Laurent, ALS is misdiagnosed with lower back problems if there is weakness, wasting and/or twitching. The main difference is that there is NO pain with ALS - that is the most important differential diagnosis. If there is pain and atrophy-weakness, the problem is compressed spine cord, the most often its disc protrusion.ALS patiens can have pain too, but its because their back muscles supporting the body are weaker and the spine is with less support. Thats why one of the strenght test is to lift up from lying to sitting without using hands.Few days ago I was pretty bad, last 2-3 days I twitch only rarely...the only change is one beer before I go to sleep and I stop taking antidepressants. Maybe strange, but my twitching is much better.