ENDONASAL TRANSPTERYGOID APPROACH TO THE INFRATEMPORAL FOSSA: CORRELATION OF ENDOSCOPIC AND MULTIPLANAR CT ANATOMY

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1 ORIGINAL ARTICLE ENDONASAL TRANSPTERYGOID APPROACH TO THE INFRATEMPORAL FOSSA: CORRELATION OF ENDOSCOPIC AND MULTIPLANAR CT ANATOMY Seid Mousa Sadr Hosseini, MD, 1 Ali Razfar, MD, 2 Ricardo L. Carrau, MD, 3 Daniel M. Prevedello, MD, 4 Juan Fernandez Miranda, MD, 5 Adam Zanation, MD, 6 Amin B. Kassam, MD 3 1 Department of Otolaryngology Head & Neck Surgery, Vali-E-Asr Hospital, Tehran University of Medical Sciences, Tehran, Iran 2 Department of Surgery Division of Head and Neck Surgery, University of California Los Angeles Medical Center, Los Angeles, California 3 Neuroscience Institute, John Wayne Cancer Institute at Saint John s Health Center, Santa Monica, California. carraurl@gmail.com 4 Department of Neurosurgery, Ohio State University Medical Center, Columbus, Ohio 5 Department of Neurological Surgery, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania 6 Department of Otolaryngology Head & Neck Surgery, University of North Carolina. Chapel Hill, North Carolina Accepted 14 December 2010 Published online 16 May 2011 in Wiley Online Library (wileyonlinelibrary.com). DOI: /hed Abstract: Background. The infratemporal fossa anatomy, from an endoscopic standpoint, is poorly understood. Our purpose was to design an anatomic model that illustrates the anatomy of the infratemporal fossa from the endoscopic standpoint and serves as a training model for surgeons interested in pursuing this endeavor. Methods. Red and blue silicone dyes were respectively injected into the great vessels of the neck. Digital data acquired from a high resolution CT scan was imported to a navigational system. An endoscopic endonasal dissection of the infratemporal fossa was completed under conditions that mimicked our operating suite. Results. A detailed anatomic dissection of the infratemporal fossa was correlated to the image guidance (navigation) system. This provided a surgical map highlighting critical neurovascular structures and illustrating the potential surgical corridors. Conclusion. A thorough understanding of the anatomy of infratemporal fossa from the endoscopic perspective allows the surgeon to plan an adequate corridor. VC 2011 Wiley Periodicals, Inc. Head Neck 34: , 2012 Keywords: endoscopy; training model; anatomy; infratemporal fossa; pterygopalatine fossa Surgical access to the infratemporal fossa is difficult, as this area is deeply seated. Briefly, the infratemporal fossa is situated beneath the floor of the middle cranial fossa, posterior to the maxillary sinus, medial to the ramus of the mandible, and lateral to the nasopharynx. The greater wing of the sphenoid bone and the subtemporal surface of the temporal bone form Correspondence to: R. L. Carrau VC 2011 Wiley Periodicals, Inc. the roof of the infratemporal fossa. The lateral pterygoid plate along with the eustachian tube forms its medial wall. The deep aspect of temporalis muscle inserting to the mandibular ramus and the temporomandibular joint bounds the infratemporal fossa in its lateral aspect (Figure 1). The infratemporal fossa houses the lateral and medial pterygoid muscles, and important neurovascular structures, such as the third branch of the trigeminal nerve (V3), the internal maxillary artery, and the carotid sheath and its contents. The lateral pterygoid muscle (LPM) occupies most of the superior infratemporal fossa. Caudally, the infratemporal fossa is primarily occupied by the medial pterygoid muscle, which inserts into the angle of mandible. Posteromedially, the infratemporal fossa contains the carotid sheath (internal carotid artery [ICA], internal jugular vein, and cranial nerves IX to XII) and styloid complex (ie, parapharyngeal space). 1 In addition, the internal maxillary artery (IMA), pterygoid venous plexus, maxillary vein, and the mandibular and chorda tympani nerves all traverse through the infratemporal fossa (ie, masticator space). 2,3 Medially, the infratemporal fossa communicates with the pterygopalatine fossa via the pterygomaxillary fissure, which is continuous with the inferior orbital fissure. A variety of benign and malignant neoplasms involve the infratemporal fossa. However, most neoplasms involving the infratemporal fossa originate from adjacent structures, such as the temporal bone, parotid gland, paranasal sinuses, nasopharynx, or temporal fossa. Juvenile angiofibroma and adenoid cystic carcinoma are the most common benign and malignant tumors involving the infratemporal fossa, Correlation of Endoscopic and Multiplanar CT Anatomy HEAD & NECK DOI /hed March

