Embolism intracranial

Embolism from thrombus within the cavity of an aneurysm is rare and is difficult to prove in cases where there maybe other potential sources of embolization. Intracranial aneurysms more commonly present with rupture and subarachnoid hemorrhage, whereas internal carotid artery aneurysms tend to cause pressure symptoms including a pulsatile and sometimes painful mass in the neck or pharynx, ipsilateral Horner s syndrome or compression of the lower cranial nerves. Extracranial vertebral artery aneurysms may cause pain in the neck and arm, a mass, spinal cord compression and upper limb ischemia (Catala et al. 1993). 

Suction thrombectomy or thromboaspiration through either a microcatheter or a guiding catheter may be an option for fresh nonadhesive clot. As discussed above, aspiration devices have the advantage of causing less embolic events and vasospasm however, the more complex design of these devices makes them more difficult to navigate into the intracranial circulation. 

Dissection of the internal carotid and vertebral arteries is a common cause of stroke, particularly in young patients. Although many occur due to trauma, it is estimated that over half occur spontaneously. The mechanism of stroke following arterial dissection is either by artery-to-artery embolism, by thrombosis in situ, or by dissection-induced lumenal stenosis with secondary cerebral hypoperfusion and low-flow watershed infarction. Occasionally, dissection may lead to the formation of a pseudoaneurysm as a source of thrombus formation. Vertebrobasilar dissections that extend intracranially have a higher risk of rupture leading to subarachnoid hemorrhage (SAH). ° ... 

Cause Most common is cerebrovascular occlusion. Other causes include intracranial hemorrhage, cardiac embolisms, infection, and clotting disorders. 

The use of acetazolamide in the presence of unrecognized cerebral edema due to fat embolism, with sudden normalization of brain C02, as occurred in this patient when her previous state of hypocapnia was no longer sustained by ventilatory effort, resulted in cerebral acidosis, vasodilatation, and a further increase in intracranial pressure. This proved catastrophic and led to brainstem herniation and brain death. Acetazolamide should be avoided if at all possible in patients with bony and traumatic brain injuries, particularly during weaning from mechanical ventilation, since it can precipitate coning in patients with raised intracranial pressure. 

More than 50% of patients with cerebral embolism have atrial fibrillation. In the majority of these patients, the underlying cardiac disease is nonvalvular. The risk of ischemic stroke and atrial fibrillation increases with age, reaching a cumulative risk of 35% during a patient s lifetime. Combined results from several randomized trials show that warfarin reduces the risk of stroke in patients with nonrheumatic atrial fibrillation by 68% (to 1.4% per year), with an excess incidence of major hemorrhage (including intracranial) of only 0.3% per year. 

In Caucasians, the vast majority of MCA occlusions are of embolic origin with emboli arising from a carotid stenosis, the aortic arch or the heart (Heinsius et al. 1998) or from the venous side in case of a patent foramen ovale. In black or Asian patients a higher prevalence of intracranial occlusive disease is found with subsequent thrombotic arterial occlusion or stenosis (Feldmann et al. 1990). 

In the past, two different basic mechanisms have been proposed to account for ischemic events in ICA occlusive disease (1) intracranial embolism and (2) a low-perfusion state also referred to as hemodynamic insufficiency. In the post-mortem arteriographic and pathologic study by Rodda and Path (1986), massive infarcts involving two major cerebral artery territories were associated with distal ICA occlusion, middle cerebral artery (MCA) territory infarcts were seen when the ICA was occluded or stenosed, and borderzone infarcts were characterized by ICA disease and limited circle of Willis anastomosis. 

Schwab et al. used mild hypothermia (33-34°C) in 20 patients with acute severe middle cerebral artery (MCA) infarction for 48-72 h and found mild hypothermia to be safe and feasible (38). Schwab subsequently reported a series of 25 patients with severe MCA infarction treated with the same protocol (39). Intracranial pressure (ICP) was monitored for 3-7 d, and was found to decrease with initiation of hypothermia. ICP increased during re warming in several patients, but not to the levels seen prior to induction of hypothermia. Pneumonia was seen in 40% of patients treated with hypothermia in this trial, which is within the expected range of occurrence in patients with prolonged ventilation (40). Shimizu et al. used mild hypothermia (33°C) in five patients with embolic infarctions involving the internal carotid artery and MCA territories. The hypothermia was maintained for 3-7 d (41). It was found to be safe, but the number of patients was too small to report any efficacy. Another acute stroke trial using convection air to induce mild hypothermia without anesthesia was found to be feasible (42). Temperatures in this trial were reduced only to 35.5°C, and shivering... 

