Hi, Joan:
This is really "fringe" advice, so take it with a truckload of salt. Hopefully it will help you should you decide to try it:
Years ago, I had an accident that caused nerve damage in one of my legs. I had no feeling whatsoever in 1/4 of that leg for six months. I did 150 hours of research in AMA Journals on the nervous system and found out that garlic (and, to a lesser extent, onions) have an inherent "X factor" that causes the respiration rate of cells in your body to increase, regardless of blood circulation. Knowing that oxygen (read: respiration) regenerates nerves, I ate an entire bulb (not a clove, but the entire bulb) of raw garlic every day for 14 days. It was tough to do, and I smelled terrible, but it completely healed the nerve in my leg (complete return of function, no tingling or loss of sensation whatsoever) in 10 days. Years later, I had much more minor numbness in another nerve. Eating raw garlic again reversed the numbness completely, this time in about 4 days.
Here's the potential problem: if garlic can regenerate nerves, I would think it might also reverse damage to the tumor (which is aberrant nerve tissue), making it also regenerate. And garlic won't likely help your trigeminal nerve if your related symptoms are due to mechanical pressure (from the tumor) on the nerve (blocking signal flow) instead of cell damage from radiation or the tumor.
Anyway, you're not likely to get any useful feedback from your doctors about the benefits of eating raw garlic. The reference about garlic and onions which I read was only one obscure paragraph tucked away in volumes of AMA Journals. I've never seen any reference to this X factor in any natural-health publications, either. This is simply a folk remedy with no confirmed direct health benefit in Western medicine. So, whether or not to try the raw-garlic regimen is a decision you'll have to make alone. But if your numbness and tingling sensations persist after doing the steroid course, it might be worth trying.
Best wishes,
TW