Causes of Nystagmus
Nystagmus results from disruption of the ocular motor systems controlling eye stability, with causes broadly categorized as infantile (onset in first 6 months) versus acquired (later onset), and further subdivided into peripheral vestibular, central neurologic, ocular/retinal, and toxic-metabolic etiologies.
Infantile Nystagmus (Onset in First 6 Months of Life)
The most common causes of infantile nystagmus include 1:
- Albinism - among the most frequent causes 1
- Retinal diseases - including retinal dystrophies and other retinal disorders 1, 2
- Low vision or visual deprivation - such as congenital cataracts or optic nerve hypoplasia 1, 2
- Fusion maldevelopment syndrome - occurs in children with otherwise normal ocular development and retinal function 1
These infantile causes are typically diagnosed through clinical ophthalmological examination and genetic workup rather than neuroimaging 1.
Acquired Nystagmus (Later Onset)
Central Neurologic Causes
Acquired nystagmus frequently indicates central nervous system pathology, particularly affecting the brainstem and cerebellum 3:
- Stroke/infarction - particularly affecting the midbrain, pons, or medulla 3, 4
- Demyelinating disorders - multiple sclerosis is the most common cause of acquired pendular nystagmus 5
- Mass lesions and tumors - including optic pathway gliomas (2% of pediatric cases) and brainstem/cerebellar tumors 1
- Cerebellar degeneration syndromes - both hereditary and acquired cerebellar ataxias 3, 4
- Chiari malformations - found in 3.4% of pediatric neuroimaging studies for nystagmus 1
- Hemorrhage - brainstem or cerebellar bleeding 3
- Wernicke encephalopathy - a dangerous but treatable cause 6
Specific Central Nystagmus Patterns and Their Localizations
Downbeat nystagmus (DBN) - the most common pathological central nystagmus type, typically indicates cerebellar dysfunction affecting the flocculus bilaterally 3. In 88% of cases, lesions localize to the cerebellum, with causes including infarction, cerebellar degeneration, multiple sclerosis, and developmental anomalies 4.
Upbeat nystagmus (UBN) - also indicates cerebellar or brainstem pathology 3.
Gaze-evoked nystagmus in all directions - indicates cerebellar dysfunction from multiple causes including antiepileptic drugs, chronic alcohol abuse, or neurodegenerative cerebellar disorders 3.
Purely vertical gaze-evoked nystagmus - localizes to midbrain lesions 3.
Purely horizontal gaze-evoked nystagmus - localizes to pontomedullary lesions 3.
Peripheral Vestibular Causes
Vestibular nystagmus results from dysfunction of 1:
- Labyrinth disorders - peripheral vestibular apparatus pathology 1
- Vestibular nerve lesions - including VIII cranial nerve tumors 1
- Benign paroxysmal positional vertigo (BPPV) - though imaging is unnecessary with typical nystagmus on Dix-Hallpike testing 7
Toxic-Metabolic Causes
- Anticonvulsant drug toxicity - particularly phenytoin and other antiepileptics 3, 4
- Chronic alcohol abuse - causes cerebellar dysfunction 3
- Metabolic diseases - including leukodystrophies and mitochondrial diseases 1
- Genetic disorders - Gaucher disease type 3, Niemann-Pick type C 3
Other Acquired Causes
- Ocular palatal tremor syndrome - a common cause of acquired pendular nystagmus 5
- Pharmacological intoxication - various medications beyond anticonvulsants 5
- Granulomatous disorders - can produce pendular nystagmus 5
- Spasmus nutans - rare form appearing at 1-3 years with triad of nystagmus, head bobbing, and torticollis 1
Critical Clinical Distinctions
Neuroimaging is indicated when 1, 2:
- Late onset nystagmus (beyond 6 months of age)
- Concurrent neurological symptoms present
- Decreased visual acuity accompanies nystagmus
- Asymmetric, unilateral, or progressive nystagmus patterns
- Atypical features such as lack of response to treatment maneuvers
MRI brain is the preferred imaging modality, detecting acute brain lesions in 11% of cases with atypical presentations versus only 6% with CT 7. Approximately 15.5% of children undergoing MRI for isolated nystagmus have abnormal intracranial findings 1.
Treatable causes requiring urgent identification include Wernicke encephalopathy, Niemann-Pick type C (treatable with miglustat), and downbeat/upbeat nystagmus (treatable with aminopyridines) 3.