I also have had this problem for almost 1 year.  My chiropractor was the one who noticed it and did an adjustment to the back of my neck.  The swelling went down immediately a little bit.  She then had me do light therapy to clean my lymphatic system (I think).  It helped for a while but then the swelling came back and I did the treatments again.  She now thinks there is more to it since it keeps coming back.  She is thinking it is something viral and wants me to have a thryroid scan.  My chiropractor has seen this before and had the gal go in for a thyoid scan and it was found to have cancer on their thyroid.  I will be asking my doctor for the scan to hopefully rule out anything like that.  I will keep you posted on what happens.