is related to injury, X-rays and an MRI can help identify a broken bone or other damage affecting your walking ability. Depending on the cause, treatment might include surgery, physical therapy, and medications to manage pain or other symptoms. If the condition is caused by cancer, treatments for the underlying cancer might improve the symptoms of LEMS.
LEMS can lead to weakness in the muscles that control the eyes, mouth, and other parts of the face. This may cause problems with vision, including double vision (diplopia) and eyelid drooping (ptosis). Weakness in these muscles can also make it difficult to speak and swallow and cause slurred or mumbled speech.
Autonomic nervous system dysfunction symptoms are common in people with LEMS, such as dry mouth, difficulty swallowing, constipation, and impotence in men. To diagnose LEMS, your doctor will review your medical history and perform a physical exam. They will then order blood tests to detect antibodies linked with LEMS, known as anti-calcium channel antibodies.
These tests are typically performed by a neurologist specializing in nerves and muscle disorders. Other diagnostic procedures may include electromyography (EMG), which uses thin wire electrodes to test muscle activity, and diagnostic imaging, such as magnetic resonance imaging (MRI) or computed tomography (CT).
Researchers have found that the symptom of breathing problems (dyspnea) is more common in people with LEMS than in those who don’t. In up to 60% of cases, LEMS is connected to underlying cancer, most commonly small-cell lung cancer. But even in cases where no cancer is detected, the immune system may produce antibodies that cross-react with voltage-gated calcium channels (VGCC) at the neuromuscular junction.
These disrupt everyday nerve-to-muscle communication. Consequently, muscle weakness occurs mainly in the legs but can also affect muscles of the arms, hands, and muscles that control breathing and swallowing. Like Myasthenia gravis (MG), a doctor can usually suspect LEMS based on your medical history and physical exam. But it can take time to receive the correct diagnosis, particularly if the condition is associated with cancer.
An underlying cancer is found in about half of all LEMS cases. The most common type of cancer found is small-cell lung cancer. People with LEMS associated with cancer have a longer life span than those with idiopathic LEMS. In most people, symptoms of LEMS start in the legs.
They may feel heavy and unsteady, like walking through water. Over time, the weakness will spread to muscles farther from the body’s trunk, such as the arms and face. It is less common for LEMS to affect the torso, but it can happen. People with LEMS can also experience problems with automatic body functions, such as a dry mouth and constipation in men or impotence in women.
The antibodies that cause LEMS can also affect the muscles that move the eyelids, causing them to droop (ptosis) or to make double vision. Eyeglasses or contact lenses can correct this problem and, in some cases, surgery. The weakness can also interfere with chewing, swallowing, and breathing. This can lead to a shortened life span in some people.