What is the difference between fasciculations and myoclonus? how do you tell the difference?

Spasms vs. Constant.: To my knowledge and a somewhat imprecise answer without much pathophysiology is simply that fasciculations can be likened to "spasms", i.e. are intermittent whereas myoclonus essentially translates to constant, uncontrollable jerks (clonus) of the muscle (myo). Myoclonus to my mind is generally an indicator of a more ominous problem.