Nystagmus is a rhythmic, involuntary back-and-forth movement of the eyes. A slow phase moves the gaze away from the target, followed by a second movement that brings the gaze back to the target. The term originates from the Greek words “nystagmos” (drowsiness) and “nustazein” (to nod off).
Involuntary repetitive eye movements are broadly classified into two types based on their nature.
Jerky nystagmus consists of a fast phase and a slow phase, with the direction of the fast phase indicating the direction of the nystagmus. It often has a null point, and patients may exhibit an abnormal head posture (face turn) to align the eyes with the null point.
Pendular nystagmus lacks distinct fast and slow phases, showing nearly equal velocity back-and-forth movements. It rarely has a null point and is often associated with poor vision.
Based on onset age and cause, nystagmus is divided into congenital and acquired types.
The prevalence of pathological nystagmus is 24 per 10,000 people, with a slightly higher tendency in European populations. Sarvananthan et al. reported a prevalence of 16.6 per 10,000, with albinism-related infantile nystagmus being the most common cause. In adults, the prevalence is 26.5 per 10,000, with neurological disorders constituting the largest group 1). For infantile nystagmus, Nash et al. reported an annual incidence of 6.72 per 100,000 children, and the birth prevalence of infantile nystagmus is 1 in 821 births 1). Acquired nystagmus accounts for 17% in children and 40% in adults 1).
This article covers the following six important types in pediatric ophthalmology:
| Type | Onset | Main Features | Course |
|---|---|---|---|
| Congenital Jerky Nystagmus | Early infancy | Fast phase + slow phase, null point, dampened by convergence | Persists throughout life |
| Pendular nystagmus | Early infancy | Constant velocity to-and-fro, often sensory deficit type | Depends on underlying disease |
| Nystagmus blockage syndrome | Infancy | Nystagmus suppressed in adduction, esotropia | Surgery may be indicated |
| Latent nystagmus | Congenital | Appears when one eye is covered, direction reverses with fixing eye | Often no treatment needed |
| Spasmus nutans | Within first 2 years of life | Triad (nystagmus, head nodding, abnormal head posture) | Most resolve spontaneously |
| Periodic alternating nystagmus | Congenital/Acquired | Direction changes every 100–240 seconds | Surgical indication exists |
Spasmus nutans syndrome (SNS) is a type of acquired nystagmus that usually develops within the first two years of life. Its clinical features are the triad of nystagmus, head nodding, and torticollis. Most cases are idiopathic benign conditions that resolve spontaneously within 2–3 years 1). However, optic glioma has been reported in about 15% of cases, making imaging studies mandatory to rule it out 1). Rarely, it is also associated with retinal dystrophies such as congenital stationary night blindness (CSNB).
The prognosis is generally very good, but subclinical nystagmus may persist until 5–12 years of age. Since refractive errors and strabismus that cause amblyopia are common, careful clinical monitoring is necessary.
No treatment can completely eliminate nystagmus. However, refractive correction and surgery can reduce nystagmus amplitude and improve abnormal head posture. If binocular visual acuity is good, there is usually no major interference with daily life.
It presents as jerk nystagmus with fast and slow phases. Convergence reduces the nystagmus, and there is a null zone (direction where nystagmus amplitude is smallest). Abnormal head posture (face turn) is observed to bring the null zone to the front. The slow phase of congenital nystagmus shows an increasing velocity pattern, which distinguishes it from nystagmus blockage syndrome. It is a lifelong condition, but many patients maintain good binocular visual acuity.
It shows equal-velocity to-and-fro movements without distinct fast and slow phases. Few cases have a null zone, and many have poor visual acuity. It appears in conditions that cause poor central fixation, such as albinism, optic atrophy, optic nerve hypoplasia, and macular hypoplasia (sensory defect type). Fundus examination is essential; if optic atrophy is found, further evaluation for septo-optic dysplasia should be pursued.
This is a form of congenital nystagmus in which the nystagmus is suppressed by adducting one or both eyes. Esotropia appears a few months after birth. Because the patient fixates with the adducted eye (cross-fixation), an abnormal head posture turning toward the fixating eye is observed. When the adducted eye is abducted, a jerk nystagmus appears in the direction of abduction.
