U.S. Sen. John Fetterman's health is in the spotlight again after he felt "lightheaded" Wednesday night and was admitted to the hospital for observation.
It is not yet clear what caused the symptoms, though his office says initial tests found no evidence of one possible cause: a stroke.
The Pennsylvania politician suffered a stroke nine months ago, placing him at increased risk for having another one. Among other conditions that can cause lightheadedness are dehydration, infections, reactions to medication, and heart disease.