What are the causes of vertical nystagmus?

Vertical Nystagmus: Causes and Clinical Significance

Vertical nystagmus is predominantly a red-flag sign of central nervous system pathology affecting the cerebellum, brainstem (particularly the cervicomedullary junction, midbrain, or medulla), or posterior fossa structures, and demands urgent neuroimaging to exclude stroke, demyelinating disease, or structural lesions. 1, 2

Primary Central Causes

Cerebellar and Brainstem Lesions

Downbeat nystagmus is the most common pathological vertical nystagmus pattern and strongly indicates bilateral floccular dysfunction or cervicomedullary junction pathology. 1, 2, 3, 4, 5

• Upbeat nystagmus localizes to midbrain or medullary lesions, with the midbrain generating vertical eye movements as a fundamental anatomical principle. 2, 3, 4, 5
• Pure torsional nystagmus without vertical components suggests midbrain pathology. 3, 4

Vascular Etiologies

• Posterior circulation stroke (brainstem or cerebellar infarction) accounts for approximately 25% of acute vestibular syndrome presentations, rising to 75% in high-risk vascular populations. 2, 6
• Critically, 75-80% of stroke-related acute vestibular syndrome presents without focal neurologic deficits, making vertical nystagmus a crucial diagnostic clue. 2
• Vertebrobasilar insufficiency produces episodes typically lasting less than 30 minutes and may precede stroke by weeks to months. 2, 6
• Cerebellar hemorrhage, though rare, is life-threatening and requires immediate recognition. 2

Demyelinating Disease

• Multiple sclerosis involving the brainstem or cerebellar peduncles accounts for approximately 4% of acute vestibular syndrome cases. 2
• Convergence retraction nystagmus is particularly associated with dorsal midbrain syndrome in multiple sclerosis. 2

Structural Lesions

• Chiari malformation is found in 3.4% of children with isolated nystagmus. 2
• Optic pathway glioma accounts for 2% of children with isolated nystagmus. 2
• Posterior fossa tumors, including vestibular schwannomas, must be systematically excluded. 2, 6
• Arteriovenous malformations can cause acquired vertical nystagmus. 2

Metabolic and Toxic Causes

• Wernicke's encephalopathy produces characteristic patterns: initial spontaneous upbeat nystagmus that may change to downbeat nystagmus with gaze changes, convergence, or vestibular stimuli. 7
• Leukodystrophies and mitochondrial diseases are associated with acquired nystagmus. 2
• Chronic alcohol abuse affecting cerebellar function produces gaze-evoked nystagmus in all directions. 5
• Antiepileptic medications (particularly phenytoin, carbamazepine) can cause vertical nystagmus. 2, 6

Rare Peripheral Causes

While vertical nystagmus is overwhelmingly central in origin, one case report documents purely vertical upbeat nystagmus in bilateral posterior canal BPPV without central pathology on imaging. 8 However, this remains an exceptional finding and should never delay urgent evaluation for central causes.

Critical Distinguishing Features of Central Vertical Nystagmus

Central vertical nystagmus does not fatigue with repeated testing, is not suppressed by visual fixation, and often persists without modification during repositioning maneuvers. 1, 2, 6

• Pure vertical nystagmus (upbeat or downbeat) without a torsional component is pathognomonic for central pathology. 1, 2, 6
• Downbeat nystagmus on Dix-Hallpike maneuver without a torsional component indicates central disease, not BPPV. 9, 1, 2, 6
• Baseline vertical nystagmus present without any provocative maneuvers mandates urgent neuroimaging. 1, 2, 6
• Gaze-evoked vertical nystagmus is definitively central, indicating brainstem or cerebellar pathology. 2, 6, 5

Associated Clinical Features

• Severe postural instability with falling is characteristic of central vertical nystagmus, particularly in vertebrobasilar insufficiency and cerebellar lesions. 2, 6
• Additional neurological symptoms—dysarthria, dysmetria, dysphagia, sensory or motor deficits, diplopia, or Horner's syndrome—frequently accompany central vertical nystagmus. 2, 6
• Permanent dizziness, postural imbalance, and gait disorder are typical of downbeat and upbeat nystagmus. 3
• Oscillopsia (jumping images) and reduced visual acuity are cardinal symptoms. 3

Mandatory Imaging Protocol

MRI of the brain with diffusion-weighted imaging is mandatory when vertical nystagmus is identified. 1, 2

• The American College of Radiology recommends thorough neuro-ophthalmological and neuroradiological workup with MRI, noting that CT scans may not adequately visualize posterior fossa structures. 1
• CT imaging has a diagnostic yield of less than 1% for isolated dizziness but can identify acute cerebellar hemorrhage. 2, 6
• In children with isolated nystagmus who undergo MRI, 15.5% have abnormal intracranial findings. 2

Critical Pitfalls to Avoid

Do not mistake central vertical nystagmus for BPPV. Posterior canal BPPV produces torsional upbeating nystagmus with a 5-20 second latency, crescendo-decrescendo pattern, resolution within 60 seconds, and fatigability—none of which characterize pure vertical nystagmus. 9, 1, 2, 6

Do not rely on the absence of focal neurologic deficits to exclude stroke. One-third to two-thirds of posterior circulation strokes present without focal findings, and 11% of patients with acute persistent vertigo but no focal signs have acute infarct on imaging. 2

Do not delay imaging for treatment trials. Failure to respond to peripheral vertigo treatments (e.g., canalith repositioning) is itself a red flag requiring urgent MRI. 1, 2, 6