Myasthenic syndrome; Eaton-Lambert syndrome; Lambert-Eaton myasthenic syndrome; LEMS; LES
Lambert-Eaton syndrome (LES) is a rare disorder in which faulty communication between nerves and muscles leads to muscle weakness.
LES is an autoimmune disorder. This means your immune system mistakenly targets healthy cells and tissues in the body. With LES, antibodies produced by the immune system attack nerve cells. This makes nerves cells unable to release enough of a chemical called acetylcholine. This chemical transmits impulses between nerves and muscles. The result is muscle weakness.
LES may occur with cancers such as small cell lung cancer or autoimmune disorders such as vitiligo, which leads to a loss of skin pigment.
LES affects men more often than women. Common age of occurrence is around age 60 years. LES is rare in children.
Weakness or loss of movement that can be more or less severe, including:
- Difficulty climbing stairs, walking, or lifting things
- Muscle pain
- Drooping of the head
- The need to use the hands to get up from a sitting or lying position
- Problems talking
- Problems chewing or swallowing, which may include gagging or choking
- Vision changes, such as blurry vision, double vision, and problem keeping a steady gaze
Weakness is generally mild in LES. Leg muscles are mostly affected. Weakness may improve after exercise, but continuous exertion causes fatigue in some cases.
Symptoms related to the other parts of the nervous system often occur, and include:
- Blood pressure changes
- Dizziness upon standing
- Dry mouth
- Erectile dysfunction
- Dry eyes
- Decreased sweating
Exams and Tests
The health care provider will perform a physical exam and ask about the symptoms. The exam may show:
Possible loss of muscle tissue
Weakness or paralysis that gets slightly better with activity
Tests to help diagnose and confirm LES may include:
- Blood tests to look for the antibodies that attack the nerves
- Electromyography (EMG) to test the health of the muscle fibers
- Nerve conduction velocity (NCV) to test the speed of electrical activity along nerves
CT scan and MRI of the chest and the abdomen, followed by bronchoscopy for smokers may be done to exclude cancer. PET scan may also be done if a lung tumor is suspected.
The main goals of treatment are to:
- Identify and treat any underlying disorders, such as lung cancer
- Give treatment to help with the weakness
Plasma exchange, or plasmapheresis, is a treatment that helps remove from the body any harmful proteins (antibodies) that are interfering with nerve function. This involves removing blood plasma that contains the antibodies. Other proteins (such as albumin) or donated plasma are then infused into the body.
Another procedure involves using intravenous immunoglobulin (IVIg) to infuse a large amount of helpful antibodies directly into the bloodstream.
Medicines that may also be tried include:
- Drugs that suppress the immune system's response
- Anticholinesterase drugs to improve muscle tone (although these are not very effective when given alone)
- Drugs that increase the release of acetylcholine from nerve cells
Symptoms of LES may improve by treating the underlying disease, suppressing the immune system, or removing the antibodies. However, paraneoplastic LES may not respond as well to treatment. (Paraneoplastic LES symptoms are due to an altered immune system response to a tumor). Death is due to underlying malignancy.
Complications of LES may include:
- Difficulty breathing, including respiratory failure (less common)
- Difficulty swallowing
- Infections, such as pneumonia
- Injuries from falls and problems with coordination
When to Contact a Medical Professional
Call your provider if symptoms of LES develop.
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Moss HE. Eyelid and facial nerve disorders. In: Liu GT, Volpe NJ, Galetta SL, eds. Liu, Volpe, and Galetta's Neuro-Ophthalmology. 3rd ed. Philadelphia, PA: Elsevier; 2019:chap 14.
Sanders DB, Guptill JT. Disorders of neuromuscular transmission. In: Daroff RB, Jankovic J, Mazziotta JC, Pomeroy SL, eds. Bradley's Neurology in Clinical Practice. 7th ed. Philadelphia, PA: Elsevier; 2016:chap 109.