Embolization of plaque debris or thrombus may block a more distal vessel. Emboli are usually the cause of obstruction of the anterior circulation intracranial vessels (Lhermitte et al. 1970 Ogata et al. 1994), at least in white males in whom intracranial disease is relatively rare. Since emboli follow the prevailing direction of flow in a vessel, most emboli... 

Thrombophilias and other causes of hypercoagulability are rare causes of stroke (Matijevic and Wu 2006). Antithrombin III deficiency, protein C deficiency, activated protein C resistance owing to factor V Leiden mutation, protein S deficiency and plasminogen abnormality or deficiency can all cause peripheral and intracranial venous thrombosis. Thrombosis is usually recurrent and there is often a family history. Thrombophilia may cause arterial thrombosis, although the alternative diagnosis of paradoxical embolism should always be considered in patients with these disorders. It should be noted that deficiencies in any one of the factors associated with thrombophilia may be an incidental finding and cannot necessarily be assumed to be the cause of stroke. 

Telangiectasias are collections of dilated capillaries that are usually of no clinical significance (Milandre et al. 1987). They may be associated with hereditary hemorrhagic telangiectasia (the Osler-Weber-Rendu syndrome), but this is more likely to be associated with neurological complications from a pulmonary arteriovenous malformation with right-to-left shunting, such as cerebral hypoxia, brain abscess, paradoxical and septic embolism, or from an associated intracranial arteriovenous malformation or aneurysm (McDonald et al. 1998). 

Delayed corneal epithelial wound healing, PSC, decreased resistance to infection, decreased tear lysozyme, eyelid and conjunctiva hyperemia/edema/angioneurotic edema, subconjunctival hemorrhage, translucent blue sclera, increased lOP, myopia, exophthalmos, intracranial hypertension causing papilledema, diplopia, EOM paresis and eyelid ptosis, retinal hemorrhages (secondary to injection), central serous choroidopathy, abnormal ERGA EP, retinal embolic phenomenon (injection). 

Streptokinase is contraindicated in patients with nlcerative wounds, active internal bleeding, recent trauma with possible internal injuries, visceral or intracranial malignancy, ulcerative cohtis, diverticulitis, severe hypertension, acute or chronic hepatic or renal insufficiency, uncontrolled hypoco-agnlation, chronic pulmonary disease with cavitation, sub-acnte bacterial endocarditis or rheumatic valvular disease, recent cerebral embolism, thrombosis, or hemorrhage, and diabetic hemorrhagic retinopathy, becanse excessive bleeding may occur. 

Interest in thrombolytic therapy for acute ischemic stroke re-emerged with reports of successful thrombolysis for arterial thrombosis in the peripheral vascular system. Local lA infusion was found to have higher rates of recanalization compared with systemic IV delivery of thrombolytics without increased levels of hemorrhagic complications IV use of UK and SK was found to provide clinical benefit in patients with pulmonary embolism [5, 6]. In the early 1980s, lA infusion of UK or SK for acute MI was shown to be highly effective [5, 6]. At the same time, technical advances in endovascnlar microcatheter and microguidewire design made access to the intracranial vessels safer... 

Abstract This chapter focuses on the vascular applications of injectable biomatetials. Two clinically relevant vascular conditions, cerebral arteriovenous malformations and intracranial aneurysm, will be discussed in terms of endovascular embolization. This chapter then outlines available embolic materials used to treat each condition, as well as highlighting new injectable biomaterials developed for embolization purposes. 

In a study by Fanning et al. (2007) 100 intracranial aneurysms were embolized with HydroCoils in conjunction with bare platinum coils, where a basket of bare platinum coils were positioned in the aneurysm, followed by the introduction of HydroCoils. The treatment group showed a 20% increase in the mean packing density when the same number of coils was used in the control... 

Embolic materials for both intracranial AVMs and aneurysms have come a long way since the first endovascular embolization procedure was carried out. Much advancement to this branch of neurosurgery came about because of an emphasis on development of equipment that was better suited to endovascular techniques. Some of these inventions include flow-directed microcatheters, endovascular balloons, and re-designed stents. Owing to a greater capacity to perform endovascular techniques with suitable equipment, the development of better embolic materials has followed. Now, there are a variety of techniques and materials that endovascular neurosurgeons have at their disposal, all of which provide a variety of benefits, yet have considerable drawbacks. Efforts are always being made to improve current materials and techniques, as well as to... 

For further information about intracranial aneurysms, arteriovenous malformations, endovascular embolization techniques, and interventional neuroradiology, see the books listed below. 

Lanzino, G., Kanaan, Y., Perrini, P., Dayoub, H. Fraser, K. (2005) Emerging concepts in the treatment of intracranial aneurysms stents, coated coils, and liquid embolic agents. Neurosurgery, 57, 449-459. 

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