Amyotrophic lateral sclerosis (ALS) is a neurological disease that affects the nervous system and causes muscle weakness and interferes with physical functions.

ALS is a type of motor neuron disease that causes nerve cells to gradually break down and die.

The early symptoms of the disease are muscle twitching and weakness in one of the limbs or a slurred speech. As the disease progresses it can affect the ability to control the muscles required to move, speak, eat and breathe.


Early symptoms of ALS include:

  • Difficulty walking or tripping
  • Difficulty performing normal daily activities
  • Weakness in the leg, feet or ankles
  • Hand weakness or clumsiness
  • Slurred speech or difficulty swallowing
  • Muscle cramps and twitching in the arms, shoulders and tongue
  • Difficulty holding the head up or keeping a good posture

The symptoms of the disease typically begin in the hands, feet or limbs and gradually spread to other body parts. As it progresses, the disease weakens the muscles eventually affecting chewing, swallowing, speaking and breathing.

On the other hand, ALS does not usually impact bowel or bladder control, senses or thinking abilities.


In 5 to 10% of cases ALS is inherited. The other cases are considered to appear at random.

Nevertheless, scientists have identified a few possible causes of ALS:

  • Gene mutation: Inherited ALS can result from various genetic mutations although inherited ALS is almost identical to the non-inherited form of the disease.
  • Chemical imbalance: A chemical messenger in the brain called glutamate is frequently found to be abnormally high in people with ALS. The glutamate can be found around the nerve cells in the spinal fluid where excess of glutamate can be toxic and damaging to some nerve cells.
  • Disorganized immune response: An immune system that attacks the body’s normal cells can cause death of nerve cells.
  • Mishandled proteins: Protein mishandling within the nerve cells can cause abnormal forms of the proteins to accumulate in the cells causing the nerve cells to eventually die.

Risk factors

Risk factors for ALS include:

  • Heredity: 5 to 10% of ALS cases are inherited (familial ALS). The children of people with familial ALS have a 50-50 chance of developing the disease.
  • Age: The most common cases of ALS are found in people of ages between 40 and 60.
  • Gender: Men are more likely to develop ALS than women before the age of 65.

Environmental factors that increase the risk of ALS:

  • Smoking: Smokers carry twice the bigger risk of ALS than nonsmokers. Quitting smoking can eventually lower the risk.
  • Lead exposure
  • Military service: Exposure to certain chemicals or metals, traumatic injuries, infections and intense exertion during military service can increase the risk of ALS.


ALS is a progressive disease that can cause the following complications:

  • Breathing problems. ALS eventually paralyzes the muscles necessary for breathing. There are devices used to assist the breathing; however, in latter stages of the disease tracheostomy (surgically made hole in the front of the neck leading to the trachea) may be a better option for full-time use of a respirator that helps inflate and deflate the lungs. Respiratory failure is the most common cause of death in people with ALS. Death usually occurs within 3 to 5 years after the initial symptoms
  • Speaking problems. The problems with speaking begin as mild word slurring that becomes more severe over time. As time passes, speech becomes difficult for other people to understand and therefore people with ALS rely on other forms of communication.
  • Eating problems. ALS affects the muscles that control swallowing causing dehydration and malnutrition. Other complications involve food, liquid or saliva entering the lungs, which can lead to pneumonia. A feeding tube can be used to reduce these risks and manage the complications
  • Dementia. ALS can cause difficulties in decision making and memory problems that may lead to a later diagnosis of a form of dementia called frontotemporal dementia.