Fragments of viral genetic material show up with unusual frequency in patients with amyotrophic lateral sclerosis, or ALS, but rarely in other people, a new study shows. The report, in the January Neurology, provides the strongest evidence yet that a virus may have a hand in killing nerve cells in this lethal disease.
Although a small percentage of cases is attributable to an inherited mutation, the cause of most ALS is unknown. The illness first attacks the nerve cells in the spinal cord that carry messages to muscles in the legs and arms. It shuts down the signals in these motor neurons, causing the muscles to wither. ALS, also known as Lou Gehrig's disease, typically results in respiratory failure. Death usually occurs 2 to 5 years after symptoms begin.