Ischemic Stroke Workup

Updated: May 27, 2020
  • Author: Edward C Jauch, MD, MS, FAHA, FACEP; Chief Editor: Helmi L Lutsep, MD  more...
  • Print
Workup

Approach Considerations

Imaging studies

Emergent brain imaging is essential for excluding mimics (SAH, ICH, masses) and potentially confirming the diagnosis of ischemic stroke. Noncontrast CT scanning is the most commonly used form of neuroimaging in the acute evaluation of patients with apparent acute stroke. A lumbar puncture is required to rule out meningitis or subarachnoid hemorrhage when the CT scan is negative but the clinical suspicion remains high. Multimodal CT imaging with the addition of CT angiography and CT perfusion to NCCT has the potential to identify large vessel occlusions and areas of salvagable tissue.

MRI with magnetic resonance angiography (MRA) has been a major advance in the neuroimaging of stroke. MRI not only provides great structural detail but also can demonstrate early cerebral edema. In addition, MRI has proved to be sensitive for detection of acute intracranial hemorrhage. However, MRI is not as available as CT scanning is in emergencies, many patients have contraindications to MRI imaging (eg, pacemakers, implants), and interpretation of MRI scans may be more difficult.

Carotid duplex scanning is one of the most useful tests in evaluating patients with stroke. Increasingly, it is being performed earlier in the evaluation, not only to define the cause of the stroke but also to stratify patients for either medical management or carotid intervention if they have carotid stenoses.

Digital subtraction angiography is considered the definitive method for demonstrating vascular lesions, including occlusions, stenoses, dissections, and aneurysms.

For more information, see Cerebral Revascularization Imaging.

Laboratory studies

Extensive laboratory testing is not routinely required before decisions are made regarding fibrinolysis. Testing can often be limited to blood glucose, plus coagulation studies if the patient is on warfarin, heparin, or one of the newer antithrombotic agents (eg, dabigatran, rivaroxaban). A complete blood count (CBC) and basic chemistry panel can be useful baseline studies. 

Additional laboratory tests are tailored to the individual patient and may include the following:

  • Cardiac biomarkers

  • Toxicology screen

  • Fasting lipid profile

  • Erythrocyte sedimentation rate

  • Pregnancy test

  • Antinuclear antibody (ANA)

  • Rheumatoid factor

  • Homocysteine level

  • Rapid plasma reagent (RPR)

A urine pregnancy test should be obtained for all women of childbearing age with stroke symptoms. The safety of the fibrinolytic agent recombinant tissue-type plasminogen activator (rt-PA) in pregnancy has not been studied in humans (ie, the agent is in the FDA pregnancy category C).

Next:

Brain Imaging With CT Scanning and MRI

CT scanning

Imaging with CT scanning has multiple logistic advantages for patients with acute stroke. Image acquisition is faster with CT scanning than with MRI, allowing for assessment with an examination that includes noncontrast CT scanning, CT angiography (CTA), and CT perfusion scanning in a short amount of time. Expedient acquisition is of the utmost importance in acute stroke imaging because of the narrow window of time available for definitive ischemic stroke treatment with pharmacologic agents and mechanical devices.

CT scanning can also be performed in patients who are unable to tolerate an MR examination or who have contraindications to MRI, including implantable pacemakers, some aneurysm clips, or other ferromagnetic materials in their bodies. Additionally, CT scanning is more easily accessible and commonly located in the ED, which is helpful for patients who require special equipment for monitoring or life support. [65, 66]

MRI

Previously, conventional (spin echo) MRI may take hours to produce discernible findings in acute ischemic stroke. Diffusion-weighted imaging (DWI) is highly sensitive to early cellular edema, which correlates well with the presence of cerebral ischemia. For this reason, many centers include DWI in their standard brain MRI protocol. DWI MRI can detect ischemia much earlier than standard CT scanning or spin echo MRI can and provides useful data in patients with stroke or transient ischemic attack (TIA). (See the image below.) [1, 67, 68, 69]  

Magnetic resonance imaging (MRI) scan in a 70-year Magnetic resonance imaging (MRI) scan in a 70-year-old woman with a history of left-sided weakness for several hours. An axial T2 fluid-attenuated inversion recovery (FLAIR) image (left) demonstrates high signal in the lentiform nucleus with mass effect. The axial diffusion-weighted image (middle) demonstrates high signal in the same area, with corresponding low signal on the apparent diffusion coefficient (ADC) maps, consistent with true restricted diffusion and an acute infarction. Maximum intensity projection from a 3-dimensional (3-D) time-of-flight magnetic resonance angiogram (MRA, right) demonstrates occlusion of the distal middle cerebral artery (MCA) trunk (red circle).

The most commonly used technique for perfusion MRI is dynamic susceptibility, which involves generating maps of brain perfusion by monitoring the first pass of a rapid bolus injection of contrast through the cerebral vasculature. Susceptibility-related T2 effects create signal loss in capillary blood vessels and parenchyma perfused by contrast.

