ALS affects approximately 5 in every 100,000 people. There are fewer than 20,000 US cases per year, making ALS very rare. Most people diagnosed with ALS are between the ages of 40 and 70. Men have a 20% higher likelihood of developing ALS, but after the age of 65, both women and men have an equal chance of developing ALS. ALS is more common in Caucasians and non-Hispanics, explaining the reason that ALS is more common in the Midwest and Northeast of the United States instead of the West and South. In addition, although the reason is still unclear, studies have shown that military veterans are twice as likely to develop ALS.

Around 90% of all ALS cases are sporadic, meaning that they occur without any previous family history. Although some genetic variations are known to put people more at risk for developing sporadic ALS, the cause of sporadic ALS is largely unknown. Some possible causes for sporadic ALS include abnormalities in the immune system, mitochondrial abnormalities and dysfunction, excess Glutamate (a type of neurotransmitter) production that accumulates around nerve cells, and environmental factors including trauma, exposure to toxic materials, diet, etc. The abnormalities in the immune system largely revolve around a particular immune cell called microglia, which can be both beneficial and harmful in preventing ALS. Mitochondrial abnormalities are caused by mitochondria, which are organelles that provide energy for the cell, that are not functioning properly. A Glutamate build-up is also another possible cause for sporadic ALS. In ALS, Glutamate, a neurotransmitter that carries signals between different nerve cells, accumulates around the nerve cells after it has performed its job of passing the signal between the nerve cells, causing complications. In addition, exposure to toxic materials, such as exposure to cyanobacteria, was first identified to cause ALS after the revelation that the number of ALS cases in Gulf War veterans was twice the amount of what was anticipated because of the environmental toxins they were surrounded by.

The remaining 10% of the cases of ALS are familial and are caused by an inherited gene. Most familial ALS cases have been caused by autosomal dominant inheritance. This means that the ALS gene mutation is not on the X or Y chromosome. Since it is a dominant condition, the person will develop ALS even if they inherit only one copy of the gene. In familial ALS, the genes that are most often mutated are the SOD1 gene or C9orf72 gene. Mutations on the SOD1 gene are responsible for 30% of familial ALS in Asian populations as well as 15% in European populations. The SOD1 gene was the first gene to be identified as one of the main causes of familial ALS. When the SOD1 gene is not mutated, it’s primary function is to make an enzyme called superoxide dismutase, which helps with the breakdown of toxic charged particles in the body. The C9orf72 gene makes a protein that is abundant in nerve cells. When a repeat expansion mutation occurs on the C9orf72 gene, it is linked to ALS as well as some forms of dementia. A repeat expansion mutation occurs when a string of DNA base-pairs gets repeated beyond a certain length, known as the “threshold length.”

The symptoms of ALS can vary from person to person because it depends on which nerve cells are affected. Generally, there is no pain in the early stages of ALS, and pain is also very uncommon in the late stages of ALS. ALS first starts in the limbs, feet, and hands, but eventually spreads to other parts of the body. As it spreads, the muscles begin to weaken as nerve cells are progressively being destroyed. Eventually, this can affect the ability to carry out normal activities. It may become difficult to walk, chew, swallow, and breathe. In addition, affected individuals often experience weakness in their ankles or hands, clumsiness, and spasticity (tightness in the muscles). The pseudobulbar affect (crying, laughing, or yawning at inappropriate times), slurred speech, muscle cramps, and twitching in the shoulders, arms, and tongue are all signs of ALS. In addition, dementia, in particular frontotemporal dementia, can accompany ALS. Some symptoms of frontotemporal dementia include loss of judgement, changes in eating habits, loss of empathy and other interpersonal skills, and increase in repetitive compulsive behaviors. They may also have some speech problems such as hesitant speech and trouble with using and understanding language.

ALS is typically diagnosed after an affected individual displays multiple symptoms and signs during a physical examination. In particular, signs of degeneration in the upper and lower motor neurons indicate the presence of ALS. In general, degeneration of upper motor neurons causes spasticity (tightness and stiffness in muscles), while degeneration of lower motor neurons usually lead to flaccidity (floppy and extremely loose limbs and muscles). However, some of the symptoms of ALS overlap with various other conditions. Therefore, a more detailed neurological examination is required.

Tests to confirm ALS diagnosis include:

• Electromyography (EMG) → measures the electrical activity of muscle cells, which helps to indicate the health of the nerves and the muscles they control

• Nerve Conduction Study (NCS) → asses the ability for a nerve to send a signal to a muscle

• Magnetic Resonance Imaging (MRI) → helps produce a detailed image of spinal cord and brain through the use of radio waves and magnetic fields, allowing doctors to eliminate conditions that may present the same symptoms as ALS

• Doctor may advise other tests, such as blood and urine tests, in order to eliminate the possibility of other conditions that present themselves in similar ways

Although there is no cure for ALS yet, there are various treatments available that can help alleviate some of the symptoms. Multidisciplinary treatment plans can provide the best care for those struggling with ALS. The FDA has approved the drugs Riluzole and Edaravone as effective treatments for ALS. Riluzole is a drug that helps to reduce the damage of motor neurons by targeting the excess glutamate production in affected individuals, but it does not reverse the damage that has already been done by ALS. Riluzole can prolong affected individuals’ lives by a few months. Edaravone helps to slow the deterioration of daily functioning for affected individuals. In addition, physicians can prescribe affected individuals with drugs to help manage their symptoms of muscle cramps, stiffness, etc. Physical therapy can also help the affected individual’s unaffected muscles strengthen and improve cardiovascular health without overworking the muscles. Some examples of this physical activity can include swimming, walking, and stretching. Wheelchairs and braces may also be helpful to help the affected individual conserve energy. Speech therapists may also be useful in allowing affected individuals to continue verbally communicating. Nutritional support is also extremely important to increase strength. A doctor may also recommend Noninvasive Ventilation (NIV) to provide breathing support.

The rate of ALS progression varies across individuals and is difficult to predict. Survival ranges from many months to more than a decade after the first symptoms present themselves. The most common cause of death is respiratory failure. If given a multidisciplinary treatment plan, affected individuals can continue to live productive lives for many years.

https://www.als.org/understanding-als/who-gets-als

https://www.cdc.gov/mmwr/volumes/67/wr/mm6707a3.htm

https://www.mayoclinic.org/diseases-conditions/amyotrophic-lateral-sclerosis/symptoms-causes/syc-20354022

https://www.mda.org/disease/amyotrophic-lateral-sclerosis/causes-inheritance

https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Amyotrophic-Lateral-Sclerosis-ALS-Fact-Sheet#:~:text=ALS%20is%20primarily%20diagnosed%20based,the%20presence%20of%20the%20disease

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3787117/

https://www.expansionrx.com/expansion-repeat-disorders/

https://www.nursingcenter.com/journalarticle?Article_ID=696953&Journal_ID=417221&Issue_ID=696930#:~:text=When%20differentiating%20upper%20and%20lower,motor%20disorders%20usually%20cause%20flaccidity.