Causes of muscle weakness in multiple sclerosis
The reason you’re able to walk, put on your clothes, and grab a glass off your kitchen shelf is because of the connection between your brain and muscles. Your brain controls the action, sending electrical signals to your muscles via a network of nerves. Those signals tell your muscles to move.
When you have multiple sclerosis (MS), your immune system attacks your nerves. It destroys myelin, an insulating substance that surrounds and protects nerve fibers.
As myelin is damaged, scar tissue can form on the nerves. This can prevent nerve signals from traveling correctly from your brain to certain parts of your body.
Nerve damage can leave your muscles stiff or weak, reducing your ability to move and perform everyday activities. The weakness often occurs only on one side of your body or just in your legs or trunk.
Weakness, like other MS symptoms, may come and go as you experience flare-ups and remissions during the course of the disease.