Cross Section at the Level of the Trigeminal Nerve
The medial field of the pontine tegmentum is occupied by the nuclei of the tegmentum. These nuclei, of which only the inferior cen-tral tegmental nucleus (B25) is well defined,belong to the reticular formation. In the lateral field, the trigeminal complex has reached its widest expansion; lateral is the pontine nucleus of the trigeminal nerve (principal nucleus) (B26), medial to it the motor nucleus of the trigeminal nerve (B27),and dorsal the nucleus of the mesencephalic trigeminal root (B28). Afferent and efferent fibers unite to form the strong trunk emerg-ing at the anterior aspect of the pons.
The lateral lemniscus (AB17), the trapezoidbody (AB15), and the adjacent posterior nu-cleus of the trapezoid body (AB19) lie ven-trally to the trigeminal nuclei. The following ascending and descending pathways can be recognized: the posterior longitudinalfasciculus (AB12), the medial longitudinal fasciculus (AB11), and the central tegmental tract (AB13).
AB29 Pontine tegmentum.
AB30 Pontine bulb.