From the Guidelines
If a stroke workup reveals negative findings on CTA, CTP, and non-contrast MRI of the head, a comprehensive cardiac evaluation is essential to identify potential cardiac sources of embolism, and further testing should be guided by clinical suspicion and patient-specific factors, as recommended by the American Heart Association/American Stroke Association 1.
Key Recommendations
- Proceed with a comprehensive cardiac evaluation including a 12-lead ECG, continuous cardiac monitoring for at least 24-48 hours, and transthoracic echocardiogram to assess for cardiac sources of embolism such as patent foramen ovale, atrial fibrillation, or valvular disease.
- Consider extended cardiac monitoring with a 30-day event monitor if initial monitoring is negative but suspicion remains high.
- Additional blood work should include complete lipid panel, hemoglobin A1c, inflammatory markers (ESR, CRP), and hypercoagulability testing in younger patients or those without traditional risk factors.
- Carotid ultrasound may detect atherosclerotic disease missed on CTA, particularly in the neck vessels.
- For patients with recurrent symptoms or strong clinical suspicion despite negative imaging, consider conventional cerebral angiography which may identify small vessel abnormalities, vasculitis, or reversible cerebral vasoconstriction syndrome.
Rationale
The American College of Radiology recommends that CT head without IV contrast, MRI head without IV contrast, or MRA head without IV contrast is usually appropriate for the initial emergent imaging of patients with a clinical presentation suggestive of acute stroke 2. However, if initial imaging is negative, further evaluation is necessary to identify potential stroke mimics and occult causes of cerebrovascular events. The American Heart Association/American Stroke Association recommends a comprehensive diagnostic evaluation, including cardiac evaluation, blood tests, and imaging studies, to gain insights into the etiology of stroke and plan optimal strategies for preventing recurrent stroke 1.
Additional Considerations
- The choice of imaging techniques should be influenced by both the time urgency for patient evaluation and the complexity of the literature on acute stroke imaging, as noted by the American Society of Neuroradiology, the American College of Radiology, and the Society of Neurointerventional Surgery 3.
- Approximately 10-15% of ischemic strokes can have initially negative advanced imaging, particularly with small or brainstem infarcts, or when imaging is performed very early after symptom onset before changes become apparent.
- A standardized imaging approach, with all relevant imaging studies conducted in as few sessions as possible, is most practical and efficient, as recommended by the American College of Radiology 4.
From the Research
Stroke Workup
If a patient has a negative Computed Tomography Angiography (CTA), Computed Tomography Perfusion (CTP), and Magnetic Resonance Imaging (MRI) head without contrast, the following steps can be considered:
- Further evaluation may be needed to determine the cause of the patient's symptoms, as a negative result does not completely rule out the possibility of a stroke or other conditions 5.
- The patient's medical history, physical examination, and laboratory results should be taken into account to guide further diagnostic testing 6.
- Additional imaging tests, such as a repeat CTA or MRI with contrast, may be considered if the patient's symptoms persist or worsen 7.
Considerations for Further Testing
- The decision to perform further testing should be based on the patient's individual clinical presentation and medical history 6.
- The use of Computed Tomography Perfusion (CTP) imaging can provide valuable information on cerebral blood flow and perfusion, which can aid in the diagnosis and management of stroke patients 5, 7.
- Magnetic Resonance Imaging (MRI) can also provide detailed images of the brain and blood vessels, which can help identify the cause of the patient's symptoms 7.
Limitations of Current Evidence
- The current evidence is limited to the studies reviewed, and more research may be needed to fully understand the role of CTA, CTP, and MRI in the diagnosis and management of stroke patients 8, 9.
- The studies reviewed were focused on specific aspects of stroke diagnosis and management, and may not provide a comprehensive understanding of the topic 6, 5, 7.