Recanalisation procedures are applied prophylactically to dilate stenosed arteries in order to improve cerebral perfusion to prevent a stroke or as a therapeutic measure to recanalize an occluded artery in order to restore cerebral circulation in acute stroke patients.
Acute cerebro-vascular occlusions must be treated immediately. Most of these occlusions which may cause severe strokes are caused by emboli originating from the heart oder from stenoses of the carotid arteries. Recanalisation is achieved by fibrinolytic dissolution of these emboli. Prior to the administration of fibrinolytic enzymes like urokinase or rTPA, a major completed infarction or a haemorrhage of the brain tissue has to be excluded by CT or MRT examination because if this has happened, fibrinolysis is too dangerous. Otherwise, fibrinolysis is carried out by an intravenous approach during the first 3 hours, but can also be performed later by a direct endovascular approach through an intra-arterial catheter if the patient comes too late to hospital. This applies also for acute occlusions of the vertebrl or basilar artery without a strict time limit. If fibrinolysis fails, mechanical fragmentation and suction of the embolus through the catheter can be tried to open the vessel.
Stenoses of the carotid arteries are usually localized at the cervical carotid bifuraction and are caused by atherosclerotic plaques and calcifications. These plaques are either removed by operations (carotid endarterectomy), or the narrow part is dilated by the inflation of a balloon inside the artery. After dilatation, a stent is deployed to maintain the arterial diameter. According to a recent trial (SPACE) both procedures, the endarterectomy and the stenting, carry a similar risk of neurological complications (below 5%). In the vertebral arteries however, stenting is preferred because the surgical approach is more difficult. Dilatation and stenting is the only possible intervention in case of symptomatic intracranial arterial stenoses resistent to anticoagulative therapy. To prevent the formation of new blood clots within the stents, medical treatment with antiplatelet drugs is necessary over several years after stenting, and there is some risk of restenosis. Thank to recent technical improvement of the stent design, this complication rate is now well below 30%.
Acute occlusion of basilar artery (left) and reopening by intra-arterial thrombolysis (right)
Dilatation and stenting of carotid stenosis (before stenting: left, middle; after stenting: right)