Can facial twitching be a sign of an impending stroke?

Not usually: Facial twitching is often a sign of irritability of facial nerve. Can be caused by pressure on nerve by vessel or tumor.

Not likely: Facial twitching may indicate impending seizure, stroke does not usually make things twitch. Most commonly twitches or facial tics are harmless, some need micro-vascular decompression.

Fibers contracting: The brain sends messages to the muckes (via nerves) to tell the muscle to move. Occasionally, the chemicals that mediate this process allow for a muscle (or part of a muscle) to contract without any planned action. Causes range from nothing at all ( most prople get them occasionally) to fatigue to vitamin/ mineral imbalance. If happening frequently, see your doctor to rule out systemic reason.