Brain MRI Without Contrast is Recommended for Evaluating Dizziness
MRI head without IV contrast is the recommended imaging modality for evaluating dizziness when imaging is indicated, as it provides the highest diagnostic yield (approximately 4%) compared to CT (<1%) for detecting potential causes of dizziness.
Clinical Decision Algorithm for Imaging in Dizziness
When Imaging is Indicated:
- For nonspecific dizziness without vertigo, ataxia, or other neurologic deficits, MRI head without IV contrast may be useful in high-risk patients for detecting posterior circulation infarcts, which account for approximately 70% of positive findings 1
- In acute persistent vertigo with an abnormal neurologic examination or HINTS examination consistent with central vertigo, MRI head without IV contrast is strongly recommended 1
- For chronic recurrent vertigo associated with unilateral hearing loss or tinnitus, MRI head and IAC (internal auditory canal) without and with IV contrast is recommended to exclude vestibular schwannoma or other causes 1
- For chronic recurrent vertigo with brainstem neurologic deficits, MRI head without IV contrast is useful for evaluation of posterior circulation infarcts 1
When Imaging is NOT Indicated:
- Brief episodic vertigo triggered by specific head movements (likely BPPV) does not require imaging unless there are atypical features 1
- Acute persistent vertigo with normal neurologic examination and HINTS examination consistent with peripheral vertigo (likely vestibular neuritis) generally does not require imaging 1
Diagnostic Yield of Different Imaging Modalities
- MRI without contrast has a diagnostic yield of approximately 4% in isolated dizziness, with ischemic stroke being the most common abnormality (70% of positive findings) 1
- CT head without contrast has a very low diagnostic yield (<1%) and poor sensitivity (20-40%) for detecting causative etiologies in dizziness 1
- CT angiography (CTA) has a low diagnostic yield (approximately 3%) and does not provide additional information over non-contrast CT in isolated dizziness 1
- Specialized MRI protocols incorporating multiplanar high-resolution DWI show the highest sensitivity for posterior circulation strokes 2
Cost-Effectiveness Considerations
- MRI-based evaluation leads to lower long-term costs and higher quality-adjusted life years (QALYs) compared to CT-based approaches 2
- Patients who undergo MRI, compared to those who undergo CT with CTA alone, show greater frequency of critical neuroimaging results (10.1% vs 4.7%), changes in secondary stroke prevention medication (9.6% vs 3.2%), and subsequent cardiac evaluations (6.4% vs 1.0%) 3
Risk Factors for Central Causes of Dizziness
- Older age, hypertension, atrial fibrillation, non-whirling type of dizziness symptoms, and combined neurological symptoms increase the likelihood of central causes 1
- History of ischemic stroke, presence of presyncope, and absence of nystagmus are associated with central lesions in patients with isolated dizziness 4
Important Caveats and Pitfalls
- Noncontrast CT has very low sensitivity (28.5%) and will miss many central causes of dizziness, particularly in the posterior fossa 5
- Even MRI will miss approximately one in five patients with stroke if imaging is obtained early after symptom onset 5
- Neuroimaging should not be the only tool for ruling out stroke and other central causes in patients with acute dizziness 5
- Clinical assessment, including HINTS examination by a trained specialist, remains crucial in determining the need for imaging 1, 6