How can I differentiate between vestibular migraines and Idiopathic Intracranial Hypertension (IIH)?

Differentiating Vestibular Migraine from Idiopathic Intracranial Hypertension (IIH)

The key distinction is that vestibular migraine presents with recurrent episodic vertigo lasting 5 minutes to 72 hours with migrainous features, while IIH presents with persistent headache, papilledema on fundoscopic exam, and elevated intracranial pressure on lumbar puncture—these are fundamentally different conditions that rarely overlap in presentation. 1

Critical Diagnostic Features of Vestibular Migraine

Vestibular migraine requires ≥5 episodes of vestibular symptoms (vertigo, head-motion dizziness) lasting 5 minutes to 72 hours, with moderate to severe intensity. 1, 2 The episodes are episodic and recurrent, not continuous. 3, 4

Required Migrainous Features (≥50% of episodes):

• Headache with at least two characteristics: one-sided location, pulsating quality, moderate/severe intensity, or aggravation by physical activity 1, 2
• Photophobia and phonophobia 1
• Visual aura (bright scintillating lights, zigzag lines, scotoma lasting 5-60 minutes) 1

Temporal Pattern:

• Episodes last 5 minutes to 72 hours (30% have minute-long episodes, 30% hours-long, 30% days-long) 1
• Attack-free intervals between episodes where patients may be asymptomatic or have minor persistent dizziness 5, 6

Critical Diagnostic Features of IIH

IIH presents with persistent daily headache (not episodic vertigo), papilledema on fundoscopic examination, and elevated opening pressure >25 cm H2O on lumbar puncture. 1

Key IIH Characteristics:

• Papilledema is the hallmark finding—this is absent in vestibular migraine 1
• Headache is typically daily and persistent, not episodic like vestibular migraine 1
• 68% of IIH headaches have migrainous phenotype (throbbing, photophobia, phonophobia), which can cause confusion 1
• Visual symptoms in IIH are transient visual obscurations (brief blackouts lasting seconds), not the expanding scintillating scotomas of migraine aura 1
• No true vertigo or vestibular symptoms are part of IIH diagnostic criteria 1

Algorithmic Approach to Differentiation

Step 1: Characterize the Primary Symptom

• If episodic vertigo/dizziness is the dominant complaint: Consider vestibular migraine 1, 2
• If persistent daily headache is the dominant complaint: Consider IIH 1

Step 2: Perform Fundoscopic Examination

• Papilledema present: IIH is likely; proceed to neuroimaging and lumbar puncture 1
• No papilledema: IIH is effectively ruled out; vestibular migraine remains possible 1

Step 3: Assess Episode Duration and Pattern

• Episodes lasting 5 minutes to 72 hours with symptom-free intervals: Vestibular migraine 1, 3, 4
• Continuous daily symptoms without clear episodes: Not vestibular migraine; consider IIH if headache-predominant 1

Step 4: Count Vestibular Episodes

• ≥5 documented episodes of moderate-to-severe vertigo: Meets vestibular migraine criteria 1, 2
• Fewer episodes or no true vertigo: Does not meet vestibular migraine criteria 3, 4

Step 5: Assess Migrainous Features During Episodes

• Migrainous features (headache, photophobia, phonophobia, visual aura) present during ≥50% of vestibular episodes: Vestibular migraine 1, 2
• No temporal association between vestibular symptoms and migraine features: Does not meet vestibular migraine criteria 3, 4

Physical Examination Red Flags

Findings Suggesting Central Pathology (Not Vestibular Migraine or IIH):

• Downbeating nystagmus without torsional component on Dix-Hallpike 1, 7
• Direction-changing nystagmus without head position changes 1, 7
• Gaze-evoked nystagmus (beats right with right gaze, left with left gaze) 1, 7
• Cranial nerve abnormalities, dysarthria, dysphagia, dysmetria 7

These findings mandate neuroimaging to exclude stroke, multiple sclerosis, or cerebellar pathology. 1, 7

Common Diagnostic Pitfalls

Pitfall 1: Assuming All Migrainous Headaches with Dizziness Are Vestibular Migraine

The dizziness must be true vestibular symptoms (vertigo, not lightheadedness), must occur in discrete episodes lasting 5 minutes to 72 hours, and must meet the ≥5 episode threshold. 1, 3, 4 Non-specific dizziness or continuous imbalance does not qualify.

Pitfall 2: Missing IIH Because Headache Has Migrainous Features

68% of IIH patients have migrainous-type headaches, but the key differentiator is papilledema on fundoscopic exam. 1 Always perform fundoscopy in patients with persistent headache, especially in young obese women.

Pitfall 3: Over-Testing Clear Vestibular Migraine Cases

When Barany criteria are clearly met (≥5 episodes, 5 min-72 hr duration, migraine history, migrainous features in ≥50% of episodes), routine neuroimaging and vestibular function testing are not needed. 7, 2 Testing is only indicated for atypical features, central signs, or treatment failure. 7

Pitfall 4: Confusing Visual Symptoms

• Vestibular migraine aura: Expanding scintillating scotomas over 5-20 minutes, lasting <60 minutes 1
• IIH visual symptoms: Transient visual obscurations (seconds-long blackouts), not expanding visual phenomena 1

When Additional Testing Is Required

Indications for Neuroimaging and Lumbar Puncture:

• Papilledema on fundoscopic exam (mandatory for IIH diagnosis) 1
• Abnormal cranial nerve examination 7
• Atypical nystagmus patterns suggesting central pathology 1, 7
• Severe persistent headache with visual symptoms 7
• Failure to respond to appropriate vestibular migraine treatment 7

Practical Clinical Scenario

A 28-year-old woman with BMI 35 presents with daily headaches for 3 months, worse in the morning, with photophobia. No episodic vertigo. Fundoscopy shows bilateral papilledema. Diagnosis: IIH. Proceed to MRI brain/MRV and lumbar puncture. 1

A 35-year-old woman reports 8 episodes over 6 months of spinning vertigo lasting 2-6 hours, with throbbing right-sided headache and photophobia during 6 of the episodes. Fundoscopy normal. Diagnosis: Vestibular migraine. Initiate lifestyle modifications and consider prophylactic therapy. 1, 8, 2