Lou Gehrig's disease damages motor neurons in the brain and spinal cord. Motor neurons are nerve cells that control muscle movement. Upper motor neurons send messages from the brain to the spinal cord, and lower motor neurons send messages from the spinal cord to the muscles. Motor neurons are an important part of the body's neuromuscular system. The neuromuscular system enables our bodies to move and is made up of the brain, many nerves, and muscles. Things that we do every day - like breathing, walking, running, lifting stuff, and even reaching for a glass of water - are all controlled by the neuromuscular system.
Here's how the neuromuscular system works: If you want to make a fist, your brain first sends signals through upper motor neurons to the area in your spinal cord that controls your hand muscles. Then lower motor neurons in your spinal cord signal the muscles in your hand to move and make a fist.
Over time, Lou Gehrig's disease causes these motor neurons in the brain and spinal cord to shrink and disappear, so that the muscles no longer receive signals to move. As a result, the muscles become smaller and weaker. Gradually the body becomes paralyzed (say: par-uh-lized), which means that the muscles no longer work. However, someone with ALS, even at an advanced stage, can still see, hear, smell, and feel touch. The nerves that carry feelings of hot, cold, pain, pressure, or even being tickled, are not affected by Lou Gehrig's disease. The parts of the brain that allow us to think, remember, and learn are also not affected by the disease.
Although this disease can strike anyone, it is extremely rare in kids. According to the ALS Association, most people who develop Lou Gehrig's disease are adults between 40 and 70. Only 2 out of every 100,000 people will get the disease each year. Because it is not contagious, you can't catch ALS from someone who has the disease.
Among ALS cases in the United States, 5% to 10% are hereditary, which means the disease runs in certain families. This is called familial (say: fuh-mee-lee-ul) ALS. At least 90% of cases are not inherited; this is called sporadic (say: spuh-rah-dik) ALS.
Researchers continue to study ALS as they try to understand why it happens, and how the disease damages the motor neurons in the brain and spinal cord. As they learn more about the disease, researchers can continue to develop new and better treatments.