Continent-ocean boundary along the western sector of the South Scotia Ridge

The South Scotia Ridge (SSR) is a submerged structural high located at the eastern continuation of the Antarctic Peninsula and representing the Scotia-Antarctica transform plate boundary. A three-dimensional geological model of a sector of the SSR was built using reflection seismic and sea-floor bathymetry. The model covers the boundary between the oceanic crust of the Scotia Sea and the continental crust of the South Scotia Ridge, where the orientation of the SSR structure changes from SW-NE to W-E. Most of the active faults are located within the continental crust, however, deformation locally involves the oceanic crust and appears connected to the orientation and geometry of the fault system which defines the continent-ocean boundary. The 3D geological model helps visualize a western and central province where the active boundary involves continental blocks, the continental slope, the oceanic basement and sediments, and an eastern province where the sedimentary cover is not deformed and the oceanic basement dips underneath the continent. Moving from west to east, the NW-dipping main transtensional fault system becomes almost vertical in the central sector with an almost pure sinistral strike-slip movement. To the east, a south-dipping plane is progressively less inclined and changes orientation: here evidence of shortening is visible

Postprocedural emboli in carotid artery stenting: where do they come from?

We read with great interest the study by Sztriha et al1 evaluating the early clinical outcome in a large sample of unprotected carotid artery stenting procedures. Although randomized studies comparing endovascular treatment with endarterectomy are showing encouraging results in favor of the endovascular approach,2,3 cerebrovascular complications can occur during and in the early period after the procedure. Whereas intraprocedural complications may be caused by carotid plaque embolization and then they may be affected by the expertise of the physicians performing the procedures and by the development in endovascular technologies such as the use of protection devices, the etiopathogenesis of the cerebrovascular symptoms occurring after the end of the procedure may be unclear. Sztriha et a observed cerebrovascular complications in 14 of 245 (5.4%) consecutive patients included in their study; most of these (9/14 [64.3%]) occurred after the procedure and involved the vascular territory of the carotid artery undergone to stenting (8/9 [88.9%]), but neither restenosis nor reperfusion damage was present. Also, Qureshi et a reported periprocedural cerebrovascular complications in 14 of 111 (13%) patients and mostly (71.4%) after the procedure. Can the passage of atherosclerotic material through the stent mesh explain postprocedural embolization? We observed the case of a 73-year-old women treated with stenting for symptomatic 80% right internal carotid artery stenosis proven by selective angiography according to North American Symptomatic Carotid Endarterectomy Trial criteria. The intracranial angiogram obtained by selective injection of right internal carotid artery showed a moderate stenosis of the right pericallosal artery (Figure). Transcranial Doppler evaluation showed low mean flow velocity (38 cm/s) in the right carotid siphon and blood flow inversion in the right anterior cerebral artery precommunicating tract. A self-expanding stent (Carotid Wallstent monorail, Boston Scientific) was deployed inside the carotid artery and a residual stenosis degree 30% was obtained. The next day, the patient experienced sudden motor impairment in the distal segment of her left leg without other neurological deficits. Carotid duplex scanner examination excluded restenosis and transcranial Doppler showed normal mean flow velocity (62 cm/s) on the right carotid siphon and normal blood flow direction with normal mean flow velocity values (54 cm/s) in the right anterior cerebral artery precommunicating tract. Moreover, transcranial Doppler monitoring prolonged for minutes on the right middle cerebral artery showed no microembolic event. Cranial MR diffusion-weighted image performed 12 hours after the onset of symptoms revealed an area of recent ischemia in the right frontomesial cortex located in the vascular territory of the stenosed pericallosal artery (Figure). This case shows that the postprocedural complication was likely caused by the intracranial hemodynamic changes after cerebral reperfusion. Particularly, the increase of blood flow velocity in the intracranial right carotid artery territory after revascularization could determine the detachment of embolic debris from the pericallosal artery stenosis leading to the frontal medial infarction. Therefore, we suggest that the presence of intracranial stenoses distal to cervical arteries stenoses should be considered during selection of candidates to endovascular treatment because they might be represent a harbinger of postprocedural cerebral ischemic complications

Adaptive position control of an underwater high depth vehicle

B2

Stroke and age-brain barrier: how many bricks in the wall?

Although older people contribute more and more to the increasing social burden of stroke, they are often excluded from potentially effective treatments in clinical practice. With the aim to separate myth from reality, we have examined the barriers preventing such therapies (with reference to atrial fibrillation, thrombolysis, carotid stenosis and patent foramen ovale) in the elderly. We conclude that elevated age alone should not be considered an exclusion criterion and both stroke physicians and researchers should make efforts to greatly improve management of these patients