Foramen Rotundum Ct

Pterygopalatine Fossa and Pterygoid Process

On axial images the pterygopalatine fossa is a thin rectangular fat filled space between the pterygoid process of the sphenoid bone - posteriorly - and the perpendicular plate of the palatine bone - anteriorly, the latter being not separable on CT or MR from the posterior maxillary sinus wall, therefore appearing "fused" into a single bone structure (Fig. 2.20). On sagittal images the space progressively narrows downward where it connects to the pterygopalatine canal (Fig. 2.21).

The pterygopalatine fossa communicates with five different areas: the middle cranial fossa, through the pterygoid (vidian) canal and foramen rotundum/ca-nal; the orbit, through the inferior orbital fissure; the masticator space - or infratemporal fossa - through the pterygomaxillary fissure; the choana, through the sphenopalatine foramen; the oral cavity, through the greater and lesser palatine canals.

Within the pterygopalatine fossa are the pterygo-palatine ganglion, part of the maxillary nerve, terminal branches of the internal maxillary artery (the sphenopalatine artery) and fat.

On coronal planes, the pterygoid canal is lower and medial compared to the foramen rotundum, which is higher up, more lateral and larger. Moreover, the foramen rotundum may actually consist of a simple groove - rather than of a complete canal - running on the superior aspect of the pterygoid process (Fig. 2.22). On the axial plane, the pterygoid canal has a more triangular (or "trumpet-like") appearance, being larger at its anterior opening into the pterygo-palatine fossa. It communicates, posteriorly, with the foramen lacerum, ending in front of the petrous apex, whereas the foramen rotundum/canal reaches the fluid-content of the Meckel cave. Depending on the degree of sphenoid sinus pneumatization, the ptery-goid canal may be almost entirely within the bone, partially or completely surrounded by the sinus.

On coronal MR, the maxillary nerve may be clearly identified using VIBE sequences (Fig. 2.22c). A hy-pointense rounded structure is shown within the foramen, surrounded by homogeneous enhanced signal, probably due to tiny vessels running along the foramen and the nerve. Due to its smaller size, the pterygoid nerve is not usually demonstrated by this technique, only the enhanced vessels within the canal are detected.

The pterygopalatine fossa transmits the infraorbital nerve and artery to the orbit via the inferior orbital fissure. This fissure separates the orbital

Foramen Rotundum

Fig. 2.20a-f. Axial CT through the vertical extent of the pterygopalatine fossa from the upper down to the lower limit. a The rectangular pterygopalatine fossa (PPF) opens posteriorly into the foramen rotundum (FR), superolaterally into the inferior orbital fissure (IOF). Arrow points to the sphenopalatine foramen. b The pterygoid - vidian - canal (black arrowheads) has a large anterior opening. Laterally the PPF communicates with the infratemporal fossa via the pterygomaxillary fissure (PMF). c The foramen ovale (FO) and spinosum (FSp) are demonstrated on the greater sphenoid wing. Perpendicular plate of the palatine bone (p). d-f Progressive narrowing of the PPF and onset of greater (GPC) and lesser (LPC) palatine canals. Greater palatine foramen (GPF), pterygoid fossa - scaphoid fossa - (PF)

Fig. 2.20a-f. Axial CT through the vertical extent of the pterygopalatine fossa from the upper down to the lower limit. a The rectangular pterygopalatine fossa (PPF) opens posteriorly into the foramen rotundum (FR), superolaterally into the inferior orbital fissure (IOF). Arrow points to the sphenopalatine foramen. b The pterygoid - vidian - canal (black arrowheads) has a large anterior opening. Laterally the PPF communicates with the infratemporal fossa via the pterygomaxillary fissure (PMF). c The foramen ovale (FO) and spinosum (FSp) are demonstrated on the greater sphenoid wing. Perpendicular plate of the palatine bone (p). d-f Progressive narrowing of the PPF and onset of greater (GPC) and lesser (LPC) palatine canals. Greater palatine foramen (GPF), pterygoid fossa - scaphoid fossa - (PF)

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JTi A

Sphenopalatine Foramen

Fig. 2.21a-d. Sagittal CT through the pterygopalatine fossa from medial to lateral. a Most medial aspect of the fossa (PPF), posteriorly communicating with the pterygoid - vidian -canal (VC), completely surrounded by a largely pneumatizing sphenoid sinus (SS). b The whole vertical extent of the fossa and the greater palatine canal (GPC) are located posteriorly to the "fused" perpendicular plate of the palatine bone and posterior maxillary sinus wall. The white arrow indicates the posterior opening of the pterygoid canal in front of the petrous apex. c The lesser palatine canal (LPC) runs laterally and posteriorly to the greater one. The fossa superiorly communicates with the inferior orbital fissure (IOF). d The most lateral aspect of the fossa, posteriorly it continues into the foramen rotundum (FR)

Vidian Canal

Fig. 2.21a-d. Sagittal CT through the pterygopalatine fossa from medial to lateral. a Most medial aspect of the fossa (PPF), posteriorly communicating with the pterygoid - vidian -canal (VC), completely surrounded by a largely pneumatizing sphenoid sinus (SS). b The whole vertical extent of the fossa and the greater palatine canal (GPC) are located posteriorly to the "fused" perpendicular plate of the palatine bone and posterior maxillary sinus wall. The white arrow indicates the posterior opening of the pterygoid canal in front of the petrous apex. c The lesser palatine canal (LPC) runs laterally and posteriorly to the greater one. The fossa superiorly communicates with the inferior orbital fissure (IOF). d The most lateral aspect of the fossa, posteriorly it continues into the foramen rotundum (FR)

a floor from the lateral orbital wall. Because it is angled about 45° to the orientation of the infraorbital canal, the infraorbital nerve has a "bayonet-like" shape as it runs from the infraorbital canal into the pterygopalatine fossa (Fig. 2.23). The infraorbital canal runs parallel to the orbital floor, between the middle and lateral third, except for its anterior por tion where it bends downward to the infraorbital foramen (Fig. 2.24).

