Radiological predictors of hemorrhagic transformation after acute ischemic stroke: An evidence-based analysis

Abstract

Hemorrhagic transformation (HT) is one of the most common adverse events related to acute ischemic stroke (AIS) that affects the treatment plan and clinical outcome. Identification of a sensitive radiological marker may influence the controversial thrombolytic decision in the setting of AIS and may at a minimum indicate more intensive monitoring or further prophylactic interventions. In this article we summarize possible radiological biomarkers and the role of different radiological modalities including computed tomography (CT), magnetic resonance imaging, angiography, and ultrasound in predicting HT. Different radiological indices of early ischemic changes, large ischemic lesion volume, severe blood flow restriction, blood-brain barrier disruption, poor collaterals and high blood flow velocities have been reported to be associated with higher risk of HT. The current levels of evidence of the available studies highlight the role of the different CT perfusion parameters in predicting HT. Further large standardized studies are recommended to compare the sensitivity and specificity of the different radiological markers combined and delineate the most reliable predictor.

Keywords: Computed tomography; Digital Subtraction Angiography; hemorrhagic transformation; magnetic resonance; predictors.

Figure 1.

Noncontrast computed tomography (CT) of the brain showing (a) early sign of cerebral ischemia, (b) hyperdense middle cerebral artery sign and (c) Alberta Stroke Program Early CT Score 5 with evidence of hemorrhagic transformation.

Figure 2.

Assessment of clot burden score: Two points are subtracted for each thrombus preventing contrast opacification in the proximal M1, distal M1 or supraclinoid internal carotid artery (ICA) and one point each for M2 branches, A1 and infraclinoid ICA.

Figure 3.

Computed tomography brain angiography showing M1 occlusion with (a) absent collaterals, collateral score 0; (b) collateral filling less than 50% (collateral score: 1); (c) collateral filling greater than 50% (collateral score: 2) and (d) collateral filling 100% (collateral score: 3).

Figure 4.

(a) Noncontrast computed tomography; computed tomography perfusion maps including (b) cerebral blood volume, (c) cerebral blood flow, (d) mean transit time and (e) Tmax showing a large area of matched deficit indicative of core infarct in the right middle cerebral artery territory.

Figure 5.

Noncontrast magnetic resonance imaging showing evidence of leukoaraiosis in the form of hyperintensity both in T2 and fluid-attenuated inversion recovery sequences.

Figure 6.

Magnetic resonance (a) diffusion and (b) perfusion showing evidence of restricted blood flow in the left middle cerebral artery territory.

Figure 7.

Susceptibility-weighted imaging magnetic resonance imaging showing evidence of small, rounded, homogeneous, and hypointense lesions suggestive of cerebral microbleeds.

Figure 8.

Angiography of the right internal carotid artery showing evidence of capillary blush.

Figure 9.

(a) Pretherapeutic parametric blood flow wash-in rate color-coded images showing restricted diffusion in the middle cerebral artery territory, (b) post-therapeutic parametric blood flow wash-in rate color-coded images showing middle cerebral artery recanalization after treatment, and (c) noncontrast computed tomography showing evidence of hemorrhagic transformation.

Figure 10.

Transtemporal transcranial color-coded duplex (TCCD) insonation of the left middle cerebral artery showing elevated peak systolic velocity. LT MCA: left middle cerebral artery, SV: sample volume, PSV: peak systolic velocity, EDV: end diastolic velocity, TCD: transcranial doppler, PI: Pulsatility Index.

Figure 11.

Summary of the hemorrhagic transformation radiological biomarkers in noncontrast computed tomography (CT) brain, computed tomography angiography, and computed tomography perfusion. ASPECTS: Alberta Stroke Program Early CT Score; CBF: cerebral blood flow; CBV: cerebral blood volume; MTT: mean transit time.