ALS (amyotrophic lateral sclerosis) is a disease of the parts of the nervous system that control voluntary muscle movement. In ALS, motor neurons (nerve cells that control muscle cells) are gradually lost. As these motor neurons are lost, the muscles they control become weak and then nonfunctional.

Loss of voluntary muscles can lead to an inability to walk, to swallow and to speak. Those in the advanced stages of ALS may become unable to eat, move or breathe independently.

It’s important to note that the involuntary muscles, such as those of the heart, gastrointestinal tract, bowel and bladder, and those that regulate sexual functions are not directly affected in ALS. Hearing, vision and touch generally remain normal.

Mild cognitive impairment in ALS is not uncommon, but severe cognitive impairment, known as “dementia,” can also occur in a small fraction of people with the disease. Some with ALS may experience involuntary laughing or crying spells that are unrelated to their emotional state. Called involuntary emotional expression disorder, or “pseudobulbar affect,” this symptom can be treated with medication.

ALS affects everyday activities

In the early stages of ALS, muscles may be weak and soft, or stiff, tight and spastic. Muscle cramping and twitching (fasciculations) occurs, as does loss of muscle bulk (atrophy).

Symptoms may be limited to a single body region or may affect more than one region. The person may experience fatigue, poor balance, slurred words, a weak grip, tripping when walking or other minor symptoms. Sometimes this stage occurs before a diagnosis is made.

In the middle stages of ALS, symptoms become more widespread. Some muscles are paralyzed, while others are weakened or unaffected. Fasciculations may continue.

Unused muscles may cause contractures, in which the joints become rigid, painful and sometimes deformed. If a fall occurs, the person may not be able to stand back up alone. Driving is relinquished. Weakness in swallowing muscles may cause choking, greater difficulty eating and managing saliva.

Weakness in breathing muscles can cause respiratory insufficiency, especially when lying down. Some people experience bouts of uncontrolled and inappropriate laughing or crying (pseudobulbar affect).

In the late stages of the disease, most voluntary muscles are paralyzed. The muscles that help move air in and out of the lungs are severely compromised. Mobility is extremely limited, and help is needed in caring for most personal needs. Poor respiration may cause fatigue, fuzzy thinking, headaches and susceptibility to pneumonia. (Respiratory insufficiency is a leading cause of death in ALS.) Speech, or eating and drinking by mouth, may not be possible.

Each person’s disease course is unique.

There is no cure for ALS, but medications can help manage some symptoms and potentially slow the course of the disease. Modern technology has allowed people with ALS to compensate to some degree for almost every loss of function, making it possible even for those with almost no muscle function to continue to breathe, communicate, eat, travel and use a computer.