Questions:
Infantile (congenital) Nystagmus
5. What are the characteristics, associated conditions, concerns, and treatment for infantile nystagmus?

Other Types of Infantile Nystagmus
6. What are the characteristics and associated conditions for latent nystagmus?
7. What are the characteristics, associated conditions, concerns, lesion location and treatment for spasmus nutans?
8. What are the characteristics, and lesion location for infantile monocular pendular nystagmus?

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Questions with answers:
5. What are the characteristics, associated conditions, concerns, and treatment for infantile nystagmus?
Characteristics
Onset noted within first 3 months of life.
Horizontal nystagmus (mixed pendular and jerk); may have a rotary component
Horizontal in upgaze.
May have a null point or head turn/tilt.
Waveform can be dramatic.
Often a reverse response to optokinetic stimulus may be seen (fast phase in direction of moving optokinetic nystagmus tape).
No oscillopsia.
Associated conditions  
Sensory visual loss that may produce infantile nystagmus: ocular and oculocutaneous albinism, achromatopsia, optic nerve aplasia or hypoplasia, Leber infantile amaurosis, optic nerve or retinal coloboma, aniridia, and retinal dystrophies (cone dystrophies, Infantile stationary night blindness).
Concerns
Children with nystagmus should undergo a thorough ophthalmologic examination because it is common to find that the underlying visual loss is from a variety of retinal, optic nerve, or cerebral etiologies.
If the nystagmus is dissociated or monocular, associated with neurological signs or symptoms, of later onset (i.e. acquired) or spasmus nutans is present then one must rule out a structural neurological abnormality.
Pendular nystagmus in a patient with oscillopsia suggests that the nystagmus is acquired.
Infantile periodic alternating nystagmus is often underdiagnosed.
Treatment
1. Use base-out prisms to induce convergence (dampens the nystagmus and may improve visual acuity).
2. Use prisms to shift the viewing position into the null region.
3. Contact lenses may dampen the nystagmus.
4. Gabapentin may dampen the nystagmus.
5. Surgical procedures include moving the extraocular muscles to place the null zone in primary position (Kestenbaum procedure) and recessing all four horizontal rectus muscles to decrease their tension (large-recession procedure).

Other Types of Infantile Nystagmus
6. What are the characteristics and associated conditions for latent nystagmus?
Characteristic
A varient of infantile nystagmus.
Not evident during binocular fixation.
Appears when either eye is covered (uncovered eye beats away from the covered eye).
Associated conditions
Most commonly seen in infantile esotropia.
Often seen with amblyopia, Down syndrome, and with any lesion disrupting binocular development in the first 6 months of life.

7. What are the characteristics, associated conditions, concerns, lesion location and treatment for spasms nutans?
Characteristic
Triad of head nodding, nystagmus, and abnormal head posture.
The onset is typically in the first year of life.
Usually benign.
Often spontaneously resolves.
May be sporadic or familial.
Typically intermittent, asymmetric, dissociated, or may be frankly unilateral.
Ocular oscillations are typically high frequency, small amplitude (“shimmering”), and usually horizontal in direction (but may have a vertical, torsional, or combination features).
Associated conditions
Most cases are benign.
Some children harbor an underlying anterior visual pathway tumor (optic nerve, chiasm, third ventricle, or thalamic glioma).
Most patients with an optic pathway glioma would be expected to have concomitant visual loss, strabismus, proptosis, optic atrophy, or other signs of the tumor.
It is also reported with arachnoid cyst, Leigh’s subacute necrotizing encephalomyelopathy, Infantile stationary night blindness, retinal dystrophy, and Bardet-Biedl syndrome.
Concerns/Lesion location
Neuroimaging: preferably cranial MRI with contrast.
Especially if there is an associated visual loss or a history of neurofibromatosis type 1 (associated with optic pathway glioma)
Treatment The benign form of spasmus nutans requires no treatment.
If the symptoms are caused by another condition, that condition must be treated.

8. What are the characteristics, and lesion location for infantile monocular pendular nystagmus?
Characteristics
Usually due to visual loss.
With bilateral visual loss, there is bilateral nystagmus.
Nystagmus is greater in the eye with the poorest vision.
Location
Often optic neuropathy or chiasmal glioma

The information below is from: Neuro-ophthalmology Illustrated-2nd Edition.

