Motor neurone disease (sometimes called Lou Gehrig’s disease or Amyotrophic lateral sclerosis) is a chronic, progressive, almost always fatal neurological disease. 

These are the nerve cells which move muscles when we speak, walk, swallow, and move our body. These diseases get worse with time. They cause increasing disability and, eventually, death. There is no known cure.
It is marked by slow but steady death of the nerve cells in the central nervous system that control voluntary muscle movement. That is, people can no longer move, but their heart still beats. 

Amyotrophic lateral sclerosis (ALS) is the most common of the five types of motor neuron disease. About 5 to 10% of cases are directly inherited from a person's parents. 

The disorder causes muscle weakness and muscle shrinking (atrophy) throughout the body. Both the upper motor neurons and the lower motor neurons die, making them stop sending messages to the muscles. Unable to function, the muscles gradually weaken and waste away (atrophy). Eventually, the ability of the brain to start and control voluntary movement is lost. However, even patients in later stages of the disease may still have the same intelligence, memory, and personality they had before it started.

Symptoms 
Motor neurone disease does not show many symptoms, making it very hard to diagnose. It usually affects people ages 40-60. The earliest symptoms may include twitching, cramping, or stiffness of muscles; muscle weakness affecting an arm or a leg; slurred and strange-sounding nasal speech; or having a difficult time chewing or swallowing. These general symptoms then develop into clear weakness or atrophy that may cause a physician to believe that a person has ALS.

The parts of the body affected by early symptoms of ALS depend on which muscles in the body are affected first. About 75% of people have limb onset ALS. In some of these cases, symptoms first affect one of the legs, and patients have awkwardness when walking or running or they notice that they are tripping or stumbling more often. Other limb onset patients first see the effects of the disease on a hand or arm as they have a difficult time with simple tasks requiring hand dexterity, or ability to move small things, such as buttoning a shirt, writing, or turning a key in a lock.

About 25% of cases are bulbar onset ALS. These patients first have difficulty speaking clearly. Speech becomes hard to understand and slurred. Speaking through the nose and softer talking are often the first symptoms. Difficulty swallowing, and loss of tongue movement follow. Eventually total loss of speech and ability to keep the airway clear when swallowing are experienced.

Treatment 
There is no cure for ALS. However, the Food and Drug Administration (FDA) has approved the first drug treatment for the disease: riluzole. Riluzole is believed to reduce damage to motor neurons. Clinical trials with ALS patients showed that riluzole gives a better chance of survival by several months, mainly in those with a hard time swallowing. The drug also allows more time before a patient needs breathing help by a ventilator or tracheotomy. Riluzole does not heal the damage already done to motor neurons.

Other treatments for ALS are designed to make symptoms less painful and improve the quality of life for patients.

References 

Diseases