sudden onset dementia symptomsexamples of onsetsudden onset of extreme dizzinesssudden onset vertigo and headachesevere vertigo sudden onsetsudden onset of dizziness and fatiguesudden onset dementia in elderlyvascular dementia sudden onsetsudden onset vertigo and nauseaquick onset of dizzinesssudden onset of seizures in adultssudden onset dizzy spells