What is the most likely etiology of a patient presenting with acute onset of severe headache and vertigo?

Posterior Circulation Stroke (Vertebral Artery Dissection or Cerebellar Infarction)

In a patient presenting with abrupt onset of severe headache and vertigo who cannot stand despite being alert and oriented, posterior circulation stroke—particularly vertebral artery dissection with cerebellar involvement—should be most strongly considered as the primary etiology. 1, 2, 3

Critical Diagnostic Reasoning

Why Stroke Must Be Prioritized

• Up to 25% of patients presenting with acute vestibular syndrome have posterior circulation stroke, rising to 75% in high vascular risk cohorts 3
• Critically, 75-80% of stroke patients with acute vestibular syndrome have NO focal neurologic deficits, making this presentation deceptively benign-appearing 3
• The combination of severe headache (especially posterior/occipital) with acute vertigo and severe imbalance is a classic presentation of vertebral artery dissection 4, 5

Distinguishing Features in This Case

The patient's inability to stand despite being alert and oriented is the key red flag that distinguishes this from benign peripheral vertigo:

• Benign paroxysmal positional vertigo (BPPV) causes brief episodes lasting seconds to <1 minute with position changes, not continuous severe vertigo preventing standing 1, 3
• Vestibular neuritis could cause severe vertigo lasting hours, but the acute severe headache component makes stroke more likely 3
• Vestibular migraine typically has episodes lasting 5 minutes to 72 hours with migrainous features, but the acute presentation with inability to stand warrants stroke exclusion first 1, 6

Immediate Diagnostic Approach

Clinical Examination Priority

Perform the HINTS examination immediately (if trained in its use):

• Head Impulse Test: Normal response in a dizzy patient suggests central cause 2
• Nystagmus: Direction-changing nystagmus suggests central pathology 2
• Test of Skew: Vertical misalignment indicates central lesion 2
• HINTS has greater sensitivity than early MRI for detecting stroke when properly performed 2

Red Flags for Central Pathology

Look specifically for:

• Downbeating nystagmus on Dix-Hallpike (especially without torsional component) 1
• Direction-changing nystagmus without head position changes 1
• Gaze-holding nystagmus or baseline nystagmus without provocation 1
• Associated symptoms: visual blurring, dysarthria, dysphagia, dysmetria, or sensory changes 1

Imaging Strategy

First-Line Imaging

MRI with diffusion-weighted imaging (DWI) is the diagnostic test of choice:

• More sensitive than CT for acute posterior circulation infarction 1
• MRI/MRA can detect vertebral artery dissection and cerebellar infarction 1, 4
• Fat-suppressed T1-weighted sequences can visualize mural hematoma in dissection 1

When CT is Appropriate

• Non-contrast CT head if MRI unavailable or to exclude hemorrhage emergently 1
• CT has only ~2% positivity rate for all dizziness presentations but is faster and doesn't require sedation 1

Common Pitfalls to Avoid

• Never dismiss isolated vertigo without focal findings as benign—11% have acute infarct on imaging 3
• Do not assume normal vital signs exclude stroke; this patient's BP 132/82 is unremarkable but doesn't rule out dissection 4, 5
• Thunderclap headache pattern occurs in only 20% of vertebral artery dissections, so absence doesn't exclude it 5
• The posterior occipital headache location is highly characteristic of vertebral dissection 4, 5

Alternative Diagnoses to Consider (After Stroke Excluded)

If imaging excludes stroke:

• Acute cerebellitis: Can present with truncal ataxia, headache, and vertigo; may show cerebellar enhancement on MRI 1
• Vestibular migraine: Requires ≥5 prior episodes and migraine history; not a first-episode diagnosis 1, 6
• Posterior fossa mass: Would typically have more gradual onset but can present acutely 1

The acute presentation, severe headache, and complete inability to stand mandate immediate stroke evaluation with MRI/MRA or CT if MRI unavailable. 1, 2, 3