Under binocular viewing, nystagmus is not observed, but when one eye is occluded, nystagmus appears. It is a horizontal conjugate jerk nystagmus, with the fast phase toward the non-occluded (fixating) eye. The direction of the fast phase changes when the fixating eye changes, a feature unique to this condition among nystagmus types. It is often discovered during refractive measurements with an autorefractometer. When combined with monocular amblyopia or esotropia, nystagmus may appear even under binocular viewing (manifest latent nystagmus), in which case differentiation from congenital jerk nystagmus is necessary.
This is a condition that develops in infancy, and caregivers often notice the following symptoms and seek medical attention.
Nystagmus
High frequency, small amplitude: Fine eye movements described as “shimmering.”
Disconjugate: Asynchronous oscillations with different amplitude and direction between the eyes. Often pendular waveform.
Multidirectional: Horizontal, vertical, torsional, etc., varying with gaze direction.
Intermittent: May be monocular, asymmetric, or intermittent. Worsens with fixation or near effort.
Head Nodding
Head nodding: Irregular low frequency (2–3 Hz), with horizontal, vertical, and torsional components.
Compensatory mechanism: Thought to be a compensatory mechanism to control nystagmus.
Torticollis
Abnormal head posture: Often head turn or torticollis.
Compensatory mechanism: Occurs as compensation for nystagmus, similar to head nodding.
Fundus findings are usually normal 1). Visual acuity is generally good, and nystagmus tends to improve or disappear over time 1). It may be confused with congenital nystagmus or coexist with it. While congenital nystagmus persists throughout life, spasmus nutans resolves spontaneously within a few years, which is a key point for differentiation.
This is a horizontal nystagmus in which the direction of nystagmus changes with a period of approximately 120 seconds (range 100–240 seconds). Visual acuity is often relatively good. It is frequently accompanied by abnormal head posture, and it is characteristic that the direction of head turn is not fixed, with the same person showing both right and left head turns.
Since nystagmus is induced when one eye is occluded, monocular visual acuity becomes worse than binocular visual acuity. For visual acuity measurement, the fogging method (testing without occlusion by placing a high plus lens over one eye) is used. The patient should be aware that monocular visual acuity tests, such as those required for obtaining a driver’s license, may be disadvantageous.
The causes of nystagmus vary depending on the type.
Congenital motor nystagmus has unknown etiology and pathogenesis. Genetic predisposition is suggested, but the established mechanism has not been elucidated.
Pendular nystagmus (sensory deficit type) is caused by diseases that lead to poor central fixation. Typical causative diseases include albinism, optic atrophy, optic nerve hypoplasia, and macular hypoplasia.
Nystagmus blockage syndrome is a condition that occurs when congenital nystagmus is suppressed by adduction of the eyes.
The cause of latent nystagmus is unknown. It is frequently associated with amblyopia and esotropia.
Most cases of spasmus nutans are idiopathic (unknown cause) and benign. Studies of monozygotic twins suggest a genetic predisposition, but no specific gene locus has been identified. Rarely, it is associated with the following conditions.
Periodic alternating nystagmus can be congenital or acquired; congenital cases appear early in life.
ENG (electronystagmography) is useful for analyzing the slow-phase waveform of nystagmus. Congenital nystagmus shows an increasing-velocity slow phase. In contrast, nystagmus blockage syndrome shows a decreasing-velocity slow phase, which is the key differentiating point. Recording jerk nystagmus during abduction enables diagnosis of nystagmus blockage syndrome.
ENG is also useful for differentiating manifest latent nystagmus. When the fixating eye changes under occlusion, the direction of jerk nystagmus reverses, which helps distinguish it from congenital rhythmic nystagmus.
Fundus examination is essential for pendular nystagmus. If optic atrophy is found, further evaluation for septo-optic dysplasia should be pursued.
Many cases are discovered when nystagmus is absent under binocular viewing but is induced by monocular occlusion during autorefractometer measurement. Diagnosis is confirmed by the appearance of nystagmus with monocular occlusion and its disappearance with both eyes open.
The diagnosis of spasmus nutans is made clinically. If the triad (nystagmus, head nodding, and torticollis) is confirmed, diagnosis is possible 1). However, tests to rule out intracranial lesions and retinal dystrophy are important.
Since there is overlap between spasmus nutans syndrome and retinal diseases, exclusion of retinal disease is essential before confirming the diagnosis 1).
