My mother currently finished her 3rd week of radiation treatment and is feeling extremely dizzy and wobbily. Her primary doctor told her that it is from a sinus infection - my question is, could this be a side effect from the radiation? The medication the doctor gave her to relieve the sinus infection has not worked yet. Could the symptoms I have described be a side effect from the radiation? If so, what should I have her do?

Yes, dizziness is fairly common, especially in the post Tx. There can be many reasons for it, malnutrition, dehydration, pain meds, etc. Sinus infections and pressure on the inner ear can cause dizziness or vertigo as well. Have her be very careful standing up or getting out of bed. There were many times that I almost blacked out doing that.

If she is taking an antibiotic be prepared for a thrush bloom as well.