2 FIGURE 1. Basal skull view. The boundaries of the infratemporal fossa are delineated by the dotted line. Note that the lateral pterygoid plate and eustachian tube constitute the medial wall of infratemporal fossa and temporomandibular joint (TMJ) and temporalis muscle form its lateral wall. The carotid and jugular foramens are located in posterior part of infratemporal fossa. respectively. Other various tumors may arise within the infratemporal fossa including sarcomas, lymphomas, schwannomas, and meningiomas. 4 Multiple surgical approaches to the infratemporal fossa have been proposed including lateral preauricular and postauricular approaches, anterior trans-maxillary or trans-nasal approaches, and inferior transmandibular approaches. 3 Among others, traditional anterior approaches to the infratemporal fossa include the extended maxillary sinusotomy, Le Fort I and/or II osteotomies, maxillary swing, and facial translocation. 4 Recently, endoscopic endonasal transpterygoid approaches have provided new corridors to access a variety of pathologies in the paramedian and lateral skull base. Endoscopic endonasal transpterygoid approaches were first described to access the lateral recess of the sphenoid sinus 5 7 and was subsequently modified and expanded to manage lesions of the petrous apex, middle cranial fossa, and infratemporal fossa. 8 Understanding the complex anatomic relationships of the infratemporal fossa from the endoscopic perspective is mandatory before attempting an endoscopic endonasal transpterygoid approache Familiarity with microsurgical anatomy of infratemporal fossa and dissection techniques via anterior and lateral approaches is helpful but may not be sufficient to dominate this area. 2,3,13 16 The purpose of this study was to provide a detailed endoscopic anatomic description of the infratemporal fossa correlated to CT multiplanar imaging. We describe the endoscopic transpterygoid approach and discuss the benefits and limitations of this corridor. MATERIALS AND METHODS We performed our Committee for Oversight of Research Involving the Dead-approved anatomic studies at the Minimally Invasive Neurosurgery Center anatomy laboratory at the University of Pittsburgh Medical Center. Major vessels of the neck, including the common carotid and vertebral arteries and the internal jugular veins were identified and respectively injected with red and blue silicone dyes. A high resolution CT scan was performed and the data was imported to a Stryker navigational system (Kalamazoo, MI). Five cranial screws, spaced around the head, served as fixed landmarks for the registration. We used a 0 endoscope coupled to a high definition camera and monitor (Karl Storz Endoscopy, Tuttlingen, Germany) to provide visualization during most of the dissections; thus, emulating the environment of our operating room. An AIDA system (Karl Storz Endoscopy, Tuttlingen, Germany) was used to record and save images (JPG format) and videos of the dissections (MPEG-2 format). Still photographs were obtained to define and document the anatomic relationships of the endoscopic anatomy and to be correlated with the multiplanar CT views provided by the image guidance system. A high-speed electric drill and endoscopic dissecting instruments (Karl Storz Endoscopy, Tuttlingen, Germany) were used as needed. We used a Total Performance System drill (Stryker Co., Kalamazoo, MI) with an angled hand-piece and 3 to 4 mm rough diamond (hybrid) short and long burrs. RESULTS We began our approach with the preparation and expansion of the sinonasal corridor followed by the harvesting of the Hadad Bassagastaguy nasoseptal flap. 17 We removed the inferior half of the middle turbinate and then completed anterior and posterior ethmoidectomies, ipsilateral to the infratemporal fossa dissection. A large middle meatus nasoantral window, extending from the nasolacrimal duct anteriorly to the sphenopalatine foramen posteriorly and from the lamina papyracea superiorly to the inferior turbinate inferiorly, allows the exposure of the posterior wall of the antrum (superior half), and the sphenopalatine foramen with its sphenopalatine and posterior nasal arteries. This window allows the exposure of the cephalic half of the pterygopalatine fossa and superomedial infratemporal fossa. An endoscopic medial maxillectomy, however, is most commonly needed to expose the entire height of the posterior wall of maxillary sinus; therefore, allowing an extended dissection of the pterygopalatine fossa and infratemporal fossa exposing and controlling their caudal area. Removal of the posterior wall of the antrum is completed with 1 to 2 mm Kerrison Rongeurs, osteotomes, curved ethmoid forceps and curettes, or high-speed drill (Figure 2A and 2B). 314 Correlation of Endoscopic and Multiplanar CT Anatomy HEAD & NECK DOI /hed March 2012

