Nystagmus 101

Question 1

What does nystagmus mean?

Answer 1

Derived from the Greek word, “nmstagmos”, which was used to describe the wobbly head movements of a sleepy or inebriated individual
Rhythmic, oscillating motions of the eyes are called nystagmus.
The to-and-fro motion is generally involuntary

Question 2

What does vertical nystagmus generally mean?

Answer 2

Central pathology
Less common
Often a sign of serious brain damage

Question 3

What are the two typical types of nystagmus?

Answer 3

Jerk - fast phase and slow phase (slow away from object or regard and a fast saccadic phase toward target)
Pendular - oscillate with equal speed, no fast and slow phase (sinusoidal)

Question 4

What defines the nystagmus direction?

Answer 4

By the fast component

Question 5

How do you measure the magnitude of nystagmus?

Answer 5

You need to look at cycles per second to measure the magnitude of pendular nystagmus
Find the slope for jerk

Question 6

How should nystagmus be described?

Answer 6

Waveform
Direction
Amplitude
Frequency
Intensity
The examiner should also note the positions of gaze in which the nystagmus occurs and whether the intensity changes with gaze direction

Question 7

What is alexander’s law/phenomenon?

Answer 7

Jerk nystagmus is usually accentuated in amplitude upon gaze in the direction of the fast component (hindered in the direction away from the fast phase and helped in the direction of the fast phase)
Becomes lesser if you look where the eye wants to go

Question 8

What is torsional or rotary nystagmus?

Answer 8

Pure torsional nystagmus is a sign of a central disorder
Torsional or rotary nystagmus mixed with vertical or horizontal components is much more common is usually an indication of a peripheral disorder (like BPPV)

Question 9

What is a runaway nystagmus?

Answer 9

Increasing or decreasing velocity

Question 10

Is horizontal jerk nystagmus with slow phases increasing velocity usually congenital?

Answer 10

Yes
May result from chiari malformation

Question 11

Is vertical nystagmus with exponential slow phases increasing velocity usually congenital?

Answer 11

No
May be secondary to acquired cerebellar disease

Question 12

Can pendullar nystagmus be congenital or acquired?

Answer 12

Yes

Question 13

When is the slow phase amplitude reduced?

Answer 13

Fixation
Enhanced by darkness, frenzel lenses, or closing the eyes

Question 14

What is nystagmus caused by a leaky integrator?

Answer 14

Occurs only in an eccentric gaze position
Gaze evoked
The eyes are unable to maintain the eccentric position and drift back to the primary position with a decreasing velocity, reflecting a passive movement resisted by the viscous forces of orbital soft tissues
The defect may reside in the brain stem “neural integrator” or its connections (such as in the cerebellum), which mediates eye deviation
Also called gaze-paretic nystagmus

Question 15

Are some nystagmus patterns specific and permit reasonably accurate neuroanatomic diagnosis?

Answer 15

Yes
Other patterns are more general and indicate dysfunction somewhere in the posterior fossa

Question 16

Are there several types of benign nystagmus seen in infancy?

Answer 16

Yes
Congenital nystagmus (CN) is the most common infantile nystagmus
Others are latent/manifest latent nystagmus (LMLN) and the pendular nystagmus of spasmus nutans

Question 17

What causes congenital nystagmus?

Answer 17

The direct result of an ocular motor control instability that may develop with or without an accompanying sensory deficit

Question 18

What are some characteristics of congenital nystagmus?

Answer 18

Binocular
Similar amplitude in both eyes
Usually uniplanar (horizontal)
Distinctive waveforms
Diminished by convergence
Increased by fixation attempt (similar to central pathology, but not central)
Superimposition of latent component
Inversion of the optokinetic reflex
Associated head oscillation
No oscillopsia
Abolished in sleep

Question 19

What is latent/manifest latent nystagmus?

Answer 19

A jerk nystagmus with either a linear or decreasing velocity exponential slow phase identical to that of gaze-paretic nystagmus
Occasionally, when both eyes are closed, a jerk nystagmus with a linear slow phase is present. Classically, “pure” or “true” latent nystagmus (LN) occurs only with uniocular fixation
There is no nystagmus with both eyes viewing, but when one eye is occluded, nystagmus develops in both eyes, with the fast phase toward the uncovered eye
LN is congenital
Several cases of MLN associated with fibroplasia

Question 20

What is spasmus nutans?

Answer 20

There is no nystagmus with both eyes viewing, but when one eye is occluded, nystagmus develops in both eyes, with the fast phase toward the uncovered eye
A rare constellation of ocular oscillation, head nodding, and torticollis that begins in infancy (usually between 4 and 18 months of age) and disappears in childhood (usually before 3 years of age)
The nystagmus is generally bilateral (but it can differ in each eye and may even be strictly monocular), and it oscillates in horizontal, torsional, or vertical directions
Spasmus nutans may sometimes be mimicked by tumors of the optic nerve, chiasm, or third ventricle

Question 21

What is acquired pendular nystagmus?

