How is an isolated episode of vertigo differentiated from a stroke?

Differentiating Isolated Vertigo from Stroke

The HINTS examination (Head Impulse, Nystagmus, Test of Skew) is the most effective method for differentiating isolated vertigo due to stroke from benign peripheral causes, with properly performed HINTS being even more sensitive than early MRI (100% versus 46%) for detecting stroke. 1

Key Diagnostic Approaches

Clinical Assessment

• Acute Vestibular Syndrome (AVS) classification is crucial:

  • Isolated AVS: Vertigo without other neurologic deficits
  • AVS with associated neurologic findings: Higher stroke probability

• Red flags suggesting stroke 2:

  • Sudden severe headache
  • New neurological symptoms
  • Inability to walk or stand
  • Persistent vomiting
  • Altered mental status

HINTS Examination

The HINTS exam is the cornerstone of differentiation:

1. Head Impulse Test:

   • Normal (negative) head impulse: Suggests central cause (stroke)
   • Abnormal (positive) head impulse: Suggests peripheral cause

2. Nystagmus Evaluation:

   • Direction-changing nystagmus: Suggests central cause
   • Unidirectional horizontal nystagmus: Suggests peripheral cause

3. Test of Skew:

   • Vertical misalignment of eyes: Suggests central cause
   • No vertical misalignment: Suggests peripheral cause

When performed by specially trained practitioners, a complete HINTS triad consistent with peripheral vertigo is highly reliable - in one study of 610 emergency department patients, none with peripheral HINTS findings had abnormalities on CT/MRI 1.

Stroke Risk in Isolated Vertigo

Despite the benign appearance, stroke risk in isolated vertigo is significant:

• 11.3% of patients with isolated vertigo/dizziness had stroke lesions on imaging 3
• Most stroke lesions were small and localized in the cerebellum (84% of cases) 3
• Patients hospitalized for vertigo have a 3.01-times higher risk for stroke over 4 years compared to the general population 4

Imaging Considerations

• MRI brain (without contrast) is preferred when central causes are suspected 2
• CT has limited sensitivity for posterior fossa lesions
• Imaging may be unnecessary if HINTS examination by specially trained providers is available and negative for central causes 1
• In high-risk patients or those with abnormal HINTS, MRI is recommended even with normal neurologic examination 1

Common Pitfalls

1. Overreliance on normal neurologic examination: Up to 80% of patients with AVS related to infarct may have no associated focal neurologic deficits 1

2. Inappropriate use of CT: While CT use for vertigo has increased dramatically, detection rates of central pathology remain very low (<1%) in those with normal neurologic examination 1

3. Inadequate HINTS technique: When performed by non-experts, HINTS shows mixed results in accuracy 1

4. Failure to recognize presentation mode significance: Patients who present specifically because of vertigo (rather than reporting it incidentally) have significantly higher risk for future stroke (13.4 vs. 5.4 per 100 person-years) 5

5. Missing posterior circulation strokes: Small infarcts in the cerebellum or brainstem can present with vertigo without other localizing symptoms 6

Risk Stratification

Patients with ≥3 vascular risk factors have a 5.51-fold higher risk for stroke than those without risk factors 4. Consider these factors when determining the need for imaging and follow-up.

Diagnostic Algorithm

1. Perform HINTS examination (if trained)
2. If HINTS suggests central cause OR if high vascular risk profile exists, proceed to MRI
3. If isolated vertigo persists >48 hours, consider MRI even with normal examination
4. For patients with ataxic pursuit eye movements on examination, have high suspicion for cerebellar infarction 7

Remember that posterior inferior cerebellar artery territory strokes are most frequently implicated in isolated vertigo presentations 3, 6.