3 The lateral exposure provided by a medial maxillectomy, however, is limited by the surgeon s inability to displace the nasolacrimal duct with the rod lens endoscope or dissection instruments. Bringing the instruments from the contralateral side of the nose, which in turn requires a posterior septectomy, may enhance this angle of approach. To dissect the most lateral aspect of the infratemporal fossa, however, it is best to extend the medial maxillectomy anteriorly; thus, achieving the necessary line of sight. This modification includes the removal of the remaining inferior turbinate and anterior aspect of the inferior meatus with backbiting rongeurs, osteotomes, or high-speed drill. In select cases, the removal may be confined to the area inferior to the nasolacrimal opening. For a full exposure, however, we remove the piriform aperture and ascending process of the maxilla, dissecting the lacrimal duct and transecting it sharply (endoscopic Denker s approach). Exposure of the piriform aperture requires a vertical incision just anterior to the head of the inferior turbinate, right over the edge of the aperture. This edge can be palpated with a blunt dissector to optimize the placement of the incision, which is then carried through the periosteum down to the bone. Extension of the dissection laterally, after a subperiosteal plane, exposes the entire anterior maxilla including the infraorbital foramen, its corresponding nerve, and the inferior orbital rim. The medial maxillectomy is then extended anteriorly to remove the piriform aperture and laterally to remove the anterior maxillary wall until the entire lateral wall of the antrum is in direct and full view. This modification allows the placement of the endoscope and dissecting instruments in such a way that the line of sight extends to encompass the most lateral aspect of the infratemporal fossa. In the contralateral side, a Hadad Bassagastaguy nasoseptal flap is harvested and transposed into the ipsilateral antrum. This requires a large maxillary antrostomy similar to that described as part of the infratemporal fossa dissection. It is critical to harvest the Hadad Bassagastaguy nasoseptal flap from the contralateral side, as its pedicle and proximal blood supply would be sacrificed ipsilateral to the infratemporal fossa dissection. A generous posterior septectomy allows a bimanual technique traversing both sides of the nasal FIGURE 2. (A) Photograph of an endoscopic endonasal pterygopalatine fossa dissection with exposure of the medial infratemporal fossa (ITF). Multiplanar images on the left represent point A which corresponds to the infratemporal crest (origin of deep temporalis muscle). Multiplanar images on the right represent point B that corresponds to the inferior edge of the foramen rotundum. Note that infraorbital nerve separates the infraorbital fissure (IOF) from the infratemporal fossa and that the temporalis muscle defines the lateral border of infratemporal fossa. ION, infraorbital nerve; TM, temporalis muscle; DPA, descending palatine artery; SPA, sphenopalatine artery; PNA, posterior nasal artery; IT, inferior turbinate. (B) Photograph obtained after an endoscopic endonasal medial maxillectomy. Multiplanar images on the left represent point A which is at the medial and caudal aspect of the temporalis muscle. Multiplanar images in the right represent point B which indicates the fusion between the pterygoid plates and the posterior wall of maxillary sinus. ION, infraorbital nerve; TM, temporalis muscle; LPM, lateral pterygoid muscle; IMA, internal maxillary artery; VN, vidian nerve. (C) Photograph obtained during an endoscopic endonasal dissection demonstrating a pterygopalatine fossa and medial infratemporal fossa dissection. 1 ¼ infraorbital nerve, 2 ¼ pterygopalatine ganglion, 3 ¼ vidian nerve, 4 ¼ sphenopalatine artery, 5 ¼ greater palatine nerve, 6 ¼ infraorbital artery. Correlation of Endoscopic and Multiplanar CT Anatomy HEAD & NECK DOI /hed March

