Arjen Lindenholz

193 General Discussion 9 Aparticularsubfieldinintracranialatherosclerosisthatmayinfluenceatherosclerotic burden assessment in clinical practice is intra-arterial thrombectomy (and other intraluminal procedures). Several studies have shown evidence of vessel wall changes after intra-arterial treatment (IAT). 65-67 Stent-retrievers cause mechanical sheer stress when the deployed stent with the trapped culprit thrombus is retracted, while thrombosuction devices use negative pressure to aspirate the culprit thrombus; both exert forces that might be detrimental to the vessel wall. 66- 68 Histopathological studies showed that depending on the type of device used, the vessel wall was more or less affected after the procedure, mostly favoring for thrombosuction devices. 66,67 Using 7T intracranial vessel wall MRI, vessel wall enhancement after thrombosuction was seen more often than in a control group without IAT, and mostly ipsilateral to the occlusion site ( Chapter 7 ). 69 This is in line with another 7T MRI study investigating the effect of stent-retriever devices on the intracranial vessel wall, 70 and with several 3T MRI studies. 71-74 All these studies show comparable results in the detection of post-endovascular vessel wall changes. Although the possibility that IAT devices cause (transient or permanent) changes to the intracranial vessel wall, it will likely not affect their use in the acute setting. It is important to become familiar with these radiological findings as this type of treatment is performed with increasing frequency. 75 Nonetheless, additional insight in the persistence of these vessel wall changes and their possible risk for future complications (e.g., dissections or re-stenosis) may aid in device optimization and in future may change the indications for follow-up imaging on an individual-patient level. Besides intracranial atherosclerosis (and iatrogenic complications thereof), intracranial vessel wall MRI has the potential to correctly diagnose many other intracranial vasculopathies that may be less common, and therefore less investigated than atherosclerosis, but that pose a bigger clinical challenge because they often mimic each other on lumenographic imaging studies. 1,2,4 Actually, in clinical practice the most common indication to use intracranial vessel wall MRI is not assessment of atherosclerotic burden, but diagnosing possible cerebral vasculitis. 4 Several studies have shown the additional benefit of vessel wall MRI in different types of vasculitis, such as herpes zoster, tuberculous or radiation-induced vasculitis. 76-79 Although differentiating between these individual types on vessel wall MRI is difficult, the typical enhancement pattern may help the radiologist differentiating vasculitis from other vasculopathies, like reversible vasoconstriction syndrome (RVCS) and intracranial atherosclerosis that require a completely different treatment approach. 48,80,81 Also, the treatment effect after steroid therapy for vasculitis can be evaluated with a decrease in vessel wall enhancement as a measure of success. 4 Intracranial aneurysms are another example for which emerging diagnostic evidence points to a significant role of intracranial vessel wall MRI: the presence or absence of aneurysm wall