What Causes Pressure And Numbness On The Left Side Of The Head?

I m actually asking for a family member, age 73. She felt today like she had a hat on her head -- a pressure, I guess, then, in feeling her head, she found that the area on the left side at the bottom of her skull was completely numb to the touch. This was so frightening, but after a while went away. She keeps getting waves of nausea also. She is getting over a cold at this time. Four years ago at this very time of the month, she was getting chemotherapy for Breast Cancer. She wonders if her body is remembering!? (She is now cancer free -- according to an appointment a couple months ago.)