Nystagmus
Nystagmus is an involuntary back-forth, up-down, or rotating eye movement.
Nystagmus can also suggest problems with the vestibular system.
slow phase - deregulated vestibular stimulus cuases drift
fast phase - cortical correction (this is the direction of the nystagmus)
problem with vestibular input to eom system
paralytic nystagmus - right ear is busted
irritative nystagmus - right ear is overactive - slow drift to left, so right beating nystagmus
Can be caused by benign paroxysmal positional vertigo (BPPV)
Testing nystagmus
It can be induced physiologically by turning the eyes far to one side: ask the person to follow a pen and ask them to hold the gaze for a few seconds at the end of the change.
or by injecting water into the ear canal.
caloric testing
- cold water in the canal causes a change in temperature
- COWS - cold opposite, warm same
- cheap
- can test each ear
- can't do if there's a hole in the eardrum
rotation chair testing
- tests both lateral canals
- ask patients to look straight at you
Can be caused by
- vertigo
- alcohol
Rotatory nystagmus
CN IV or brain stem problems
Direction-changing nystagmus
CN III and VI and cerebellum