Nerves and nerve tracts at the pontomedullary junction. Corticospinal fibers (as well as corticobulbar and corticopontine fibers) descend from the cerebral cortex through the crus cerebri within the midbrain and into the pons and medulla. The corticospinal fibers form the medullary pyramids before decussating and descending into the spinal cord as the lateral corticospinal tract. Corticopontine fibers synapse with deep pontine nuclei; the latter give rise to second-order pontocerebellar fibers that cross the midline,  enter the middle cerebellar peduncle, and terminate in the contralateral cerebellum.  The facial and vestibulocochlear nerves emerge from the lateral pontomedullary junction near the cerebellopontine angle. The anterior median fissure separates the pyramids, which are flanked laterally by the inferior olives. The anterolateral or preolivary sulci intervene between the pyramids and the olives. From these sulci emerge the roots of the hypoglossal nerve. The roots of the glossopharyngeal, vagus, and accessory nerves emerge in a rostro-caudal sequence from the postolivary sulci. Choroid plexus material (unlabeled) can be seen protruding from the right lateral foramen (of Luschka) of the fourth ventricle.  (Image courtesy of PA Rubino)