Jan. 13, 2000 (Indianapolis) -- Although amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, has been described since the mid-1890s, its origin is still not known. The results from studying one possible scenario, infection by an enterovirus (EV), a type of virus, have lead to conflicting outcomes. Research published in the January edition of the journal Neurology rekindles the debate on persistent infection with EV and how it may be associated with ALS.
ALS is a progressive disease that attacks the neurons controlling the movement of voluntary muscles such as the legs, arms, or the muscles used for speech. The neurons gradually disintegrate, preventing them from properly delivering their instructions to the muscles. ALS appears in either inherited or random forms. The inherited form accounts for only about 5% to 10% of all cases of ALS.
"Although ALS is a clinically well-defined motor neuron disease (MND), little is known about [it]," writes lead author Bruno Lina, MD, PhD, from the Laboratoire de Virologia, Centre National de Référence por les Entérovirus in Lyon, France. "Among the different causes that have been hypothesized, conflicting results have been reported about the possible role of a persistent EV infection."
The researchers looked for indications of EV genetic material in the spinal cords of 17 patients with ALS and 29 healthy people for comparison. They found such evidence in almost 90% of those with the disease, but only 3.4% of the healthy people. In addition, 13 of the ALS patients were found to have pieces of genetic material that closely matched the EV known as echovirus 7.
"There is no evidence yet that the virus we detected is involved somehow in the neuronal death and course of the disease," writes Lina. "Further work is required to confirm that the virus we detected [can cause ALS] and to determine how this persistent EV infection has occurred."
R. Glenn Smith, MD, PhD, assistant professor at the Baylor College of Medicine in Houston, is "cautiously optimistic" about the results of this study, but stresses that a lot of work remains before doctors can be comfortable establishing EV as the primary cause of ALS.
"This is certainly not the first attempt to document that a virus might be associated with this disease," he says in an interview with WebMD. "However, we don't know yet that a virus is involved with -- much less causes -- the disease. Even if a virus turns out to be the cause of ALS, it is very likely there are other factors that must be present to trigger it."
Jill Heemskerk, PhD, who is with the National Institute of Neurological Disease and Stroke in Bethesda, Md., thinks this is very interesting and promising research. However, she notes that viruses have been implicated before without evidence they cause the disease.
"This is an especially interesting first cut on a possible cause for ALS," says Heemskerk in an interview to gain an objective view of the study. "To [identify] a potential cause is great, especially in these neuromuscular diseases. Once you have a reason, you have a target to try and hit for curing this disease. However, establishing this, or anything else, as the cause is still a few years away, with curing even further down the line."