What Causes Cold Shakes And Body Aches With History Of Chordoma Brain Tumor?

my mom had choradoma brain tumor about two yrs ago. she has been having really bad cold shakes and body aches which i think is the flu and she is suffering the symptoms a little more worse because of the radiation she had underwent. but she thinks other wise because she has not had any other symptoms whats your professional opinion on this is it somthing to worry about... by the way ive given her excedrin and tea