Nystagmus at the extremes of gaze is normal.
Horizontal nystagmus may be due to:
- vestibular lesions - acutely the nystagmus is away from the affected side
- cerebellar lesions - tends to be fast nystagmus and towards the affected side
- MS - suspect if nystagmus is more in the eye which is abducting
- benign positional vertigo - suspect if nystagmus varies with head position
- peripheral lesion - suspect if also tinnitus/other signs
Down beat nystagmus is associated with:
- Arnold Chiari malformations
- Syringobulbia (not sure what these are? revise battle 11.3!)
Upbeat nystagmus is associated with:
- cerebellar vermis lesions
- organophosphate poisoning
Sticking with eyes we're now going to consider miosis....