Rather than "weakness vs. fatigue," I would say weakness leads to fatigue because it requires more energy to accomplish what you might want to do. I got my ALS diagnosis Nov. 2010 after an 8-month workup, during which time the weakness in my neck, shoulders and back became increasingly worse at what to me was a frightening pace. I saw my neurologist three times, and it was not until the third visit and the second EMG that she firmed up her suspicion that I had ALS. Apparently doctors have certain guides that dictate when a problem becomes a certain disease. My neurologist said that at least three limbs had to be involved. She thinks the spine should be regarded as a limb but the medical establishment does not. My legs passed muster on the first EMG but not my arms. Three months later I was experiencing more cramping, twitching and weakness in the legs. I had fallen two or three times. Another EMG showed that the legs were indeed involved. I can't do much for very long without having to sit down or lie down. My wife, who is 80 also, does the heavy lifting around here. The fine motor skillls are becoming more difficult to perform. At the start of the 8-mnth workup to the ALS diagnosis, a physical therapist, gave me some very simple exercises which have proved quite helpful in using muscles and warding off atrophy. I go to gym from time to time. I use a walker from time to time. I am still driving. I am fortunate in that I do not suffer any great pain. Nor do I have a problem with sleeping.
--Gene