M01.02.005 The Pterygopalatine Fossa

The pterygopalatine fossa is a bilateral, cone-shaped depression extending from the infratemporal fossa to the nasal cavity via the sphenopalatine foramen. It is located between the maxilla, sphenoid, and palatine bones and communicates with several regions of the skull and facial skeleton via numerous canals and foramina. Its small volume combined with the numerous structures that pass through makes this a complex region for anatomy students.

Borders of the Pterygopalatine Fossa

The pterygopalatine fossa is bordered by:

• Anterior: Posterior wall of the maxillary sinus.
• Posterior: Pterygoid process of the sphenoid bone.
• Inferior: Palatine bone and palatine canals.
• Superior: Inferior orbital fissure of the eye.
• Medial: Perpendicular plate of the palatine bone.
• Lateral: Pterygomaxillary fissure.

Contents of the Pterygopalatine Fossa

The pterygopalatine fossa contains important neurovascular structures, including the maxillary nerve and its branches, the pterygopalatine ganglion, and the maxillary artery and its branches.

Maxillary Nerve (CNV2)

The maxillary nerve, the second branch of the trigeminal nerve (CNV2), passes from the middle cranial fossa into the pterygopalatine fossa through the foramen rotundum. It gives off numerous branches within the fossa, including the infraorbital, zygomatic, nasopalatine, superior alveolar, pharyngeal, and greater and lesser palatine nerves. The maxillary nerve also communicates with the pterygopalatine ganglion via the pterygopalatine nerves.

Pterygopalatine Ganglion

The pterygopalatine ganglion is the largest parasympathetic ganglion associated with branches of the maxillary nerve. It is predominantly innervated by the greater petrosal branch of the facial nerve (CNVII). Postsynaptic parasympathetic fibers from the ganglion provide secretomotor innervation to the lacrimal gland and mucosal glands of the oral cavity, nose, and pharynx.

Maxillary Artery

The maxillary artery, a terminal branch of the external carotid artery, gives rise to several branches within the pterygopalatine fossa. These include the sphenopalatine artery (to the nasal cavity), descending palatine artery (to the hard and soft palates), infraorbital artery (to the lacrimal gland and some eye muscles), and posterior superior alveolar artery (to the teeth and gingiva).

Foramina and Canals

The pterygopalatine fossa is connected to various regions of the skull through seven openings that transmit blood vessels and nerves:

1. Pterygomaxillary Fissure: Connects the infratemporal fossa with the pterygopalatine fossa, transmitting the posterior superior alveolar nerve and the terminal part of the maxillary artery.
2. Foramen Rotundum: Connects the pterygopalatine fossa to the middle cranial fossa, transmitting the maxillary nerve.
3. Pterygoid Canal: Runs from the middle cranial fossa and through the medial pterygoid plate, carrying the nerve, artery, and vein of the pterygoid canal.
4. Pharyngeal Canal: Communicates with the nasopharynx, carrying the pharyngeal branches of the maxillary nerve and artery.
5. Inferior Orbital Fissure: Forms the superior boundary of the pterygopalatine fossa, transmitting the zygomatic branch of the maxillary nerve and the infraorbital artery and vein.
6. Greater Palatine Canal: Lies in the inferior boundary, transmitting the descending palatine artery and vein, and the greater and lesser palatine nerves.
7. Sphenopalatine Foramen: Connects the pterygopalatine fossa to the nasal cavity, transmitting the sphenopalatine artery and vein, and the nasopalatine nerve.

Clinical Relevance

Maxillary Nerve Block

For extensive dental surgery, a maxillary nerve block might be necessary. The maxillary nerve in the pterygopalatine fossa is often approached intraorally via the greater palatine canal.

Chronic Epistaxis

The sphenopalatine artery, often referred to as the artery of epistaxis, can be a source of chronic nosebleeds. In such cases, the artery can be ligated surgically via the maxillary sinus to control bleeding.