Surgical anatomy of pterygopalatine fossa

Pterygopalatine fossa is a small space between the posterior surface of the Maxilla and the Pterygoid process of the Sphenoid bone. Its an inverted ‘tear-drop’ shaped space between bones on the lateral side of the skull immediately posterior to the maxilla. It is wider superiorly, becomes narrowed inferiorly, and ends in the pterygopalatine canal (greater palatine canal).^​1,2​

Pterygopalatine fossa communicates with both the nasal and oral cavities, the infratemporal fossa, the orbit, the pharynx, and the middle cranial fossa through 8 foramina. Three-dimensional understanding of this space is important for the rhinologist and skull-base surgeon for both the control of epistaxis and the removal of skull base lesions. The pterygopalatine space technique is utilized to deal with lesions in the spaces posterior to the maxillary sinus, including the pterygopalatine space and lateral sphenoid recess. Pathologic processes in this space are uncommon, with the most typical disease processes being juvenile nasopharyngeal angiofibroma, neurogenic tumors, a perineural extension of sinonasal malignancy, and meningoencephaloceles.^​3,4​

BOUNDARIES of Pterygopalatine fossa

• It can be considered as a pyramidal space:
• ANTERIOR: posterior surface of maxilla below floor of orbit
• POSTERIOR: lateral pterygoid plate and a part of medial plate also
• MEDIAL: perpendicular plate of palate, The sphenopalatine foramen is located on the upper aspect of the perpendicular
plate.
• LATERAL: pterygomaxillary fissure separates it from infratemporal fossa.
• SUPERIOR: undersurface of the sphenoid bone and orbital process of the palatine bone
• INFERIOR: ABSENT (the post wall meets the ant wall and between them is greater palatine canal)

Pterygopalatine fossa communications^​2,3​ –

1) the middle cranial fossa
2) infratemporal fossa
3) floor of the orbit
4) lateral wall of the nasal cavity
5) oropharynx
6) roof of the oral cavity

Openings of the Pterygopalatine Fossa

Eight openings

1. Inferior orbital fissure
2. Pterygomaxillary fissure
3. Sphenopalatine foramen
4. Foramen rotundum
5. Pterygoid (vidian) canal
6. Pharyngeal canal
7. Greater pterygopalatine canal
8. Lesser pterygopalatine canal

Superiorly

Inferior Orbital Fissure
• Lies between the pterygomaxillary fossa and the orbit.
• Transmits –
Maxillary nerve of eN v (trigeminal nerve)
Zygomatic nerve
Infraorbital vessels
Veins to the pterygoid plexus
Ophthalmic vein

Laterally

Pterygomaxillary Fissure
• Lies between the pterygomaxillary fossa and the infratemporal fossa.
• Transmits the maxillary vessels.

Medially

Sphenopalatine Foramen
• Lies between the pterygomaxillary fossa and the nasal cavity.
• Is located near the posterior end of the middle turbinate.
• Transmits – Sphenopalatine vessels
Nerve supplying the septum and the lateral wall of the nose

Posteriorly

Foramen Rotundum – Transmits the maxillary nerve from the middle cranial fossa to the pterygomaxillary
fossa.

Pterygoid (Vidian) Canal
Lies medial and inferior to the foramen rotundum.
A 7- to IO-mm wide vertical crest of bone separates it from the foramen rotundum.
Transmits the vidian nerve in its route to the sphenopalatine ganglion.

