Introduction

The thalamus is a large ovoid structure composed of several groups of grey-matter nuclei. The right and left thalami are strategically located at the top of the brainstem and act to provide a key relay to and from the cerebral cortex. Because of its complex anatomy and vascularization, the thalamus can give rise to a great variety of hemorrhagic and ischemic stroke syndromes. These various syndromes are characterized by prototypic clinical findings and abnormalities revealed by imaging that allow clinicians to locate an infarct in one of the thalamic nuclear groups and to infer the identity of the occluded artery and the pathogenesis of the stroke.

Blood supply to the thalamus

Knowledge of the vascular anatomy and supply zones of the thalamus is mandatory if one is to understand the clinical findings in patients with thalamic infarcts and hemorrhages. The thalamus receives most of its blood supply from four arterial pedicles that arise from the basilar artery bifurcation, the posterior communicating artery (PCoA), and the proximal portions of the posterior cerebral arteries (PCA) (Fig. 34.1).

Polar artery

The polar artery (also called the tuberothalamic, anterior internal optic: Duret (1874), or premamillary pedicle: Foix & Hillemand (1925a) usually arises from the PCoA. In about one-third of hemispheres, the polar artery is missing, and its territory is supplied by the thalamic–subthalamic arteries from the same side (Percheron, 1976a). The polar artery supplies the anteromedial and anterolateral regions of the thalamus, including the reticular nucleus, the mamillothalamic tract, part of the ventral lateral nucleus, the dorsomedial nucleus, and the lateral aspect of the anterior thalamic pole (Percheron, 1976a). The anterior nucleus is not supplied by the polar artery.