The thalamus is a conglomerate consisting of more than 100 nuclei. It functions as the last relay site of all the afferent pathways, with the exception of the olfactory pathway. Thus, it is the "gateway to consciousness". The aim of this study is to provide an overview of the functional anatomy of the thalamus and its blood supply. Furthermore, the most frequent pathologies leading to bilateral lesions of the thalamus will be described. These disorders include, above all, vascular disorders, which must be differentiated into arterial ischemia and venous infarctions, but also different tumors, infectious and demyelinating diseases, as well as metabolic-toxic alterations.