Pediatric Imaging

What Imaging Should You Order for a Child with Sickle Cell and Suspected Acute Stroke?

May 29, 2026 · Pouyan Golshani, MD, Interventional Radiologist

An 8-year-old with a known history of sickle cell disease presents to the emergency department with the sudden onset of left-sided facial droop and arm weakness that has persisted for an hour. The clinical team is concerned for an acute cerebrovascular event, a known and devastating complication of his underlying condition. The immediate question is which imaging study will most accurately and safely diagnose an acute stroke, identify the underlying vasculopathy, and guide urgent management like exchange transfusion. This article details the clinical workflow for this specific scenario.

According to the American College of Radiology (ACR) Appropriateness Criteria, for a child with sickle cell disease and a new focal neurologic deficit, MRA head without IV contrast is rated Usually Appropriate as the initial imaging study.

Who Fits This Clinical Scenario?

This guidance applies to a specific and high-risk patient population: a child with known sickle cell disease (SCD) presenting with signs of an acute stroke. The key inclusion criteria are:

Patient: A child (infant to adolescent).
Underlying Condition: Diagnosed sickle cell disease.
Presentation: A new, focal neurologic deficit that is fixed or progressively worsening. This includes symptoms like hemiparesis, aphasia, facial droop, or visual field cuts.

It is critical to distinguish this scenario from similar presentations that require a different diagnostic approach. This workflow does not apply if:

The patient does not have sickle cell disease. While the imaging choice may be similar, the pre-test probability of specific vasculopathies changes. This is covered in the sibling scenario for nonsickle–cell related stroke.
The primary concern is trauma. In cases of head injury, a non-contrast head CT is typically the first-line study to evaluate for fracture or intracranial hemorrhage.
Symptoms are transient, non-focal, or suggestive of seizure. A global headache or a seizure without a persistent postictal focal deficit may prompt a different workup, though stroke remains on the differential.

What Diagnoses Are You Working Up in This Scenario?

In a child with sickle cell disease and focal deficits, the differential diagnosis is centered on cerebrovascular pathology unique to SCD. The choice of imaging is designed to rapidly identify or exclude these conditions.

Acute Ischemic Stroke: This is the most immediate and life-threatening concern. In SCD, strokes are often caused by large-vessel vasculopathy. Progressive stenosis of the distal internal carotid arteries and the proximal middle and anterior cerebral arteries leads to vessel occlusion and subsequent infarction. Sickled red blood cells can also contribute to sludging and microvascular occlusion.

Moyamoya Syndrome: This is a progressive, steno-occlusive disease of the large intracranial arteries, with the formation of fine collateral vessels at the base of the brain. Moyamoya is a well-known complication of sickle cell disease and a major risk factor for both ischemic and hemorrhagic strokes. MRA is the ideal non-invasive modality to visualize this characteristic vascular pattern.

Silent Cerebral Infarct (SCI): While the clinical presentation is acute, the imaging may reveal evidence of prior, clinically unapparent strokes. SCIs are extremely common in children with SCD and are a significant risk factor for future overt strokes and cognitive impairment. Identifying their presence is crucial for long-term management and risk stratification.

Hemorrhagic Stroke: Although less common than ischemic stroke in this population, hemorrhage can occur, often related to ruptured aneurysms that form in the fragile moyamoya collateral vessels or from reperfusion injury. Imaging must be able to reliably detect acute blood products.

Why Is MRA Head Without IV Contrast the Recommended Study?

The ACR designates MRA head without IV contrast as Usually Appropriate because it directly addresses the primary pathology in SCD-related stroke without ionizing radiation or contrast agents. In practice, this is typically ordered as part of a comprehensive non-contrast brain MRI protocol.

The complete examination—MRI brain with MRA head, both without contrast—provides two critical pieces of information:

Parenchymal Assessment (MRI): Diffusion-Weighted Imaging (DWI) is exceptionally sensitive for detecting cytotoxic edema from an acute ischemic infarct within minutes of onset. Other sequences like FLAIR can show established infarcts, and gradient echo (GRE) or susceptibility-weighted imaging (SWI) are highly sensitive for hemorrhage, both acute and chronic (hemosiderin).
Vascular Assessment (MRA): Time-of-flight (TOF) MRA creates detailed images of the intracranial arteries, allowing for direct visualization of the stenosis, occlusions, and abnormal collateral vessels characteristic of the vasculopathy seen in SCD and moyamoya.

This combined approach offers the highest diagnostic yield for the most likely etiologies in this specific clinical scenario.

Why Other Studies Are Rated Lower

CT head without IV contrast: While also rated Usually Appropriate, it serves a more limited role. It is fast and excellent for ruling out acute hemorrhage. However, it is notoriously insensitive to early ischemic stroke and provides no information about the underlying vascular anatomy. Its use of ionizing radiation (Pediatric RRL: ☢☢☢ 0.3-3 mSv) is a key disadvantage compared to MRI’s 0 mSv dose. It is often a pragmatic first choice when MRI is not immediately available, but MRI/MRA should follow.
CTA head with IV contrast: This is rated Usually Not Appropriate as an initial study. While it provides excellent vascular detail, it requires both IV contrast and a significant radiation dose (Pediatric RRL: ☢☢☢☢ 3-10 mSv). Given that non-contrast MRA can answer the vascular question effectively and safely, CTA is reserved for cases where MRA is contraindicated or inconclusive.

