spasm is tightening of muscles which are challenged, as far as I know. Not a quick sharp stab. If muscles are weakened, they tighten up to have strength. This is why taking Zanaflex for my leg spasms (many years ago) produced so much weakness that I could barely walk. I can walk, even though my legs tend to spasm more if I do so. It is very important to keep doing the leg stretches which I learned from my Physician's Assistant, who is as good as a PT when it comes to helpful exercise. Last night I did them before bedtime and I had no spasm during the night and did not awaken with it.

But I agree with others here that Sam's pains are nerve shocks more than spasm.
However, spasm CAN be a brief thing, quick and over. I presume there are different kinds of spasm, and I'm not an expert on those definitions.