RESUMEN
Collateral circulation plays an important role in the clinical and radiological outcome after acute ischemic stroke. Several modalities are used to evaluate these alternative pathways with a growing interest in recent years. We conducted a literature review of studies evaluating collaterals at the acute phase of a carotid territory ischemic stroke. Most of them were based on conventional angiography and CT angiography, several on the basis of MRI and transcranial Doppler and, more recently, on the basis of dynamic CT angiography, which seems to be the most appropriate modality. Populations studied in these publications are often heterogeneous (especially concerning the occlusion site and the treatments performed) and many classifications have been proposed.