Can ALS Be Triggered by Nerve Injuries?

Amyotrophic Lateral Sclerosis (ALS) is a progressive neurodegenerative disease that affects as many as 30,000 people in the US and sees around 5,000 new cases each year. Most people had little or no knowledge of the disease at all until a few years ago when the ALS ice bucket challenge went viral on social media, creating worldwide awareness of this condition.

In ALS, the neurons in the brain and spinal cord which influence muscle movement gradually begin to die off. When these connections start to fail, it causes muscle atrophy. It is a disease that is more common in people over the age of 60 (although some are diagnosed in their teenage years or early 20s) and there is currently no known cure.

The statistics related to mortality are quite startling. Typically, half of the patients with the condition will live three or more years after being diagnosed. Only around 10% will survive for more than ten years.

Causes of ALS

Research into ALS needs to continue if we are to truly understand this disease and how to potentially cure it in the future. There still remains some uncertainty around what actually causes ALS, although researchers have made some progress in this area in recent years.

• There doesn’t seem to be a clear genetic component, at least in the vast majority of cases. When a genetic connection is identified, it applies to only 5% of patients.
  
• There is little to implicate the way patients have lived their lives, including things such as eating the wrong food, taking drugs or drinking or smoking.
  
• Recent research may suggest that the condition can be exacerbated or set off by nerve injuries. This could explain why soldiers and athletes seem especially prone to the disease.

Here we take a closer look at the research relating to nerve injuries and what it means to individuals who have ALS.

Nerve Injuries and ALS

People who take part in strenuous physical activity, such as athletes, are thought to be at more risk from being affected by ALS. There has also been evidence to suggest a connection between ALS and the military and soldiers are, of course, another group of individuals who are subjected to strenuous physical activity.

While there has been plenty of anecdotal evidence of this connection, the main study of note has been carried out on rats at the University of Illinois in Chicago. The rats were genetically engineered to develop ALS and showed an abnormal inflammatory response close to the area where their peripheral nerve damage was instigated.

As with ALS in humans, that inflammation and weakness started to spread gradually from the original injury site. While experiments on animals do not indicate that the same mechanism is taking place in humans, the anecdotal evidence from athletes and soldiers seems to back the notion of initial nerve damage increasing the likelihood of ALS.

Problems will often start in a single location like the hand or leg and then slowly spread to the rest of the body. According to Dr Jeffrey Loeb who carried out the research:

“Our results show that a single nerve injury, which is small enough that it only causes temporary weakness in normal animals, can start a cascade of inflammation in the spinal cord that initiates and causes the disease to spread in genetically-susceptible animals.”

What may be happening here relates to elements in the body called microglia. These are cells that seem to be prevalent in higher numbers around areas where an initial injury occurred. Microglia play an important role in ‘pruning’ damaged synapses connecting one nerve cell to another.

Along with increased microglia, there was also a significant reduction in synapses over time. This could mean something like a chain reaction going on, similar to what happens as ALS progresses.

One of the curious things about ALS is how it starts in a localized area and then starts to spread much like a virus. With the vast majority of ALS patients not presenting an easily identifiable cause, it’s likely that this is just one way the disease might start to manifest.

Ongoing ALS Research

There’s much still to learn about ALS and it’s by no means certain that nerve damage is a contributory factor in all instances where it is found.

Initiatives like the ‘ALS Ice Bucket Challenge‘, as well as being a fun activity to take part in on social media, actually helped raise money for research initiatives which eventually went on to identify a new gene, NEK1 which has a link to the disease.

The better we can understand what triggers ALS, the more likely we are to find a cure or at least discover ways to manage the condition more effectively and improve the prognosis for individuals who receive an ALS diagnosis.

Summary

While research continues to try and determine the causes of ALS, the theory that it could, in some cases, be caused by an initial smaller nerve injury gives cause for optimism in the fight against this disease. A lot more research needs to be undertaken, however, before we can be sure that this is a major contributing factor.