see more

UNITED STATES - SEPTEMBER 26: The Pfizer Inc. headquarters in New York, U.S., on Wednesday, Sept. 26, 2007. Pfizer Inc.'s experimental kidney cancer treatment shrank tumors in a mid-stage clinical trial, giving the world's largest drugmaker a potential back-up for its Sutent cancer medicine. (Photo by Robert Caplin/Bloomberg via Getty Images)

UNITED STATES - SEPTEMBER 26:  The Pfizer Inc. headquarters in New York, U.S., on Wednesday, Sept. 26, 2007. Pfizer Inc.'s experimental kidney cancer treatment shrank tumors in a mid-stage clinical trial, giving the world's largest drugmaker a potential back-up for its Sutent cancer medicine.  (Photo by Robert Caplin/Bloomberg via Getty Images)

see more

MRI Brain Scan of head and skull with hand pointing

MRI Brain Scan of head and skull with hand pointing

see more

Doctor viewing CT scan result of brain on digital tablet for abnormalities

Doctor viewing CT scan result of brain on digital tablet for abnormalities

see more

MRI scan of human brain and skull

MRI scan of human brain and skull

see more

Male Alzheimer's patient on bed, reminders on dresser drawers

Male Alzheimer's patient on bed, reminders on dresser drawers