4 cavity. In general, the posterior septectomy needs to be extended to a level that is anterior to the posterior wall of the antrum. This extensive posterior septectomy allows the visualization of the entire posterior wall of the maxillary sinus using a 0 endoscope that crosses over from the contralateral side of the nose. As the removal of the posterior and lateral walls of the antrum expose the pterygopalatine and infratemporal fossae, the dissection could be performed through the contralateral side without the need to use angled endoscopes. A wide sphenoidotomy is completed after identifying key anatomic landmarks. In a coronal plane, one may visualize the letter H with its vertical limbs composed by the lateral walls of the sphenoid sinus and the medial pterygoid plates (lateral wall of the posterior choana) and the floor of the sinus forming its horizontal limb. Trifurcation of the medial pterygoid plate with the lateral wall and floor of the sphenoid sinus forms a wedge-shaped area ( pterygoid wedge ) that contains the vidian canal. It also contains the palatovaginal canal with the pharyngeal artery that can be identified as they travel toward the nasopharynx. Just lateral to the palatovaginal canal, lies the vidian (pterygoid) canal with the vidian artery and nerve. Before removing the inferolateral aspect of the rostrum of the sphenoid, its mucoperiosteum is dissected laterally and the area is carefully inspected for these landmarks. Subsequently, the bony trifurcation of vomer, sphenoid sinus floor, and inter-sinus septum is removed and the sphenoidotomy is extended in all directions. Ultimately, the sphenoidotomy should yield a sphenoid sinus roof that is in plane with the roof of the nose and lateral walls that are in plane with the laminae papyracea bilaterally. Intersinus and intrasinus septations frequently inserted in the ICA and optic nerve canals; thus, their removal should be completed using cutting instruments and/or the high-speed drill. 18 Stripping of the sphenoid sinus mucosa facilitates the identification of critical landmarks including the sella turcica, the ICA, and the optic nerve canals. In the live patient, however, this step should be weighed against the prolonged healing and possible crusting formation associated with denuded bone. short course of the infraorbital nerve (ION) traverses the infraorbital fissure, just after arising from the maxillary nerve near the foramen rotundum, and before entering the infraorbital canal. This portion of the ION accurately delineates the border between infratemporal fossa and IOF, after the ION medially and posteriorly leads to the foramen rotundum. Transpterygoid Dissection. For the transpterygoid infratemporal fossa dissection, we exposed the base of the pterygoid plates and transected the vidian nerve. Using a high-speed drill, the maxillary nerve (V2) was followed into Meckel s cave, identifying the mandibular nerve (V3) and the dura of middle fossa. The sulcus tubae, which houses the cartilaginous part of the eustachian tube, is situated posterior and medial to the foramen ovale. Infratemporal Fossa Dissection. The lateral pterygoid plate is the anterior and medial boundary of the infratemporal fossa, whereas, the temporalis muscle constitutes its lateral boundary. The junction of the infraorbital canal and the posterior maxillary sinus wall is just medial to the vertical fibers of the temporalis muscle. This point can be used as a proxy landmark to divide the infratemporal fossa and the pterygopalatine fossa from the endoscopic perspective. We can define 5 planes of dissection in the infratemporal fossa, as we move from an anterior (superficial) and medial to posterior (deep) and lateral planes (Figure 3). The first plane of dissection is between the LPM medially and the deep part of the temporalis muscle and mandibular ramus laterally. The IMA, which enters the infratemporal fossa posteriorly and Pterygopalatine Fossa Dissection. After dissecting and removing the fat of the pterygopalatine fossa, the main terminal branches of the IMA were identified including the infraorbital, descending palatine, vidian, sphenopalatine, and posterior nasal arteries (Figure 2C). All branches, except the infraorbital artery, were transected to expose the underlying neural structures including the infraorbital, descending palatine, vidian, and pharyngeal nerves. The pterygomaxillary fissure, which represents the boundary between the pterygopalatine fossa and the infratemporal fossa, is continuous with the infraorbital fissure (IOF). A FIGURE 3. Planes of dissection of the infratemporal fossa. First plane is between lateral pterygoid muscle (LPM) and temporalis muscle. Second plane includes the LPM. Third plane lies medial to V3 and its branches. Fourth plane is between medial pterygoid muscle (MPM) and tensor veli palatini muscles. Fifth plane contains the internal carotid artery (post-styloid parapharyngeal space). 316 Correlation of Endoscopic and Multiplanar CT Anatomy HEAD & NECK DOI /hed March 2012

