Doctors at Boston's Massachusetts General Hospital upgraded Teresa Heinz Kerry's condition from fair to good after she took ill last weekend on Nantucket Island, CNN reported.
Kerry spokesman Glen Johnson said doctors had not yet concluded what caused the seizure, though many possibilities had "thankfully" been ruled out.
Heinz Kerry, 74, next will be transferred to Spaulding Rehabilitation Hospital in Boston.
Joan Rivers refuses to apologize for kidnapping joke
Humongous iceberg slowly drifts away from Antarctica