Differentiated pattern of nystagmus between canalolithiasis and cupulolithiasis in BPPV.

• A. Canalolithiasis: delayed-onset geotropic nystagmus; cupulolithiasis: immediate-onset persistent nystagmus with sustained vertigo due to debris adheres to cupula.
• B. Canalolithiasis: immediate-onset vertical nystagmus; cupulolithiasis: delayed horizontal nystagmus.
• C. Canalolithiasis: immediate-onset persistent nystagmus; cupulolithiasis: delayed-onset geotropic nystagmus.
• D. Canalolithiasis and cupulolithiasis have identical nystagmus patterns.

Answer: (A)

A key distinction here is where the debris causing BPPV is located and how that affects the velocity and duration of the eye movements after you change head position.

In canalolithiasis, the otoconia are free-floating in the canal. When a provocative position is assumed, the endolymph flow takes a moment to start moving the particles, so there is a brief delay before symptoms appear. The nystagmus is geotropic (toward the ground ear) and short-lived because the particles move with the flow and then settle, causing only a transient response.

In cupulolithiasis, debris sticks to the cupula itself. Gravity continuously deflects the cupula as the head is held in a provocative position, so there is little to no delay and the vertigo with nystagmus can be persistent, lasting as long as the position is maintained.

Thus, the description that matches this pattern is canalolithiasis with delayed-onset geotropic nystagmus, and cupulolithiasis with immediate-onset persistent nystagmus.