5 terior to the lateral pterygoid plates. Removal of the LPM provides access to the lateral, medial, and posterior walls of the infratemporal fossa and opens a corridor to adjacent structures (Figure 5A and 5B). The third plane of dissection (Figure 3) is posterior to the lateral pterygoid plate, medial to the middle meningeal artery and V3, and extends laterally to the temporomandibular joint (TMJ). The medial pterygoid muscle (MPM), originating from the medial FIGURE 4. Photograph obtained during an endoscopic endonasal dissection of the medial infratemporal fossa. A dissection plane medial to the lateral pterygoid muscle (LPM) has been elevated to illustrate the pterygoid venous plexus. LPMU, upper head of LPM; LPML, lower head of LPM; TM, temporalis muscle; IMA, internal maxillary artery; DTN, deep temporal nerve; BN, buccal nerve; PVP, deep part of pterygoid venous plexus; LPP, lateral pterygoid plate; FO, foramen ovale. inferiorly, passing between the neck of mandible and sphenomandibular ligament, is the dominant structure in this plane. It travels anteriorly and superiorly toward the pterygopalatine fossa. The deep temporal artery, vein, and nerve are in the deepest aspect of this plane (deep surface of the temporalis muscle). The maxillary vein runs with the IMA and has multiple branches that pass through the LPM. There is an extensive network of venous channels lateral to the LPM, forming the superficial pterygoid venous plexus. A large venous plexus in the deep aspect of the infratemporal fossa, near the mandibular condyle, represents the confluence of the superficial and deep venous plexuses. One or 2 branches of the anterior division of mandibular nerve pass between 2 heads of the lateral pterygoid muscle and cross the infratemporal fossa. A consistent branch is the buccal nerve that passes inferiorly to supply sensation to the cheek. The second plane of dissection (Figure 3) encompasses the LPM. The LPM comprises 2 heads that occupy most of the infratemporal fossa. The superior head attaches to the infratemporal surface of the greater wing of the sphenoid bone and the lower head originates from the lateral pterygoid plate. After detaching the lower head from the lateral pterygoid plate and displacing it laterally, the deep pterygoid venous plexus comes into view (Figure 4). The epicenter of this plexus encompasses the area of the foramen ovale and foramen spinosum. Sensory branches of the posterior division of the mandibular nerve, exiting the foramen ovale, and the middle meningeal artery, entering the foramen spinosum, appear within the deep part of the pterygoid venous plexus just pos- FIGURE 5. (A) Photograph obtained during an endoscopic endonasal dissection illustrating the infratemporal fossa after removal of lateral pterygoid muscle (LPM). Note the position of mandibular condyle in the posterior and lateral aspect of the infratemporal fossa. Multiplanar images on the left represent point A which indicates the lateral border of infratemporal fossa (infratemporal crest). Multiplanar images in the right represent point B which indicates the most medial point of mandibular condyle. DTN, deep temporal nerve; MN, masseteric nerve; BN, buccal nerve; ATN, auriculotemporal nerve; MMA, middle meningeal artery; IAN, inferior alveolar nerve; LN, lingual nerve; DTA, deep temporal artery; MC, transected insertion of lateral pterygoid muscle (to the mandibular condyle); IMA, divided end of internal maxillary artery. (B) Photograph obtained during an endoscopic endonasal dissection illustrating a transpterygoid dissection. Multiplanar images in the left represent point (A) which indicates foramen ovale. Multiplanar images in the right represent point B which indicates the dura of the middle fossa. FR, foramen rotundum; TG, trigeminal ganglion; ICA, internal carotid artery; FO, foramen ovale; V3, mandibular nerve; VN, vidian nerve; ET, eustachian tube. Correlation of Endoscopic and Multiplanar CT Anatomy HEAD & NECK DOI /hed March

6 FIGURE 6. Photograph obtained during an endoscopic endonasal dissection illustrating the third plane of dissection. Multiplanar images in the left represent point A that indicates the base of the styloid process. Multiplanar images in the right represent point B that indicates the tip of the styloid process. Styloid diaphragm (SD) has opened to show the stylopharyngeus (SPM) muscle. Note the relationship of internal carotid artery to the styloid process. PG, parotid gland; MPM, medial pterygoid muscle. aspect of the medial pterygoid plate in the pterygoid fossa, occupies the inferior part of this plane. The eustachian tube and its associated muscles occupy the superior aspect. A significant amount of fat separates the eustachian tube and its accompanying muscles from neurovascular structures superiorly and MPM