From the Guidelines
The most common diagnostic test for stroke is a noncontrast computed tomography (NCCT) scan of the brain. This non-invasive imaging test is typically the first test performed when a stroke is suspected because it can be done quickly, is widely available in emergency departments, and can rapidly distinguish between an ischemic stroke (caused by a blood clot) and a hemorrhagic stroke (caused by bleeding in the brain) 1.
Key Points
- NCCT scanning of all patients with acute stroke has been shown to be cost-effective primarily because of the detection of acute intracranial hemorrhage (ICH) and the avoidance of antithrombotic treatment in these patients 1.
- Although diffusion-weighted magnetic resonance imaging (DW-MRI) is more sensitive than CT for detecting acute ischemic stroke (AIS), routine use in all patients with AIS is not cost-effective 1.
- The diagnosis of ischemic stroke can be made accurately on the basis of the clinical presentation and either a negative NCCT or one showing early ischemic changes, which can be detected in the majority of patients with careful attention 1.
- Systems should be established so that brain imaging studies can be performed within 20 minutes of arrival in the ED in at least 50% of patients who may be candidates for IV alteplase and/or mechanical thrombectomy 1.
Diagnostic Approach
While CT scans are the initial test of choice, they may be followed by magnetic resonance imaging (MRI), which provides more detailed images and can detect early ischemic changes that CT might miss. Other diagnostic tests that may be performed include CT angiography or MR angiography to examine blood vessels, carotid ultrasound to check for blockages in neck arteries, and various blood tests to rule out other conditions or identify stroke risk factors.
Clinical Considerations
The severity of stroke, based on the findings detected by neurological examination, is a strong indicator of prognosis. Several reliable and well-validated scoring systems have been developed; each has strengths and limitations. Among these scales, the National Institutes of Health Stroke Scale (NIHSS) has come into widespread use in the United States.
Recommendations
NCCT is the preferred initial imaging test for patients with suspected acute stroke, as it is widely available, quickly performed, and can distinguish between ischemic and hemorrhagic stroke, guiding immediate treatment decisions 1.
From the Research
Diagnostic Testing for Stroke
The most common diagnostic testing for stroke includes:
- Noncontrast head computed tomography (CT) as the initial imaging tool to evaluate stroke, due to its sensitivity for hemorrhage, rapid acquisition, and widespread availability 2, 3
- CT angiography (CTA) as a follow-up study to identify intracranial large vessel occlusions and cervical carotid or vertebral artery disease 2
- Magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) to provide valuable insights for outcomes prognostication and stroke etiology 2, 4, 5
Imaging Modalities
Different imaging modalities are used in the diagnosis and management of acute stroke, including:
- CT perfusion, which is widely used in endovascular therapy trials and benefits from multiple commercially available machine-learning packages 2
- Optical coherence tomography (OCT), positron emission tomography (PET), and single-photon emission computerized tomography (SPECT), which offer similar insights 2
- Non-contrast MRI sequences, such as T1-weighted imaging (T1WI), T2-weighted imaging (T2WI), fluid-attenuated inversion recovery (FLAIR), and diffusion-weighted imaging (DWI) 5
Clinical Scenarios
In clinical scenarios, multimodal imaging approaches can be tailored to gain mechanistic insights for a range of cerebrovascular pathologies 2
- The choice of imaging modality (MRI vs. CT) can affect therapy safety and patient outcome, with MRI-based thrombolysis associated with reduced rates of symptomatic intracranial hemorrhage (SICH) and early death 4