Surface topography of the cochlear nuclei in humans: two- and three-dimensional analysis.

We used three-dimensional reconstruction to study the cochlear nuclear complex (CN) in postmortem adult brains. Resulting data show that the largest part of the CN surface, particularly the dorsal cochlear nucleus (DCN), is fully within the lateral recess of the fourth ventricle. The surface of another subdivision, the ventral cochlear nucleus (VCN), is also almost entirely within the recess, except for a narrow zone adjacent to the caudoventral border of the nucleus. The caudal portion of the exposed zone of the VCN is in the vicinity of the rootlets of the glossopharyngeal (IX) nerve, and the ventral portion is close to the terminal part of the vestibulocochlear (VIII) nerve. The border between the intraventricular part of the CN and the extraventricular portion and also the terminal part of the VIII nerve approximately coincides with the line of attachment of the inferior medullary velum of the fourth ventricle (tenia of the choroid plexus). In the narrow strip of this ventral most part of the tenia we did not observe big blood vessels or neurons. Accordingly this could be a reasonably safe surgical route to the intraventricular surface of the CN.