Nystagmus Flashcards
Dissociated nystagmus
when the nystagmus only occurs in the ABducting eye - responsible lesion is ipsilateral to the poorly-adducting eye.
Classic example = INO (2/2 demyelination or stroke resulting in disruption of the ipsilateral MLF)
Debate whether this movement is a true nystagmus or instead, a series of saccades.
Normal ADduction of the involved eye on convergence.
Other possible causes of dissociated nystagmus include myasthenia gravis and following surgical weakening of one eye’s medial rectus muscle.
Spasmus nutans
asymmetric typically horizontal “shimmering” nystagmus* = LOW-amplitude, HIGH-frequency nystagmus
Usually benign, typically resolves by age 6
TRIAD:
(1) head nodding
(2) monocular or asymmetric nystagmus
(3) torticollis (i.e. abnormal or stiff neck position).
*can also be vertical or rotary. It is typically of the pendular variety.
Associated with?
Chiasmal glioma
Tumors of the parasellar/hypothalamic area can present with a nearly indistinguishable nystagmus (Heimann-Bielschowsky phenomenon); therefore perform neuroimaging in all cases of spasmus nutans (controversial).
-nystagmus resembling spasmus nutans can occur in children with certain retinal disorders:
CSNB or rod/rod-cone dystrophy. Therefore, do ERG if patient has abnormal eye exam (pupils, DFE)
CSM (central, steady, and maintained)
describes fixation on a target
used to estimate VA in 0 to 2 yo
C and S = monocular checks (one eye covered), while M is a binocular check.
location of the corneal light reflex when the patient fixates a handlight: Eye fixates centrally = C, or eccentrically = nC
steadiness of fixation as the handlight is motionless and also slowly moved about: eye keeps steady fixation on the target = S, or if the eye wanders or searches for the target = uS.
When the occluder is removed from the covered eye (in a cover-uncover test), if the eye stays fixated on the target = M, or when the occluder is removed from the covered eye, the previously covered eye then picks up fixation = uM.
(Ability of the patient to maintain fixation with 1 eye and then the opposite eye as it is uncovered from the occluder)
nC suggests congenital retinal disease, blind eye
uS suggests nystagmus
uM suggests amblyopia (one eye has preferred fixation)
Jerk nystagmus
Fast-beating component defines the direction of the nystagmus.
Ex: “left jerk nystagmus” indicates that the fast component = left-beating. Therefore 2/2 Alexander’s law, the nystagmus dampens on right gaze, the child would adopt a left head turn.
Cyclic esotropia
rare form of strabismus occurring in ~1:4000 strabismus patients. It is well known for its unpredictable response to different forms of therapy EXCEPT for muscle surgery which is usually curative.
SO myokymia
monocular “oscillopsia” - vertical or torsional
otherwise neurogically-normal individual
-acquired disorder of irritation of the CN IV resulting in intermittent, high-frequency, low-amplitude contractions of the superior oblique muscle
-majority: idiopathic
but very rarely:inciting compressive lesion such as a neoplasm or vascular anomaly
no associated brainstem nuclei abnormalities
Rx: systemic medications (carbamazepine and phenytoin), timolol gtts.
Surgery: SO tenectomy with simultaneous IO weakening.
Latent nystgamus
usually Dx in early childhood
horizontal BILATERAL jerk nystagmus manifests only when either eye is occluded (fast phase is AWAY from occluded eye)
Null point in adduction
good VA with both eyes open, but worsens when either eye is covered
If amblyopic, becomes?
manifest latent nystagmus
MC in: (likely occurs 2/2 early disruption of binocular vision)
congenital esotropia
DVD pts
Fog eye with +5.00 lens instead of occluding
Characteristic waveform= exponential DECREASE in the slow phase velocity (OPPOSITE that of congenital motor nystagmus which shows an exponential INCREASE in the slow phase velocity).
Mnemonic: think latent/slowing down.
Ex: left jerk nystagmus when the right eye is occluded (and vv). The child will want to look toward the RIGHT (i.e. adduction of the left eye) and therefore head to the LEFT.
Alexander’s law
“Alexander’s law” states that the nystagmus is more pronounced when gaze is directed toward the side of the fast-beating component.
Ex: in right jerk nystagmus, worsens in right gaze and improves on left gaze.
Different types of nystagmus
Downbeat – cervicomedullary junction (e.g. Chiari type 1 malformation), cerebellar flocculus
See-saw – parasellar area (e.g. craniopharyngioma), midbrain
Opsoclonus – neuroblastoma [usually from adrenals]
Periodic alternating nystagmus – cervicomedullary junction, cerebellar nodulus
Upbeat – cerebellum, medulla, midbrain
Spasmus nutans – usually no tumor; but similar nystagmus with parasellar/hypothalamic tumors
See saw nystagmus
Suprasellar lesion (e.g. craniopharyngioma)
- one eye is “going up” while the other eye is “going down” just like the playground device
- disconjugate nystagmus: one eye that elevated and intorts while another eye depresses and extort
Rx: removal of the responsible lesion. Also, baclofen and clonazepam may help dampen this nystagmus.
