Lambert-Eaton vs. Myasthenia Gravis

  • Medical
  • Thread starter greghouse
  • Start date
In summary, Lambert-Eaton myasthenic syndrome (LEMS) and myasthenia gravis (MG) are both autoimmune disorders that affect the neuromuscular junction. However, LEMS specifically targets the calcium channels on the pre-synaptic axon terminal, while MG targets the receptor muscles Na/K-channels. This results in different muscle groups being affected, with LEMS causing weakness in the limbs and MG causing weakness in the bulbar muscles used for swallowing, speaking, and chewing. The electromyogram (EMG) patterns for these disorders also differ, with LEMS showing a progressive increase in initial low-amplitude potential and MG showing increased variability in neuromuscular transmission. Further studies are needed to understand
  • #1
greghouse
38
0
How comes the clinical presentation differs between LE and MG? In both cases anti-bodys attack the neuromuscular junction, LE attacks the calcium channels on the pre-synaptic axon terminal, and MG the receptor muscles Na/K-channels... Why is there difference in symptoms?
 
Biology news on Phys.org
  • #2
Here are two links explaining the diseases and symptoms with general descriptions of the causes (you may have seen these already, but for the sake of ensuring everyone else knows what is being talked about, this should help).
http://www.emedicine.com/emerg/TOPIC325.HTM
http://www.emedicine.com/NEURO/topic181.htm

The simplest answer (and only one) I can offer on this is that they affect different muscle groups. Autoimmune disorders can be tissue specific, or more general, and I don't have any explanation for you of why they target the muscle groups they do. Otherwise, the symptoms are similar in terms of inducing muscle weakness or loss of function, it's just that one affects the limbs first while the other is more likely to affect the bulbar muscles first (the ones used for swallowing, speaking, chewing).
 
  • #3
"LEMS is most often a paraneoplastic syndrome associated with small-cell carcinoma, which it may precede. Like myasthenia gravis, it is an autoimmune disorder. Unlike myasthenia gravis, the weakness improves with exertion, and oculobulbar involvement is rare except for ptosis."

"Repetitive electric stimulation at 50-Hz applied to the ulnar nerve at the wrist normally elicits from the abductor of the fifth finger an evoked response of ≥ 5 mV, which may increase no more than 50%. In the case we describe, the electromyogram (EMG) showed that the initial lowamplitude potential was at 0.54 mV and increased progressively to 1.82 mV, a change of 237%. This EMG pattern is a diagnostic feature of Lambert-Eaton myasthenic syndrome (LEMS)."
(Lambert-Eaton myasthenic syndrome: Monique D'Amour, Gilles Gariepy, Joseph Braidy. Canadian Medical Association. Journal. Ottawa: Jan 2, 2007. Vol. 176, Iss. 1; pg. 38, 1 pgs)


"This variability is highly sensitive to neuromuscular transmission abnormalities and is increased in MG patients. Neuromuscular blocking is the failure of transmission of one of the potentials, when one of the muscle fibers fails to transmit an action potential because the EPP does not reach the necessary threshold. The American Association of Neuromuscular & Electrodiagnostic Medicine has developed guidelines for electrodiagnostic testing for evaluation of MG (88)."
(Myasthenia gravis: past, present, and future: Bianca M Conti-Fine, Monica Milani, Henry J Kaminski. Journal of Clinical Investigation. Ann Arbor: Nov 2006. Vol. 116, Iss. 11; pg. 2843, 12 pgs)

It looks like End Plate Potential is inhibited in MG and increased in LEMS and fast twitch or slow twitch muscles are more or less susceptible.
 
  • #4
Care to link that?
 

1. What is the difference between Lambert-Eaton and Myasthenia Gravis?

Lambert-Eaton and Myasthenia Gravis are both autoimmune disorders that affect the neuromuscular junction, but they have different underlying causes and symptoms. Lambert-Eaton is caused by antibodies attacking calcium channels in the neuromuscular junction, while Myasthenia Gravis is caused by antibodies attacking acetylcholine receptors. Additionally, Lambert-Eaton primarily affects muscles in the lower body, while Myasthenia Gravis can affect muscles throughout the body.

2. How are Lambert-Eaton and Myasthenia Gravis diagnosed?

Both disorders can be diagnosed through a combination of medical history, physical examination, and diagnostic tests. Doctors may also use a blood test to check for the presence of specific antibodies related to each disorder.

3. Can Lambert-Eaton and Myasthenia Gravis coexist?

Yes, it is possible for a person to have both Lambert-Eaton and Myasthenia Gravis. This is known as Lambert-Eaton/Myasthenic syndrome and it is a rare condition that can make diagnosis and treatment more complex.

4. What are the treatment options for Lambert-Eaton and Myasthenia Gravis?

Treatment for both disorders typically involves managing symptoms and addressing the underlying autoimmune response. This may include medications to improve muscle strength and reduce the autoimmune response, as well as physical therapy to maintain muscle function.

5. Are there any known risk factors for developing Lambert-Eaton or Myasthenia Gravis?

The exact cause of these disorders is not fully understood, but there are some risk factors that may increase the likelihood of developing them. These include a family history of the disorders, certain types of cancer, and exposure to certain toxins. However, many cases of Lambert-Eaton and Myasthenia Gravis occur in people with no known risk factors.

Similar threads

  • Biology and Medical
Replies
1
Views
3K
Back
Top