Unfortunately, because ACM is still rather rare, we don't often find specialists with hundreds of surgeries under their belts. Watch out for anyone who promises you you will be cured. Or that all of your symptoms will disappear. While these are things to hope for, and are certainly possible, you should also be prepared for a lesser result. A good result is often defined in the research papers as a halt in the progression of symptoms.
Many people get relief from some of their worst symptoms.
Many people stay the same. A few get worse. Be sure and talk about this. Standards vary from place to place, but you should know how often you will need to see the doctor, get an MRI etc, etc. assuming all is well. A few people were told they needed no further followup after the surgery.