According to Stone's spokesperson Cindi Berger, the 43-year-old Basic Instinct actress was admitted to the hospital after suffering from severe headaches.
Berger said in a statement that an angiogram was performed on Sunday determined that the likely cause was a tiny aneurysm that required no treatment.
An aneurysm is a ballooning-out of the wall of an artery, vein or the heart due to weakening of the wall by disease. It can be caused by injury or an abnormality present at birth and are often caused or aggravated by high blood pressure.
"Ms. Stone will be hospitalized for observation for the rest of the week. Doctors expect no further problems or complications. She is resting comfortably," Berger said.
Stone was brought to the hospital by her husband, San Francisco Chronicle executive editor Phil Bronstein.
Stone's first real break came playing Arnold Schwarzenegger's kick-boxing secret agent "wife" in Paul Verhoeven's sci-fi actioner Total Recall in 1990. In 1995, Stone was nominated for an Oscar for her role in Casino.