Pharyngeal Canal
Opens into the lateral aspect of the roof of the choanae.
Transmits –
Pharyngeal branches of the sphenopalatine ganglion
Pharyngeal branches of the internal maxillary artery to the nasopharynx

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Contents of Pterygopalatine fossa^​2​ –

Internal maxillary artery
Foramen rotundum — maxillary division of trigeminal
Sphenopalatine ganglion and nerve
Vidian nerve – formed by contributions of lesser petrosal and deep petrosal nerves, passes through pterygoid canal to synapse in pterygopalatine ganglion, provides autonomic innervation to nasal cavity, nasopharynx and lacrimal glands

While not serving a particular function, this space enables the transit of several crucial structures through various foramina. The foramen rotundum connects the PPF to the middle cranial fossa. The pterygoid canal, also known as the vidian canal, links the PPF to the middle cranial fossa. The palatovaginal canal connects the PPF with the nasal cavity and nasopharynx. Anteriorly, the inferior orbital fissure connects the PPF to the orbit. Medially, the sphenopalatine foramen offers access to the nasal cavity Laterally, the pterygomaxillary fissure links the PPF to the infratemporal fossa. Lastly, inferiorly, the greater palatine canal connects the PPF to the mouth.

The nervous and vascular structures are situated anteroinferiorly and posterosuperior, respectively within the pterygopalatine fossa. The sphenopalatine artery, which is a branch of the internal maxillary artery, is found between the sphenoid and palatine bones and goes into the nasal cavity at the sphenopalatine foramen. The maxillary division of the vidian nerve and the trigeminal nerve go into from the posterior wall of the PPF.

The maxillary division of the trigeminal nerve moves through the foramen rotundum. The vidian nerve traverses through the pterygoid canal. They come together to form the pterygopalatine ganglion and after that branch into the infraorbital nerve and the greater and lesser palatine nerves. The infraorbital nerve exits through the inferior orbital fissure and the greater and lesser palatine nerves go through the greater and lesser palatine foramina respectively.

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The primary site of disease is managed initially, and after that the margins are cleared in the PPF. A medial maxillectomy is performed at first with inferior and middle turbinate removal. This enables total visualization of the maxillary sinus. After creating the transmaxillary corridor, the trans pterygopalatine fossa approach proceeds by elevating the mucosa that overlies the medial pterygoid wedge to expose the sphenopalatine artery. The sphenopalatine artery is then ligated, and the associated mucosa is resected down off of the medial pterygoid plate.

With this down, the bone of the posterior maxillary wall is removed, and the coming down palatine artery is cauterized and ligated. It must be noted that sacrifice of the palatine artery is not always necessary for access and tumor removal within the PPF, however it can be taken to get to the more lateral and deeper infratemporal fossa. The Vidian nerve is then encountered and typically sacrificed. With this done and the orbital process of the palatine bone drilled away, the whole fossa is mobile and can be resected or pushed laterally to access to the infratemporal fossa and pterygoid musculature.

Approaches to Pterygopalatine Fossa^​3–5​

-TRANS ANTRAL APPROACH
-TRANS NASAL APPROACH
-TRANS PALATAL APPROACH

These will be discussed in next question, meanwhile you can refer the citations.

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References –

1. 1.

   Derinkuyu B, Boyunaga O, Oztunali C, Alimli A, Ucar M. Pterygopalatine Fossa: Not a Mystery! Can Assoc Radiol J. 2017;68(2):122-130. doi:10.1016/j.carj.2016.08.001
2. 2.

   Cappello Z, Potts K. statpearls. April 2019. http://www.ncbi.nlm.nih.gov/books/NBK513269/.
3. 3.

   Chung H, Moon I, Cho H, et al. Analysis of Surgical Approaches to Skull Base Tumors Involving the Pterygopalatine and Infratemporal Fossa. J Craniofac Surg. 2019;30(2):589-595. doi:10.1097/SCS.0000000000005108
4. 4.

   Yang L, Hu L, Zhao W, Zhang H, Liu Q, Wang D. Endoscopic endonasal approach for trigeminal schwannomas: our experience of 39 patients in 10 years. Eur Arch Otorhinolaryngol. 2018;275(3):735-741. doi:10.1007/s00405-018-4871-1
5. 5.

   Xue Z, Liu J, Bi Z, et al. Evolution of transmaxillary approach to tumors in pterygopalatine fossa and infratemporal fossa: anatomic simulation and clinical practice. Chin Med J (Engl). 2019;132(7):798-804. doi:10.1097/CM9.0000000000000142