Laterally, the pterygopalatine fossa communicates with the retromaxillary fat of the masticator space/infratemporal fossa via the pterygomaxillary fissure; medially it transmits the nasopalatine nerve (a branch of the maxillary nerve), posterior supe-

Masticator Space Pterygomaxillary Space

Fig. 2.22a-c. Coronal plane through the pterygoid process. a,b TSE T2 and enhanced SE T1 sequences in the same patient. On the right side the foramen rotundum is a groove, on the left a complete canal. On T2 and Gd-T1, V2 appears as a small hypointense structure within the foramen. Arrowheads indicate the anterior (oval) opening of the pterygoid canal. c Enhanced VIBE sequence (0.5-mm thickness) shows V2 probably surrounded by enhanced veins, similar to the adjacent cavernous sinus where III and IV nerves are demonstrated. Enhancing vessels surround the pterygoid nerve (VN). Bilateral pneumatized anterior clinoids (AC). Optic nerve (ON), hypophysis (HY), superior orbital fissure (SOF), rostrum of the splenoid bone (r), lateral pterygoid plate (LPP)

Fig. 2.22a-c. Coronal plane through the pterygoid process. a,b TSE T2 and enhanced SE T1 sequences in the same patient. On the right side the foramen rotundum is a groove, on the left a complete canal. On T2 and Gd-T1, V2 appears as a small hypointense structure within the foramen. Arrowheads indicate the anterior (oval) opening of the pterygoid canal. c Enhanced VIBE sequence (0.5-mm thickness) shows V2 probably surrounded by enhanced veins, similar to the adjacent cavernous sinus where III and IV nerves are demonstrated. Enhancing vessels surround the pterygoid nerve (VN). Bilateral pneumatized anterior clinoids (AC). Optic nerve (ON), hypophysis (HY), superior orbital fissure (SOF), rostrum of the splenoid bone (r), lateral pterygoid plate (LPP)

Fossa Pterygopalatine Cyst

Fig. 2.23a-d. Axial SE T1 Gd-enhanced images through the pterygopalatine fossa. a The PPF communicates with the foramen rotundum, posteriorly. The hypointense linear structure running through the foramen rotundum is the maxillary nerve (V2). Meckel cave (MC). b The pterygoid (vidian) canal (black arrows, VC) has a wider anterior opening into the PPF, it reaches posteriorly the foramen lacerum/petrous apex. Bayonet-like course of the infraorbital nerve (ION) from PPF into the infraorbital fissure. Mandibular nerve (V3). c Inferior narrowing of the PPF. Medial (MPP) and lateral (LPP) pterygoid plates. d Opening of the greater palatine canal (GPF) at the level of the hard palate

Fig. 2.23a-d. Axial SE T1 Gd-enhanced images through the pterygopalatine fossa. a The PPF communicates with the foramen rotundum, posteriorly. The hypointense linear structure running through the foramen rotundum is the maxillary nerve (V2). Meckel cave (MC). b The pterygoid (vidian) canal (black arrows, VC) has a wider anterior opening into the PPF, it reaches posteriorly the foramen lacerum/petrous apex. Bayonet-like course of the infraorbital nerve (ION) from PPF into the infraorbital fissure. Mandibular nerve (V3). c Inferior narrowing of the PPF. Medial (MPP) and lateral (LPP) pterygoid plates. d Opening of the greater palatine canal (GPF) at the level of the hard palate

Infraorbital Canal
Fig. 2.24. Sagittal plane through the infraorbital canal and infraorbital nerve (ION), parallel to the orbital floor until its anterior portion where it turns downward (arrowheads) toward the foramen. Foramen ovale (FO), lesser palatine foramen (LPF)

rior nasal nerves, and the sphenopalatine vessels into the nasal cavity via the sphenopalatine foramen. Inferiorly, the fossa progressively narrows to end in the greater and lesser palatine canals. Along the first are the greater palatine nerve and vessels, the ascending palatine artery and the lesser palatine nerves run within the second canal. The greater palatine foramen opens at the angle formed by the junction of the perpendicular plate with the horizontal plate of the palatine bone (Fig. 2.4).

The anterior two thirds of the hard palate are formed by the palatine processes of the maxillary bones, posteriorly they articulate with the horizontal plates of the palatine bone.

From the pterygoid process arise two plates, the medial more vertically oriented than the lateral one that diverges from the sagittal plane. Posteriorly they enclose a space called the pterygoid - scaphoid - fossa. The lateral - external - pterygoid muscle inserts on the external surface of the lateral plate, the medial - internal - pterygoid muscle arises from the medial surface of the same plate (within the scaphoid fossa). The tensor veli palatini muscle inserts on the medial plate, its tendon runs downward, under a curved process of the medial pterygoid plate (hamulus) to reach the soft palate.

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Responses

  • mirabella
    What fat space the temporal pterygoid space communicate with through inferior orbital fissure?
    7 years ago
  • almaz
    What cranial nerve is in the foramen rotundum?
    7 years ago
  • nora
    What fat space the temporal pterygoid space communicates with through inferior orbital fissure?
    4 years ago

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