Anatomical Variations and Relationships of the Infratemporal Fossa: Foundation of a Novel Endonasal Approach to the Foramen Ovale

Abstract

Objective Access to the infratemporal fossa (ITF) is complicated by its complex neurovascular relationships. In addition, copious bleeding from the pterygoid plexus adds to surgical challenge. This study aims to detail the anatomical relationships among the internal maxillary artery (IMA), pterygoid plexus, V _3, and pterygoid muscles in ITF. Furthermore, it introduces a novel approach that displaces the lateral pterygoid plate (LPP) to access the foramen ovale. Design and Main Outcome Measures Six cadaveric specimens (12 sides) were dissected using an endonasal approach to the ITF modified by releasing and displacing the LPP and lateral pterygoid muscle (LPTM) as a unit. Subperiosteal elevation of the superior head of LPTM revealed the foramen ovale. The anatomic relationships among the V ₃ , pterygoid muscles, pterygoid plexus, and IMA were surveyed. Results In 9/12 sides (75%), the proximal IMA ran between the temporalis and the LPTM, whereas in 3/12 sides (25%), the IMA pierced the LPTM. The deep temporal nerve was a consistent landmark to separate the superior and inferior heads of LPTM. An endonasal approach displacing the LPP in combination with a subperiosteal elevation of the superior head of LPTM provided access to the posterior trunk of V ₃ and foramen ovale while sparing injury of the LPTM and exposing the pterygoid plexus. The anterior trunk of V ₃ traveled anterolaterally along the greater wing of sphenoid in all specimens. Conclusion Displacement of the LPP and LPTM provided direct exposure of foramen ovale and V ₃ avoiding dissection of the muscle and pterygoid plexus; thus, this maneuver may prevent intraoperative bleeding and postoperative trismus.

Keywords: V 3; foramen ovale; infratemporal fossa; internal maxillary artery; lateral pterygoid plate.

Fig. 1

( A ) The branches of the internal maxillary artery on right side. ( B ) The greater palatine nerve and lesser palatine nerve. DPA, descending palatine artery; IOA: infraorbital artery; ION, infraorbital nerve; PSAA, posterosuperior alveolar artery; SPA, sphenopalatine artery.

Fig. 2

( A ) A line illustration of the drilling (green line) between the medial (blue arrow) and LPP (red arrow). ( B ) The bony ridge (enclosed dotted line, right side) was drilled to facilitate the separation of LPP (arrow). ( C ) The lateral pterygoid muscle and LPP were displaced laterally as a unit. DPA, descending palatine artery; LPP, lateral pterygoid plates; MPTM, medial pterygoid muscle.

Fig. 3

( A ) The fascia of the lateral pterygoid muscle (right side) was preserved (arrow), and the posterior trunk of V ₃ was exposed. ( B ) The lingual nerve and inferior alveolar nerve lie on the surface of medial pterygoid muscle. TM, temporalis muscle.

Fig. 4

( A ) The chorda tympani (right side) joins the lingual nerve. ( B ) The sphenoidal spine. IAN, inferior alveolar nerve; LPTM, lateral pterygoid muscle; SD, styloid diaphragm; SML, sphenomandibular ligament.

Fig. 5

( A ) The superior head of the LPTM is elevated from the greater wing of sphenoid in a subperiosteal fashion (green arrow). ( B ) The pterygoid venous plexus (red arrow) located deep to the LPTM. ( C ) The communicated venous plexus (green arrow) connecting the pterygoid venous plexus and the cavernous sinus crossing the foramen ovale was present. LPTM, lateral pterygoid muscle.

Fig. 6

( A ) The IMA (right side) travels between the temporalis muscle and the lateral pterygoid muscle. ( B ) The auriculotemporal nerve runs superior to IMA (right side). ( C ) The middle meningeal artery (right side) travels upward between the branches of V ₃ . ATN, auriculotemporal nerve; IAN: inferior alveolar nerve; IMA, internal maxillary artery; IOA, infraorbital artery; ION, infraorbital nerve; LN, lingual nerve; MR: mandible ramus; SML, stylomandibular ligament.

Fig. 7

( A ) The IMA (right side) pierces between the superior (LPTM-S) and inferior (LPTM-I) heads of lateral pterygoid muscle. ( B ) The middle meningeal artery (right side) also travels upward between branches of V ₃ . ATN, auriculotemporal nerve; IMA, internal maxillary artery; IAN, inferior alveolar nerve; LN, lingual nerve; MR, mandible ramus; TM, temporalis muscle.

Fig. 8

( A ) The deep temporal nerve (right side) located at the medial border of the temporalis muscle; ( B ) the DTN constitutes a separation between superior (LPTM-S) and inferior (LPTM-I) heads of lateral pterygoid muscle. ( C ) The anterior trunk of V ₃ (right side). BN, buccal nerve; MN, masseteric nerve; LPTN, lateral pterygoid nerve (cut in this specimen).