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Lambert-Eaton myasthenic syndrome

Myasthenic syndrome; Eaton-Lambert syndrome; Lambert-Eaton syndrome; LES

Lambert-Eaton myasthenic syndrome (LEMS) is a rare disorder in which faulty communication between nerves and muscles leads to muscle weakness.

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Causes

LEMS is an autoimmune disorder. This means your immune system mistakenly targets healthy cells and tissues in the body. With LEMS, 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.

LEMS may occur with cancers such as small cell lung cancer or autoimmune disorders such as vitiligo, which leads to a loss of skin pigment.

LEMS affects men more often than women. The most common age of occurrence is around age 60 years. LEMS is rare in children.

Symptoms

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 LEMS. 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 may include:

• Blood pressure changes
• Dizziness upon standing
• Dry mouth
• Erectile dysfunction
• Dry eyes
• Constipation
• Decreased sweating

Exams and Tests

Your health care provider will perform a physical exam and ask about your symptoms. The exam may show:

• Decreased reflexes
• Possible loss of muscle tissue
• Weakness or paralysis that gets slightly better with activity

Tests to help diagnose and confirm LEMS 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

A CT scan and an MRI of the chest and the abdomen, followed by bronchoscopy for smokers may be done to evaluate for cancer. PET scan may also be done if a lung tumor is suspected. You may be referred to an oncologist (cancer specialist) to determine if other cancer testing is needed.

Treatment

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:

• Medicines that suppress the immune system's response
• Anticholinesterase medicines to improve muscle tone (although these are not very effective when given alone)
• Medicines that increase the release of acetylcholine from nerve cells

Outlook (Prognosis)

Symptoms of LEMS may improve by treating the underlying disease, suppressing the immune system, or removing the antibodies. However, paraneoplastic LEMS may not respond as well to treatment. (Paraneoplastic LEMS symptoms are due to an altered immune system response to a tumor). Death is due to underlying malignancy.

Possible Complications

Complications of LEMS 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

Contact your provider if symptoms of LEMS develop.

Related Information

Weakness
Muscle cramps
Myasthenia gravis
Antibody
Cancer
Autoimmune disorders

References

Guptill JT, Sanders DB. Disorders of neuromuscular transmission. In: Jankovic J, Mazziotta JC, Pomeroy SL, Newman NJ, eds. Bradley and Daroff's Neurology in Clinical Practice. 8th ed. Philadelphia, PA: Elsevier; 2022:chap 108.

Kaminski HJ. Disorders of neuromuscular transmission. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 390.

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.

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Review Date: 6/13/2024  

Reviewed By: Joseph V. Campellone, MD, Department of Neurology, Cooper Medical School at Rowan University, Camden, NJ. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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