What is the preferred initial imaging study, Computed Tomography (CT) head or Magnetic Resonance Imaging (MRI) brain, for patients presenting with dizziness?

From the Guidelines

For patients presenting with dizziness, MRI brain is generally the preferred initial imaging study over CT head, as it provides superior visualization of the posterior fossa structures, including the brainstem and cerebellum, which are often implicated in causes of dizziness such as stroke, multiple sclerosis, or tumors 1. MRI can detect small infarcts, demyelinating lesions, and subtle structural abnormalities that may be missed on CT. Additionally, MRI does not expose patients to ionizing radiation.

The diagnostic yield of noncontrast MRI head in patients presenting to the emergency department with isolated dizziness is low (w4%), but MRI changes the diagnosis up to 16% of the time, acutely in 8% of cases 1. In patients with acute vestibular syndrome (AVS) and a normal neurologic examination, the most common causes of symptoms are vestibular neuritis and labyrinthitis, neither of which has associated findings on CT imaging 1. However, a lack of associated neurologic deficits does not exclude a central cause such as infarct, and various bedside tests like the HINTS examination have been developed to distinguish AVS of benign cause from posterior circulation infarct 1.

In acute persistent vertigo with an abnormal neurologic examination or HINTS examination by a trained specialist consistent with central vertigo, posterior circulation infarct is suspected, and MRI head without IV contrast is recommended 1. The choice between these imaging modalities should be guided by the patient's clinical presentation, the suspected underlying cause of dizziness, and the urgency of diagnosis. In many cases, a thorough clinical evaluation including a detailed history and physical examination may be sufficient before proceeding to advanced imaging.

Some key points to consider when choosing between CT head and MRI brain for patients with dizziness include:

• The ability of MRI to detect small infarcts and demyelinating lesions that may be missed on CT
• The lack of ionizing radiation exposure with MRI
• The importance of clinical evaluation, including a detailed history and physical examination, in guiding the choice of imaging modality
• The use of bedside tests like the HINTS examination to distinguish between central and peripheral causes of vertigo
• The recommendation for MRI head without IV contrast in cases of suspected posterior circulation infarct 1.

Overall, MRI brain is the preferred initial imaging study for patients presenting with dizziness, due to its superior visualization of posterior fossa structures and ability to detect small infarcts and demyelinating lesions 1.

From the Research

Imaging Studies for Dizziness

• The choice between Computed Tomography (CT) head and Magnetic Resonance Imaging (MRI) brain for patients presenting with dizziness depends on various factors, including the suspected underlying cause and the need for detailed imaging of the brain and its vessels 2, 3, 4.
• MRI is generally considered more sensitive than CT for detecting acute brain lesions, including ischemic stroke, which can cause dizziness 2, 4.
• A study published in 2023 found that patients who underwent MRI had a higher frequency of critical neuroimaging results and changes in secondary stroke prevention medication compared to those who underwent CT with CTA alone 2.
• Another study published in 2020 proposed a clinical pathway for deciding which patients with dizziness should undergo brain imaging, suggesting that patients with HINTS-negative acute vestibular syndrome may not require imaging, while those with acute imbalance, central oculomotor signs, or focal abnormalities may benefit from imaging 3.
• A cost-utility analysis published in 2019 found that MRI of the inner ear and cerebellopontine angle was the most useful test for identifying the cause of vertigo and dizziness, while cranial CT scans had a lower yield 5.
• A cost-effectiveness study published in 2024 found that specialized MRI was the most cost-effective strategy for evaluating patients with dizziness, resulting in higher quality-adjusted life years (QALYs) and lower long-term costs compared to other imaging strategies 4.
• Older studies have also highlighted the usefulness of MRI in diagnosing vertebrobasilar insufficiency, a potential cause of vertigo and dizziness, by detecting high signals in the basal ganglia or pontine base and vertebral artery asymmetry or basilar artery twisting 6.

Key Findings

• MRI is more sensitive than CT for detecting acute brain lesions and ischemic stroke.
• The choice of imaging study depends on the suspected underlying cause and the need for detailed imaging of the brain and its vessels.
• Specialized MRI is the most cost-effective strategy for evaluating patients with dizziness.
• Clinical pathways can help guide the decision to undergo brain imaging in patients with dizziness.