What's the next step for a patient with right-sided body weakness and a normal non-contrast computed tomography (CT) head scan?

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Next Step: Obtain MRI Brain with Diffusion-Weighted Imaging (DWI) and Vascular Imaging

For a patient presenting with right-sided body weakness and a normal non-contrast CT head, the next step is to obtain MRI brain with diffusion-weighted imaging (DWI) and vascular imaging (MRA or CTA) to evaluate for acute ischemic stroke, as CT has limited sensitivity for early infarction and MRI is superior for detecting acute parenchymal injury. 1, 2, 3

Immediate Diagnostic Priorities

Why CT Was Insufficient

  • Non-contrast CT head is essential as the initial study to exclude hemorrhage before any intervention, but it has significant limitations for detecting acute ischemia 1, 2
  • CT may appear normal in the hyperacute phase of stroke (first 6-24 hours) even when significant ischemia is present 1, 3
  • MRI with DWI is more sensitive than CT for detecting acute parenchymal injury and can identify ischemic changes within minutes of onset 3, 4
  • In a direct comparison study, MRI detected acute hemorrhage with equivalent accuracy to CT (96% concordance) while being superior for all other pathology 3

Required Imaging Studies

MRI Brain Protocol:

  • MRI brain without and with IV contrast including DWI sequences is the preferred next imaging study 1, 2
  • DWI-MRI can detect acute ischemia that is invisible on CT and helps determine eligibility for interventions 1
  • If MRI is unavailable or contraindicated, proceed directly to vascular imaging with CTA 1

Vascular Imaging:

  • CTA head and neck with IV contrast should be obtained urgently to assess for large vessel occlusion (LVO) 1, 2
  • CTA has high sensitivity and specificity (>90%) for detecting intracranial LVO and is the most rapid means of vascular assessment 1, 5
  • The American College of Radiology recommends CTA from aortic arch to vertex to evaluate both extracranial and intracranial circulation 2

Critical Clinical Considerations

Time-Sensitive Nature

  • Right-sided body weakness lasting 3 days strongly suggests ischemic stroke in the left hemisphere circulation 2
  • The duration (3 days) indicates this is beyond the hyperacute window, but delayed presentations still require complete workup 1, 2
  • Even with symptom duration beyond typical intervention windows, identifying the vascular territory and mechanism is essential for secondary prevention 1

Alternative Diagnoses to Consider

Cerebral Venous Thrombosis (CVT):

  • CVT can present with prolonged symptoms followed by focal deficits and may not be visible on standard CT 2
  • If clinical suspicion exists, obtain CT venography or MR venography as standard imaging may miss this diagnosis 2

Hemorrhagic Transformation:

  • While initial CT was normal, delayed hemorrhagic transformation of an ischemic stroke can occur 3
  • MRI gradient recalled echo (GRE) sequences are more sensitive than CT for detecting hemorrhage, including microbleeds 3

Mass Lesions:

  • Brain tumors, abscesses, or other mass lesions can present with focal deficits 2
  • MRI with contrast is superior to CT for detecting and characterizing mass lesions 1, 4

Common Pitfalls to Avoid

Do Not Assume Normal CT Excludes Stroke

  • Critical error: Dismissing stroke based solely on normal non-contrast CT 2, 3
  • The American Heart Association warns against delaying neuroimaging or assuming benign etiology in patients with new neurological deficits 2
  • CT sensitivity for acute ischemia in the first 6 hours is limited, and many strokes are CT-negative initially 1, 3

Do Not Order Contrast-Enhanced CT as Next Step

  • In the acute non-traumatic setting with normal non-contrast CT, contrast-enhanced CT rarely changes management 6
  • A study of 322 emergency cases found that contrast CT revealed clinically significant abnormalities in only 3 of 241 patients with normal non-contrast CT, and none altered acute management 6
  • Proceed directly to MRI or vascular imaging rather than contrast CT 1, 2

Do Not Delay Vascular Imaging

  • Even if beyond typical intervention windows, vascular imaging is essential for determining stroke mechanism and guiding secondary prevention 1
  • Large vessel occlusion may still be present and could benefit from intervention in selected cases with favorable imaging profiles 1

Algorithmic Approach

  1. Confirm normal non-contrast CT excluded hemorrhage and large territory infarction 1

  2. Obtain MRI brain with DWI, FLAIR, GRE, and contrast-enhanced sequences 1, 2, 3

  3. Obtain vascular imaging (CTA head/neck or MRA) to assess for LVO and vascular pathology 1, 2

  4. If MRI contraindicated or unavailable:

    • Proceed with CTA head and neck immediately 1
    • Consider CT perfusion if available to assess tissue viability 1

  5. If CVT suspected based on clinical presentation (preceding headache, atypical features):

    • Add CT venography or MR venography 2

  6. Additional workup based on imaging findings:

    • If LVO identified: neurology/neurosurgery consultation for potential intervention 1
    • If no vascular occlusion: focus on stroke mechanism workup (cardiac imaging, hypercoagulable evaluation) 1

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

2
Guideline

Diagnostic Approach to Acute Neurological Deficits

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

4
Research

Imaging after head trauma: why, when and which.

Child's nervous system : ChNS : official journal of the International Society for Pediatric Neurosurgery, 2000

5
Guideline

CT Head Imaging in Essential Hypertension

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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