No doctor will guarantee positive results w/ ES surgery. The multitudinous experiences of so many forum members here dictates that most people gain at least some level of symptom relief & some complete symptom relief. If your husband has bilateral ES, symptoms often remain after one styloid is removed & these will only go once the second one is gone.
I think part of the reason that doctors don’t guarantee results is because they have no way of knowing how well the irritated nerves will recover after surgery. Our bodies are designed to thrive & survive which is why they are constantly working to fix what they perceive is wrong inside. Sometimes those “fixes” cause more problems than they fix (e.g. ES). Getting pressure of the cranial nerves affected in your husband’s case will give them an opportunity to heal which in turn should decrease or eliminate his symptoms.
Many of my symptoms got worse after my first surgery because they were being caused by the remaining styloid. Once I had my second surgery, my overall symptoms disappeared abt 95% but it was a gradual healing process over many months after that surgery.