Introduction Nucleus ventralis anterior (VA) is the most anterior member in the external segment of the human thalamus and probably represents a rostral extension of nucleus ventralis lateralis (VL), from which it is not sharply delimited.13The characteristic reticulated appearance of VA in transverse sections stained for myelin results from the coarse medullated fiber bundles which pass through it. Many of these fibers represent the most rostral projections of the thalamic radiation and therefore are components of the anterior limb of the internal capsule. Some fibers, however, myelinate before the internal capsule.11The nucleus may be subdivided into a pars magnocellularis and a pars principalis on the basis of cell size. The pars magnocellularis is dorsomedial in position and in man is separated from the nucleus anterior ventralis (AV), nucleus submedius (SM), and nucleus medialis ventralis (MV) by the fibers of the mammillothalamic tract, although some of the cells