At any given time, there are over 30,000 patients diagnosed with ALS living in the United States; the number world-wide is estimated to be at least 450,000. Generally speaking, someone is diagnosed with ALS every 90 minutes. The life-time incident rate for an average person is often estimated at between 1 in 400 to 1 in 600 people - similar to that of multiple sclerosis.
A comprehensive report conducted by the National Academies' Institute of Medicine (IOM) supports the association between service in the U.S. military and increased risk of developing ALS. The IOM was charged with reviewing and evaluating all relevant scientific literature on ALS and veterans. It concludes that there exists "suggestive evidence of an association between military service and later development of ALS." Since 2000, studies have been conducted to assess the ALS incidence rate in Gulf War veterans. Most notably, a study jointly funded by the VA and DOD concluded that those deployed in the first Gulf War were twice as likely to develop ALS as their non-deployed counterparts, and potentially, at younger ages. Air Force veterans, it determined, faced the highest risk, at 2.7 times that of those not serving. In 2005, The Harvard School of Public Health broadened the case for ALS's military relevance. Its epidemiological study found that men with a history of any military service in the last century were nearly 60% more likely to die of ALS than men in the general population. The recent IOM report refers to this study as "well-designed and well-conducted." In July 2008, in response to the evidence, Secretary of Veterans Affairs Dr. James B. Peake announced that ALS is to be considered a presumptively compensable illness for all veterans with 90 days or more of continuously active service in the military.
ALS is essentially a diagnosis of exclusion; elimination of other possible diseases until ALS is left as the only diagnosis.
Who gets ALS and why?
There are two broad categories of ALS - sporadic ALS (sALS, essentially of unknown cause) and familial ALS (fALS, with a direct genetic cause). Familial ALS makes up about 10% of all ALS cases and occurs when specific genetic mutations are inherited and passed down through generations. More than 30 genes have been identified with mutations associated with ALS.
The remaining 90% of cases are sporadic ALS, meaning there is no known history of the disease in the family. There are many theories outlining potential causes of ALS including oxidative stress mitochondrial dysfunction, immune system over activity, glutamate toxicity and toxic exposures. ALS appears to affect men at a higher rate than women below the ages of 65. For men and women over the age of 70, incidence appears to be the same. It is important to note that familial ALS and sporadic ALS are seemingly indistinguishable clinically from one another. For more information, visit the What is ALS? section of the website.
ALS is considered to be a fatal disease, with more than 75% patients succumbing to respiratory failure. The average rate of survival is often estimated at 30 months after symptom onset, but progression varies, and up to 10% are estimated to survive 10 years or longer. Survival could also be potentially extended if a patient opts for mechanical ventilation.
How does the disease start and is progression constant?
The initial signs of ALS varies from patient to patient. Many patients experience weakness in a specific muscle group, such as in the leg, or the front part of the foot resulting in difficulty walking, refered to as 'foot drop'. This initial muscle weakness will, with varying progression, typically spread to other parts of the body. Symptoms beginning in the chest or neck and mouth area is often referred to as bulbar onset.
Currently, there is no effective therapeutic approved for use by the FDA that has been identified to stop the disease's progression or prevent onset. Rilutek is a drug that has been approved for use in the treatment of ALS; however it offers a very modest effect which has usually been described as a three-month life extension. The effectiveness of Rilutek varies from patient to patient, and all medical treatment decisions should be made in careful consultation with one's physician or other qualified medical professionals charged with their care.
Here at TDI, we evaluate ALS drug candidates in a mouse model of the disease called SOD1 G-93A. This is a widely accepted model for human ALS. This model is based on a version of the mutated human SOD1 gene, which is associted with 10-20% of inheritated cases of the disease. Mice or rats bred to carry multiple copies of the altered human gene develop symptoms very similar to clinical ALS. These animals provide a basis for evaluation of drug efficacy potential in studies that are similar to a clinical trial as well as a source for tissue for experimentation.
Most ALS patients do not experience pain, but discomfort could be related to the loss of connection and reconnection of axons and muscles that are sometimes understood as fasciculations or deep tissue muscle spasms.
There have been attempts to apply risk association to various environmental factors or lifestyle choices, but no series of reports have been conclusive enough to substantiate a particular factor risk alone. The general consensus is that 90-95% of cases of ALS have no known cause, with the remaining 5-10% being familial ALS, or related to a genetic mutation. While there have been "clusters" of ALS cases, none have been directly linked to any specific factor. Certain bacteria has been targeted as the potential culprit, however, the research linking them has yet to be considered conclusive. Copper and other heavy metals are consistently thought to play a role in the development or progressive nature of ALS; however, efforts to remove heavy metals from an ALS patient with correlating benefits have not been successful. ALS is often misdiagnosed as Lyme's Disease. Both diseases manifest in similar ways, and ALS researchers are curious about the potential use of this information to provide targets. However, to date, they have failed to make a connection and execute specific therapeutic programs around it. There are a number of therapeutic strategies that target ALS as if it was caused by a virus, as the disease does have a tendency to spread in fairly specific ways. The vast majority of non-genetics related cases of ALS act in a heterogeneous manner, which makes pattern development difficult to detect or link to the characteristics of any known virus.
Currently, stem cell therapeutics is not a truthfully viable option for ALS, however there is some interesting work being done both in the US and abroad. The idea of regenerating motor neurons and axons is still a long way from being implementable in the clinic for a large group of people. The current FDA approved stem cell trials for ALS deliver directly to the central nervous system via laminectomy, a very difficult and dangerous procedure that could leave a person with diminished physical ability or worse. Consequently, these trials have very limited enrollment, and are only accepting very late stage ALS patients that have already lost most voluntary control over their muscles. Mesenchymal stem cells, found in bone marrow, have not been looked at sufficiently in the preclinical setting. They are not as flexible, or potent, as embryonic/fetal/iPS cells, so there would be challenges to using them, especially for therapeutic development.
There is no conclusive evidence that ALS affects mental health. There is some evidence emerging that there is a level of dementia or other cognitive issues (frontal temporal dementia or pseudo-bulbar effects) that shows up in a relatively significant number of patients, but the level to which it takes to measure it is very challenging and nearly always shows up later in the process. It may be more related to general malaise and exhaustion than a direct result of the disease's progression. However, the American Academy Neurology has added to their general care practices of ALS patients a recommendation to rate, scale and monitor mental health capacity throughout the individual's disease progress.
What genetic tests are avaialble for familial ALS? What do they involve and where are they done?
There are commercially available tests for three of the most common genetic mutations associated with familial ALS: SOD1, Fus1, and TDP-43. For SOD1, a blood test is used to determine the presence of the gene; however, this mutation only accounts for about 5% of all cases of ALS. The test can be ordered through your primary care physician, and there may be a cost, depending on health insurance policies. The results take several months to be returned because there is only one company, Athena Diagnostics, processing the test. Making the decision to be genetically tested cannot be taken lightly; as such, there are rigorous pre- and post-test meetings that take place with a genetic councilor.