In my case i'm 22 , i have twitching n n jerking in some body muscle , left leg and arm feal weak on and off , could that mean als , what's the % ?

<1% chance of ALS.: It is common for people to experience muscle twitching phenomena. Be healthy, eat right, exercise, & do not worry. In the early stages amyotrophic lateral sclerosis presents with increasing weakness in one limb, usually a hand. Fasciculations (twitching muscle fibers) are usually subtle. Then speech & swallowing difficulties are seen, as is difficulty walking. Still worried? your MD can do a test.