I Am Concerned About My Husband. He Has Been Having

i am concerned about my husband. he has been having severe headache's for about 7 month's. so bad he get's up in the middle of the night with them.we went to the dr's and he said it was sinus problems.I have noticed he has been forgetting more things and sometimes has trouble sleeping where he never has before. Would a pet scan be a consideration to have? i work with dimentia patient's and am worried about this.