Arjen Lindenholz

Our university hospital has a dedicated research department focused on both research and clinical applications of 7T MRI. One of our clinical studies is the Intracranial Vessel Wall MR Imaging (IVI) study, a recently completed cross-sectional study that over the past 10 years has included patients with acute ischemic stroke or transient ischemic attack for dedicated intracranial vessel wall MRI at 7T. While evaluating the intracranial arterial vessel walls of these patients for possible vessel wall lesions, we noticed that some of the patients had striking unilateral (and often concentric) enhancing vessel wall thickening, which seemed to be mainly present in stroke patients treated with intra-arterial thrombectomy. This led us to hypothesize that this procedure may cause transient or perhaps even permanent intracranial vessel wall changes, which could be visualized using 7T vessel wall MRI.

Intra-arterial thrombectomy (IAT) is a minimally invasive interventional procedure currently available for patients presenting with acute ischemic stroke and a proximal intracranial arterial occlusion. In these patients, the occluded artery is reopened by means of mechanical thrombectomy using either a stent retriever or thrombosuction device, or both. If successful, it restores blood flow to the affected brain parenchyma, increasing the chance of neurologic recovery. There is some evidence that IAT may affect the intracranial vessel wall, but limited in vivo MR imaging studies are available, especially on the effects of thrombosuction devices in IAT, which are the mainstay in our center. To investigate whether IAT by means of thrombosuction causes vessel wall damage, vessel wall enhancement of IVI study participants was compared between those who received IAT (IAT group) and those who did not (non-IAT group).

Our analyses showed that vessel wall enhancement was indeed more often present in participants in the IAT group compared with those in the non-IAT group (79% versus 49%). Furthermore, in post-IAT patients, enhancement was more often unilateral than contralateral to the side of IAT (86% versus 14%) and more often had a concentric configuration, as compared to eccentric enhancement, which is generally associated with atherosclerotic plaques. We did not find these differences in the non-IAT group. Although our results—and those of studies at 3T using stent retriever devices—suggest that IAT devices may indeed cause transient or permanent damage to the intracranial vessel wall, this will not affect their use in the acute setting. IAT has been proved beneficial in the short and long term in a selected group of patients and is part of standard clinical care. For radiologists assessing intracranial vessel wall MRI, however, it is important to become acquainted with these MR imaging findings, as both IAT and intracranial vessel wall MRI are increasingly being performed.

An important next step will be histopathologic evaluation of these enhancing foci, as their true nature is not fully elucidated; is it focal inflammation or endothelial damage caused by mechanical forces exerted on the vessel wall, or underlying enhancing atherosclerotic plaque? Unraveling the true nature of these enhancing foci will not only provide more information on whether the enhancement will be transient or permanent, but will also add valuable insight into the possible risks associated with them (eg, dissections or restenosis). This may in the future guide indications for initial treatment and follow-up imaging on an individual-patient level.

Read this article at AJNR.org …