Which condition is characterized by sudden, severe episodes of dizziness?

The condition characterized by sudden, severe episodes of dizziness is Benign Paroxysmal Positional Vertigo (BPPV). BPPV is specifically caused by changes in the position of the head, leading to brief but intense episodes of vertigo. It occurs when tiny calcium carbonate crystals, called otoconia, become dislodged from their usual location in the inner ear and migrate into one of the semicircular canals. This abnormal stimulus to the balance system results in the sensation of spinning (or vertigo) when the head is moved in certain positions.

In contrast, Meniere's disease includes additional symptoms such as ear fullness, tinnitus, and fluctuating hearing loss, which are not limited to sudden episodes of dizziness alone. Vestibular neuritis is typically characterized by severe dizziness or vertigo that can last for days, but it doesn't have the positional triggers of BPPV. Labyrinthitis, while it can cause dizziness, usually occurs following an infection, leading to prolonged and more severe symptoms because it affects the inner ear more broadly rather than being triggered by specific movements.

Thus, BPPV's hallmark feature of sudden, positional vertiginous episodes distinguishes it from other conditions affecting balance and dizziness.