A Look at the Different Classification Types of ALS

Amyotrophic Lateral Sclerosis (ALS) is a disease that damages motor neurons. These vital structures in the human body carry information between the brain and the rest of the body. They are also involved in automatic processes such as breathing, blood pressure and reflex actions.

ALS normally starts in a localized part of the body but gradually spreads. Someone who has recently been diagnosed may, for example, have difficulty doing up the buttons on their shirt or weakness in their legs.

• As the neurons become damaged and die, the individual will gradually begin to lose motor function and sensation in more parts of their body.
• Although relatively rare, ALS is incurable and typically only half of those with the disease survive more than three years.
• It’s estimated that there are close to half a million people in the world who have the disease.

Are There Different Types of ALS?

ALS can be defined in different ways depending on its root cause and the clinical onset. As far as the underlying cause is concerned, the two different types are familial ALS and sporadic ALS.

When classifying the disease in terms of clinical onset, the two different terms used are spinal ALS and bulbar ALS.

Other forms of the disease are Guamanian ALS, which is more common in one location in the Pacific around the island of Guam, and Juvenile ALS which affects younger people.

Read on to learn more about each of the aforementioned types of ALS.

ALS Classified by Underlying Cause

The most common type amyotrophic lateral sclerosis is sporadic ALS. In the USA, it accounts for over 90% of cases and essentially means that there is no genetic component that might have influenced the development of the disease.

Familial ALS accounts for the rest of diagnoses in the USA (between 5 and 10%) and it means there is a genetic influence at work. One or more family members have also had the disease and this has influenced the individual’s own diagnosis.

While there needs to be more work carried out in this area, the research suggests that if someone has the relevant gene there is a 50% risk of ALS being passed on to a child. The most common gene defect (accounting for as much as 40% of cases) is C9orf72 which holds the instruction for making a protein that is common in neurons.

Other genetic factors include ALS with an association to frontotemporal dementia. Another may be linked to Parkinson’s Disease.

Familial vs sporadic types of ALS are still the subject of much research. The common theory today is that many sporadic diagnoses might, in fact, have a genetic connection. A lot more work needs to be done in this area before we fully understand what is going on.

ALS Classified by Clinical Onset

Another way of classifying ALS is how it presents in the clinical arena. There are two types here:

• Spinal ALS: This exhibits as muscle weakness in areas like the arms and legs and accounts for around 60% of cases. This is a relatively fast-acting form of the disease and fatality can occur within 3 and 5 years.
• Bulbar ALS: This is less common and affects areas like speech and swallowing first, something that tends to come later in spinal ALS. Bulbar ALS is known to affect women more than men and is usually seen in older people over the age of 70. Paralysis can follow very quickly, often within one or two years.

Other types of ALS

Types of amyotrophic lateral sclerosis can also vary because of where they occur and the age of the person they affect.

• Guamanian ALS occurs in only one part of the world in the Pacific. Although the exact cause is not known, it could be that there is a genetic component here that has not yet been discovered. It’s present in Guam and the Trust Territories of the Pacific.
• Juvenile ALS is extremely rare and typically begins to show in childhood or before the patient is 25. Initial symptoms can include facial spasticity and spastic gait and it affects upper and lower motor neurons. There are several subtypes and a strong genetic component.
• Primary Lateral Sclerosis is a slowly progressing form of the disease and can take many years to become debilitating and fatal. Some people can maintain the ability to walk if only using a stick or support, while in others, the progression of the disease will mean the patient requires a wheelchair.

The Research Continues

We still have much to learn about the different types of amyotrophic lateral sclerosis. While there may be more to a genetic component than was first thought, the vast majority of those affected are diagnosed with sporadic ALS.