Nerve
Greater petrosal nerve
Facial-nerve fibers for tears and mucous secretion
High-yield
Greater petrosal carries preganglionic parasympathetic fibers; deep petrosal carries postganglionic sympathetic fibers. Their shared route is the nerve of the pterygoid canal.
Overview
The greater petrosal nerve separates from CN VII near the geniculate ganglion and crosses the floor of the middle cranial fossa. Near the foramen-lacerum region it joins the sympathetic deep petrosal nerve. Together they form the nerve of the pterygoid canal, which enters the pterygopalatine fossa. Parasympathetic fibers then synapse in the pterygopalatine ganglion; sympathetic fibers pass through it.
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Reference facts
- Origin
- A branch of CN VII at the geniculate region; its parasympathetic cell bodies lie in the superior salivatory/lacrimal region, not in the sensory ganglion
- Course
- Exits the greater-petrosal hiatus, runs beneath the dura near the trigeminal ganglion and proceeds toward foramen lacerum, joining deep petrosal fibers before entering the pterygoid canal
- Motor
- Preganglionic parasympathetic fibers relay in the pterygopalatine ganglion; outgoing fibers reach lacrimal and nasal, palatal and nasopharyngeal mucous glands
- Sensory
- Carries palatal taste afferents toward the geniculate ganglion and brainstem taste pathway
Clinical correlation
Injury to this pathway can reduce tearing and mucous secretion. A proximal facial-nerve lesion may combine these effects with facial weakness, but isolated greater-petrosal injury need not paralyze the face. Apparent eye dryness also depends on eyelid closure and the ocular surface.
Frequently asked questions
Where does the greater petrosal nerve arise?
A branch of CN VII at the geniculate region; its parasympathetic cell bodies lie in the superior salivatory/lacrimal region, not in the sensory ganglion.
What muscles does the greater petrosal nerve supply?
Preganglionic parasympathetic fibers relay in the pterygopalatine ganglion; outgoing fibers reach lacrimal and nasal, palatal and nasopharyngeal mucous glands.
What is the sensory distribution of the greater petrosal nerve?
The greater petrosal nerve carries sensation from the carries palatal taste afferents toward the geniculate ganglion and brainstem taste pathway.
What is the course of the greater petrosal nerve?
Exits the greater-petrosal hiatus, runs beneath the dura near the trigeminal ganglion and proceeds toward foramen lacerum, joining deep petrosal fibers before entering the pterygoid canal.