Pterygopalatine ganglion

The pterygopalatine ganglion is a parasympathetic ganglion which is situated inside the pterygopalatine fossa. It is formed by cell bodies of post-ganglionic parasympathetic neurons.

The pterygopalatine ganglion gives of a number of branches, including the:

1. Palatine nerves (to hard and soft palate),

2. Pharyngeal nerves (to pharyngeal mucosa and glands),

3. Nasal and nasopalatine nerves (to mucosa of lateral and medial walls and roof of nasal cavity),

4. Orbital nerves (to orbital periosteum).

5. The pterygopalatine ganglion is also intimately related to the maxillary (V2) nerve, which hovers over it inside the pterygopalatine fossa. Here, two short ganglionic nerves serve as communicating bridges between the ganglion and the maxillary nerve. This anatomical link widens the accessibility range of neurons from the pterygopalatine ganglion for innervating additional parts of head and neck region, via branches of maxillary nerve.

The pterygopalatine ganglion receives three important roots to it, namely the sensory, parasympathetic and sympathetic roots.

The sensory root comprises of general somatic sensory neurons which transmit general sensations from areas including the face, oral cavity (mucosa, gums, uvula, soft and hard palate), nasal mucosa, tonsils, pharynx and orbital periosteum. These sensory neurons reach out to the pterygopalatine ganglion via its branches (1 to 4; enlisted above). These neurons traverse un-relayed through the ganglion to enter maxillary nerve via the ganglionic branches and end up synapsing inside the trigeminal sensory ganglion.

The parasympathetic root of pterygopalatine ganglion comprises of preganglionic parasympathetic fibers which arise from the brainstem (superior salivatory nucleus of facial nerve) and travel through the greater petrosal nerve. While, the sympathetic root comprises of postganglionic sympathetic fibers, which come off from the internal carotid artery plexus, as the deep petrosal nerve. The two petrosal nerves merge with each other to form the nerve of pterygoid canal (a.k.a. the Vidian nerve). The latter enters the pterygopalatine fossa to communicate both parasympathetic and sympathetic roots to the pterygopalatine ganglion. Amongst these two roots, the pre-ganglionic parasympathetic neurons synapse with the postganglionic neuronal cell bodies inside the ganglion, whereas the sympathetic neurons–already postganglionic by this time–pass un-relayed through the pterygopalatine ganglion.

Like the sensory root, both postganglionic parasympathetic and sympathetic neurons use the ‘ganglionic branches’ as portals, to enter the maxillary nerve. The autonomic neurons, subsequently travel through the maxillary and ophthalmic divisions of the trigeminal nerve to provide secretomotor signals to the lacrimal gland, mucous membranes of the nasal cavity, nasopharynx, oropharynx, upper oral cavity and some meningeal and cerebral blood vessels.