inferiorly. Posteriorly we identify the deep lobe of the parotid, styloid process, and stylopharyngeus muscle (Figure 6). A fourth plane of dissection (Figure 3) exists between the medial pterygoid and the tensor veli palatine muscles. A venous plexus lies between these 2 muscles and extends posterior to the tensor veli palatini muscle. The origin of the medial pterygoid muscle may be transected and its upper half resected to expose the styloid diaphragm. The styloid diaphragm is a thick fascia that covers the styloid complex and ICA. It separates the post-styloid compartment (carotid sheath) from the pre-styloid compartment (deep lobe of parotid) and attaches to the skull base. The ICA lies immediately medial to the styloid complex in the fifth and last plane of dissection (Figure 3). The MPM covers a major portion of the parapharyngeal ICA in the inferior infratemporal fossa; thus, its identification needs removal of the MPM. The styloid diaphragm must also be dissected to expose the parapharyngeal ICA. Exposure of the vertical bony carotid canal requires resection of the cartilaginous and eustachian tube (Figure 7). DISCUSSION Various lateral and anterior approaches have been described to access the infratemporal fossa. 3,19 21 Lateral approaches include a combination of preauricular or postauricular incisions, parotidectomy with facial nerve dissection and preservation, displacement or resection of the mandibular condyle, orbito-zygomatic osteotomies, displacement of the temporalis muscle with or without coronoid transection, identification and/or transposition of the petrous ICA, and a temporal or pterional craniotomy. In addition to exposing the infratemporal fossa, these approaches can be extended to expose the sphenoid sinus, nasopharynx, sella, clivus, jugular fossa, cranial nerves, cervical ICA, and petrous apex. Possible sequelae or risks include postoperative TMJ pain, dysfunction and trismus, facial paralysis, and hearing loss. 22 Anterior approaches to the infratemporal fossa use the air space of the maxillary sinus as part of the corridor. Anterior approaches can be divided into traditional transmaxillary and endoscopic transmaxillary approaches. A variety of modifications of the traditional transmaxillary approaches have been proposed including the use of facial, sublabial and palatal incisions, Le Fort I and II osteotomies, maxillary sinusotomy, and partial or total maxillectomy. 2,15,23 The extent of exposure obtained with the anterior approaches is comparable to that obtained with lateral approaches. However, the anterior approaches provide a more direct access to the median cranial base than the lateral approaches. Their morbidity includes facial deformity, infraorbital nerve injury, epiphora, dental injury, frontalis nerve deficit, pterygoid plexus venous bleeding, medial canthus misalignment, dental malocclusion, eustachian tube dysfunction, masticatory problems, and trismus. An endoscopic sublabial transmaxillary approach has been previously described. 24,25 It was originally introduced to approach the pterygopalatine fossa, lateral sphenoid sinus, and retrobulbar lesions with or without endonasal access. In this approach, entry to FIGURE 7. Photograph obtained during an endoscopic endonasal dissection illustrating the fifth plane of the infratemporal fossa dissection. Multiplanar images on the left represent point A that indicate the edge of carotid canal. Multiplanar images on the right represent point B that indicates sulcus tubae and eustachian tube. ION, infraorbital nerve; ICA, internal carotid artery; VN, vidian nerve; TVP, tensor veli palatini muscle; MPM, divided part of medial pterygoid muscle; TM, temporalis muscle; SPM, stylopharyngeus muscle; GPN, glossopharyngeal nerve. 318 Correlation of Endoscopic and Multiplanar CT Anatomy HEAD & NECK DOI /hed March 2012

7 the infratemporal fossa follows a corridor that involves anterior and posterior maxillary sinusotomies. It requires that the origin of the LPM be dissected and displaced laterally so that a subtemporal craniotomy can be opened. One drawback is the limited extent of the craniotomy, which in turn may limit the management of some pathologies arising in this complex area. Its clinical applications remain undefined. Clinical applications of endoscopic endonasal approaches for the management of lesions of the anterior skull base including cribiform, planum sphenoidale, tuberculum sellae, sella, middle and lower clivus, craniovertebral junction, and C1 have been previously documented A transpterygoid dissection expands the lateral exposure; thus, gaining access to Meckel s cave, infratemporal fossa, middle cranial fossa, and petrous apex Compared to lateral approaches to the infratemporal fossa, the endonasal endoscopic transpterygoid approach provides better visualization and more direct exposure of midline structures such as the paranasal sinuses, nasopharynx, eustachian tube, sella, and clivus. Bleeding from the pterygoid venous plexus is expected, therefore, hemostatic agents (eg, thrombin/gelatin, oxidized methylcellulose paste, and microfibrillar collagen), bipolar cautery and warm saline irrigation need to be available. 