The story of the cerebral collateral circulation began a very long time ago, more than a century.1
As early as 1987, an angiographic study performed in patients with a subacute proximal MCA occlusion provided evidence of the clinical impact of the velocity of the retrograde collateral filling. Authors of this study found that if the conduction time of contrast medium, from the intracranial siphon to the insular portion of the MCA (M2) through the anterior cerebral arteries, was higher than 5 seconds, then an extensive CT hypodensity would develop.2 Two years later, Bozzao et al3 demonstrated that the presence of a good collateral circulation during the first 6 hours after a stroke reduced the size of the final parenchymal brain damage in patients with middle cerebral artery stem–trunk occlusion. In 2002, by using a multivariate analysis applied to a cohort of about 100 patients with MCA M1 occlusion mostly treated with intra-arterial thrombolysis, Kucinski et al4 demonstrated that the angiographic degree of collateralization was the only predictive factor of clinical outcome.
The in vivo visualization of the leptomeningeal arterial supply was only possible by using conventional angiography until 1997, the date of the first attempt to visualize the collateral circulation by using CT angiography.5 CTA clot burden score and collateral score were described only 12 years … more »