I hate to throw rain on this theory, but my fasciculations dramatically DECLINED after I started Lexapro. It is no coincidence, I believe, that the Lexapro also dramatically (albeit gradually) reduced my overall stress about my health (or lack thereof) as I took it. Ever since I have come to much better grips about my overall well being, and a sense of better control over my health anxiety, my twitches, etc. have DRAMAtically subsided or even disappeared for stretches.
One thing to remember about Lexapro (as with all SSRI's) - it creates a paradoxical effect when first started. This can last up to eight weeks for some, and can be somewhat severe depending on the person, their psychological state when starting the meds, etc. In other words, if the underlying driver for muscle tension and fasics etc. is a generalized anxiety disorder that has overtaxed the neuromuscular system (as I now fully believe is the case based on my own experience - one where 18 months after its dreadful start, I am almost "cured" when in control of my anxiety, and suffer from flare ups when I let it get away from me), the paradoxical effects of the Lexapro can actually stimulate and perpetuate the drivers for the underlying cause of the problem. Even if you didn't feel the twitches or other symptoms prior to starting the meds, it is more than likely that the driver for these physical symptoms was latent and existing when the meds were started.
I am neither a Lexapro salesman or a doctor, but simply one of the fortunate many who have weathered the whole ugly storm, learned significantly from the time and phases that passed, and now face the mental challenge of keeping the loosely connected pieces together to try and construct a long-term recovery. I have been away from this site for many months, and now feel strong enough to return and share insights from the "other side". I hope this helps some...
JG