What Is ALS (Amyotrophic Lateral Sclerosis)?

Because ALS is a progressive disease, its symptoms are typically subtle in the beginning. People with the condition may notice a slight weakness in the hands, feet, arms, or legs that develops over a few days to a few weeks.

With time, more nerve cells die, and the weakness affects other limbs. Occasionally, the initial symptoms include trouble swallowing or slurred speech. As ALS worsens,  other symptoms may develop:

• Muscle twitches and cramps
• Loss of motor control
• Arm and leg impairment
• Regularly dropping objects
• Tripping or falling
• Periods of uncontrollable crying or laughing
• Ongoing fatigue
• Trouble breathing
• Paralysis

ALS can be extremely difficult to diagnose early in its development, largely because the symptoms are similar to many other conditions. Typically, the diagnostic process will involve tests to rule out other diseases. Electromyography (EMG) uses needles that a technician inserts into various muscles. This process records the muscles’ electrical activity, determining if there is an issue.

Along with an EMG, a doctor usually orders a nerve conduction study (NCS) to see if the nerves can correctly send signals to muscles throughout the body. In some cases, doctors use magnetic resonance imaging (MRI) to reveal evidence of different diagnoses with similar symptoms. These include multiple sclerosis, herniated discs, and spinal cord tumors. Even some infectious diseases like Lyme disease and syphilis can cause ALS-like symptoms.

Experts will often classify ALS cases in two different ways: sporadic or familial. The vast majority of people with ALS—roughly 90%—have sporadic ALS, which means they have no known family history of the condition. They also do not have any genetic mutation that researchers have linked to the disease.

Currently, nobody knows what causes sporadic ALS, though experts believe that genetic and environmental factors are equally important.

The other classification of ALS, familial, accounts for between 10% and 15% of cases. Experts have identified over 40 genes that have links to familial ALS, with four of these genes being responsible for over half of familial ALS patients.

In families with a history of ALS, there is a 50% chance that each offspring will inherit one of these gene mutations, developing the disease.

As research on ALS has advanced, scientists have identified several subtypes of the disease. Generally, three subtypes are most significant. The first, classical ALS, involves both upper motor neuron and lower motor neuron degeneration, meaning it affects the brain and the spinal cord.

Primary lateral sclerosis (PLS) affects only the upper motor neurons of the brain, and progressive muscular atrophy (PMA) involves degeneration of only the lower motor neurons in the spinal cord. Classical ALS occurs roughly 70% of the time, with PLS and PMA accounting for 5% each. Rarer and less understood subtypes account for the remainder.

ALS progression can be extremely unique. In general, the early stages of the condition feature muscle weakness or stiffness. The middle stages involve loss of control, weakness, and paralysis. Finally, most people with ALS lose the ability to dress, walk, write, speak, or even breathe and swallow.

The speed of progression can differ dramatically from person to person. Additionally, progression does not necessarily occur in a straight line. Some symptoms may not worsen for months, only to suddenly get dramatically worse.

Current treatments cannot reverse the damage, but they can slow the progression of ALS. They can also limit the chance of complications and allow people with the condition to live more comfortable lives. A variety of medications slow the loss of muscle control and function decline, and some may increase life expectancy by up to six months.

Many doctors will also recommend physical therapy and breathing care to maintain functions like moving and breathing for as long as possible. As ALS progresses, people with the disease may need to use some form of ventilation while sleeping.

Along with the typical medical interventions, most people benefit from nutritional support. Research shows that people with ALS need more calories than people without the disease, even if they are not exercising as often. However, chewing and swallowing can become extremely difficult, increasing the risk of aspirating or choking.

In many cases, a feeding tube is the safest and most effective way to provide nutrition to people with medium- to late-stage ALS. Some people may require palliative care to help ease pain and discomfort while undergoing other treatments.

ALS has no cure. In the majority of cases, the disease will progress over three to five years. By the end of its progression, ALS will have made voluntary muscle movements impossible and impaired breathing. Most individuals with ALS die from respiratory failure.

The average survival period is about three years, with 20% of people living five years, 10% for 10 years, and 5% for 20 years or longer. In extremely rare cases, a person may suddenly rebound and even regain function. However, these reversals are usually transient, and the damage often returns within 12 months.

Research into ALS and its causes and cures is ongoing. Many groups focus on identifying the genes responsible for ALS and how to use gene editing to avoid the condition entirely. Some scientists believe that “turning off'' certain genes could also prevent ALS. The development of biomarkers that help diagnose ALS is also a major area of research. Earlier diagnoses could result in more effective treatments.

Additionally, experts are constantly developing new medications, gene therapies, antibodies, and cell therapies that could manage or even cure ALS.