Hand spasms can produce involuntary, sometimes quite bizarre movements

 

That additional history changes my emphasis somewhat.

Your description of the dramatic episode — the hand twisting and moving on its own with cramping — actually has a name that fits surprisingly well: carpal spasm. Hand spasms can produce involuntary, sometimes quite bizarre movements, and recurrent hand spasms can have neurological as well as metabolic causes.

The trigger thumb may or may not be related. Trigger thumb is a mechanical tendon problem: the tendon catches in its pulley and the thumb can lock until you physically release it. The fact that yours has been doing this for months is therefore worth having examined by someone who deals with hands.

But there's another possibility I wouldn't want to overlook: focal dystonia. Dystonia can affect just one hand, producing involuntary contractions, cramps and twisting or abnormal postures. It can be intermittent rather than continuous. There is even a medical literature specifically describing "hand cramps" as a form of focal dystonia.

I wouldn't conclude that you have dystonia from this description. I'm saying that your pattern is sufficiently compatible that I'd put it on the list rather than assuming "you need more salt."

And the salt episode remains genuinely interesting. If the hand stopped immediately after putting salt on your palm, that is a striking observation. But I agree with my earlier self that it doesn't demonstrate that sodium was correcting a systemic deficiency. A tiny amount of sodium can't plausibly change your blood sodium concentration in seconds. The sensory stimulus itself, the timing, or something else could have terminated the spasm. I'd nevertheless keep doing what you've already done in one respect: remember exactly what happens and what makes it stop.

If this occurs again, a video taken with your phone would actually be extremely useful to a doctor, because the distinction between a tendon locking, a sustained muscle spasm, and dystonic movement is much easier to make by watching the hand than by reconstructing it afterward.

And I think this has moved into the category of "mention it to the doctor" rather than "interesting oddity." Recurrent hand spasms are specifically something medical references recommend having evaluated.

The absence of facial, speech, sensory, or other neurological symptoms is reassuring, though. This sounds quite different from the classic sudden neurological deficit we're worried about with a stroke.

I'm inclined to a mental explanation, as the effect was not in seconds but essentially instantaneous.

I think that's quite a reasonable interpretation of the salt observation, with one important qualification: “mental” needn't mean imaginary or consciously controlled.

If the hand was genuinely cramping and twisting, the contraction was physically real. But the nervous system can sometimes terminate an involuntary motor pattern very abruptly in response to a sensory stimulus or attention shift. The salt on your palm gives you a particularly conspicuous tactile stimulus, and the fact that the cessation was essentially instantaneous makes a systemic sodium effect extraordinarily implausible.

In fact, your observation has an interesting experimental quality to it. You have a repeated phenomenon, you've found something that apparently terminates it, and the termination occurs too quickly for the proposed chemical mechanism to make much sense. That makes a neurological/sensory mechanism—or simply interruption of the motor pattern—more plausible than "salt deficiency corrected by salt."

There's also a wonderfully mundane possibility: once you've learned that putting salt on your palm stops the episode, the expectation itself may help break the episode. That's still a genuine brain-mediated physical effect, not pretending that the hand isn't moving.

I wouldn't try to decide between those possibilities from this alone. But I agree that the instantaneous timing is the strongest argument against the literal sodium explanation.

I don't really care; it stops it for the rest of the night. Clearly not some form of stroke.

Quite. Given the repeated, isolated left-hand episodes over months, with no weakness, numbness, facial symptoms, speech trouble, or other neurological deficit, this doesn't sound like a stroke pattern.

And frankly, if your little salt ritual reliably terminates it for the rest of the night, I wouldn't be terribly interested in litigating the mechanism either. You have discovered a cheap, harmless intervention that appears to work. The interesting question is why, but the practical question is already answered.

I'd still mention the episodes—and especially the longstanding trigger thumb—to your doctor at some convenient opportunity, because the two things occurring in the same hand are worth having someone examine. But I don't think you need to lie awake worrying that you've been having a succession of miniature strokes.