something else to look into is the ALS/mycoplasma link. mycoplasma are tiny bacteria with no cell walls and can hide out in the body for long periods of time. the body produces no antibodies against mycoplasma bacteria until the disease is quite progressed so it can be almost impossible to test for it in the dormant stage.
has your brother ever been in the armed services? the ALS rate for vets is 60% higher than for the rest of the population. with Gulf War Vets its even higher. one theory is that the soldiers that served during the Gulf War recieved vaccines that contained an altered form of "mycoplasma fermentans" which is a highly destructive organism.
if i were your brother i would get a broad spectrum mycoplasma test, they are not that expensive, although they need to be ordered by a clinic since the blood needs to be refrigerated immediately after being drawn.
some have reported great success with the Antibiotic drugs doxycycline or tetrycycline as mycoplasma treatments. the pennicillin based Antibiotic drugs have no affect on mycoplasma.
if you do a google search on "ALS + mycoplasma" you get all kinds of interesting articles. here are two.