A 42-year-old woman undergoes surgical removal of a benign tumor in the pterygopalatine fossa. Several weeks later, she reports dryness of the left eye and decreased nasal secretions on the same side. On physical examination, taste on the anterior two thirds of the tongue is intact, facial movement is normal, and pupillary light reflexes are normal bilaterally.
Damage to which of the following structures most likely explains her symptoms?
The correct answer is:
C) Pterygopalatine ganglion
The pterygopalatine ganglion contains postganglionic parasympathetic neurons that supply the lacrimal gland and glands of the nasal cavity, palate, and pharynx. Preganglionic parasympathetic fibers originate from the facial nerve, travel through the greater petrosal nerve and nerve of the pterygoid canal, and synapse in the pterygopalatine ganglion. Postganglionic fibers then distribute to target glands by traveling with branches of the maxillary division of the trigeminal nerve and, for lacrimation, ultimately with the lacrimal branch of the ophthalmic division. Injury to this ganglion can therefore cause ipsilateral dry eye and decreased nasal secretions without necessarily impairing facial expression, taste, or pupillary reflexes.
Answer choice A: Ciliary ganglion, is incorrect. The ciliary ganglion receives preganglionic parasympathetic fibers from the oculomotor nerve and supplies the sphincter pupillae and ciliary muscle. Injury would impair pupillary constriction and accommodation rather than causing decreased lacrimation and nasal secretions.
Answer choice B: Otic ganglion, is incorrect. The otic ganglion receives preganglionic parasympathetic fibers from the glossopharyngeal nerve via the lesser petrosal nerve. Postganglionic fibers travel with the auriculotemporal nerve to the parotid gland, so injury would decrease parotid salivation rather than lacrimation or nasal gland secretion.
Answer choice D: Submandibular ganglion, is incorrect. The submandibular ganglion receives preganglionic parasympathetic fibers from the facial nerve through the chorda tympani and lingual nerve. It supplies the submandibular and sublingual glands, so injury would reduce salivation from those glands rather than causing dry eye and decreased nasal secretions.
Answer choice E: Vagus nerve, is incorrect. The vagus nerve provides parasympathetic innervation to thoracic and abdominal viscera through the proximal two thirds of the transverse colon. It does not provide parasympathetic secretomotor innervation to the lacrimal gland or nasal mucosa.
Key Learning Point
The pterygopalatine ganglion receives facial nerve preganglionic parasympathetic fibers and provides postganglionic secretomotor innervation to the lacrimal gland and nasal mucosal glands.
