Head Imaging for Patients with Two Episodes of Dizziness
For patients with two episodes of dizziness without neurological deficits or other concerning features, no imaging is typically recommended as the diagnostic yield is low (approximately 4%).
Diagnostic Approach to Dizziness
When evaluating a patient with dizziness, the first step is to categorize the type of dizziness:
- Acute Vestibular Syndrome (AVS): Continuous dizziness lasting days to weeks
- Triggered Episodic Vestibular Syndrome: Brief episodes triggered by specific actions
- Spontaneous Episodic Vestibular Syndrome: Episodes not triggered by specific actions
- Chronic Vestibular Syndrome: Dizziness lasting weeks to months
Key Diagnostic Tests
- Dix-Hallpike maneuver: To diagnose BPPV (Benign Paroxysmal Positional Vertigo)
- Supine Roll Test: For lateral canal BPPV if Dix-Hallpike is negative
- HINTS examination: Head-Impulse, Nystagmus, Test of Skew (92.9% sensitivity, 83.4% specificity for central causes)
Imaging Recommendations Based on Clinical Presentation
No Imaging Recommended:
- Typical BPPV with positive Dix-Hallpike test 1
- Brief episodic vertigo triggered by specific head movements 2
- Isolated dizziness without neurological deficits (low yield <1%) 2, 1
MRI Head Without IV Contrast Recommended:
- Acute persistent vertigo with abnormal neurologic examination 2
- HINTS examination consistent with central vertigo 2, 1
- High vascular risk patients even with normal exam 2, 1
- Dizziness with neurological deficits 2
CT Head Without IV Contrast:
- May be considered when MRI is not immediately available for high-risk patients 2, 1
- Low sensitivity (28.5%) compared to MRI (79.8%) for central causes 3
Risk Factors That May Warrant Imaging
Imaging should be considered if the patient has:
- Older age
- Hypertension
- Atrial fibrillation
- Non-whirling type dizziness
- Combined neurological symptoms 2
Diagnostic Yield of Imaging
- MRI has approximately 8% diagnostic yield for detecting intracranial pathology in dizziness 4
- CT has lower effectiveness compared to MRI (15% abnormal findings on CT vs. 27% on MRI) 5
- In more than 90% of cases, radiological findings are not related to vertigo 6
Red Flags Warranting Imaging
- Direction-changing nystagmus without changes in head position
- Downbeating nystagmus on Dix-Hallpike
- Baseline nystagmus without provocative maneuvers
- Failure to respond to appropriate repositioning maneuvers
- Associated neurological symptoms or signs 1
Conclusion
For a patient with only two episodes of dizziness without other concerning features, imaging is not routinely recommended due to low diagnostic yield. However, if the patient has risk factors for stroke or central causes, MRI head without contrast is the preferred imaging modality, with CT as an alternative when MRI is not available.