FIG 4. Subimages (55 x 55-mm field of view) of the brain stem.

A, Axial section obtained at the level of the upper midbrain. Very fine fibers that originate from the oculomotor nucleus run through and around the red nucleus and converge to the roots of the oculomotor nerves (green). Note that fibers of the cerebral peduncles are running at a slight angle through the plane (yellow dots with lines).

B, Axial section obtained at the level of the lower midbrain. The arrow indicates the decussation of the superior cerebellar peduncle.

C, Axial section (110 x 110-mm field of view) obtained at the level of the midbrain-cerebrum junction. The fibers of the optic tract (arrows) connect to the lateral geniculate bodies. Fibers of the optic radiation (pink) pass lateral to the optic tract.

D, Axial section obtained at the level of the pons, through the roots of the trigeminal nerve (green). Fibers of the craniocaudal tracts (superior cerebellar peduncle, medial longitudinal fasciculus, tectospinal tract, dorsal and ventral trigeminothalamic tracts, central tegmental tract, spinothalamic tract, and rubrospinal tract) can be seen in the posterior part of the pons (pink). The yellow dots indicate fibers of the pyramidal and the frontopontine tracts.