Nerve
Lesser petrosal nerve
The otic-ganglion route for parotid secretion
High-yield
Parotid secretomotor route: inferior salivatory nucleus → CN IX → tympanic plexus → lesser petrosal nerve → otic ganglion → auriculotemporal nerve.
Overview
The lesser petrosal nerve carries parasympathetic fibers originating with CN IX from the tympanic plexus toward the otic ganglion. It reaches the middle cranial fossa from the temporal bone and crosses toward the skull base near foramen ovale. Its exit is variable: descriptions include foramen ovale, a separate canaliculus innominatus, foramen spinosum and the sphenopetrosal region.
Learning this group? Read How to memorize the cranial nerves.
Reference facts
- Origin
- Arises from the tympanic plexus, principally carrying CN IX parasympathetic fibers; communicating fibers from neighboring nerves can contribute
- Course
- Traverses the middle-fossa floor and leaves through a variable skull-base route to reach the otic ganglion; foramen ovale is one recognized route
- Motor
- Preganglionic parasympathetic fibers from the inferior salivatory nucleus; postganglionic fibers then travel separately with the auriculotemporal nerve to the parotid
- Sensory
- No standard independent skin sensory territory is assigned to it. The parent tympanic plexus also carries middle-ear sensory fibers, and communicating contributions make the small nerve's composition variable
Clinical correlation
Variation in this small nerve's course matters when interpreting skull-base lesions or operating nearby. Injury can interrupt parasympathetic input to the parotid. The conventional foramen-ovale route is a teaching pattern, not a dependable description of every individual.
Frequently asked questions
Where does the lesser petrosal nerve arise?
Arises from the tympanic plexus, principally carrying CN IX parasympathetic fibers; communicating fibers from neighboring nerves can contribute.
What muscles does the lesser petrosal nerve supply?
Preganglionic parasympathetic fibers from the inferior salivatory nucleus; postganglionic fibers then travel separately with the auriculotemporal nerve to the parotid.
What is the sensory distribution of the lesser petrosal nerve?
No standard independent skin sensory territory is assigned to it. The parent tympanic plexus also carries middle-ear sensory fibers, and communicating contributions make the small nerve's composition variable.
What is the course of the lesser petrosal nerve?
Traverses the middle-fossa floor and leaves through a variable skull-base route to reach the otic ganglion; foramen ovale is one recognized route.