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A new era of stroke treatment may have begun with mechanical thrombectomy (MT) by fully deployed closed-cell self-expanding stents (stent-triever). Multiple case series and the first randomised controlled trials (RCTs) have now been published. More studies are under way involving large numbers of patients, which in turn has resulted in less strict "pragmatic" study protocols. Problems with current trials include a lack of standardisation in the conduct of the recanalisation procedure, the definition of primary endpoints such as the grade of arterial recanalisation and tissue reperfusion, and the post-surgical care provided. In Part 1 of this two part series, we outline the current situation and the major research questions.

We report four patients with late angiographic follow-up of spontaneous occlusion of residual cerebral arteriovenous malformation after partial embolisation. Discussion is focused on the possible mechanisms leading to obliteration according to the latest concepts on angioarchitectural remodelling, malformation development and evolution with a brief review of the literature.

Three recent, simultaneous publications report the neutral results of three randomized studies (SYNTHESIS Expansion, Interventional Management of Stroke (IMS) III, and Mechanical Retrieval and Recanalization of Stroke Clots Using Embolectomy (MR RESCUE)) comparing IV thrombolysis therapy or standard care (MR RESCUE) to the endovascular treatment (EVT) of acute ischemic stroke (AIS) [1–3]. The results of these three trials might lead to the erroneous conclusion that endovascular treatment has no or little place in the management of AIS. However, careful analysis of the IMS III, SYNTHESIS, and MR RESCUE studies is mandatory prior to assessment of the value of EVT of AIS. Also, the limits of the current and future trials should be outlined. The European Society of Minimally Invasive Neurological Therapy (ESMINT) and European Society of Neuroradiology (ESNR) represent the interventional neuroradiology community in Europe and have engaged in the definition of rules regarding trials evaluating the EVT of AIS [4, 5]. It is clearly their role to provide a precise analysis of recent and future trials. In the last 20 years, treatment of AIS has evolved to include neuroprotection, IV thrombolysis (IVT), and endovascular treatment. Despite numerous studies of a very large number

Based on current data and experience, the joint working group of the European Society of Minimally Invasive Neurological Therapy (ESMINT) and the European Society of Neuroradiology (ESNR) make suggestions on trial design and conduct aimed to investigate therapeutic effects of mechanical thrombectomy (MT). We anticipate that this roadmap will facilitate the setting up and conduct of successful trials in close collaboration with our neighbouring disciplines.

A review of 4,500 angiograms yielded 11 patients with dissection of the vertebral arteries who had MRI and (in 4 patients) MR angiography (MRA) in the acute phase of stroke. One patient with incidental discovery at arteriography of asymptomatic vertebral artery dissection and two patients with acute strokes with MRI and MRA findings consistent with vertebral artery dissection were included. Dissection occurred after neck trauma or chiropractic manipulation in 4 patients and was spontaneous in 10. Dissection involved the extracranial vertebral artery in 9 patients, the extra-intracranial junction in 1, and the intracranial artery in 4. MRI demonstrated infarcts in the brain stem, cerebellum, thalamus or temporo-occipital regions in 7 patients with extra- or extra-intracranial dissections and a solitary lateral medullary infarct in 4 patients (3 with intracranial and 1 with extra-intracranial dissection). In 2 patients no brain abnormality related to vertebral artery dissection was found and in one MRI did not show subarachnoid haemorrhage revealed by CT. Intramural dissecting haematoma appeared as crescentic or rounded high signal on T1-weighted images in 10 patients examined 3-20 days after the onset of symptoms. The abnormal vessel stood out in the low signal cerebrospinal fluid in intracranial dissections, whereas it was more difficult to detect in extracranial dissections because of the intermediate-to-high signal of the normal perivascular structures and slow flow proximal and distal to the dissection. In two patients examined within 36 h of the onset, mural thickening was of intermediate signal intensity on T1-weighted images and high signal on spin-density and T2-weighted images. MRA showed abrupt stenosis in 2 patients and disappearance of flow signal at and distal to the dissection in 5. Follow-up arteriography, MRI or MRA showed findings consistent with occlusion of the dissected vessel in 6 of 8 patients.