Review ArticleAssessment of Arterial Collateralization and Its Relevance to Intra-arterial Therapy for Acute Ischemic Stroke
Section snippets
Intravenous Thrombolysis
The guiding principle of acute stroke treatment is the timely recanalization of occluded arteries, leading to restoration of cerebral blood flow. Intravenous tissue plasminogen activator (IV-tPA) is shown to improve outcomes as shown by the National Institute of Neurological Disorders and Stroke trial and the Safe Implementation of Thrombolysis in Stroke Monitoring Study registry.1, 2, 3 Following the European Cooperative Acute Stroke Study III trial and pooled data from the large IV-tPA
Poor Clinical Outcomes Despite Good Recanalization
Although endovascular techniques have shown better recanalization rates than intravenous thrombolysis, this has not been matched by a corresponding improvement in clinical outcomes (Table 1). In the MultiMERCI trial, recanalization rate of 69.5% was achieved, but good clinical outcome remained 36% with a mortality rate of 34%.10 The Penumbra Pivotal Stroke trial demonstrated an 81.6% recanalization rate with only 25% positive clinical outcome.11
Several possible mechanisms have been put forward
Human
The development of the cerebral collateral circulatory channels during embryonic stages parallels development of the nervous system. At the fifth week of gestational age, 4 pairs of presegmental arteries originate from the primitive internal carotid artery (ICA): the trigeminal arteries, the otic arteries, the hypoglossal arteries, and the proatlantal intersegmental arteries. By the sixth gestational week, dorsal to the presegmental arteries, bilateral longitudinal neural arteries unite to form
Animal Model
The dynamics of collateral blood flow during ischemic stroke remain little known owing to heterogeneity in patient demographics and treatment options despite of the advent of medical technology imaging. Animal model studies offer greater experimental control and facilitate an understanding of collateral vascular dynamics. Early studies in animal models showed that the pyriform branch of the MCA has collateral communication with the ACA and that the parietal and temporal branches collateralize
Conclusions
There is accumulating evidence that clinical outcomes after IA therapy is critically dependant on arterial collateralization. However, the prognostic role of collateralization has not been definitively established given the lack of a uniform grading system consequent of poorly defined parameters and individual variability in the Circle of Willis. Notwithstanding advances in the imaging of collateral circulation, its validity requires standardization in assessment methods. Further trials are
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Flow diversion within seven days after stroke onset is associated with favorable outcome in anterior circulation stroke
2017, Journal of Clinical NeuroscienceCitation Excerpt :However, higher financial cost and contrast-dependency have limited the usage of contrast-CT in clinical practice, particularly in developing countries and patients with renal inadequacy or iodine contrast allergy. Transcranial Doppler ultrasound (TCD) is a cheaper, safer, noninvasive and portable method to provide real-time hemodynamic information of the brain [5]. It can demonstrate a specific pattern of high velocities/low resistance flow to the ipsilateral anterior (ACA) or posterior (PCA) cerebral arteries in the setting of acute MCA occlusion [6].
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