Anatomical boundaries of the region
The deep lateral facial region has well-defined osseous and myo-glandular boundaries:
- Superiorly the region is bounded by the greater wing of the sphenoid bone.
- Anteriorly the boundary is formed by the maxillary tuberosity (tuber maxillae, or facies infratemporalis).
- Posteriorly the space is closed by the deep part of the parotid gland.
- Inferiorly the boundary is marked by the level of the angle of the mandible — the site of attachment of the masseter and medial pterygoid muscles.
Fascial spaces and their contents
Within the region in question, two main fascial spaces are distinguished, separated from each other by the lateral pterygoid muscle.
1. Temporopterygoid space (spatium temporopterygoideum)
This space is localized between the temporalis muscle (externally) and the lateral pterygoid muscle (internally). Within its limits lie:
- Maxillary artery (a. maxillaris).
- Pterygoid venous plexus (plexus venosus pterygoideus).
2. Interpterygoid space (spatium interpterygoideum)
It is located deeper, lying between the lateral and medial pterygoid muscles. Here passes the mandibular nerve (n. mandibularis) and its branches:
- Auriculotemporal nerve (n. auriculotemporalis).
- Buccal nerve (n. buccalis).
- Lingual nerve (n. lingualis).
- Inferior alveolar nerve (n. alveolaris inferior).
Topographic features: The lateral pterygoid muscle runs toward the neck of the mandibular condyle. The buccal nerve (n. buccalis) has a characteristic course: it emerges between the two heads of the lateral pterygoid muscle and courses most medially toward the lateral wall of the oral cavity. The buccal artery (a. buccalis), branching from the maxillary artery, accompanies this nerve but most commonly lies on the superficial surface of the lateral pterygoid muscle.
Interpterygoid fascia and anesthesia errors
The interpterygoid fascia (fascia interpterygoidea) covers the superficial surface of the medial pterygoid muscle. Its anatomical feature is that it is pierced by only one neurovascular bundle — the inferior alveolar bundle (a., v. et n. alveolares inferiores).
All other branches of the third division of the trigeminal nerve (including the lingual nerve) remain covered by this multilayered fascia.
Clinical significance: This structure explains cases of incomplete anesthesia during mandibular block anesthesia near the mandibular foramen (foramen mandibulare). The anesthetic solution (e.g., novocaine) may surround only the inferior alveolar nerve, which has pierced the fascia, whereas the lingual nerve remains securely isolated behind the fascial barrier.
Pterygoid venous plexus
The pterygoid venous plexus is located directly within the fascia of the lateral pterygoid muscle and may even surround it. It plays the role of a crucial node where blood outflow pathways intersect.
Blood outflow from the plexus occurs into the retromandibular vein (v. retromandibularis). Further, blood exits the parotid gland, merges with the facial vein, and empties into the internal jugular vein (v. jugularis interna).
Of particular danger are the anastomoses of this plexus, as they serve as pathways for the spread of infection:
- With the cavernous sinus of the dura mater — via emissary veins of the foramen lacerum.
- With the inferior ophthalmic vein — via the inferior orbital fissure.
- With the facial veins — via the deep facial vein.
Briefly: answers to topical questions
Through which skull foramen does the mandibular nerve exit into the deep lateral facial region?
The mandibular nerve (n. mandibularis) exits the cranial cavity through the foramen ovale. Upon exit, it enters the infratemporal fossa, where it divides into anterior (primarily motor) and posterior (primarily sensory) groups of branches. This nerve is the third division of the trigeminal nerve and innervates the tissues of the mandible as well as the masticatory muscles.
Through which skull base foramina does the pterygoid plexus communicate with the cavernous sinus?
The pterygoid venous plexus communicates with the cavernous sinus via the foramen lacerum and the carotid canal.
- Foramen lacerum (foramen lacerum) — anastomosis occurs via the emissary veins passing through it.
- Carotid canal (canalis caroticus) — communication is provided via the internal carotid venous plexus (plexus venosus caroticus internus), which is located along the course of the internal carotid artery.
What branches does the maxillary artery give off within the deep lateral facial region?
The maxillary artery (a. maxillaris) within the deep facial region (infratemporal and pterygopalatine fossae) gives off branches from its three segments:
- Mandibular segment — inferior alveolar artery (a. alveolaris inferior) and middle meningeal artery (a. meningea media).
- Pterygoid segment — buccal artery (a. buccalis), masseteric artery (a. masseterica), anterior and posterior deep temporal arteries (aa. temporales profundae anterior et posterior), and pterygoid branches (rr. pterygoidei).
- Pterygopalatine segment — infraorbital artery (a. infraorbitalis), posterior superior alveolar arteries (aa. alveolares superiores posteriores), descending palatine artery (a. palatina descendens), artery of the pterygoid canal (a. canalis pterygoidei), and sphenopalatine artery (a. sphenopalatina).
What nerves innervate the lateral pterygoid muscle?
The lateral pterygoid muscle is innervated by motor fibers of the mandibular nerve (n. mandibularis), which is the third division of the trigeminal nerve. Before entering the mandibular canal, small branches to the nerves to the pterygoid muscles arise from the main trunk. These fibers provide full motor innervation to this masticatory muscle.
Class and exam questions
What nerves pass through the interpterygoid space?
The interpterygoid space contains the mandibular nerve (n. mandibularis) and its branches: the auriculotemporal, buccal, lingual, and inferior alveolar nerves.
Why might numbness of the tongue fail to occur during mandibular block anesthesia?
The lingual nerve is isolated by the multilayered interpterygoid fascia. Upon injection of an anesthetic at the foramen mandibulare, the solution may encompass only the inferior alveolar nerve, which pierces this fascia, leaving the lingual nerve intact.
Where can a purulent infection spread from the pterygoid venous plexus?
Due to venous anastomoses, infection can penetrate into the cavernous sinus of the dura mater, the inferior ophthalmic vein, as well as the superficial facial veins.
What else to study on this topic
- Branching and topography of the maxillary artery (a. maxillaris)
- Detailed structure of the lateral and medial pterygoid muscles
- Mechanism of infection spread via emissary veins of the foramen lacerum
- Technique of mandibular block anesthesia taking fascial sheaths into account
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