So, of course it wasn't intended to exist at all. Gene Roddenberry's vision of how Spock should deal with his enemies was far simpler: He'd punch them square in the jaw.
That's right, just a big ol' sock to the teeth. In an episode titled "The Enemy Within," an evil Captain Kirk terrorizes the Enterprise, and Spock is tasked with subduing him. He was supposed to do this by throwing a haymaker and knocking Kirk straight out. Despite being given a golden opportunity to punch William Shatner right in his enormous head, Spock declined, saying it was out of character. And here is where, in fact, Leonard Nimoy proved that he understood the character of Spock better than the people who wrote for him. Of course Vulcans would have a more restrained, logical way to subdue a man rather than giving him a flailing knuckle sandwich.
Plus, fight scenes need such complex choreography.
Instead, Nimoy suggested that Vulcans should have the power to shoot energy from their fingertips, and that placing said fingers on a prominent nerve would cause the enemy to receive a moderate shock and be knocked harmlessly unconscious. OK, it's not very scientific (although lightning fingers would certainly make masturbation more interesting), but it adheres to the central rule of sci-fi: Nobody will care as long as it's awesome.