Causes of Nystagmus
Nystagmus results from disruption of the eye movement control systems (vestibular, smooth pursuit, saccadic, optokinetic, or fixation systems) and can be broadly categorized into peripheral vestibular causes, central neurological causes, ocular/sensory causes, and idiopathic forms 1.
Primary Categories and Specific Etiologies
Peripheral Vestibular Causes
- Benign Paroxysmal Positional Vertigo (BPPV) - the most common cause of peripheral vertigo, triggered by specific head movements with characteristic nystagmus patterns 2
- Ménière's disease
- Vestibular neuritis and labyrinthitis 2
- Superior canal dehiscence syndrome
- Perilymphatic fistula
- Post-traumatic vertigo 2
Central Neurological Causes
Central positional nystagmus (CPN) accounts for up to 12% of patients with positional nystagmus 3. Key etiologies include:
- Stroke (particularly posterior circulation/vertebrobasilar territory) 4, 3
- Cerebellar and brainstem lesions - including infarction, tumors, and structural abnormalities 3, 5
- Demyelinating diseases (multiple sclerosis) 2, 3, 6
- Cerebellar and spinocerebellar degeneration syndromes 5
- Developmental anomalies affecting pons and cerebellum 5
- Vestibular migraine 4, 2, 3
- Vertebrobasilar insufficiency 2
- Wernicke encephalopathy 1
- Autoimmune/paraneoplastic diseases 3
Ocular and Sensory Defect Causes
In infantile nystagmus specifically, ocular disease is the leading cause (44% of cases), with albinism and ocular malformations being most frequent 7. Sensory defect causes include:
Infantile Nystagmus
The prevalence is 6.1 per 10,000 live births, but six times higher in preterm infants (28.4/10,000) compared to term infants (4.4/10,000) 7. Causes break down as:
- Ocular disease: 44%
- Idiopathic: 32%
- Neurological disorders and genetic syndromes: 20%
- Prematurity alone: 4% 7
In infants without obvious ophthalmological findings, 30% have underlying neurological causes including congenital brain malformations, metabolic disorders, and genetic white matter disorders 8.
Other Important Causes
- Pharmacological toxicity - particularly anticonvulsant drugs 6, 5
- Metabolic disorders 2, 6, 8
- Genetic disorders 6, 8
- Granulomatous disorders 6
Critical Clinical Distinctions
Distinguishing Peripheral from Central Causes
Central nystagmus often presents with downward-beating nystagmus in head-hanging position or apogeotropic nystagmus in lateral supine positions, and is typically associated with other cerebellar or brainstem signs 3. Unlike BPPV, central positional nystagmus does not improve with therapeutic liberatory maneuvers 3.
The cerebellum is involved in 88% of downbeat nystagmus cases, with characteristic impaired pursuit, impaired optokinetic nystagmus, and inability to suppress vestibulo-ocular reflex 5.
Red Flags Requiring Imaging
Imaging is unnecessary for typical BPPV with characteristic nystagmus on Dix-Hallpike testing 4. However, imaging is indicated for:
- Negative or atypical Dix-Hallpike testing despite positional symptoms
- Lack of response to repositioning maneuvers
- Associated neurological signs
- Short-term symptom recurrence 4
Common Pitfalls
- Misdiagnosing central causes as BPPV when nystagmus patterns are atypical
- Failing to perform visual electrophysiology early in infantile nystagmus when ophthalmological examination is uninformative 8
- Missing medication toxicity as a reversible cause
- Not recognizing that vestibular migraine can mimic various vertigo presentations 4