Plasma exchange hasn't been shown to help primary progressive or secondary progressive multiple sclerosis (MS).
It may also help treat other diseases that damage the coating around your spinal cord and nerves, such as Guillain-Barré syndrome, chronic inflammatory demyelinating polyneuropathy, and myasthenia gravis. After plasma exchange, people with Guillain-Barré syndrome or chronic inflammatory demyelinating polyneuropathy are more likely to regain muscle strength and walk without help.