Cleveland — Doctors in New York have been keeping a close eye on Secretary of State Hillary Clinton after a blood clot formed in her head.

Clinton has a blood clot behind her right ear in a vein between her brain and skull. Her doctors say the clot didn't result in a stroke or neurological damage.

"This is something that is not affecting the brain tissue itself. Having said that, if the clot obstructed blood from draining out of her skull, her brain could swell and become damaged," said Dr. Cathy Sila, a professor of neurology at Case Western Reserve University's School of Medicine in Cleveland.

Doctors say it's key to stabilize the clot. Clinton's physicians are treating her with blood thinners.

"It prevents the clot from getting larger," Sila said.

Some risk factors for blood clots include prolonged bed rest, sitting for long periods of time, being over 60, pregnancy and smoking.

Clinton, 65, suffered a concussion earlier this month after she fell at her home. She is also being monitored for other conditions related to her concussion.

"Sometimes, when people have a concussion, they have pretty bad headaches, dizziness and vertigo," Sila said.

Depending on the severity of the concussion, symptoms can last a couple of weeks.

Clinton's doctors say she is in good spirits, engaging with her family and staff, and is making excellent progress.