Expansion
Peripheral nystagmus is unidirectional and fatigable; central nystagmus is not
Expansion
| Feature | Peripheral | Central |
|---|---|---|
| Direction | Unidirectional, fast phase away from the lesion | May be direction changing |
| Plane | Horizontal or horizontal-torsional | May be vertical or purely torsional |
| Effect of fixation | Suppressed | Not suppressed |
| Fatigability | Fatigues | Persistent |
| Associated features | Hearing loss, tinnitus, severe vertigo | Other brainstem or cerebellar signs |
| Head impulse test | Abnormal | Normal |
Alexander’s law: peripheral nystagmus intensifies when looking in the direction of the fast phase.
Types worth recognising:
- Gaze-evoked: on lateral gaze, from drugs (phenytoin, alcohol), cerebellar disease or fatigue
- Downbeat: craniocervical junction lesions such as Arnold-Chiari malformation
- Upbeat: brainstem lesions
- Pendular: congenital, or from demyelination
The HINTS examination (Head Impulse, Nystagmus, Test of Skew) is more sensitive than early MRI for posterior circulation stroke in acute vertigo, and a normal head impulse test in a patient with acute persistent vertigo is the alarming finding.