Anatomic Moment: Osseous Anatomy of the Pterygopalatine Fossa

The pterygopalatine fossa (PPF) represents a major pathway of spread of malignancy and infection from the head and neck into the skull base. The ability to precisely locate tumor and infection on CT and MR imaging studies is crucial for performing biopsies and planning treatment. Determining the exact margins of the PPF is problematic, because they are not strictly defined even in the anatomic literature. The obliquely oriented upper part of the perpendicular plate of the palatine bone and the pterygoid process form a small pyramidalshaped fossa that probably was called the PPF because it contains the pterygopalatine ganglion (1) (Fig 1B and C). However, axial CT studies define a larger fossa, which incorporates the pyramidal-shaped fossa and has its posterolateral margin at the lateral edges of the base of the pterygoid process and the fused pterygoid plates (Fig 1C and D). By conventional usage and in this article, this larger fossa is designated the PPF (2). The PPF is bounded posteriorly by the fused pterygoid plates and the base (root) of the sphenoid bone, medially and more superiorly anteromedially by the palatine bone, and anteriorly by the maxillary bone (2–10) (Figs 2–5). When viewed laterally, the PPF appears as a narrow and inferiorly tapering space contiguous with the more anteriorly positioned inferior orbital fissure and formed by the gap between the curving margins of the maxillary and sphenoid bones (Fig 2A and C). This gap is bridged inferiorly and medially by the palatine bone. The palatine bone has a unique configuration made up of different parts that enable it to fuse anteriorly with the maxillary bone and posteriorly and superiorly with the sphenoid bone. The palatine bone has a shape like a right angle when viewed frontally, owing to its horizontal and perpendicular plates (Fig 4B). The horizontal plates of each palatine bone unite in the midline to form the posterior third of the hard palate, which fuses with the palatine processes of the maxillary bones to form the complete hard palate (Fig 6C). The perpendicular plate fuses anteriorly with the rough posterior surface of the medial wall of the maxillary bone, thus covering part of the maxillary hiatus of the maxillary sinus. Posteriorly, the perpen-