The levels of evidence (class I-IV) supporting the recommendations and ratings of recommendations (A-C, good clinical practice point [GCPP]) are defined at the end of the "Major Recommendations" field.
Imaging of the Brain
Non-contrast computed tomography (CT) scan is the established imaging procedure for the initial evaluation of patients with stroke to document or exclude intracerebral hemorrhage (ICH) and subarachnoid hemorrhage (SAH) (class II, level C). However, CT use has been consecrated more by availability than by randomized studies comparing its effectiveness with magnetic resonance imaging (MRI). Either CT or MRI should be used for the definition of stroke type and treatment of stroke (class I, level A).
Given the controversial nature of data on early CT infarct signs involving more than one-third of the territory of the middle cerebral artery (MCA) as predictors of the outcome of intravenous (IV) recombinant tissue plasminogen activator (rtPA) treatment, the presence of such signs cannot be construed as an absolute contraindication to thrombolysis in the first 3 hours after stroke (class IV, level GCPP). Perfusion CT is helpful when MRI is not available and for the study of stroke patients for whom MRI is contraindicated (class IV, level GCPP). MRI has a higher sensitivity than conventional CT for the documentation of infarction within the first hours of stroke onset, lesions in the posterior fossa, identification of small lesions, and documentation of vessel occlusion and brain edema (class I, level A). In conjunction with MRI and magnetic resonance angiography (MRA), perfusion and diffusion MR are very helpful for the evaluation of patients with acute ischemic stroke (class I, level A). Perfusion and diffusion MR are helpful to select patients for intravenous thrombolysis beyond 3 h (class II, level B). MRI with MRA is the method recommended for the diagnosis and follow-up of arterial dissection (class II, level B).
Single photon emission computed tomography (SPECT) is helpful to predict the malignant course of brain swelling with large hemispheric infarctions (class III, level C). SPECT is also helpful in the evaluation of cerebral perfusion in non-acute cerebrovascular disease, for instance in the days after a SAH (class III, level C).
Detection of Hemorrhagic Stroke
In stroke, MRI can detect acute and chronic ICH (class I, level A). Although the detection of SAH is possible with MRI, currently CT scan is the diagnostic procedure of choice (class I, level A).
Imaging of Extracranial Vessels
Ultrasonography (US) is the non-invasive screening technique indicated for the study of vessels involved in causing symptoms of carotid stenosis (class IV, GCPP). MR angiography has slightly higher sensitivity and specificity than US to determine carotid stenosis and occlusion, but other factors, such as availability, may render one procedure more useful than the other (class II, level B). CT angiography (CTA) has a sensitivity and specificity similar to MR for carotid occlusion and similar to US for the detection of severe stenosis (class II, level B). Digital subtraction angiography (DSA) is generally recommended for grading carotid stenosis prior to endarterectomy (class I, level A), but when there is concordance of non-invasive methods cerebral arteriography may not be necessary (class IV, level GCPP).
Imaging of Intracranial Vessels
Transcranial Doppler (TCD) is very useful for assessing stroke risk of children aged 2 to 16 years with sickle cell disease (class I, level A), detection and monitoring of vasospasm after SAH (class I, level A), diagnosis of intracranial steno-occlusive disease (class II, level B), diagnosis of right-to-left shunts (class II, level A), and for monitoring arterial reperfusion after thrombolysis of acute MCA occlusions (class II, level B). TCD can detect cerebral emboli and impaired cerebral hemodynamics. The presence of embolic signals with carotid stenosis predicts early recurrent stroke risk (class II, level A). The detection of impaired cerebral hemodynamics in carotid occlusion may identify a group at high risk of recurrent stroke (class III, level B).
MRA and CTA are very useful for the diagnosis of intracranial stenosis and cerebral aneurysms >5 mm (class II, level B). MRA is the recommended technique for screening cerebral aneurysms in individuals with a history of aneurysms or SAH in a first-degree relative (class II, level B). DSA is the recommended technique for the diagnosis of cerebral aneurysm as the cause of SAH (class I, level A). MRI with MRA is recommended for the diagnosis and follow-up of cerebral venous thrombosis (CVT) (class II, level B). Alternatively, CT venography is accurate and can be used for the same purpose (class III, level C).
Definitions:
Evidence Classification Scheme for a Diagnostic Measure
Class I: A prospective study in a broad spectrum of persons with the suspected condition, using a "gold standard" for case definition, where the test is applied in a blinded evaluation, and enabling the assessment of appropriate tests of diagnostic accuracy
Class II: A prospective study of a narrow spectrum of persons with the suspected condition, or a well-designed retrospective study of a broad spectrum of persons with an established condition (by "gold standard") compared to a broad spectrum of controls, where test is applied in a blinded evaluation, and enabling the assessment of appropriate tests of diagnostic accuracy
Class III: Evidence provided by a retrospective study where either persons with the established condition or controls are of a narrow spectrum, and where test is applied in a blinded evaluation
Class IV: Any design where test is not applied in blinded evaluation OR evidence provided by expert opinion alone or in descriptive case series (without controls)
Rating of Recommendations
Level A rating (established as useful/predictive or not useful/predictive) requires at least one convincing class I study or at least two consistent, convincing class II studies.
Level B rating (established as probably useful/predictive or not useful/predictive) requires at least one convincing class II study or overwhelming class III evidence.
Level C rating (established as possibly useful/predictive or not useful/predictive) requires at least two convincing class III studies.
Good clinical practice point (GCPP) supported primarily by expert opinion
