Lambert-Eaton myasthenic syndrome (LEMS) is a rare disease in which the immune system mistakenly attacks the nerve cell endings that convey messages to muscles. This results in progressive muscle weakness in the legs, arms, hips, and shoulders, which can limit mobility.

No cure exists for LEMS, but treatments can help manage symptoms and improve quality of life.

How are nerve signals sent?

Normally, when the brain sends a nerve signal from the brain to the muscles, it is sent as an electrochemical signal. At the end of the nerve cell where it interacts with muscle (the neuromuscular junction), the electrical signal is converted into a chemical message. The nerve cell ending releases a neurotransmitter or signaling molecule called acetylcholine into the neuromuscular junction. Acetylcholine binds to receptors found on the other side of the junction, i.e. on the muscle cell carrying the message across and signaling the muscle to contract.

After the nerve signal has been sent, enzymes called cholinesterases break down excess acetylcholine in the neuromuscular junction, resetting the junction so that it is ready to receive the next message.

In LEMS, the immune system attacks the nerve cell endings, meaning that nerve signals are weaker. Without stimulation from the nervous system, muscles weaken and atrophy as the disease progresses.

What are cholinesterase inhibitors?

Cholinesterase inhibitors are chemicals that block the enzyme that breaks down acetylcholine. When cholinesterase inhibitors are present, acetylcholine lingers in the neuromuscular junction instead of being cleared immediately. This means that a stronger, longer-lasting nerve signal can be sent.

Cholinesterase inhibitors for LEMS

Cholinesterase inhibitors have not been approved to treat LEMS specifically, but may be prescribed off-label. They are usually only mildly effective in treating LEMS, but for some patients, this is sufficient to manage the symptoms of the disease.

Pyridostigmine is the most commonly used cholinesterase inhibitor for LEMS.

Other cholinesterase inhibitors include:

Other information

Cholinesterase inhibitors can cause side effects such as diarrhea, abdominal cramps, and excessive saliva production.

 

Last updated: Oct. 16, 2019

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Lambert-Eaton News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.

Emily holds a Ph.D. in Biochemistry from the University of Iowa and is currently a postdoctoral scholar at the University of Wisconsin-Madison. She graduated with a Masters in Chemistry from the Georgia Institute of Technology and holds a Bachelors in Biology and Chemistry from the University of Central Arkansas. Emily is passionate about science communication, and, in her free time, writes and illustrates children’s stories.
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Özge has a MSc. in Molecular Genetics from the University of Leicester and a PhD in Developmental Biology from Queen Mary University of London. She worked as a Post-doctoral Research Associate at the University of Leicester for six years in the field of Behavioural Neurology before moving into science communication. She worked as the Research Communication Officer at a London based charity for almost two years.
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Emily holds a Ph.D. in Biochemistry from the University of Iowa and is currently a postdoctoral scholar at the University of Wisconsin-Madison. She graduated with a Masters in Chemistry from the Georgia Institute of Technology and holds a Bachelors in Biology and Chemistry from the University of Central Arkansas. Emily is passionate about science communication, and, in her free time, writes and illustrates children’s stories.
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