Locked-in syndrome can result from a stroke or injury. Neurological ailments, such as Lou Gehrig's disease, also are culprits. The damage from the condition or injury blocks the message transmission path that initiates voluntary movement. Normally, a series of electrical impulses pass from brain cells along nerves to trigger the release of chemical messages, which eventually signal the muscles to move. Most or all of the muscles in locked-in patients never receive the messages.
Some patients have a few spared muscles in areas such as the eyes.
Computer programs occasionally aid their communication by detecting the remnant muscle movement, but often the muscles are difficult to control or easily tire. For decades it seemed beyond science's reach to help these patients. But then researchers began to investigate a long shot idea. Maybe they could bypass the muscles and power computer communication devices directly from the brain. Following years of research, the strategy, reminiscent of a science fiction movie, is now starting to show promise in real life.