Answer 21

May reflect brainstem or cerebellar dysfunction or both
It occurs in patients with vascular or demyelinating disease.
In the latter, it has been regarded as a sign of cerebellar nuclear lesions
Multivectorial and usually associated with head tremor
Marked dissociation between the two eyes often exists and may not correlate with differences in visual acuity from coexisting optic neuropathy
Despite the dissociation, the oscillations of the two eyes are phase locked, even when there is a difference in their frequencies

Question 22

What is acquired horizontal jerk nystagmus?

Answer 22

Vestibular
We generally delimit vestibular nystagmus as being consequent to dysfunction of the vestibular end-organ, nerve, or nuclear complex within the brain stem
It is a horizontal-torsional or purely horizontal primary-position jerk nystagmus with a linear slow phase
The nystagmus intensity increases with gaze toward the fast phase (obeying Alexander’s law); it decreases and, with central lesions, may reverse directions upon gaze toward the direction of the slow phase
The symptom of vertigo usually coexists
Acute lesions of the cerebellar flocculus (the vestibulocerebellum) can produce a similar nystagmus
Cases of discrete cerebellar infarction are quite rare
Nystagmus may accompany episodic attacks of ataxia

Question 23

What is gaze evoked nystagmus?

Answer 23

Gaze-evoked nystagmus is elicited by the attempt to maintain an eccentric eye position, and it is the most common form of nystagmus encountered in clinical practice
Patients recovering from a central gaze palsy show a phase in which lateral gaze movement is possible but cannot be maintained in the deviated position; that is, the eyes drift back slowly toward primary position

Question 24

What are three types of nystagmus that are considered normal phenomena?

Answer 24

Fatigue Nystagmus (extreme gaze position or for a time exceeding 30 seconds)
Unsustained end point nystagmus (few beats over the recommended degrees)
Sustained end point nystagmus
(30 degrees or less is generally the sweet spot)

Question 25

What is torsional nystagmus?

Answer 25

A purely torsional nystagmus never occurs with vestibular end-organ disease the term “rotary nystagmus” is used interchangeably
When of small amplitude, torsional nystagmus may reflect a medullary lesion
Larger amplitude torsional nystagmus may be congenital, but when it is acquired it often indicates diencephalic (thalamic) involvement, in which case it is the underlying pattern in see-saw nystagmus

Question 26

What is periodic alternating nystagmus?

Answer 26

An extraordinary ocular motor phenomenon in which a persisting horizontal jerk nystagmus periodically changes directions
May be congenital or acquired

Question 27

What are some characteristics of congenital periodic alternating nystagmus?

Answer 27

May be associated with albinism
Has the slow-phase waveform of an increasing velocity exponential
Usually lacks the well-defined stereotypes periodicity seen in acquired PAN
Periodicity is markedly influenced by changes in gaze position, supporting the hypothesis that the PAN is a result of a temporal shift in the null zone

Question 28

What is downbeating nystagmus?

Answer 28

Nystagmus gaze position with the fast phase beating in a downward direction

Question 29

Do patients with brainstem disease or drug intoxications have downbeating nystagmus?

Answer 29

No
Usually lack gaze-evoked downward nystagmus despite nystagmus in all other fields of gaze

Question 30

What is a major cause of downbeating nystagmus?

Answer 30

Craniocervical junction, such as arnold chiari malformations
Could also be spinocerebellar degeneration (correctable)
*difficult to ascertain if it is the most common cause

Question 31

Can downbeat nystagmus coexist with PAN?

Answer 31

Yes, both can be suggestive of an abnormality of the craniocervical junction
A variety of miscellaneous conditions have also been reported to produce downbeat nystagmus
Examples: anticonvulsant, alcohol, and lithium intoxication; magnesium deficiency; B12 deficiency; brain stem encephalitis; alcoholic cerebellar degeneration; dolichoectasia of the ventral artery; and vertebral artery occlusion (systemic things can affect the central system too)

Question 32

What is upbeating nystagmus?

Answer 32

Fast phase beating upward
Rarely reflects drug intoxication
Less common
Most often, the nystagmus is acquired and indicates structural disease, usually of the brain stem
Could be a result of meningitis, Wernicke’s encephalopathy, or organophosphate poisoning (site of lesion unknown)
With convergence, upbeat may enhance or convert to downbeat
The slow-phase waveform is usually linear but may be an increasing-velocity exponential

Question 33

What is rebound nystagmus?

Answer 33

Direction of gaze-evoked horizontal nystagmus
During sustained ocular deviation or a horizontal gaze-evoked nystagmus that, on refixation to primary position, transiently beats in the opposite direction
The sign is often present in patients with cerebellar disease

Question 34

Can schwannomas result in obscure clinical vestibular manifestations?

Answer 34

Yes, because they are slow growing
Vestibular nystagmus beating contralateral to the lesion may be present, particularly if fixation is eliminated
As the tumor expands to compress the brain stem, a slow, gaze-evoked ipsilateral nystagmus is often added