The key points for differentiating each disease type are shown below.
| Differential Category | Main Diseases | Key Points for Differentiation |
|---|---|---|
| Congenital nystagmus | Fast phase + slow phase, null point present | Decreases with convergence, persists lifelong |
| Pendular nystagmus | Albinism, optic atrophy, foveal hypoplasia | Sensory deprivation type, poor visual acuity |
| Nystagmus blockage syndrome | Congenital nystagmus + esotropia | ENG slow phase is decelerating type |
| Latent nystagmus | Appears only when one eye is occluded | Direction reverses with alternating fixation eye |
| Manifest latent nystagmus | Associated with amblyopia and esotropia | Requires differentiation from congenital jerk nystagmus |
| Spasmus nutans | Triad (nystagmus, head nodding, abnormal head posture) | Onset in infancy, spontaneous remission |
| Periodic alternating nystagmus | Direction alternates with a cycle of 100–240 seconds | Direction of abnormal head posture is inconsistent |
| Optic pathway glioma | Spasmus nutans-like nystagmus | Must be ruled out by MRI |
| SN-like nystagmus | Optic nerve hypoplasia, achromatopsia, congenital stationary night blindness, hypomyelinating leukodystrophy | Differentiation by ERG and MRI |
Studies have shown that the presence or absence of intracranial lesions cannot be determined by clinical findings alone, and differentiation based on imaging is necessary.
Differentiation is made by the slow-phase waveform on electronystagmography (ENG). The slow phase of congenital nystagmus is of increasing velocity, whereas that of nystagmus blockage syndrome is of decreasing velocity. In manifest latent nystagmus, the direction of the jerk nystagmus reverses with a change in the occluded eye, which also aids differentiation.
Wearing fully corrective glasses is the basis of treatment. If age-appropriate visual improvement is not achieved with full refractive correction, prism therapy or contact lens use should be attempted early. Soft contact lenses may provide nystagmus suppression through the eyelid contact sensory reflex.
Three types of prism therapy are used.
In cases of head-position nystagmus, the classroom seat should be arranged so that the blackboard is in the direction of the resting position, and teachers should be informed not to forcibly correct the abnormal head posture.
Surgical treatment aimed at shifting the resting position is performed.
Medial rectus recession is the basic procedure. Additional Faden procedure or unilateral resection-recession may also be performed. Note that even if strabismus surgery corrects the eyes to orthotropia, they tend to return to esotropia. When performing strabismus surgery for cosmetic purposes, determine the amount of correction by prism adaptation test, and decide the surgical method and amount mainly based on recession. Attention should also be paid to preventing amblyopia in the non-dominant eye (non-fixating eye), and achieving stereopsis is often difficult.
Large recession of the four horizontal rectus muscles is effective for both cosmetic purposes and reduction of nystagmus amplitude.
If binocular visual acuity is good, treatment is not necessary. If amblyopia or esotropia is present, standard treatment for each condition should be performed. During visual acuity testing, use fogging method, and explain to the patient and guardians that monocular occlusion may result in worse visual acuity than binocular visual acuity.
Spasmus nutans is a self-limited condition and usually does not require specific medication or surgical treatment 1). The basics of management are as follows:
Reports on long-term prognosis indicate that some cases have poor visual acuity or insufficient stereopsis due to complications such as esotropia, alternating hypertropia, and amblyopia; therefore, careful follow-up is currently considered necessary.
Abnormal head posture is a compensatory posture using the null zone of nystagmus, so it should not be forcibly corrected. At school, seat the child so that the blackboard is in the direction of the null zone. Surgery such as the Kestenbaum procedure may reduce abnormal head posture by moving the null zone to the front.
For acquired nystagmus, select medication according to the type.
| Type of Nystagmus | First-Line Drug | Alternative/Adjuvant Drug |
|---|---|---|
| Downbeat nystagmus (DBN) | 4-aminopyridine (4-AP) | Clonazepam, memantine |
| Upbeat nystagmus (UBN) | Baclofen | Memantine, 4-AP |
| Periodic alternating nystagmus (PAN) | Baclofen | Memantine |
| Acquired pendular nystagmus | Gabapentin, memantine | — |
Drug-induced nystagmus (due to sedatives, antiepileptic drugs, alcohol, lithium, etc.) can be expected to improve with discontinuation or dose reduction of the causative drug. For nystagmus associated with BPPV, the canalith repositioning procedure (Epley maneuver) is effective.