PAN
rare entity -congenital or acquired
In both forms, the jerk nystagmus lasts for approximately 60-90 seconds in one direction. There is then a period of no nystagmus for 10-20 seconds and then a resumption of jerk nystagmus in the opposite direction.
The child with PAN may demonstrate alternating head turning to take advantage of the shifting null point (e.g. right head turn [i.e. left gaze] during the right jerk phase).
Though the cause of PAN is currently unknown, it is thought to be due to a state of vestibular overactivity. Congenital PAN also has been associated with oculocutaneous albinism.
The acquired form of PAN is usually associated with a lesion of the cervicomedullary junction (e.g. cerebellar nodulus or uvula). Other causes of acquired PAN include: multiple sclerosis, Chiari I malformation, and cerebellar degenerations.
congenital motor nystagmus
Horizontal, conjugate
Onset < 6 months
“CONGENITAL” mnemonic
Convergence and eye closure dampen the nystagmus;
Oscillopsia = usually absent;
Null zone is present;
Gaze position does not change the direction of nystagmus;
Equal amplitude and frequency of nystagmus in each eye;
Near acuity is good because convergence dampens the nystagmus;
Inversion (reversal) of optokinetic nystagmus occurs*;
Turning of head or abnormal head posture to allow eyes to enter a null zone leads to better visual acuity;
Absent nystagmus during sleep;
Latent nystagmus occurs.
Associated with? Ocular albinism Achromatopsia Leber’s Congenital Amaurosis Aniridia
Esotropia + Nystagmus?
Nystagmus Blockage Syndrome
(Esotropia that “eats up” prism)
*“paradoxical inversion of the OKN response.”
Ex: In other forms of jerk nystagmus, if a child with right jerk nystagmus views an OKN drum rotating to the left (thus stimulating pursuit left and jerk right), his nystagmus would increase in amplitude. However in a child with CMN, his right jerk nystagmus would actually dampen or even reverse to become a left jerk nystagmus. This peculiar phenomenon ONLY occurs in congenital motor nystagmus.
oculopalatal myoclonus
very unique - ONLY HAS SLOW PHASES
bilateral acquired nystagmus that is vertical and pendular in nature
Associated with nystagmus: rhythmic movements of the face, soft palate, pharynx, tongue, larynx, diaphragm, or even the extremities. Patients may suffer recurrent involuntary noises from contraction of the larynx and/or diaphragm.
Usually caused by a brainstem stroke affecting the central tegmental tract which runs from the inferior olivary nucleus in the medulla to the red nucleus in the midbrain.
Cerebellar input from the flocculus connects to the inferior olivary nucleus and has some some poorly defined role in maintaining stability of the eye. The triangle formed by these three structures (the cerebellar flocculus, the inferior olivary nucleus in the medulla, and the red nucleus in the midbrain) is called the triangle of Guillain-Mollaret (or alternatively the triangle of Mollaret). Disruption of fibers along this triangle of circuitry results in oculopalatal myoclonus.
Interestingly, the onset of nystagmus usually occurs months to years after the inciting stroke. Also for unclear reason there is hypertrophy of the inferior olivary nucleus on MRI in these patients which is highly specific for oculopalatal myoclonus.
square wave jerk
def: “nystagmoid” eye movement that is not a true nystagmus but rather a type of saccadic intrusion. Microsaccadic fixation disturbance
LACKS a fast / slow phase and characteristically has a small amplitude (0.5 degrees to 5 degrees).
Square-wave jerks are commonly seen as bilateral small horizontal shifts (or “intrusions”) from fixation during examination followed by a pause and then a quick return to fixation.
SWJs are often seen in normal patients but when there are more than 9 per minute, the Dx of Parkinson’s disease or progressive supranuclear palsy should be considered (both commonly exhibit numerous square-wave jerks). Or cerebellar dz of various kinds.
Monocular nystagmus of childhood
Slow, irregular, vertical
Seen in:
blind kids
MS
spasmus nutans (transient, fast-beating, low amplitude nystagmus with abnormal head movements and postured found during the first 5 years of life)
Associated with?
Chiasmal and hypothamaic gliomas
Combined with poor vision?
Heimann-Bielschowsky phenomenon (monocular, small amplitude vertical nystagmus)
Congenital nystagmus waveform
HIGH YIELD FACT: slow phase velocity in congenital nystagmus accelerates over time before initiation of the fast phase
distinguishing feature from the slow phase wave form of latent nystagmus which does not show this characteristic.
