What Is Lambert-Eaton Syndrome?

Lambert-Eaton syndrome, or LES, is a disease of the neuromuscular junctions, meaning the sites where nerves enter the muscles and stimulate them to act. It is sometimes referred to as Lambert-Eaton myasthenic syndrome. Persons with LES experience chronic muscle weakness and fatigue, along with difficulties in standing, walking, talking, chewing, and swallowing. LES can also result in vision problems. There is no permanent cure for LES but a variety of treatments have been developed to control symptoms and slow the disease’s progress. Fortunately, it’s a relatively rare disorder, with only about 400 known cases currently in the U.S.

What Are the Symptoms of Lambert-Eaton Syndrome?

LES primarily impacts the skeletal muscles – the ones that power physical movement and voluntary activity. This results in symptoms such as:

• Weakness and fatigue
• “Pins and needles” sensations in the hand and feet
• Difficulties in standing up, walking, lifting objects, and negotiating stairs
• Droopy eyelids
• Dry mouth
• Problems talking, chewing, and swallowing
• Troubled breathing
• Issues with bladder and bowel control
• Erectile dysfunction in men

LES symptoms are similar to those of myasthenia gravis, another neuromuscular disorder.

What Causes Lambert-Eaton Syndrome?

LES is an autoimmune disease in which your body’s defenses against intrusive infection begin attacking some aspect of your internal chemistry instead. In the case of LES, antibodies damage the calcium channels associated with nerve endings in the muscles. This inhibits the nerves from releasing a chemical, call acetylcholine, that stimulates physical activity. Without these signals to act, the muscles become weak and fatigued, seemingly neglected by the brain.

There is a second important cause of LES. In about 60 percent of cases, a person with LES will have also developed small cell lung cancer. In fact, LES may be one of the side effects of your body’s ongoing battle with this disease. Persons with cancer-related LES tend to be smokers and over 60 years of age. Individuals with LES and no cancer typically see LES emerge around 35 years of age. There may be a genetic factor in play with this latter version of LES.

How Is Lambert-Eaton Syndrome Diagnosed? 

There are a number of diagnostic options for determining whether you’ve developed LES:

• Medical history and physical exam: Your physician will conduct a physical exam, record your symptoms, and look into your medical history. 
• Neurological exam: A series of tests involving muscle strength, muscle tone, reflexes, coordination, balance, and sense of touch will evaluate your neurological health. 
• Blood analysis: Antibodies attacking neuromuscular junctions can be detected in blood tests.
• Electromyography: By inserting tiny electrodes in your muscles, your physician can gain valuable information on the volume of nerve activity
• Repetitive-nerve stimulation: Your physician will send electrical currents through your muscles by means of small electrodes. He or she will be looking for a loss of conductivity as muscle fatigue increases. 

The strong statistical link between LES and small cell lung cancer will also be taken into consideration. For example, your physician might arrange a CT scan of your lungs, looking for evidence of tumors that could explain the development of this unusual medical condition.

How Is Lambert-Eaton Syndrome Treated?

The focus for treating LES is on relieving symptoms rather than offering a cure. The steps taken by your physician will depend on your age, the disease’s severity, and how rapidly it’s progressing:

Medications

Two major types of medications are available to treat LES. Cholinesterase inhibitors improve muscle neurotransmission. Corticosteroids and immunosuppressants both work to suppress immune-system response, often in combination. The side effects of these drugs can be medically problematic, limiting their usefulness.

Intravenous Therapy

Worsening symptoms can be treated with intravenous therapy:

• Plasma exchange: Plasma exchange, or plasmapheresis, is a process by which the antibodies attacking your muscle receptor sites are eliminated from the bloodstream. Blood is removed from your body and divided into two parts: cells and the liquid they’re suspended in – plasma. Only the cells are returned to your body where they help to generate new plasma free of the immune agents driving the disorder. Plasma exchange carries the risk of critical side effects, including bleeding, heart arrhythmias, cramps, and plummeting blood pressure.
• Intravenous immunoglobulin: Immunoglobulin is a source of antibodies or immune agents. Receiving doses of immunoglobulin from healthy donors can counteract the negative effects of antibodies attacking the nerves. Side effects tend to be relatively mild.

Cancer Treatment

If the underlying cause of LES is small cell lung cancer, your physician will focus on treating it first. There are two reasons for this: small cell lung cancer is more likely to be fatal and overcoming small cell lung cancer is also key to overcoming LES. Your medical team will utilize standard medical therapies for attacking small cell lung cancer, most notably radiation and chemotherapy.