For more information on MRI and MRA in this setting, see Magnetic Resonance Imaging in Acute Stroke.

Based on the central volume principle, dynamic brain perfusion data can be obtained. Cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT) can be calculated using either perfusion MRI or CT scanning. (See the image below.)

Regions of interest are selected for arterial and Regions of interest are selected for arterial and venous input (image on left) for dynamic susceptibility-weighted perfusion magnetic resonance imaging (MRI). Signal-time curves (image on right) obtained from these regions of interest demonstrate transient signal drop following the administration of intravenous contrast. The information obtained from the dynamic parenchymal signal changes postcontrast is used to generate maps of different perfusion parameters.

An evidence-based guideline from the American Academy of Neurology advises that DWI is more useful than noncontrast CT scanning for the diagnosis of acute ischemic stroke within 12 hours of symptom onset and should be performed for the most accurate diagnosis of acute ischemic stroke (level A). No recommendations were made regarding the use of perfusion-weighted imaging (PWI) in diagnosing acute ischemic stroke, as evidence to support or refute its value in this setting is insufficient. [70]

Intra-arterial contrast enhancement may be seen secondary to slow flow during the first or second day after onset of infarction. This finding has been correlated with increased infarct volume size. [71]

Previous
Next:

Other Imaging Studies in Ischemic Stroke

Transcranial Doppler ultrasonography is useful for evaluating more proximal vascular anatomy—including the middle cerebral artery (MCA), intracranial carotid artery, and vertebrobasilar artery—through the infratemporal fossa. [72] Echocardiography is obtained in all patients with acute ischemic stroke in whom cardiogenic embolism is suspected.

Chest radiography has potential utility for patients with acute stroke. However, obtaining a chest radiograph should not delay the administration of rt-PA, as radiographs have not been shown to alter the clinical course or decision-making in most cases. [73]

The use of single-photon emission CT (SPECT) scanning in stroke is still experimental and is available only at select institutions. Theoretically, it can define areas of altered regional blood flow. [74]

Conventional angiography is the gold standard in evaluating for cerebrovascular disease as well as for disease involving the aortic arch and great vessels in the neck. Conventional angiography can be performed to clarify equivocal findings or to confirm and treat disease seen on MRA, CTA, transcranial Doppler, or ultrasonography of the neck. (See the images below.)

A 48-year-old man presented with acute left-sided A 48-year-old man presented with acute left-sided hemiplegia, facial palsy, and right-sided gaze preference. Angiogram with selective injection of the right internal carotid artery demonstrates occlusion of the M1 segment of the right middle cerebral artery (MCA) and A2 segment of the right anterior cerebral artery (ACA; images courtesy of Concentric Medical).
Follow-up imaging after mechanical embolectomy in Follow-up imaging after mechanical embolectomy in 48-year-old man with acute left-sided hemiplegia, facial palsy, and right-sided gaze preference demonstrates complete recanalization of the right middle cerebral artery (MCA) and partial recanalization of the right A2 segment (images courtesy of Concentric Medical).
Cerebral angiogram performed approximately 4.5 hou Cerebral angiogram performed approximately 4.5 hours after symptom onset in a 31-year-old man demonstrates an occlusion of the distal basilar artery (images courtesy of Concentric Medical).
Image on the left demonstrates deployment of a clo Image on the left demonstrates deployment of a clot retrieval device (older generation device) in a 31-year-old man. Followup angiogram after embolectomy demonstrates recanalization of the distal basilar artery with filling of the superior cerebellar arteries and posterior cerebral arteries. The patient had complete resolution of symptoms following embolectomy (images courtesy of Concentric Medical).
Previous
Next:

Blood Studies

A CBC serves as a baseline study and may reveal a cause for the stroke (eg, polycythemia, thrombocytosis, thrombocytopenia, leukemia), identify evidence of concurrent illness (eg, anemia), or issues that may affect reperfusion strategies (thrombocytopenia). The basic chemistry panel serves as a baseline study and may reveal a stroke mimic (eg, hypoglycemia, hyponatremia) or provide evidence of concurrent illness (eg, diabetes, renal insufficiency).

Coagulation studies may reveal a coagulopathy and are useful when fibrinolytics or anticoagulants are to be used. In patients who are not taking anticoagulants or antithrombotics and in whom there is no suspicion for coagulation abnormality, administration of rt-PA should not be delayed while awaiting laboratory results.

Cardiac biomarkers are important because of the association of cerebral vascular disease and coronary artery disease. Additionally, several studies have indicated a link between elevations of cardiac enzyme levels and poor outcome in ischemic stroke.

Toxicology screening may be useful in selected patients in order to assist in identifying intoxicated patients with symptoms/behavior mimicking stroke syndromes or to identify sympathomemetic (cocaine) use, which may be the cause of the ischemic or hemorrhagic stroke . In patients with suspected hypoxemia, arterial blood gas studies define the severity of hypoxemia and may detect acid-base disturbances. However, arterial punctures should be avoided unless absolutely necessary in patients being considered for fibrinolytic therapy.

Previous