Researchers at BU found a link between head trauma and MND, thought they call it "chronic traumatic encephalomyelopathy" which is "ALS-like." I'm not entirely clear on what the distinction is.
"Over the past two years, BU researchers have linked head injuries in former athletes to depression and dementia, making headlines and leading to rule changes in the National Football League. Turns out that these problems may not be the only ones collision athletes like football players, boxers, and hockey players need to worry about. The researchers have now found a link between repetitive head trauma and a new form of motor neuron disease similar to amyotrophic lateral sclerosis (ALS), or Lou Gehrig’s disease. Their findings were published today in the September 2010 issue of the Journal of Neuropathology and Experimental Neurology."