The pterygopalatine (sphenopalatine) ganglion is one of four small parasympathetic ganglia found in the head. It resides in the pterygopalatine fossa, which is located in the superior pterygomaxillary fissure, in the anterosuperior part of the infratemporal fossa (medial to the zygomatic arch and the coronoid process of the mandible). Although it is described as being a parasympathetic ganglion, it also carries sympathetic and sensory fibers to the nasal, oral and pharyngeal regions of the head. This article will focus on the formation of the pterygopalatine ganglion, the structures it innervates and associated pathologies.
The body of the ganglion rests in the pterygopalatine fossa. The pterygopalatine fossa is a depression that lies within the pterygomaxillary fissure, inferior to the sphenopalatine foramen. This fissure is a natural furrow that is formed between the posterosuperior border of the maxilla and the anterosuperior border of the pterygoid plates. Superiorly, the fossa is bordered by the base of the sphenoid bone. Medially, the perpendicular plate of the palatine bone and part of the lateral nasal wall forms its border. Laterally, the fossa is enclosed by the coronoid process of the mandibular ramus. Inferomedially, the pterygopalatine fossa is completed by the pyramid-like process of the palatine bone that articulates with the maxilla and lateral pterygoid plate.
The cell bodies of the parasympathetic fibers of the pterygopalatine ganglion are located in the superior salivatory nucleus of the tractus solitarius in the dorsal pons of the brain stem. The cell bodies for the taste fibers that accompany the parasympathetic fibers, as well as those of the motor fibers of the chorda tympani, are also located in this region. The preganglionic parasympathetic, and some taste, fibers travel through the geniculum by way of the nervous intermedius branch of the facial nerve (CN VII). It leaves the geniculum through the internal acoustic meatus. Here, the motor and other taste fibers that formed the motor component of CN VII diverge as the chorda tympani. The chorda tympani will then travel through the stylomastoid foramen, after which it will supply the anterior tongue, salivary glands and the muscles of the face. The nervous intermedius branch continues as the greater (superficial) petrosal nerve.
Sympathetic fibers from T1 – T3 synapse at the superior cervical ganglion. Postganglionic sympathetic fibers travel through the internal carotid plexus and join the greater petrosal nerve by way of the lesser (deep) petrosal nerve in foramen lacerum. Together, these nerves become the (Vidian) nerve of the pterygoid canal. The secretomotor and vasoconstrictor fibers then enter the pterygopalatine ganglion in the pterygopalatine fossa. The ganglion is suspended – and joined – by general sensory fibers from the maxillary branch of the trigeminal nerve (CN V2), which travels superior to the ganglion by way of foramen rotundum.
Branches & Supply
The branches of the pterygopalatine ganglion carry parasympathetic, sympathetic, and general sensory fibers to several locations by way of its six branches. The mixed nerve fibers travel through the cranial ostia to innervate the nose, palate, and nasopharynx.
The nasal septum and anterior hard palate are innervated by the nasopalatine and other nasociliary branches of the medial posterior superior nasal nerves, which are branches of the pharyngeal nerve. The nerves enter the nose by way of the sphenopalatine foramen and travels across the roof of the nose. The larger nasopalatine nerve gains access distally to the hard palate via the incisive canal. The lateral posterior superior nasal nerves are named for the region of the lateral nasal wall that they innervate. It also enters the nasal cavity by way of the sphenopalatine foramen. There are also inferior lateral posterior nasal nerves that supply the area for which they are named.
The greater palatine nerves and two lesser palatine nerves each pass through their respective foramen in the perpendicular plate of the palatine bone and maxilla as they travel inferiorly. The former nerve provides mixed innervation to the mucous membrane of the hard palate, lateral posteroinferior nasal wall and the medial wall of the maxillary sinus. The latter nerves carry taste fibers from the greater petrosal nerve to the mucosa of the palatine tonsils and the soft palate. Via the palatovaginal canal, the pharyngeal nerve supplies the mucosa of the nasopharynx (specifically by the medial posterior superior nasal nerves).
Some sympathetic and parasympathetic fibers travel superiorly to enter CN V2. These fibers travel along the branches of the maxillary nerve as part of its infraorbital and posterior superior alveolar nerves. The infraorbital nerves supplies the orbital periosteum along the region’s floor as well as the mucosae of the sphenoidal and ethmoidal sinuses after entering the area via the infraorbital fossa. The posterior superior alveolar nerves supplies the maxillary sinus, upper molar teeth and their adjacent gingiva in the oral vestibule.
Nasopharyngeal angiofibromas are benign, vascular lesions that arise in the lateral aspect of the posterior wall of the nasal cavity, near the pterygopalatine fossa. These lesions are found only in pre-pubescent and adolescent males of with Celto-Germanic traits. Genetic and hormonal aetiologies have been postulated as causative factors contributing to its pathogenesis. Larger bi-lobular tumors grow into that can occupy the pterygopalatine fossa and the nasopharynx. The growth of the tumor can compress the pterygopalatine ganglion, resulted in reduced innervation to the respective areas of the nose, pharynx and hard palate. The tumors, though highly recurrent, are treated surgically.
Pterygopalatine ganglion & Headaches
Stimulation of the parasympathetic fibers of the pterygopalatine ganglion has been implicated in primary headache disorders such as cluster headaches (intense, nocturnal, unilateral periorbital pain that disrupts sleep that remits every few weeks or months) and migraines (immense pulsating regional head pain associated with photosensitivity, audio sensitivity, nausea, and vomiting). Abscission or blockade of the ganglion has been successfully used to treat these pathologies.