Jerk nystagmus

Upbeat nystagmus

• cerebellar vermis lesions

Downbeat nystagmus - foramen magnum lesions

• Arnold-Chiari malformation

https://www.youtube.com/watch?v=5q9PwJ18r_s

Evoked/transient/temporary nystagmus ⇒ BPPV

1. What is Nystagmus?

Rhythmic, involuntary oscillation of the eyes consisting of a slow drift away from fixation and a fast corrective saccade.

Classified by direction, trigger, and localisation (central vs peripheral).

2. Direction‑Based Types & Their Meaning

A. Horizontal Nystagmus

• Unidirectional (fast phase always same direction) → Peripheral
• Direction‑changing (fast phase changes with gaze) → Central

Causes: