What is Lambert Eaton Myasthenic Syndrome (LEMS)
Lambert eaton syndrome is a disease affecting a part of your body called the neuromuscular junction. It is the junction between a nerve and a muscle, where the nerve releases chemicals stimulating the muscles and causing movement.
This is an autoimmune disease, that is characterized by our own body attacking this junction, i.e our immune system attacks the neuromuscular junction using molecules called antibodies. This disrupts the nerve signals and causes a gradual decrease in the movement due to weakness in the muscles.
This weakness is seen more in the upper muscles of arms and legs i.e of the arms and thighs. The person would have difficulty lifting his arms above his head to perform daily activities like bathing or combing his hair while he would be able to move his forearm and fingers.
Type of Lambert Eaton Myasthenia Syndrome
This disease is of two types:
- Lambert eaton Myasthenia syndrome associated with small cell carcinoma of lung: Majority of patients with this disease have small cell carcinoma of lung and the onset of the disease is before the appearance of cancer.
- Non-cancer associated: Occurs due to some other autoimmune disorder. Can occur at any age and is non-sex dependant. Occurs mostly around a mean age of 35.
What are the causes of Lambert Eaton Syndrome?
Our body is protected against diseases by a defense mechanism called immunity.
Our immune system fights off any foreign substance by creating molecules called antibodies against it which destroys and eliminates the pathogen.
Sometimes, these antibodies instead of only attacking the foreign substance start attacking ones own body cells which share some similarity with the foreign substance.
Our nerve endings send signals to muscles via a chemical called the neurotransmitter, namely Acetycholine. This is released from the nerve under the influence of calcium, which enters the nerve via a gate called “voltage gated calcium channel”. Our body produces antibodies against this gate present on the cancer cells in order to destroy it. But sometimes these antibodies start attacking the gates that are normally present in our body at every nerve ending. Thus, leading to disrupted transmission of signals and weakness.
In autoimmune diseases, it has been found to have an association to certain molecules called HLA which are present on the surface of cells and which help regulate immune response. It is the disarray of these molecules which lead to self destruction.
What are the risk factors for Lambert Eaton Syndrome?
- Age: Cancer associated disease affects older age group.
- Sex: Cancer associated disease is more common in male than female.
What are the symptoms of Lambert Eaton Syndrome?
- Weakness: the person is unable to perform daily activities due to weakness felt in the muscles. This starts slowly and progressively increases over months. The muscles are affected in a stepwise pattern where there is progressive weakness of shoulder muscles, hands and feet, speech and swallowing muscles and eye movement muscles.
- Trouble walking
- Fatigue: the person gets tired easily. There is difficulty performing strenuous activities and can make even climbing up stairs a difficult task
- Tingling sensation of hands and feet
- Trouble speaking and swallowing
- Eyelid drooping
- Weakness may affect the respiratory muscles which help us breathe, thus causing breathing difficulties
- There are certain autonomic symptoms which are involuntarily controlled functions of our body such as dry mouth, dry eyes, constipation, impotence, decreased sweating, etc.
- Weight loss
- On examination, the reflexes present at joints are reduced
How can LEMS be treated?
- Cancer-related Lambert Eaton Mysathenia syndrome: The cancer is treated first using radiotherapy, chemotherapy and surgery; that itself leads to improvement in the weakness.
- There is no cure for this disease and treatment is only aimed at decreasing the symptoms and Improving the quality of life.
- Drugs which increase the release of the neurotransmitters are given which act as a supplementary pathway instead of the blocked calcium channel. For ex: pottasium channel blockers. This reduces muscle weakness.
- Drugs to improve autonomic dysfunction are given.
- In severe cases, drugs inhibiting the immune system are given thus reducing the antibodies produced against the nerves.
- Plasmapheresis can also be done, where in you replace the plasma from blood thus removing the antibodies circulating in it.
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