Pterygopalatine Fossa: Anatomy, Connections, and Surgery

The pterygopalatine fossa is a small, fat-filled space tucked deep behind the cheekbone, roughly at the level of the back of your nose. Despite being barely a centimeter wide in most people, it functions as one of the body’s most densely connected anatomical crossroads, linking the eye socket, the nasal cavity, the mouth, the middle of the skull, and the side of the face through a network of bony openings. Nerves, arteries, and autonomic fibers all pass through this tiny corridor, which is why it shows up in conversations about everything from severe nosebleeds to cluster headaches to cancer spread.

Where It Sits and What Surrounds It

The pterygopalatine fossa (often shortened to PPF) is shaped roughly like an inverted pyramid. Its walls are formed by several bones: the back wall of the maxillary sinus in front, the pterygoid plates of the sphenoid bone behind, and the palatine bone wedged between them. The roof is the underside of the sphenoid bone. It is not a space you can see or feel from the outside; it sits behind the upper jaw and below the eye socket, embedded in the architecture of the midface. On imaging, the fossa appears as a small pocket of fat surrounded by bone, which is useful because pathology that replaces that fat stands out clearly on CT or MRI scans.

What makes the PPF unusual is not its size but the sheer number of passageways that open into it. Laterally, the pterygomaxillary fissure connects it to the infratemporal fossa, the space behind the cheekbone where the chewing muscles sit. The inferior orbital fissure opens upward into the floor of the eye socket. The foramen rotundum, at the back wall, carries the maxillary nerve from the middle cranial fossa directly into the PPF. The sphenopalatine foramen leads medially into the nasal cavity. And the Vidian canal tunnels posterolaterally through the sphenoid bone toward the foramen lacerum at the skull base. Below, the greater and lesser palatine canals descend into the roof of the mouth.¹ Each of these openings carries nerves, blood vessels, or both, turning a space the size of a fingertip into a junction box that connects widely separated regions of the head.

The Blood Supply Running Through It

The dominant artery in the PPF is the third segment of the maxillary artery, the terminal portion of the main blood supply to the deep face. As this artery enters the fossa through the pterygomaxillary fissure, it fans out into several named branches. Cadaver studies show a fairly consistent pattern: the posterior superior alveolar artery branches off first (supplying the upper back teeth), followed by the infraorbital artery (heading up toward the eye socket), the artery of the pterygoid canal (traveling backward along the Vidian canal), the descending palatine artery (dropping down to the hard palate), and the sphenopalatine artery (passing medially into the nose). Roughly 86% of specimens follow this branching order.²

Still, the number of arterial branches visible at any given cross-section of the fossa varies. A radioanatomical study using CT angiography found the median number of arteries at a critical reference level was two, but the range stretched from one to four. The largest branch had a median diameter just under 2 mm. In about 41% of cases the biggest artery sat directly against the posterior wall of the maxillary sinus, and in a small number of cases the bone of that wall was notably thin.³ That matters to surgeons: any operation entering the maxillary sinus from behind risks encountering an artery pressed right up against the bone.

The branching pattern itself is not always textbook. Studies classifying the artery’s course through the fossa have identified several distinct configurations, described by their shape on dissection. The most common is an “intermediate” type where branches separate gradually, but Y-shaped, T-shaped, and M-shaped patterns also appear, each placing the arterial branches in slightly different positions relative to surrounding nerves and bone.⁴ Surgeons working in this space need to expect variation rather than count on a single reliable layout.

The Sphenopalatine Ganglion and Headache

Nestled inside the PPF is the sphenopalatine ganglion (SPG), a small cluster of nerve cells that serves as a relay station for the parasympathetic nervous system in the head. Parasympathetic fibers traveling through the Vidian nerve synapse here before fanning out to the lacrimal gland, the nasal mucosa, and the palate, controlling things like tear production, nasal secretions, and blood flow to the lining of the nose. The ganglion also has connections to the trigeminal nerve’s maxillary branch, which handles sensation across the midface.⁵

