Comparing and Contrasting Myasthenia Gravis and Labert-Eaton

Myasthenia Gravis is a chronic neuromuscular disease that causes weakness in the skeletal muscles. It commonly impacts women under 40 years old, but it can occur at any age and gender. The skeletal muscles worsen after activity and improve after periods of rest. One of the first signs that Myasthenia Gravis patients notice are ptosis and diplopia. About 15% of people can experience symptoms related to swallowing, chewing, facial expressions, and speech. There is also weakness in the arms, hands, and neck which makes it harder to hold the head up.

The main cause of Myasthenia Gravis (MG) is autoantibodies against the postsynaptic acetylcholine receptor sites. The thymus gland is also associated with MG because it remains large and gives incorrect instructions to developing immune cells. This eventually causes the production of acetylcholine receptor antibodies. There are many ways to diagnose Myasthenia Gravis. A physical and neurological exam is usually done first to check the muscle strength, tone, coordination, sense of touch, and eye movements. An edrophonium test is used where edrophonium chloride is injected to relieve weakness and test ocular muscle weakness. Electrodiagnostic, blood tests, diagnostic imaging, and pulmonary function testing can also be used for diagnosis. Treatment for myasthenia gravis includes thymectomy and anticholinesterase medications such as mestinon and pyridostigmine. These sow the breakdown of acetylcholine at the neuromuscular junction and improve transmission.

Another common disease that attacks the neuromuscular junction is Lambert-Eaton Syndrome. This autoimmune disease is associated with small cell lung cancer. Some possible symptoms are trouble walking, tingling sensation, eyelid drooping, trouble speaking/swallowing, bladder changes, and dry mouth. The tests used to diagnose Myasthenia Gravis are also used to diagnose Lambert-Eaton Syndrome. The best treatment for this syndrome is to remove the small cell lung cancer. It’s also important to avoid tobacco smoke exposure and eat more fruits and vegetables to help reduce the risk of lung cancer.

There are many similarities and differences between Myasthenia Gravis and Lambert-Eaton Syndrome. Lambert-Eaton Syndrome is caused by an antibody against the voltage gated calcium channel instead of the acetylcholine receptor. The weakness also improves with prolonged exercise while the weakness associated with Myasthenia Gravis gets worse with prolonged exercise. With repeated nerve stimulation, Lambert Eaton presents with incremental response and Myasthenia Gravis presents with a decremental response. Another major difference in regards to treatment is that acetylcholinesterase inhibitors won’t help with Lambert Eaton Syndrome as it does with Myasthenia Gravis.

References:

Johns Hopkins Medicine. (2021, August 8). Lambert-Eaton Syndrome. Lambert-Eaton Syndrome | Johns Hopkins Medicine. Retrieved January 17, 2023, from https://www.hopkinsmedicine.org/health/conditions-and-diseases/lamberteaton-syndrome

Mayo Clinic. (2021, June 22). Myasthenia Gravis. Mayo Clinic. Retrieved January 17, 2023, from https://www.mayoclinic.org/diseases-conditions/myasthenia-gravis/symptoms-causes/syc-20352036

NIH. (2022). Myasthenia gravis fact sheet. National Institute of Neurological Disorders and Stroke. Retrieved January 17, 2023, from https://www.ninds.nih.gov/myasthenia-gravis-fact-sheet