Brain imaging in stroke: insight beyond diagnosis

Abstract

Stroke, whether hemorrhagic or ischemic in nature, has the ability to lead to devastating and debilitating patient outcomes, which not only has direct implications from a healthcare standpoint, but its effects are longstanding and they impact the community as a whole. For decades, the goal of advancement and refinement in imaging modalities has been to develop the most precise, convenient, widely available and reproducible interpretable modality for the detection of stroke, not only in its hyperacute phase, but a method to be able to predict its evolution through the natural course of disease. Diagnosis is one of the most important initial roles, which imaging fulfills after the identification of existent pathology. However, imaging fulfills an even more important goal by using a combination of imaging modalities and their precise interpretation, which lends itself to understanding the mechanisms and pathophysiology of underlying disease, and therefore guides therapeutic decision-making in a patient-tailored fashion. This review explores the most commonly used brain imaging modalities, computer tomography, and magnetic resonance imaging, with an aim to demonstrate their dynamic use in uncovering stroke mechanism, facilitating prognostication, and potentially guiding therapy.

Fig. 1

Demonstration of multimodal computed tomographic (CT) acquisition, including (a) noncontrast CT, (b) CT angiography, and (c) CT perfusion. The patient is a 91-year-old man who presented with acute onset of slurred speech

Fig. 2

Demonstration of multimodal magnetic resonance imaging acquisition, including (a) diffusion-weighted imaging, (b) fluid-attenuated inversion recovery, (c) gradient recalled echocardiogram, (d) magnetic resonance angiography of the head and neck, and (e) perfusion-weighted imaging. Patient is a 65-year-old man who presented with acute onset of right hemiplegia and global aphasia

Fig. 3

Gradient recalled echocardiogrammagnetic resonance imaging sequences reveal subtle distinction in underlying etiology of hemorrhage. (a) Conflunent peticheal hemorrhagic transformation of ischemic infarct with central hypointensity in caudate and putamen and surrounding hyperintensity. (b) Slit-like cavity in the putamen with a surrounding rim of hypointensity revealing prior hemorrhage

Fig. 4

Computed tomographic scan demonstrating hemorrhagic extension of intracerebral hematoma for an 8-hour period of time. (a) Initial imaging and (b) 8-hr follow-up

Fig. 5

Hemorrhagic conversion in ischemic stroke. (a) Early evidence of ischemia on diffusion-weighted imaging in left middle cerebral artery occlusion followed by (b) hemorrhagic transformation and secondary mass effect on computed tomography

Fig. 6

Contrast retention (arrow) on follow-up computed tomographic scan after acute stroke

Fig. 7

Demonstration of tram track appearance on cerebral angiography in acute stroke showing contrast passage around the occlusive thrombus

Fig. 8

Magnetic resonance imaging diffusion-weighted imaging comparison of radiographic lesion patterns resulting from different etiologies of ischemic stroke: (a) lacune, (b), borderzone infarct, and (c) full territorial infarction of the middle cerebral artery

Fig. 9

Computed tomographichead scan demonstrating hyperdense middle cerebral artery sign (arrow)

Fig. 10

Display of arterial spin label (ASL) MRI perfusion in acute right middle cerebral artery stroke. CBF = cerebral blood flow; CBV = cerebral blood volume; DSC Tmax = dynamic susceptibility contrast, maximum temperature; DSC MTT = dynamic susceptibility contrast, mean transit time