“16.1.2 Infantile (Congenital) Nystagmus
Infantile (congenital) nystagmus is usually not noted at birth but becomes apparent during the first few months of life
Characteristics
● Horizontal nystagmus (mixed pendular and jerk); may have a rotary component.
● There are bilateral conjugate movements of the eyes.
● Nystagmus is not present during sleep.
● There may be associated latent nystagmus.
● Null point (the preferred eye position for the patient to fixate) usually results in ahead turn.
● Convergence decreases the nystagmus, and fixation increases it.
● Patients may have a head tremor that in some cases improves visual acuity.
● Reverse response to optokinetic stimulus may be seen (fast phase in direction of moving optokinetic nystagmus [OKN] tape).
  ○ Nystagmus may be seen in isolation (also called congenital motor nystagmus), or it may be associated with strabismus or afferent visual system defects (e.g., albinism (see ▶Fig. 16.4), congenital stationary night blindness, or optic nerve hypoplasia).
  ○ There is no oscillopsia, but there is decreased visual acuity (related to associated afferent conditions and to the nystagmus present in primary gaze).

Pearls
Children with nystagmus should undergo a thorough ophthalmologic examination because it is common to find that the underlying cause of the visual loss is from a variety of retinal, optic nerve, or cerebral etiologies.

Treatment
Treatment of infantile nystagmus includes the following:
● Use base-out prisms to induce convergence (dampens the nystagmus and may improve visual acuity).
● Use prisms to shift the viewing position into the null region.
● Contact lenses may dampen the nystagmus.
● Gabapentin may dampen the nystagmus.
● Surgical procedures include moving the extraocular muscles to place the null zone in primary position (Kestenbaum procedure) and recessing all four horizontal rectus muscles to decrease their tension (large-recession procedure).

Other Types of Infantile Nystagmus
Latent Nystagmus
This is a variant of infantile nystagmus that is not evident during binocular fixation but appears when either eye is covered (uncovered eye beats away from the covered eye). It is often seen in infantile esotropia (most common), often with amblyopia, and with any lesion disrupting binocular development in the first 6 months of life. It is also common in Down syndrome.

Spasmus Nutans
Spasmus nutans involves a triad of symptoms:
● Very asymmetric and occasionally monocular nystagmus (rapid pendular eye movements)
● Head nodding
● Torticollis (head tilt or head turn)
Onset is usually in the first year of life, with the nystagmus typically lasting for several months. The condition is usually benign with no neurologic abnormalities.
Neuroimaging is recommended (anterior visual pathway gliomas may mimic spasmus nutans). Ophthalmologic evaluation and possibly electroretinogram are recommended (retinal disorders causing visual loss may mimic spasmus nutans).

Infantile Monocular Pendular Nystagmus
This is usually due to visual loss (often optic neuropathy or chiasmal glioma). In cases of bilateral visual loss, there is bilateral nystagmus, with nystagmus greater in the eye with the poorest vision.”¹

Latent/Manifest Nystagmus
“…  the term, “latent”, is a misnomer. This type of nystagmus becomes clearly evident when one covers one eye, hence the original name, “latent nystagmus”²⁹. However, in virtually all cases it is also present to a lesser degree with both eyes open. This latter observation by Kestenbaum gave rise to the oxymoron, “manifest latent”³⁷. Thus, LMLN is a single condition with a name comprised of an erroneous (latent) and oxymoronic (manifest latent) term. I use “LN” when the nystagmus was recorded while one eye was occluded, “MLN” when both eyes were open and “LMLN” when discussing the nystagmus under both conditions or to indicate that this is a unitary nystagmus that may be present under either of two conditions.²

References:
1. Neuro-ophthalmology Illustrated-2nd Edition. Biousse V and Newman NJ. 2012. Theme
2. Congenital and Latent/Manifest Latent Nystagmus: Diagnosing, Treatment, Foveation, Oscillopsia and acuity. Dell‘Osso LF. Jpn J Ophthalmol. 38: 329-336, 1994

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