What is the differential diagnosis for horizontal nystagmus in a 12-year-old male?

Differential Diagnosis for Horizontal Nystagmus in a 12-Year-Old Male

In a 12-year-old with horizontal nystagmus, you must first determine whether this is acquired or longstanding, as acquired horizontal nystagmus in this age group demands urgent neuroimaging to exclude brainstem/cerebellar pathology, while longstanding cases typically represent benign sensory or fusion maldevelopment causes. 1

Initial Clinical Assessment

Critical History Elements

• Onset timing: Acquired nystagmus (appearing after 6 months of age) carries significantly higher risk for structural CNS lesions compared to infantile nystagmus 1, 2
• Associated symptoms: Concurrent neurological symptoms (headache, ataxia, diplopia, motor weakness, sensory deficits) strongly suggest central pathology 1, 3
• Visual acuity: Decreased or asymmetric vision raises concern for optic pathway lesions 1
• Positional triggers: Nystagmus provoked by specific head positions suggests vestibular causes (peripheral or central) 1, 4

Physical Examination Findings

• Nystagmus characteristics:
  • Unilateral or asymmetric nystagmus indicates neurological disease requiring immediate workup 2
  • Direction-changing horizontal nystagmus with gaze suggests central pathology 3, 5
  • Horizontal nystagmus that increases with monocular occlusion suggests latent or manifest-latent nystagmus (fusion maldevelopment syndrome) 1
• Head posture: Abnormal head turn with the fixating eye in adduction is characteristic of manifest-latent nystagmus 1
• Neurological examination: Look specifically for truncal ataxia (standing position), limb ataxia, dysarthria, cranial nerve palsies 3, 6

Differential Diagnosis by Category

Peripheral Vestibular Causes

• Benign Paroxysmal Positional Vertigo (BPPV): Lateral canal BPPV produces horizontal nystagmus (geotropic or apogeotropic) triggered by supine roll test 1, 4
• Vestibular neuritis: Unidirectional horizontal nystagmus with acute onset vertigo 3, 4
• Ménière's disease: Episodic vertigo with hearing loss 7, 4
• Superior canal dehiscence syndrome: Positional symptoms with sound/pressure sensitivity 7, 4

Central Nervous System Causes (High Priority)

• Posterior fossa tumors: Optic pathway gliomas (2% of isolated nystagmus cases), cerebellar tumors, brainstem lesions 1
• Chiari malformation: Found in 3.4% of children with isolated nystagmus 1
• Demyelinating disease: Multiple sclerosis, neuromyelitis optica spectrum disorders, acute disseminated encephalomyelitis 1, 7, 4
• Posterior circulation stroke: Cerebellar or brainstem infarction 7, 4, 6
• Metabolic/degenerative: Leukodystrophies, mitochondrial diseases 1

Ocular/Sensory Causes

• Fusion maldevelopment nystagmus syndrome: Horizontal nystagmus in children with normal retinal function, increases with monocular occlusion 1
• Retinal disorders: Retinal dystrophies, though these typically present earlier in infancy 1, 2
• Albinism: Usually presents as infantile nystagmus 1, 2
• Optic nerve hypoplasia: Sensory deprivation nystagmus 2

Vestibular Migraine

• Episodic vertigo with migrainous features, can produce horizontal nystagmus during attacks 7, 4

Diagnostic Algorithm

Step 1: Determine Urgency Based on Red Flags

Immediate neuroimaging (MRI brain with and without contrast) is indicated if: 1, 7

• Late-onset or acquired nystagmus (after 6 months of age)
• Concurrent neurological symptoms (headache, ataxia, weakness, sensory changes)
• Asymmetric or unilateral nystagmus
• Progressive nystagmus
• Downbeat component (suggests cervicomedullary junction pathology)
• Failed response to BPPV treatment maneuvers

Step 2: Positional Testing

• Dix-Hallpike maneuver: Primarily identifies posterior canal BPPV (torsional upbeating nystagmus), but horizontal nystagmus on this test warrants supine roll testing 1, 4
• Supine roll test: Diagnoses lateral canal BPPV by eliciting direction-changing horizontal nystagmus 1, 4
• Apogeotropic positional nystagmus that is treatment-refractory: Highly predictive of central cause (cerebellar lesion) rather than BPPV 3, 5

Step 3: Ophthalmologic Evaluation

• Visual acuity testing (monocular and binocular)
• Fundoscopic examination for optic nerve abnormalities
• Assessment for latent nystagmus (increases with monocular occlusion) 1
• Consider optical coherence tomography if sensory nystagmus suspected 2

Step 4: Neuroimaging Decision

MRI brain and orbits with contrast is the preferred modality 1, 7:

• 15.5% of children with isolated nystagmus have abnormal intracranial findings 1
• CT is inadequate for posterior fossa visualization 1, 7
• Dedicated orbital sequences may be added if initial brain MRI suggests orbital pathology 1

Common Pitfalls to Avoid

• Assuming all positional horizontal nystagmus is benign BPPV: Direction-changing apogeotropic nystagmus that persists despite proper repositioning maneuvers suggests cerebellar pathology 3, 5
• Missing central causes by inadequate examination: Small cerebellar lesions can produce isolated horizontal nystagmus without other obvious neurological signs; truncal ataxia only becomes apparent when standing 3
• Failing to perform both Dix-Hallpike and supine roll testing: Up to 30% of BPPV cases involve the lateral canal and will be missed without supine roll testing 4
• Ordering CT instead of MRI: CT scans do not adequately visualize posterior fossa structures 1, 7
• Dismissing nystagmus as "congenital" without proper workup: Acquired nystagmus in a 12-year-old requires thorough evaluation even if asymptomatic 1, 2