Walsh & Hoyt: Parasympathetic Pathway for Lacrimation

The cell bodies of the preganglionic neurons responsible for parasympathetic lacrimal secretion are located in the lacrimal nucleus within the tegmental portion of the pons in a small area dorsal to the superior salivary nucleus. After traversing the facial nucleus, the preganglionic axons join the sensory root of the seventh nerve (the nervus intermedius) that emerges from the lateral portion of the pons between the facial and auditory nerves). The nervus intermedius passes through the cistern of the pontine angle and then joins with the rest of the facial nerve, occupying an anterior superior position within the combined nerve as it courses laterally. The surgical anatomy of the nervus intermedius is important because it can be injured during the resection of vestibular schwannomas and other procedures in this area. Symptoms of such injuries include crocodile tears (the gustolacrimal reflex), reduced or absent tear production, and taste abnormalities. These symptoms reflect the sensory and parasympathetic components of the nervus intermedius.