ANATOMY AND MRI ANATOMY OF THE CEREBRAL I NTER-HEMISPHERIC COMMISSURES

Correlation of myelin-stained or cryotomic sections of human brain wit h inversion-recovery MR images can display the cerebral commissures as white-matter tracts (in hypersignal on MRI), crossing the mid-line. M RI shows routinely in three orthogonal planes a) the corpus callosum s tretched above the supra-tentorial ventricles, it's four portions (ros trum, genu, body and splenium) and connections with the Deep Grey Nucl ei b) the fornix, intralimbic commissure joining anteriorly the mammil lary bodies (through it's columns) to the alveus posteriorly and infer iorly (via it's two crura), arcing around the thalamus and lying over the hippocampus and the dentate gyrus as shown on the frontal sections c) the anterior commissure, white-matter tract connecting the two tem porel lobes. In axial view, the anterior commissure has the shape of b icycle handlebars, coursing posteriorly, inferiorly and laterally behi nd the head of the caudate nucleus and passes into the lateral nucleus of the globus pallidus into the inferior and middle temporal gyri. Be cause the anterior commissure is easily recognisable in all planes, it 's appears to be a important landmark for identification of the latera l and medial nuclei of the globus pallidus on axial and sagittal plane s d) at least, the posterior commissure, anterior magin of the pineal region, closely related to the superior colliculi, acquire a major imp ortance in the AC-PC line delineation becoming a reference landmark fo r stereotatical precedures.