Ed,
Do you know how long the seeds will be implanted? I had a similar procedure (also through the base of the tongue), but it was after having surgery and about 7 weeks of conventional radiation. By the time I had the implant, I was already feeling many of the nasty side effects of radiation -- mouth sores, swallowing difficulties, fatigue, etc. Those side effects continued for many weeks afterward, but it was impossible for me to tell how much was attributable to the implant vs. the regular radiation.
In my case, the implant was in place for about 30 hours, during which time I had to be in an isolation room (where somebody came around with a Geiger counter to test how much radiation I was emitting). Nurses could only come in for a couple of minutes at a time, and my husband was only allowed to visit for about 10 minutes during the treatment.
There are at least a few others here who have had some type of implant -- hopefully they will also respond about their experiences.
Cathy