NCIt definition : An episode of lightheadedness and dizziness which may precede an episode of syncope.;
Alternative definition : CTCAE: A disorder characterized by an episode of lightheadedness and dizziness which
may precede an episode of syncope.; FDA: Extremely weak; threatened with syncope.; ACC/AHA: The symptoms before syncope. These symptoms could include extreme lightheadedness;
visual sensations, such as tunnel vision or graying out; and variable degrees of altered
consciousness without complete loss of consciousness. Presyncope could progress to
syncope, or it could abort without syncope.;