shingles in the brain

About 8 years ago my 82 year old mom had shingles in the ear.  She was very sick with it and has been plagued by the side effects for years(heaviness of the head, dizzy, headaches,etc.) Two years ago she was diagnosed with stage four lung cancer(non-small cell)She had a round of chemo and radiation and was in remission for a year but now it is back .  She is presently on traceva(pill form of chemo)  Anyway here is my question 1)can you get shingles a second time in a difdernet place(perhaps the brain) and how do you diagnoise shingles of thr brain?  The reason why I am asking is becasue in the last month or so she has gotten sicker(not from the cancer) Her doctor says that she is doing fine as far as the lung cancer is concerned.  Her biggest problem and what is making her so sick is her head.  Sometimes she can  not get her head off the pillow, she is very dizzy but not with nasaeu, she has problems with her eyes and she says how heavy her head feels.  She had a spinal tap done in 2007 and a brain MRI in jan of 2008.  She is having another brain MRI this wednesday.  Pet scans in the past have not reveved anything cancer in the brain(but we understand that they don't always go up so high.  Could they tell if she had shingles on the brain from this new MRI? She has started neurtin last week.  Thank you