This dual role in both autonomic function and pain signaling has made the SPG a target for headache treatment for over a century. In cluster headache, severe one-sided attacks are accompanied by autonomic symptoms like tearing, nasal congestion, and facial sweating on the same side. These features implicate the trigeminal-autonomic reflex, a loop in which trigeminal pain signals trigger parasympathetic outflow through the SPG. Blocking or stimulating the ganglion can interrupt that loop. An early clinical trial of electrical SPG stimulation showed complete headache resolution in 11 out of 18 treated attacks, with autonomic symptoms clearing in every responder, often within minutes.⁶

Larger studies have built on those results. In a placebo-controlled trial of 28 patients with refractory chronic cluster headache, full stimulation of the SPG resolved pain in about 67% of treated attacks, compared with 7% for sham stimulation. Longer follow-up at 24 months confirmed that the technique worked as an abortive treatment, and roughly a third of patients also saw their attack frequency drop by more than half, suggesting a preventive effect from repeated use.⁷ SPG blockade using local anesthetic has also shown benefit for migraines and other headache types that involve the trigeminal-autonomic pathway.⁸

How Tumors Exploit the Fossa’s Connections

The same rich network of nerve pathways that makes the PPF useful for pain management also makes it a highway for cancer. Tumors of the palate, sinuses, and face can travel along nerves, a behavior called perineural spread, to reach areas far removed from where they started. The maxillary nerve is a particularly common route. Because it runs from the middle cranial fossa through the foramen rotundum and into the PPF, a tumor that reaches the fossa can follow it in either direction: backward toward the brain or forward toward the face and orbit. On CT, the telltale sign is obliteration of the normal fat in the fossa, replaced by soft tissue.⁹

Adenoid cystic carcinoma, a cancer with a notorious affinity for nerves, illustrates this pattern well. A documented case of adenoid cystic carcinoma arising from the cheek lining traveled along the posterior superior alveolar nerve into the PPF, then spread simultaneously forward into the orbit and backward along the maxillary nerve to the cavernous sinus beside the brain. MRI showed a continuous trail of tumor, and PET-CT confirmed that the tissue along both directions was metabolically active.¹⁰ The PPF functioned as the hub where the tumor’s path split, which has real implications for how radiation treatment fields are drawn and how surveillance imaging is planned.

Not all PPF pathology is malignant. Juvenile nasopharyngeal angiofibroma, a benign but aggressive vascular tumor found almost exclusively in adolescent males, frequently extends laterally into the PPF. In one surgical series, 97% of patients had tumor extension into the fossa, and over half had further spread into the infratemporal fossa beyond it.¹¹ Infections can use the same routes. A case report documented an upper molar tooth infection spreading through the PPF and infratemporal fossa, then upward through the inferior orbital fissure into the orbit, causing an orbital abscess.¹² The fossa’s connections do not distinguish between what is supposed to travel through them and what is not.

Treating Severe Nosebleeds

The sphenopalatine artery, one of the maxillary artery’s terminal branches, is the dominant blood supply to the back of the nose. When a posterior nosebleed will not stop with packing or cauterization applied from the front, surgeons can go after this artery endoscopically by entering the nasal cavity, identifying the sphenopalatine foramen on the lateral nasal wall, and either clipping or cauterizing the artery as it exits the PPF into the nose.

The procedure, called endoscopic sphenopalatine artery ligation, has become a standard tool for refractory posterior epistaxis. A scoping review pooling data from 16 studies and 454 patients found rebleeding in about 12% and complications in only 3%.¹³ Individual series report success rates in the range of 90% to 95%.¹⁴¹⁵ The technique works even in challenging situations like hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu disease) and pregnancy-related nosebleeds, where systemic treatments are limited.

Vidian Neurectomy for Stubborn Rhinitis

If the sphenopalatine ganglion is the relay station for parasympathetic nerve signals to the nose, the Vidian nerve is the main cable feeding into it. Cutting the Vidian nerve, a procedure called vidian neurectomy, disrupts the parasympathetic drive that causes excessive nasal secretions, congestion, and swelling. It was first described decades ago for intractable vasomotor and allergic rhinitis but fell out of favor because open surgical approaches were difficult and the results were inconsistent. Endoscopic techniques revived interest.

