Arterial vascularization of the human thalamus: extra-parenchymal arterial groups.

The problem of the arterial vascularization of the human thalamus has been debated at length. Anatomical references concerning the thalamic arterial groups are contradictory and complex, preventing any solid application in practice. It is, therefore, difficult to produce reliable anatomical radio-clinical correlation. In this work, 12 adult human cerebellums (24 hemispheres) were dissected after intra-vascular injection. With care for clarification and standardization, the extra-parenchymal thalamic arteries were classified in six groups: pre-mamillary artery, perforating thalamic arteries, thalamo-geniculate arteries, perforating branches of the postero-medial, postero-lateral and anterior choroidal arteries. Variations in the pre-mamillary artery were rare. The origin of the perforating thalamic artery was unilateral in two of three cases. The origin of the thalamo-geniculate arteries arose between the posterior cerebral artery (53%) and the posterior choroidal arteries (43%). The postero-median choroidal artery was most often single and usually gave the perforating branches for the medial aspect of the thalamus. The postero-lateral choroidal artery was frequently multiple and essentially gave the perforating branches for the superior aspect of the thalamus. The pulvinarian branches most often rose from the postero-lateral choroidal arteries (two thirds of cases) and more rarely from the postero-median choroidal arteries (one third of cases). The anterior choroidal artery is a source of thalamic vascularization by its cisternal branches running towards the lateral thalamus. It can also participate in the vascularization of the pulvinar by the plexiform branches crossing the temporal horn of the lateral ventricle. This study has allowed definition of the intra-parenchymatous arterial map of the thalamus. This mapping is essential for producing anatomical radio-clinical correlations which are pertinent for therapeutic decisions.