Nerve block are similar in nature, and in some people can last a few weeks to a month, in others can last two hours...just depends. You can do trigger point injections (a lidocaine or marcaine injection into a knotted muscle) or botox into the same places... trigger points i think the goal is to relax the muscle by making it not hurt any more. Botox relaxes the muscle by not allowing it to contract.

The trigger point injection of lidocaine or a botox injection will do similar things to a nerve block (relax the muscle) but will generally last longer than a nerve block. I haven't done trigger points myself, only botox, but I think People get trigger point injections every few weeks, botox can go 6 weeks to 6 months, though I haven't heard of 6 months from anyone except the doc. I expect those people aren't hanging around here.

poeple get either type of injection in scalene, trapezius, and pec minor muscles depending on what is spasmed.