Neurologic Imaging

What Is the Best Initial Imaging for Chronic Vertigo with Brainstem Deficits?

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What Is the Best Initial Imaging for Chronic Vertigo with Brainstem Deficits?

A 58-year-old patient describes months of intermittent, spinning vertigo. The episodes are unpredictable, lasting minutes to hours. What brings him in today is that during the last few episodes, he also experienced double vision and slurred speech, which resolved along with the vertigo. You are considering the initial imaging workup, weighing the need for vascular and parenchymal detail against radiation exposure and test availability. For this specific presentation—chronic, recurrent vertigo with associated brainstem neurologic deficits—the American College of Radiology (ACR) provides clear guidance. The most definitive initial, non-invasive study, `MRA head and neck with IV contrast`, is rated “Usually Appropriate.”

Who Fits This Clinical Scenario for Chronic Vertigo with Brainstem Deficits?

This guidance applies to a specific subset of adult patients presenting with dizziness. The key inclusion criteria are the combination of all three of the following features:

1. Chronic and Recurrent Vertigo: The symptoms have been occurring for weeks to months and happen in discrete, repeated episodes, rather than being constant. The patient experiences true vertigo—a sensation of spinning or movement.
2. Associated Brainstem Deficits: This is the critical differentiator. During or between vertiginous episodes, the patient reports other neurologic symptoms that localize to the brainstem. Examples include diplopia (double vision), dysarthria (slurred speech), dysphagia (trouble swallowing), ataxia (uncoordinated movements), or focal sensory changes or weakness.
3. Initial Imaging: This is the first advanced imaging study being ordered for this specific clinical problem.

It is crucial to distinguish this scenario from similar presentations that follow different diagnostic pathways:

  • Exclusion 1: Brief, positionally-triggered vertigo. If the vertigo lasts seconds and is reliably triggered by specific head movements (e.g., rolling over in bed, looking up), the likely diagnosis is benign paroxysmal positional vertigo (BPPV), and imaging is often unnecessary.
  • Exclusion 2: Acute, persistent vertigo. If the vertigo began suddenly and has been constant for more than 24 hours, the workup shifts to that of an acute posterior circulation stroke or cerebellitis.
  • Exclusion 3: Vertigo with isolated hearing loss or tinnitus. If the primary associated symptoms are auditory, the workup is more focused on the internal auditory canal and cerebellopontine angle to rule out pathology like a vestibular schwannoma.

What Diagnoses Are You Working Up in This Scenario?

The presence of brainstem signs alongside vertigo strongly suggests a central, rather than peripheral, etiology. The imaging workup is designed to investigate several key diagnostic possibilities, primarily vascular and structural causes within the posterior fossa.

Vertebrobasilar Insufficiency (VBI)
This is the leading concern in this clinical context. VBI refers to transiently reduced blood flow in the posterior circulation (vertebral and basilar arteries), causing episodic brainstem dysfunction. The symptoms—vertigo, diplopia, dysarthria, ataxia—are classic manifestations of these posterior circulation transient ischemic attacks (TIAs). The underlying cause is often atherosclerotic stenosis, dissection, or extrinsic compression of the vertebral arteries.

Posterior Fossa Mass or Tumor
Though less common than VBI, a structural lesion is a critical diagnosis to exclude. A tumor such as a meningioma, brainstem glioma, or metastasis can compress cranial nerves, vascular structures, or the brainstem itself, producing this constellation of symptoms. The recurrent nature can be due to intermittent changes in pressure or blood flow around the mass.

Demyelinating Disease
In younger adults especially, multiple sclerosis (MS) must be considered. An MS plaque located in the brainstem or cerebellar pathways can cause episodic vertigo and other focal neurologic deficits. The imaging workup must be sensitive enough to detect these small areas of inflammation or demyelination.

Vascular Malformations or Vasculitis
Less frequently, an arteriovenous malformation (AVM), dural arteriovenous fistula (dAVF), or large-vessel vasculitis can cause these symptoms. These conditions can lead to steal phenomena, microhemorrhages, or inflammatory stenosis of the posterior circulation vessels, resulting in transient brainstem ischemia.

Why MRA of the Head and Neck Is the Recommended First Study

For an adult with chronic, recurrent vertigo and brainstem deficits, the ACR designates `MRA head and neck with IV contrast` as “Usually Appropriate.” This recommendation is based on the modality’s ability to comprehensively evaluate both the blood vessels and the brain tissue of the posterior fossa without using ionizing radiation.

The rationale for this choice over other studies is multifaceted:

  • Comprehensive Evaluation: An MRA study provides two critical datasets in one session. The MRI sequences (like T2, FLAIR, and diffusion-weighted imaging) offer superb soft-tissue contrast to visualize the brainstem and cerebellum, making it highly sensitive for detecting tumors, demyelinating plaques, or small, chronic infarcts. The MRA portion specifically visualizes the vertebral, basilar, and posterior cerebral arteries to identify stenosis, occlusion, dissection, or aneurysms.
  • Superiority Over Alternatives:
  • CTA head and neck with IV contrast is also rated “Usually Appropriate” and provides excellent vascular detail, often faster than MRA. However, it delivers a significant radiation dose (☢☢☢ 1-10 mSv) and offers lower sensitivity for subtle parenchymal abnormalities like MS plaques or non-hemorrhagic infarcts. It is a strong alternative when MRI is contraindicated or unavailable.
  • CT head without contrast, rated “May be appropriate,” is inadequate as a primary workup tool here. While it can rule out acute hemorrhage, it has very poor sensitivity for the main differential diagnoses: ischemia, demyelination, most tumors, and vascular stenosis. An initial non-contrast CT is often a false-negative first step that delays definitive diagnosis.
  • Role of IV Contrast: Using intravenous contrast enhances both the MRI and MRA portions of the study. For the MRI, it helps identify active inflammation (as in MS) or characterize tumors. For the MRA, contrast-enhanced techniques are often more robust than non-contrast (time-of-flight) methods, especially in cases of slow or complex blood flow, providing a more accurate depiction of the vessel lumen.
  • Safety Profile: MRA involves no ionizing radiation (O 0 mSv), a key advantage for any patient, particularly if follow-up imaging may be needed.

