Hi there. You are not alone! I asked my husband to go to a couples counselor with me for a host of issues, one of them being silent treatment issues.
I also began an online program called marriagemax.com. Believe it or not, you can see changes in your marriage by taking steps solo. I feel people are sometimes too quick to throw in the towel or try to manipulate back with ultimatums. Things are sloooooowly improving between he and I. Intact I am day 4 into a silent Treatment episode myself. I am not giving him an ounce if attention for his behavior. In the past I would ask him what was wrong, etc, only to be opening up myself to some sort of emotional attack. It would lead to a horrendous argument. I feel the silent treatment was his way of throwing a tantrum. So I treat him like a toddler. I totally do not give it any power. Eventually, I think he gets bored and lonely himself and returns to being himself. My hope is that these episodes will become less and less. Meannwhile I keep busy, do fun things for myself, continue counseling And read Mort Fertels stuff on marriagemax.com.
I think it sent my husband a powerful message when I went to counseling anyway but did not leave him....it confused him but also destabilized his control patterns. Hang in there!
By the way, my counselor said that my husband might be better off with a counselor of his own instead of couples counseling....but from my experience pressuring my husband into counseling did not help....