Interrogating the Functional Correlates of Collateralization in Patients with Intracranial Stenosis Using Multimodal Hemodynamic Imaging

Abstract

Background and Purpose The importance of collateralization for maintaining adequate cerebral perfusion is increasingly recognized. However, measuring collateral flow noninvasively has proved elusive. The aim of this study was to assess correlations among (1) baseline perfusion and arterial transit time artifact, (2) cerebrovascular reactivity (CVR), and (3) the presence of collateral vessels on digital subtraction angiography (DSA). Materials and Methods The relationship between the presence of collateral vessels on arterial-spin-labeling (ASL) MRI and DSA was compared to blood-oxygenation-level-dependent (BOLD) MRI measures of hypercapnic cerebrovascular reactivity (CVR) in patients with symptomatic intracranial stenosis (n=18). DSA maps were reviewed by a neuroradiologist and assigned the following scores: 1) collaterals to the periphery of the ischemic site; 2) complete irrigation of the ischemic bed via collateral flow; 3) normal antegrade flow. ASL maps were scored according to 0) low signal; 1) moderate signal with arterial transit artifact (ATA); 2) high signal with ATA; 3) normal signal. Results In regions with normal-to-high signal on ASL, collateral vessel presence on DSA strongly correlated with declines in CVR as measured on BOLD MRI (p<0.001), most notably in patients with non-atherosclerotic disease. There was a trend toward increasing CVR with increases in the degree of collateralization on DSA (p=0.082). Conclusion Collateral vessels may have fundamentally different vasoreactivity properties than healthy vessels, a finding that is observed most prominently in non-atherosclerotic disease and to a lesser extent in atherosclerotic disease.

Signal variance-based collateral index in DSC perfusion: A novel method to assess leptomeningeal collateralization in acute ischaemic stroke

“…Another method for direct MRI-based assessment of collaterals is arterial spin labelling (ASL), which allows for visualization of collateral vessels due to its sensitivity to arterial arrival delays. [53][54][55] Reliable calculation of CBF from ASL is still under investigation. 53 However, ASL has been used for collateral assessment in chronic cerebral hypoperfusion 53,54 and acute ischaemic stroke, 55,56 providing promising results concerning the prediction of neurological outcome.…”

Applications and development of permeability imaging in ischemic stroke (Review)

“…However, since the DSA is an invasive examination, there is risk of radiation exposure and iodine allergy. In addition, the DSA surgery may induce vasospasm and ischemic stroke, making it inappropriate for dynamic observation in infants, young children, high-risk patients and patients with complex intracranial arterial stenosis (such as Moyamoya disease) (33).…”

“…Using the 320-slice CT scan, it may be possible to obtain information on perfusion in addition to the state of the entire intracerebral circulation at the same time, and the imaging quality is almost comparable with the quality of DSA, which makes the clinical application of 4D-CTA promising (42). Currently, a number of international clinical studies (such as the INSPIRE study) are using this technique to investigate the collateral circulation and cerebral perfusion, in addition to other aspects such as intracranial aneurysm and cerebral arteriovenous malformation (33,41). The 4D-CTA has a number of disadvantages, including a large one-time radiation dose of the contrast agent.…”

Impact of vessel wall lesions and vascular stenoses on cerebrovascular reactivity in patients with intracranial stenotic disease

“…Here, hypercapnic BOLD MRI is applied together with a novel time regression technique (19) that separately quantifies CVR lagtime (i.e., time for smooth muscle lining arterioles to maximally relax in response to vasoactive stimuli) and maximum CVR (i.e., amount by which arterioles are able to increase cerebral blood flow and volume in response to vasoactive stimuli). In this study, BOLD MRI was used, rather than ASL MRI, as BOLD MRI is more robust over a large range of blood arrival and vascular reactivity times, which are expected in patients with cerebrovascular disease (20,21). …”

“…In this study, BOLD MRI was used, rather than ASL MRI, as BOLD MRI is more robust over a large range of blood arrival and vascular reactivity times, which are expected in patients with cerebrovascular disease. 20,21 The purpose of this work is to compare CVR lagtime and maximum in flow territories perfused by vessels with vessel wall disease and/or stenosis to territories perfused by vessels without measurable vessel wall disease or stenosis, separately in the two patient groups. The overall hypotheses are that 1) vessel wall pathology colocalizes with arterial stenosis in the majority of patients in both groups, and 2) lower maximum CVR and prolonged CVR lagtimes are present in flow territories perfused by vessels with vessel wall pathology.…”