When ordering, specifying the clinical indication of “recurrent vertigo with brainstem signs, rule out vertebrobasilar insufficiency” is crucial for the radiology team to tailor the protocol correctly. Once you’ve decided on MRA of the head and neck, our protocol guide covers the technique, contrast, and reading principles: MRA Neck With and Without Contrast.

What’s Next After the MRA? Downstream Workflow

The results of the MRA will guide your subsequent management and referrals. The workflow typically branches based on whether a definitive cause is identified.

  • If the MRA is positive for significant vascular stenosis: This confirms a diagnosis of vertebrobasilar insufficiency. The next steps involve aggressive medical management of vascular risk factors (hypertension, hyperlipidemia, diabetes) and initiation of antiplatelet therapy. A referral to neurology or a stroke specialist is indicated for further management, which may include consideration for endovascular intervention in select cases.
  • If the MRA is positive for a tumor or mass: The immediate next step is a referral to neurosurgery and/or neuro-oncology. Further characterization with a dedicated brain MRI protocol with contrast may be required to guide biopsy or surgical planning.
  • If the MRA suggests demyelinating disease: Findings like T2/FLAIR hyperintense lesions in a characteristic distribution should prompt a referral to a neurologist specializing in multiple sclerosis. Further workup may include a spinal cord MRI and cerebrospinal fluid analysis (lumbar puncture) to confirm the diagnosis.
  • If the MRA is negative: A normal, high-quality MRA of the head and neck makes significant structural or vascular pathology much less likely. At this point, the focus may shift back to less common or non-structural causes. This could involve referral to otolaryngology or neurology for further vestibular testing (e.g., VNG, rotational chair testing) to investigate for complex peripheral vestibular disorders or vestibular migraine.

Pitfalls to Avoid (and When to Get Help)

Navigating this workup requires avoiding several common missteps that can delay diagnosis or lead to unnecessary testing.

1. Stopping at a Non-Contrast Head CT: A negative non-contrast CT provides false reassurance in this scenario. It cannot rule out the primary concerns of vascular stenosis, dissection, or demyelination.
2. Ordering the Wrong MRI/MRA: Ordering an “MRI Brain” without specifying MRA of the neck vessels is a frequent error. The pathology is often in the cervical portions of the vertebral arteries, which would be missed.
3. Ignoring Red Flags: The presence of brainstem signs with vertigo is itself a red flag for a central cause. Do not attribute these symptoms to a peripheral cause like BPPV or labyrinthitis without a thorough central workup.
4. Misinterpreting Chronic vs. Acute: This workflow is for chronic, recurrent symptoms. If the presentation is acute and persistent, the patient needs an emergency department evaluation for an active posterior circulation stroke.

If the clinical picture is complex or the imaging findings are ambiguous, a consultation with a neurologist or neuroradiologist is the appropriate next step.

Related ACR Topics and Tools

This article focuses on a single clinical scenario. For a comprehensive overview of imaging for all types of dizziness and ataxia, or to explore the technical details of the recommended studies, the following resources are available.

Frequently Asked Questions

Why is MRA preferred over CTA when both are rated ‘Usually Appropriate’ for this scenario?

While both are excellent for visualizing blood vessels, MRA is preferred as the initial study because it provides superior evaluation of the brain parenchyma (brain tissue) without using ionizing radiation. This allows for better detection of non-vascular causes like multiple sclerosis plaques, small tumors, or subtle infarcts that CTA might miss. CTA is an excellent alternative if MRI is contraindicated or unavailable.

What if my patient has a pacemaker or other contraindication to MRI?

If a patient cannot undergo an MRI, CTA head and neck with IV contrast is the best alternative. It is also rated ‘Usually Appropriate’ by the ACR for this scenario and provides excellent detail of the vasculature. Be aware of the radiation dose (1-10 mSv) and the need for IV contrast, which requires assessment of renal function.

Is an ‘MRI of the brain’ sufficient for this workup?

No, a standard ‘MRI of the brain’ is often insufficient. The pathology causing vertebrobasilar insufficiency, such as stenosis or dissection, frequently occurs in the cervical (neck) portion of the vertebral arteries. It is critical to order an ‘MRA of the head AND neck’ to ensure the entire posterior circulation, from its origin to its intracranial branches, is evaluated.

What should I do if the MRA is completely normal?

A negative high-quality MRA of the head and neck makes a major vascular or structural cause highly unlikely. The differential diagnosis would then broaden to include conditions like vestibular migraine or complex peripheral vestibular disorders. Referral to a neurologist or neuro-otologist for further clinical evaluation and specialized vestibular function testing would be the appropriate next step.

Do I need to order the MRA with and without IV contrast?

Yes, ordering the study ‘with and without IV contrast’ is recommended. The ‘without contrast’ sequences (including time-of-flight MRA) provide a baseline. The ‘with contrast’ sequences improve the accuracy of the MRA for detecting stenosis and are crucial for identifying enhancing lesions like active MS plaques or tumors on the MRI portion of the exam.

Reviewed by Pouyan Golshani, MD, Interventional Radiologist — May 30, 2026