Gaze stabilization of the eye is maintained by three mechanisms.
The localization of the neural integrator is as follows:
The etiology and pathophysiology are unknown. It has been reported that convergence reduces or eliminates the amplitude of nystagmus in about 80% of cases 1), which provides the theoretical basis for vergence prism therapy. A characteristic electronystagmography finding is that the slow phase is of increasing velocity type. Nystagmus does not completely disappear with any treatment, but it is not a problem if binocular visual acuity is good. Since monocular visual acuity measured in routine school vision screening is often worse than binocular visual acuity, it is important to explain this to patients and their families.
This is a condition in which a compensatory mechanism suppresses nystagmus by placing the fixating eye in adduction. The ENG slow phase shows a decreasing velocity pattern, which differs from congenital nystagmus (increasing velocity type), reflecting the difference in pathophysiology. The appearance of jerk nystagmus on abduction is also a basis for differentiation.
Nystagmus does not appear while binocular vision is maintained. It is induced when binocular vision is disrupted by covering one eye. When amblyopia or esotropia is present, suppression occurs in one eye even with both eyes open, resulting in manifest latent nystagmus.
Poor central fixation due to albinism, optic atrophy, optic nerve hypoplasia, or macular hypoplasia is the cause of nystagmus. It is thought that impaired development of the fixation reflex leads to constant-velocity pendular nystagmus.
The exact mechanism remains unknown. Head nodding and torticollis are considered compensatory mechanisms to reduce the frequency and asymmetry of nystagmus and improve vision. The lesion is presumed to involve the retina or optic nerve 1). Most cases are idiopathic, but when caused by chiasmal glioma, damage to the visual pathway leads to nystagmus 1).
The core mechanism is dysfunction of cerebellar GABAergic Purkinje cells, particularly those controlling downward smooth pursuit. Damage to Purkinje cells, including potassium channels, causes vertical VOR imbalance, leading to downbeat nystagmus. This is also the target mechanism for 4-aminopyridine (4-AP).
Instability of central gaze-holding structures (nucleus prepositus hypoglossi, medial vestibular nucleus, interstitial nucleus of Cajal) is the cause. Impaired integration of eye position signals leads to sinusoidal oscillations in multiple planes. In MS, demyelination in these structures results in this type of nystagmus.
Interventional studies targeting FRMD7, the causative gene for infantile idiopathic nystagmus, are ongoing. Due to its X-linked inheritance pattern, it is attracting attention as a candidate for gene replacement therapy 1).
AI-assisted waveform analysis using eye movement tracking data has been reported to potentially improve diagnostic accuracy, and its application to remote neuro-ophthalmology consultations using portable digital devices has also been reported1). The three-dimensionalization of video-oculography is enabling precise analysis of torsional nystagmus.
Ramanzini et al. (2024) reported a case of a 3-year-old boy presenting with nystagmus, global developmental delay, and diffuse hypomyelination on MRI2). Initially, Pelizaeus-Merzbacher disease (PMD) was suspected, but no pathogenic mutation was found in the PLP1 gene. Exome analysis identified a homozygous mutation in the GJC2 gene, leading to a diagnosis of Pelizaeus-Merzbacher-like disease (PMLD). Findings of hypomyelination in the brainstem and cerebellum, along with normal auditory brainstem responses, are clues for differentiating from PMD. In infants with nystagmus and developmental delay, hypomyelinating leukodystrophy should also be considered in the differential diagnosis.
Doya et al. (2022) reported a case of a 1.5-year-old girl with a chief complaint of excessive head nodding for 3 months3). The head nodding worsened with walking, emotion, and stress, diminished during concentration, and disappeared during sleep. Head MRI revealed a suprasellar arachnoid cyst (3×5×7 cm) obstructing the foramen of Monro and hydrocephalus. Neuroendoscopic cyst-ventriculostomy and cyst-cisternostomy were performed, and the head nodding completely disappeared 6 months after surgery. In infants with head nodding, it is important to consider Bobble-head doll syndrome in the differential diagnosis, and early imaging and surgical intervention lead to favorable outcomes.
