When this occurs, the nerves can’t send signals efficiently, the muscles lose their ability to respond to the commands of the brain, and the brain receives fewer sensory signals from the rest of the body. The result is weakness and an inability to feel heat, pain, and other sensations.

There is no known cure for GBS. Without treatment, GBS may get better on its own. But treatment may improve chances of a faster recovery.

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Too long, didnt research:

Alexander the Great is believed by some to have died from death.

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He is believed to have had Guillain-Barré Syndrome which gradually paralyzed him leading to him being mistaken as dead. The 6 days where his body didnt decay were attributed to his godhood by his compatriots but is interpreted as a sign of the paralysis by some modern researchers. He is likely to have been embalmed while still alive and able to feel but unable to move, scream, or look(sorry for the meme inaccuracy) at the people killing him.