Lambert-Eaton Myasthenic Syndrome

Lambert-Eaton Myasthenic Syndrome: Description, Causes and Risk Factors: Abbreviation: LEMS. Alternative Names: Carcinomatous myopathy, Eaton-Lambert syndrome, Lambert syndrome, myasthenic syndrome. Lambert-Eaton Myasthenic SyndromeLEMS is a rare autoimmune disorder of the neuromuscular junction characterized by autoantibodies against VGCC (Voltage-Gated Calcium Channel), against presynaptic voltage-gated P/Q calcium channels. These channels are also designated as active zone of the presynaptic membrane. A transient depolarization of the presynaptic membrane causes the opening of the voltage-gated calcium channels, which allows the local influx of calcium ions into the nerve terminal. This rise in calcium ion concentration results in the release of acetylcholine from the vesicles. Autoantibodies as found in Lambert-Eaton Myasthenic Syndrome lead to a cross-linking of the channels with subsequent internalisation and degradation. As a consequence the number of channels is reduced and, therefore, the release of acetylcholine. The result is an interruption of the impulse transmission to the neuromuscular end-plate of the muscle cell which eventually causes the typical myasthenic syndrome. LEMS occurs when nerves cells do not release enough of a chemical called acetylcholine, which transmits impulses between nerves and muscles. The result is muscle weakness and other symptoms similar to myasthenia gravis. However, as the muscles continue to contract, the chemical (acetylcholine) can build up in sufficient quantities for strength to get slightly better. In myasthenia gravis (MG) the autoimmune process happens on the postsynaptic level at the acetylcholine receptor of the muscle cell. In LEMS the autoimmune process takes place on the presynaptic level at the nerve terminal. Risk Factors: Cancer - Typically small cell lung carcinoma (SCLC) is present when weakness begins, or is later found in 40% of patients. In most cases the cancer is found within 2 years after the onset of Lambert-Eaton Myasthenic Syndrome . Within 4 years in virtually all cases.
  • Smoking and age at onset are major risk factors for cancer in Lambert-Eaton Myasthenic Syndrome . All patients with associated SCLC have a history of long-term smoking. Only half of patients with auto-immune Lambert-Eaton Myasthenic Syndrome are long-term smokers.
Symptoms: Symptoms may include: Difficulty chewing.
  • Difficulty climbing stairs.
  • Difficulty lifting objects.
  • Difficulty talking.
  • Drooping head.
  • Need to use hands to arise from sitting or lying positions.
  • Blurry vision.
  • Double vision.
  • Blood pressure changes.
Diagnosis: Differential Diagnosis: Myasthenia gravis.
  • Acute or chronic inflammatory demyelinating polyradiculopathy.
  • Dermatomyositis/polymyositis.
  • Inclusion body Myositis.
  • Spinal muscular atrophy.
A physical examination shows weakness or paralysis that gets slightly better with activity. Reflexes may be decreased. There may be loss of muscle tissue. Tests to help diagnose and confirm the condition may include: Electromyography (EMG): The doctor checked if you have LEMS by looking for specificneuromuscular changes in a test called electromyography. This is when the nerves are stimulated electrically andthe nerve impulses are measured in the muscles.
  • A blood testfor the antibodies may also have been used to check for Lambert-Eaton Myasthenic Syndrome .
  • Nerve conduction velocity.
  • Tensilon test.
  • As LEMS can be caused by a cancer, the doctor will check forlung cancer, especially in people who have smoked.
Treatment: For patients with small cell lung cancer, treatment of the cancer is the first priority. The surgical removal of the tumour often causes a temporary improvement of the neurological symptoms. Immunosuppressive drugs are usually not indicated. There is no known cure for Lambert-Eaton Myasthenic Syndrome . Treatment is directed at decreasing the autoimmune response through the use of steroids, plasmapheresis (involves removing blood plasma from the body and replaced it with fluid, protein, or donated plasma. This helps to make sure that any harmful proteins that are interfering with nerve function are removed from the body). Medications that suppress the immune response, such as prednisone, may improve symptoms in some cases. Medications may also include: Anticholinesterase medications such as Neostigmine or Pyridostigmine.
  • 3, 4-diaminopyridine, which increase the release of acetylcholine from nerve cells.
Disclaimer: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.

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