Long-term data on endoscopic vidian neurectomy show sustained benefit. One study followed patients for up to seven years and found that improvements in nasal obstruction and rhinorrhea persisted throughout the follow-up period, with symptom scores dropping dramatically from baseline.¹⁶ Another study comparing vidian neurectomy with standard rhinitis surgery (septoplasty and turbinate reduction) found that the neurectomy had longer-lasting efficacy for allergic rhinitis, while the structural procedures provided only short-term improvement.¹⁷

The trade-off is dry eyes. The parasympathetic fibers that the Vidian nerve carries also supply the lacrimal gland. Cutting the whole nerve can reduce tear production. In a pilot study, about 17% of patients met dry eye criteria one month after surgery, though symptoms resolved within a few months and no one qualified as having dry eye at six months. However, a measurable reduction in tear production persisted.¹⁸ A newer approach that cuts only the nasal branches of the Vidian nerve rather than the whole trunk may reduce this risk. In a comparative study, full vidian neurectomy caused persistent eye dryness in about 8.5% of patients at two years, while the selective branch technique dropped that to around 5%, with all cases resolving within the first month.¹⁹

Dental Nerve Blocks Through the Fossa

Dentists occasionally need to numb an entire side of the upper jaw at once, and one way to do that is by sending local anesthetic up through the greater palatine canal into the PPF, where the maxillary nerve sits. The technique delivers a single injection to the roof of the mouth that anesthetizes the nerve before it branches. It provides profound numbness across the back half of the upper jaw. Randomized trials comparing the greater palatine canal approach with the alternative high-tuberosity approach (injecting behind the last upper molar) have found both achieve pulpal anesthesia in 95% to 100% of first and second molars. The success rate drops to about 70% to 80% for second premolars, and neither technique reliably numbs the front teeth or first premolars.²⁰

The technique is underused in general dental practice, largely because practitioners feel unfamiliar with the anatomy and worry about complications from advancing a needle into a deep bony canal.²¹ In experienced hands, complication rates are very low. Comparative studies have found no significant differences in patient-reported pain or unpleasant sensations between the greater palatine canal and high-tuberosity techniques, and no anesthesia-related complications in either group.²²

Getting Into the Fossa Surgically

For decades, reaching the PPF surgically meant aggressive open approaches: swinging the cheek open, removing portions of the upper jaw, or entering through a large incision below the eye. These routes worked, but they left patients with significant morbidity, visible scars, and long recovery times. Endoscopic endonasal techniques changed that. By entering through the nostril, surgeons can pass through the back wall of the maxillary sinus and into the PPF with minimal disruption. The endoscopic transmaxillary transpterygoid approach provides access not only to the PPF itself but also to the infratemporal fossa, the petrous apex of the temporal bone, and Meckel’s cave, all through the nose.²³

A newer alternative goes through the eye socket instead of the nose. A transorbital endoscopic approach uses a small incision hidden in the eyelid crease and passes instruments along the floor of the orbit to reach the PPF from above. Case reports describe this route as less morbid than traditional open surgery while still providing adequate visualization and working room.²⁴ The choice between endonasal and transorbital approaches depends on what the surgeon needs to reach and how far the pathology extends.

How the Fossa Takes Shape Before Birth

The PPF does not exist as a discrete space in the early embryo. At around six weeks of development, the structures that will become the sphenopalatine and otic ganglia are still part of a single undifferentiated cell mass, continuous with the precursor of the sphenoid bone. By seven weeks, the two ganglia become recognizable as separate clusters, but they remain connected. The growing ala temporalis, a cartilaginous precursor of part of the sphenoid, gradually pushes between them. By the ninth week, the cartilage is well defined and the ganglia have begun to separate. A nerve called the nervus sphenoidalis forms secondarily to maintain communication between the two after the bone physically divides them. By fifteen weeks, the separation is complete, and the PPF has started to take its adult form as the surrounding bones ossify.²⁵ The fossa’s final shape and dimensions are then sculpted by the growth of the maxilla, palatine bone, and pterygoid plates throughout childhood and adolescence, which is one reason pediatric skull-base surgery in this region can be tricky: the landmarks are not where they will end up in an adult.