When ordering, it is best practice to request an “MRI/MRA brain stroke protocol without contrast” to ensure all necessary sequences (including DWI) are performed. Once you’ve decided on MRA head without IV contrast, our protocol guide covers the technique, contrast, and reading principles: MRA Brain Without Contrast (3D TOF).

What’s Next After MRA Head Without IV Contrast? Downstream Workflow

The results of the initial MRI/MRA will dictate the immediate and long-term management plan in close collaboration with pediatric neurology and hematology specialists.

If the study is positive for acute ischemic stroke: This is a medical emergency. The primary treatment is often an urgent red blood cell exchange transfusion to decrease the concentration of hemoglobin S and improve oxygen delivery. The presence and severity of underlying large-vessel vasculopathy on MRA will inform the need for chronic transfusion therapy to prevent stroke recurrence.
If the study is negative for an acute stroke but shows significant vasculopathy (e.g., moyamoya or severe stenosis): The patient is at very high risk for a future stroke. This finding will typically prompt initiation of chronic transfusion therapy and may lead to consideration for surgical revascularization (e.g., pial synangiosis) to improve cerebral blood flow.
If the study is negative for both acute stroke and significant vasculopathy: The clinical team should reconsider stroke mimics, such as complex migraine or a postictal state (Todd’s paralysis). Further clinical evaluation or EEG may be warranted. The presence of multiple silent cerebral infarcts, even without an acute event, may still be a trigger for initiating or escalating disease-modifying therapy.

Pitfalls to Avoid (and When to Get Help)

Navigating this high-stakes scenario requires avoiding several common pitfalls:

Delaying Imaging: Time is brain. An acute focal deficit in a child with SCD should trigger an immediate stroke alert and emergent imaging.
Accepting a Non-Diagnostic Study: A non-contrast head CT that is negative for hemorrhage does not rule out an acute ischemic stroke. If clinical suspicion remains high, do not stop the workup; proceed to MRI/MRA.
Forgetting the Vasculature: Ordering only an MRI of the brain without an MRA of the head misses the opportunity to diagnose the underlying cause (the vasculopathy), which is essential for preventing the next stroke.
Ignoring Sedation Needs: Young children often require sedation or anesthesia to obtain a high-quality, motion-free MRI. Plan for this early to avoid delays.

If the non-invasive imaging is inconclusive or if there is a consideration for endovascular intervention (rare in this initial setting), escalate immediately to a pediatric neurologist or interventional neuroradiologist.

Frequently Asked Questions

Why is MRA without contrast preferred over MRA with contrast for this initial workup?

MRA without contrast, using time-of-flight (TOF) technique, is highly effective at visualizing blood flow and vessel structure in the major intracranial arteries, which is where the vasculopathy in sickle cell disease typically occurs. It provides the necessary diagnostic information without the risks associated with gadolinium-based contrast agents, such as nephrogenic systemic fibrosis (rare) or allergic reactions. Therefore, the ACR rates MRA with contrast as ‘Usually Not Appropriate’ for the initial evaluation.

If our hospital’s MRI is down or unavailable, is a head CT and CTA an acceptable alternative?

A non-contrast head CT is a reasonable first step to rapidly rule out hemorrhage. If MRI/MRA is truly unavailable, a CTA can provide the necessary vascular information. However, this combination (CT/CTA) exposes the child to significant ionizing radiation and IV contrast. It should be considered a second-line option, and transfer to a center with MRI capability should be strongly considered if clinically feasible.

What is the role of Transcranial Doppler (TCD) ultrasound in this acute setting?

Transcranial Doppler (TCD) ultrasound is a critical tool for stroke risk *screening* in children with sickle cell disease, used to measure blood flow velocities in the large intracranial arteries. However, the ACR rates it as ‘Usually Not Appropriate’ for the diagnostic workup of an *acute* stroke. It is operator-dependent, has lower resolution than MRA, and cannot evaluate the brain parenchyma for infarction. Its role is in surveillance, not acute diagnosis.

Does this guidance change if the child has a seizure with the focal neurologic deficit?

Not initially. A seizure can be the presenting sign of an acute stroke. The primary goal remains to rapidly evaluate for ischemia, hemorrhage, and underlying vasculopathy. Therefore, MRI/MRA without contrast remains the most appropriate initial imaging test. The findings will then help determine if the seizure was caused by the stroke or if it represents a separate process.

If the MRA shows moyamoya, what is the next imaging step?

If MRA demonstrates moyamoya vasculopathy, the next step is often a conventional catheter-based digital subtraction angiography (DSA). While invasive, DSA is the gold standard for grading the severity of stenosis, fully characterizing the collateral circulation, and planning for potential surgical revascularization. This decision is always made in consultation with a multidisciplinary team including pediatric neurology, neurosurgery, and neuroradiology.

Reviewed by Pouyan Golshani, MD, Interventional Radiologist — May 29, 2026