What Is Amyotrophic Lateral Sclerosis (ALS)?

Definition

Amyotrophic lateral sclerosis (ALS) is a disease that affects the body’s nervous system. ALS is progressive — meaning it starts with mild symptoms and gradually worsens. Over time, it breaks down the nerves that connect the brain and spinal cord to the muscles of the body. When these nerves die, scarring of the nerve tissue replaces them. These changes produce the symptoms of ALS. 

There are two main types of ALS: 

1. Sporadic: This means that it’s not inherited. Sporadic ALS accounts for 90% of all cases. 

2. Familial: This means that someone inherits at least one genetic mutation that leads to ALS. Familial ALS accounts for under 10% of cases. 

ALS is also known as “Lou Gehrig’s disease.” Lou Gehrig was a famous baseball player for the New York Yankees. In 1939, Gehrig visited his doctor due to weakness and coordination issues that were affecting his game — and he was diagnosed with ALS on his thirty-sixth birthday. His humble retirement speech in 1941 brought worldwide recognition to ALS. 

Causes

A small number of ALS cases, about 5% to 10%, are inherited. This means that parents can pass down specific genetic mutations that cause ALS to their children. It’s possible these mutations run in your family when there are two or more cases of ALS within a family. 

Most cases of ALS don’t have an obvious cause. But there are a few well-established risk factors:

• Age: Most people are diagnosed with ALS between the age of 60 and 75.

• Sex: ALS is slightly more common in men, but only when someone develops the disease before the age of 70. After that, men and women seem to develop the condition at equal rates.

• Smoking: This one was a little controversial in the past, but now there’s more evidence that suggests smoking can increase someone’s risk for ALS.

Researchers have proposed several other potential risk factors. Common ones include: 

• Exposure to heavy metals and pesticides

• Repetitive head trauma

• Athletics

• Environmental exposures for people in military service 

The evidence for these links is limited, so it’s not clear if these things truly have an association with ALS. 

Symptoms

The early symptoms of ALS are different from person to person — and they can be mild and vague. Because of this, ALS can take some time to diagnose. But there are some common symptoms that many people with ALS share. 

The most common early symptoms of ALS include:

• Mild weakness of an arm or leg

• Tripping or falling

• Fatigue with usual activities

• Heavier breathing with usual activities

• Muscle twitching or spasms

• Voice changes, like hoarseness or speaking more softly

• Speech changes, like slurring of words

• Memory loss

• Changes in personality or behavior

• Increased drooling

• Tendency to choke or cough while eating or drinking

As ALS moves into the later stages, it weakens the muscles even more. The early symptoms noted above can also become more pronounced and severe.

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Stages of ALS

The symptoms of ALS steadily get worse over time. There are two main staging systems that can track someone’s symptoms.

The first one — King’s clinical staging — stages someone's condition by how many parts of the body ALS affects. The second one — the Milano-Torino (MiToS) functional staging system — tracks ALS progression by the number of abilities it affects. The abilities it measures include movement, talking, swallowing, and breathing. 

Putting these technical staging systems aside, it’s important to recognize that ALS looks a little different for each person. But there are some patterns of progression that researchers have identified in some (not all) people with ALS:

• In people whose first symptom is weakness in one arm, their symptoms typically progress to the other arm, then one leg, then the other leg. Next, speech and swallowing starts to become more difficult.

• In people whose first symptom is weakness in one leg, their symptoms typically progress to the other leg, then one arm, then the other arm. Again, their speech and swallowing symptoms typically follow later.

• In people whose first symptoms involve their speech and swallowing, their arms are typically the next body part affected.

For most people, the final stages of ALS include:

• Difficulty breathing: Weakness in respiratory muscles makes it harder to fully expand the rib cage to take deep breaths.

• Difficulty swallowing: This makes it challenging to eat and drink. It can also result in major weight loss.  

Diagnosis

There’s not a specific test that diagnoses ALS. Instead, healthcare providers make the diagnosis based on symptoms and the way they evolve over time. There are diagnostic criteria that help medical experts diagnose ALS as quickly as possible. 

When someone first starts to have symptoms of ALS, their providers often run tests to rule out other potential causes. In addition to a physical exam, tests may include: 

• Imaging: Detailed pictures of the brain and spinal cord, such as MRI scans, are not necessary to diagnose ALS, but they can help to rule out other diseases. 

• Nerve testing: Electromyography (EMG), or nerve testing, can help rule out other neurologic conditions that can cause weakness. And specific findings on EMG may also suggest a diagnosis of ALS. 

Treatments

There’s currently no cure for ALS. But there are treatments to help people do as well as possible for as long as possible. This includes things like:

• Medications: Current medication options include riluzole and edaravone (more on these in the next section). 

• Symptom management: People with ALS can have bothersome symptoms beyond weakness — like drooling, muscle cramps, and fatigue. There are many medications that can help treat these symptoms. And symptom treatment goes well beyond medications, it includes physical therapists, speech and swallow therapists, and mental health professionals. 

• Cognitive evaluation: ALS can cause memory loss and changes in behavior and mood. This can have a big impact on someone’s safety and mental health. Medications and therapists can help people and their caregivers adjust to the changes as they evolve.

• Nutrition: Weight loss due to swallowing problems can be a problem for people with ALS. Nutritionists can help develop treatment plans to keep someone well nourished. And some people elect to receive nutrition through a feeding tube that’s inserted into the stomach. 

• Breathing support: Breathing becomes a serious problem in the later stages of ALS. Physical therapy and oxygen monitors can help. When necessary, machines to aid breathing may help people with ALS feel more comfortable and maintain oxygen levels. 

Medications

No medications can cure ALS. But there are treatments that can slow the progress of ALS. Currently, there are two FDA-approved medications in the U.S.:

1. Riluzole is an oral tablet. The American Academy of Neurology recommends this as an option for everyone with ALS. 

2. Edaravone slows disease progression in some people with ALS. It’s given as an injection into your veins, 14 days at a time, with 14 day breaks.

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Planning ahead

ALS is a progressive disease without a cure. This means that people and their families often consider completing medical planning documents at some point. These documents can be complex, and they’re a very personal decision. Talking with a medical provider and loved ones about these decisions can help. Many also find it useful to get the help of a lawyer for estate planning. 

Medical planning documents vary by state. The following are some of the most common documents that people choose to complete:

• Advance directives: An advance directive is a legal document that notifies medical providers about a person’s choices for their care if they’re not able to speak for themselves. 

• Medical power of attorney: A power of attorney document specifies the person who will make medical decisions if someone is unable to communicate their wishes. 

• DNR documents: Some people may also choose to complete a DNR, or “do-not-resuscitate” order. Copies of these documents are then shared with medical providers. 

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Written by Nicole Andonian, MD