Nystagmus Flashcards
What is the definition of nystagmus?
Pathological or physiological rhythmic oscillation of the eyes - stops during sleep, usually bilateral.
What do you need to describe when assessing a patient with nystagmus?
Rhythm/waveform
Direction (if jerky)
Frequency/velocity
Amplitude
Oscillopsia
Null point
What are the types of physiological nystagmus?
End point
Post rotational
Induced by caloric testing
Optokinetic
What is end point nystagmus?
Jerky nystagmus observed when looking in extreme gazes, lasts a few seconds
What is post rotational nystagmus?
Occurs after stopping rapid rotation of the body.
Large amplitude, slow frequency, opposite direction to rotation
What is optokinetic nystagmus?
Occurs when a target is being followed.
Slow phase while following target, then fast phase to reset to fixate on next target.
(train/car window examples)
What is ‘induced by caloric testing’ nystagmus?
Test which investigates balancing mechanisms of inner ear induces nystagmus. Cold and warm water put into ear.
COWS: Cold stimulates fast phase Opposite to stimulated ear, Warm stimulates fast phase Same side to stimulated ear.
How can pathological nystagmus be classified?
Time of onset (congenital vs acquired)
Waveform (jerky vs pendular)
Cause (cerebellar vs labyrinthine)
What are the types of congenital nystagmus?
Low vision
Idiopathic
Latent
Manifest latent
Spasmus Nutans
What is low vision nystagmus?
Occurs secondary to poor vision (congenital or develops during plastic period)
Pendular with slow rhythmic oscillation
Often jerky on versions
Can be unilateral
Prognosis for good VA poor once nystagmus established
What are some common causes of low vision nystagmus?
Corneal scarring
Dense cataracts
Infantile glaucoma
Ocular albinism
Optic nerve hypoplasia
Optic atrophy
Macular hypoplasia
What is congenital idiopathic nystagmus?
Covers all manifest jerky nystagmus types present from birth/soon after with no visual defect
Bilateral
Horizontal
Fast phase changes on right and left gaze - null point between the two
Near VA better due to reduced nystagmus on convergence
Worsens on attempted fixation
What is latent nystagmus?
Only present when BSV possible
Horizontal jerk nystagmus on occlusion of one eye (fast phase towards uncovered eye)
No nystagmus when binocular
May be manifest on versions
Binoc VA better than monoc VA
What is manifest latent nystagmus?
Horizontal jerk nystagmus
Manifest with both eyes open
Amplitude increases if one eye occluded
Associated with infantile esotropia
Fast phase in direction of fixing eye
Increased intensity on abduction
May turn towards fixing eye
What is Spasmus Nutans?
Nystagmus, AHP and involuntary head movements present
Onset 3-18 months
Jerky or fine, high frequency nystagmus
Horizontal or vertical (or both)
Varies with direction of gaze
Head movements opposite to nystagmus direction and different frequency
Often resolves by 3 years
Can be result of CNS disease
What are the types of acquired nystagmus?
Labyrinth disease
Central vestibular disease
Cerebellar disease
Gaze evoked
Convergence retraction
Dissociated
See-saw
What are the features of nystagmus caused by labyrinth disease?
Horizontal jerk
Fast phase opposite side to disease
Amplitude increased on opposite side to lesion
Nystagmus suppressed by pursuit system
Nystagmus increases on foveal fixation
What are the features of nystagmus caused by central vestibular disease?
Similar to labyrinth disease plus:
may have vertical and torsional elements
What are the features of nystagmus caused by cerebellar disease (horizontal)?
Jerky nystagmus
Fast phase in direction of lesion
Large amplitude, low frequency
Amplitude increases on affected side
No compensation from pursuit system
What are the features of nystagmus caused by cerebellar disease (vertical)?
Upbeat - due to disease of anterior vermis
Downbeat - due to malformation of Arnold-Chiari (increases on downgaze)
What is gaze evoked nystagmus?
Unable to maintain eccentric gaze
Assoc with neurogenic and myogenic palsies
Fast phase towards affected side
What is convergence retraction nystagmus?
Progressive loss of upgaze
Dissociation of light-near reflex
When upgaze attempted, rhythmic retraction and convergence
What is the aetiology of convergence retraction nystagmus?
Pineal tumour
Midbrain tumour
Parinauds syndrome (compression of tectal plate caused by tumours)
What is dissociated nystagmus?
Differing oscillations in each eye
Most common cause is internuclear ophthalmoplegia (INO): abducting nystagmus
