Causes

In about 10% of cases, ALS is caused by a genetic defect. In the remaining cases, the cause is unknown.

In ALS, nerve cells (neurons) waste away or die, and can no longer send messages to muscles. This eventually leads to muscle weakening, twitching, and an inability to move the arms, legs, and body. The condition slowly gets worse. When the muscles in the chest area stop working, it becomes hard or impossible to breathe on one's own.

ALS affects approximately 5 out of every 100,000 people worldwide.

There are no known risk factors, except for having a family member who has a hereditary form of the disease.

Symptoms

Symptoms usually do not develop until after age 50, but they can start in younger people. Persons with ALS have a loss of muscle strength and coordination that eventually gets worse and makes it impossible to do routine tasks such as going up steps, getting out of a chair, or swallowing.

Breathing or swallowing muscles may be the first muscles affected. As the disease gets worse, more muscle groups develop problems.

ALS does not affect the senses (sight, smell, taste, hearing, touch). It only rarely affects bladder or bowel function, or a person's ability to think or reason.

Symptoms include:

• Difficulty breathing
• Difficulty swallowing
  • Choking easily
  • Drooling
  • Gagging
• Head drop due to weakness of the neck muscles
• Muscle cramps
• Muscle contractions called fasciculations
• Muscle weakness that slowly gets worse
  • Commonly involves one part of the body first, such as the arm or hand
  • Eventually leads to difficulty lifting, climbing stairs, and walking
• Paralysis
• Speech problems, such as a slow or abnormal speech pattern (slurring of words)
• Voice changes, hoarseness
• Weight loss

Exams and Tests

The health care provider will take a medical history, which includes strength and endurance.

A physical examination of strength shows weakness, often beginning in one area. There may be muscle tremors, spasms, twitching, or loss of muscle tissue (atrophy). Atrophy and twitching of the tongue are common.

The person's walk may be stiff or clumsy. Reflexes are abnormal. There are increased reflexes at the joints, but there may be a loss of the gag reflex. Some patients have trouble controlling crying or laughing. This is sometimes called "emotional incontinence."

Tests that may be done include:

• Blood tests to rule out other conditions
• Breathing test to see if lung muscles are affected
• Cervical spine CT or MRI to be sure there is no disease or injury to the neck, which can mimic ALS
• Electromyography to see which nerves do not work properly
• Genetic testing, if there is a family history of ALS
• Head CT or MRI to rule out other conditions
• Nerve conduction studies
• Swallowing studies
• Spinal tap (lumbar puncture)

Treatment

There is no known cure for ALS. The first drug treatment for the disease is a medicine called riluzole. Riluzole slows the disease progression and prolongs life.

Treatments to control symptoms are also helpful:

• Baclofen or diazepam may be used to control spasticity that interferes with daily activities.
• Trihexyphenidyl or amitriptyline may be prescribed for people with problems swallowing their own saliva.

Physical therapy, rehabilitation, use of braces or a wheelchair, or other orthopedic measures may be needed to maximize muscle function and general health.

Choking is common. Patients may decide to have a tube placed into their stomach for feeding. This is called a gastrostomy.

A nutritionist is very important. Patients with ALS tend to lose weight. The illness itself increases the need for food and calories. At the same time, problems with swallowing make it hard to eat enough.

Breathing devices include machines that are used only at night, and constant mechanical ventilation.

Patients should discuss their wishes regarding artificial ventilation with their families and doctors.

Support Groups

Emotional support is vital in coping with the disorder, because mental functioning is not affected. Groups such as the ALS Association may be available to help people who are coping with the disorder.

Support for people who are caring for someone with ALS is also available, and may be very helpful.

See: ALS - support group

Outlook (Prognosis)

Over time, people with ALS progressively lose the ability to function and care for themselves. Death often occurs within 3 - 5 years of diagnosis. About 25% of patients survive for more than 5 years after diagnosis.

Possible Complications

• Breathing in food or fluid (aspiration)
• Loss of ability to care for self
• Lung failure (See: Adult respiratory distress syndrome)
• Pneumonia
• Pressure sores
• Weight loss

When to Contact a Medical Professional

Call your health care provider if:

• You have symptoms of ALS, particularly if you have a family history of the disorder
• You or someone else has been diagnosed with ALS and symptoms get worse or new symptoms develop

Increased difficulty swallowing, difficulty breathing, and episodes of apnea are symptoms that require immediate attention.

Prevention

You may want to see a genetic counselor if you have a family history of ALS.

Alternative Names

Lou Gehrig's disease; ALS; Upper and lower motor neuron disease; Motor neuron disease

References

Feldman EL. Amyotrophic lateral sclerosis and other motor neuron diseases. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap. 435.

Updated: 4/27/2012

Reviewed by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Daniel B. Hoch, PhD, MD, Assistant Professor of Neurology, Harvard Medical School, Department of Neurology, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.