What imaging can disclose about suspected stroke and its Tx

NCHCT is typically performed in advance of other adjunct imaging modalities.^3,20,21 Baseline NCHCT can be performed on patients with advanced kidney disease and those who have an indwelling metallic device.

CT angiography is performed with timed contrast, providing a 3-dimensional representation of the cerebral vasculature; the entire intracranial and extracranial vasculature, including the aortic arch, can be mapped in approximately 60 seconds. CT angiography is sensitive in identifying areas of stenosis > 50% and identifies clinically significant areas of stenosis up to approximately 90% of the time.²⁶ For this reason, it is particularly helpful in identifying candidates for an interventional strategy beyond pharmacotherapeutic thrombolysis. In addition, CT angiography can visualize aneurysmal dilation and dissection, and help with the planning of interventions—specifically, the confident administration of thrombolysis or more specific planning for target lesions and EVT.

Commonly used scoring systems in acute stroke include disability assessments— not always part of the acute assessment but undertaken early in the clinical course to gauge response to treatment.

It also can help identify a host of vascular phenomena, such as arteriovenous malformations, Moyamoya disease (progressive arterial blockage within the basal ganglia and compensatory microvascularization), and some vasculopathies.^20,27 In intracranial hemorrhage, CT with angiography can help evaluate for structural malformations and identify patients at risk of hematoma expansion.²²

CT perfusion. Many stroke centers will perform a CT perfusion study,²⁸ which encompasses as many as 3 different CT sequences:

• NCHCT
• vertex-to-arch angiography with contrast bolus
• administration of contrast and capture of a dynamic sequence through 1 or 2 slabs of tissue, allowing for the generation of maps of cerebral blood flow (CBF), mean transit time (MTT), and cerebral blood volume (CBV) of the entire cerebral vasculature.

The interplay of these 3 sequences drives characterization of lesions (ie, CBF = CBV/MTT). An infarct is characterized by low CBF, low CBV, and elevated MTT. In penumbral tissue, MTT is elevated but CBF is slightly decreased and CBV is normal or increased. Using CT perfusion, areas throughout the ischemic penumbra can be surveyed for favorable interventional characteristics.^20,29

Continue to: A CT perfusion study adds...