What are the causes of nystagmus?

Causes of Nystagmus

Nystagmus is primarily caused by disorders affecting the visual pathways, vestibular system, or central nervous system structures, with specific etiologies differing fundamentally between infantile-onset (first 6 months of life) and acquired forms. 1

Infantile Nystagmus (Onset in First 6 Months)

Ocular and Visual Pathway Causes

• Albinism is one of the most common causes of infantile nystagmus 1, 2
• Retinal diseases including retinal dystrophies and congenital stationary night blindness cause sensory nystagmus 1, 3
• Vision deprivation from congenital cataracts, optic nerve hypoplasia, or structural ocular defects triggers nystagmus as a manifestation of early-onset visual impairment 1, 3
• Low vision from any cause in early life can result in infantile nystagmus 1

Idiopathic and Genetic Forms

• Idiopathic infantile nystagmus (IIN) represents the most common form, often caused by mutations in the FRMD7 gene on chromosome Xq26.2 3, 2
• Fusion maldevelopment syndrome occurs in children with normal ocular development and retinal function 1

Strabismus-Associated Forms

• Latent nystagmus (occlusion nystagmus) is characterized by horizontal jerk oscillations seen under monocular viewing conditions and is part of the infantile esotropia syndrome 4, 5
• Manifest-latent nystagmus (fusion maldevelopment nystagmus) has an identical waveform to latent nystagmus but is evident under binocular viewing conditions, with amplitude increasing during monocular occlusion 4

Acquired Nystagmus (Later Onset)

Central Nervous System Structural Lesions

• Anterior optic pathway lesions, particularly tumors such as optic pathway gliomas (found in 2% of children with isolated nystagmus), cause acquired nystagmus 1, 5
• Brainstem and cerebellar lesions, including structural or space-occupying lesions, are major causes of acquired nystagmus 1, 6
• Chiari malformation is found in 3.4% of children with isolated nystagmus 1
• Arteriovenous malformations can cause acquired nystagmus 1
• Abnormal T2 hyperintense signal in white matter is the most common MRI finding (4%) in children with isolated nystagmus 1

Demyelinating and Inflammatory Diseases

• Multiple sclerosis is particularly associated with convergence retraction nystagmus and can cause various forms of acquired nystagmus 1

Metabolic Diseases

• Leukodystrophies and mitochondrial diseases are associated with acquired nystagmus 1

Vestibular Disorders

• Peripheral vestibular pathology including Ménière's disease, vestibular neuritis, labyrinthitis, and superior canal dehiscence syndrome causes vestibular nystagmus 1, 4
• Central vestibular pathway dysfunction results in vestibular nystagmus with distinct characteristics from peripheral causes 1

Vascular Causes

• Posterior circulation transient ischemic attack and stroke can cause acquired nystagmus 4
• Vertebrobasilar insufficiency may present with isolated transient vertigo and nystagmus, potentially preceding stroke by weeks or months 1

Specific High-Risk Nystagmus Patterns Indicating Serious Pathology

Downbeat Nystagmus

• Cerebellar or cervicomedullary junction disorders strongly correlate with downbeat nystagmus, which does not fatigue or suppress with visual fixation 1, 6

Convergence Retraction Nystagmus

• Dorsal midbrain syndrome is associated with convergence retraction nystagmus, which can be caused by multiple sclerosis or structural lesions 1

Direction-Changing and Gaze-Evoked Nystagmus

• Central nervous system pathology is indicated by direction-changing nystagmus without head position changes or baseline nystagmus without provocative maneuvers 1
• Brainstem or cerebellar pathology is definitively indicated by gaze-evoked nystagmus, which does not fatigue and is not easily suppressed by visual fixation 1, 6

Critical Distinguishing Features

Benign Positional Causes (Not True Nystagmus Causes)

• Benign paroxysmal positional vertigo (BPPV) causes direction-changing nystagmus with specific positional triggers, but this must be distinguished from central causes 4
• Posterior canal BPPV produces torsional upbeating nystagmus, while lateral canal BPPV produces strongly horizontal nystagmus 4

Rare Forms Requiring Specific Evaluation

• Spasmus nutans is characterized by nystagmus, head bobbing, and torticollis, typically appearing at 1-3 years of age, and requires MRI to exclude anterior visual pathway tumors 1, 7

Common Pitfalls to Avoid

• Do not assume all infantile nystagmus is benign: 15.5% of children with isolated nystagmus have abnormal intracranial findings on MRI 1
• Do not confuse nystagmus blockage syndrome with simple infantile esotropia: children with nystagmus blockage syndrome use excessive convergence to damp nystagmus amplitude, and the esotropia magnitude increases with prism neutralization 4
• Do not mistake central nystagmus for BPPV: downbeat nystagmus on Dix-Hallpike maneuver without a torsional component indicates central pathology, not BPPV 1
• Do not rely on symptom resolution to rule out serious pathology: central nystagmus from vertebrobasilar insufficiency may present with isolated transient vertigo, potentially preceding stroke 1