Its not clear whether the neck dystonia you have is a primary coervical dystonia, which occurs sporadically without a precipitating factor, and is an disorder in and of itself
or a secondary dystonia related to muscle spasm after neck surgery. Its possible you may have had the genetic makeup for cervical dystonia all along, and muscle spasm after surgery revealed it - this is not clear and is just a hypothesis
Botox is very helpful in releiving the pain of both primary cervical dystonia or chronic muscle spasm in general. An evaluation for other causes of secondary cervical dystonia might include a review of your medications, and of your neck/nerve roots to see if there is any persistent neck problems after surgery. Primary dystonia tends to persist in life, although some rare cases it resolves. The length of treatment for secondary dystonia depends on the underlying cause and how quickly that is resolved ie further neck problems or spasm
Good luck