A blood clot's danger depends on where it is

Secretary of State Hillary Rodham Clinton, listens to a reporter ask a question during a news conference with African Union Chairperson Nkosazana Dlamini-Zuma, not seen, after their meeting at the Department of State in Washington, in this Nov. 28, 2012 file photo. Doctors treating Secretary of State Hillary Rodham Clinton for a blood clot in her head said Monday Dec. 31, 2012 that blood thinners are being used to dissolve the clot and they are confident she will make a full recovery. (AP Photo/Manuel Balce Ceneta, File)
(AP) - Blood clots like the one that Secretary of State Hillary Rodham Clinton is being treated for can occur for a host of reasons. How serious a clot is depends on where it is and why it formed. Clinton's doctors say her clot was located in a vein between the brain and the skull behind the right ear.