33 In this approach, the palatine nerve and dental branches of V2 are often sacrificed; therefore, the patient will lose sensation to the hard palate and ipsilateral upper dentition. Endoscopic endonasal transpterygoid approaches to the infratemporal fossa compares favorably with the exposure provided by traditional anterior approaches except for lesions that extend below the level of the hard palate. Its exposure is more extensive than that of an endoscopic or microscopic sublabial transmaxillary approach, therefore, allowing for the management of lesions of greater extent. Furthermore, endoscopic endonasal transpterygoid approaches avoids morbidities that are inherent to lateral and non-endoscopic anterior approaches such as cosmetic issues related to skin incision, need for bony osteotomies, or temporalis muscle manipulation, TMJ pain and dysfunction, paralysis of facial nerve branches, craniotomy, and brain retraction. Trismus can result from scarring of the pterygoid muscles. A drawback of the endoscopic endonasal transpterygoid approaches is the limited exposure of the parapharyngeal ICA. The medial pterygoid muscle, eustachian tube, and styloid diaphragm have to be mobilized to identify the ICA in the medial wall of infratemporal fossa. Proximal control of the ICA is best achieved transcervically, if necessary. This consideration is of utmost importance as it limits the indication of the endoscopic endonasal transpterygoid approaches to lesions that displace rather than invade the soft tissues of the infratemporal fossa. Benign tumors such as neurilemmomas and juvenile angiofibromas are ideal lesions. However, select lowgrade adenocarcinomas and adenoid cystic carcinomas, presenting with a displacing rather than an invasive growth pattern, can also be removed through this approach. Invasive tumors most often mandate a traditional approach that enables proximal ICA control and exenteration of the soft tissues of the infratemporal fossa. Regardless of the approach, the anatomy of the infratemporal fossa is complex and its control requires significant surgical expertise. Surgery in this area should only be attempted by a team that is well versed in its anatomic and surgical intricacies. This is especially relevant for any minimal access technique where the margin for error is small. Postoperative cerebrospinal fluid leak and ascending infection are a concern. However, the introduction of the nasoseptal flap has dramatically lowered the incidence of postoperative cerebrospinal fluid leak and the incidence of meningitis or other intracranial infection is very low. 17,34 These flaps can also cover the ICA and prevent its exposure to nasopharyngeal secretions. Healing of the surgical defect is faster using a vascularized flap than with free tissue grafts. Nasal morbidity and function after endoscopic endonasal transpterygoid approaches have raised some of valid concerns regarding bleeding, crusting and local infection. These are related to the extent of dissection and resection; therefore, the approach should be modified according to the needs of the case, taking this issue into consideration. In a prospective study, however, we found that nasal function recovers to preoperative levels around 6 months after the surgery. 35 CONCLUSION Endonasal endoscopic transpterygoid approaches have opened new corridors for the treatment of lesions affecting the infratemporal fossa. Potential morbidity associated with endoscopic transpterygoid approaches seems less than that of open approaches. A detailed understanding of the anatomy of infratemporal fossa from the endoscopic perspective allows the surgeon to plan an adequate corridor, and complete the resection in a safe manner. REFERENCES 1. Berkovitz B. Infratemporal region and temporomandibular joint. In: Standring S, editor. Gray s Anatomy. 39th ed. Philadelphia, PA: Elsevier Churchill Livingstone; pp Hitotsumatsu T, Rhoton AL Jr. Unilateral upper and lower subtotal maxillectomy approaches to the cranial base: microsurgical anatomy. Neurosurgery 2000;46: ; discussion Isolan GR, Rowe R, Al Mefty O. 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