Establishing a Zonal Anatomic Scheme for the Parapharyngeal Space and Infratemporal Fossa Based on Five Surgical Approaches

Objective To develop an anatomical zonal scheme for the parapharyngeal space and infratemporal fossa based on various surgical approaches, including the transnasal posterior maxillary sinus wall approach, the transnasal antrostomy approach, the transoral medial pterygomandibular fold approach, the transoral posterior pharyngeal wall approach, and the transoral retromolar approach. Methods Ten sides from five fresh cadaveric heads were dissected using endoscopic transnasal and transoral approaches to explore the parapharyngeal space and infratemporal fossa. Anatomical landmarks and relationships were observed and recorded for each approach to define the anatomical boundaries of each dissection zone. Results Based on the surgical approaches, the parapharyngeal space and infratemporal fossa were divided into five zones: Zone NO (transnasal posterior maxillary sinus approach), located posterior to the posterolateral wall of the maxillary sinus, laterally to the deep surface of the temporalis muscle, inferiorly to a plane above the maxillary sinus floor, superiorly to the middle cranial fossa floor, medially to the lateral pterygoid plate, medial to the ramus of the mandible and the temporalis muscle attachment, anteriorly to the posterior maxillary sinus fat space, and posteriorly to the styloid process and its associated fascia; Zone NI (transnasal pterygoid approach), encompassing the pterygopalatine fossa (including the medial pterygoid plate), tensor veli palatini muscle, levator veli palatini muscle, cartilaginous portion of the eustachian tube, parapharyngeal muscle group, and nasopharyngeal mucosa; Zone B (transoral infra-pterygomandibular fold medial approach), located inferior to the maxillary sinus floor, inferior to the lateral pterygoid muscle, medial to the medial pterygoid muscle, and medial to the deep lobe of the parotid gland, anterior to the stylomandibular fascia; Zone C (transoral lateral molar approach), located medial to the ascending ramus of the maxilla, lateral to the medial pterygoid muscle, inferior to the lateral pterygoid muscle, and lateral to the deep temporalis muscle group; and Zone D (transoral posterior pharyngeal approach), encompassing the retrostyloid space and part of the jugular foramen area, specifically the area posterior to the styloid process and its associated muscles and stylomandibular fascia (styloid septum), and anterior to the deep cervical fascia (prevertebral fascia). Conclusion This study proposes a revised zonal anatomy of the parapharyngeal space and infratemporal fossa based on different surgical approaches, aiming to provide a reference for preoperative assessment and surgical planning to minimize injury to vital neurovascular structures and muscles.