Differentiate canalithiasis from cupulolithiasis in BPPV.

• A. Canalithiasis: free-floating otoconia causing brief vertigo with head movement; cupulolithiasis: otoconia adherent to cupula causing prolonged vertigo with certain positions
• B. Canalithiasis: fixed otoconia; Cupulolithiasis: absence of otoconia
• C. Canalithiasis: longer vertigo; Cupulolithiasis: brief vertigo
• D. Canalithiasis: inner ear infection; Cupulolithiasis: inflammation

Answer: (A)

The distinction being tested is where the otoconia are and how that location changes the duration of vertigo. In canalithiasis, the otoconia are free-floating in a semicircular canal. When you move into a provocative head position, these loose particles shift and briefly deflect the cupula, causing vertigo that lasts only a short time. In cupulolithiasis, the otoconia are attached to the cupula, making it heavier; as soon as you assume the provoking position, vertigo starts and tends to persist as long as the head remains in that position, often minutes. So the best description is free-floating debris causing brief vertigo in canalithiasis, versus otoconia adherent to the cupula causing prolonged vertigo in cupulolithiasis. The other statements don’t fit the mechanisms (they imply fixed or absent otoconia, or non-BPPV processes).