Approach to Meckel's Cave and the Middle Cranial Fossa

LABORATORY INVESTIGATION J Neurosurg 130:227–237, 2019

Endoscopic anterior transmaxillary “transalisphenoid” approach to Meckel’s cave and the middle cranial fossa: an anatomical study and clinical application

*Huy Q. Truong, MD,1 Xicai Sun, MD,1,2 Emrah Celtikci, MD,1 Hamid Borghei-Razavi, MD, PhD,1 Eric W. Wang, MD,3 Carl H. Snyderman, MD, MBA,3 Paul A. Gardner, MD,1 and Juan C. Fernandez-Miranda, MD1

Departments of 1Neurological Surgery and 3Otolaryngology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; and 2Department of Otolaryngology, Eye, Ear, Nose, and Throat Hospital, Shanghai Medical College of Fudan University, Shanghai, People’s Republic of China

OBJECTIVE Multiple approaches have been designed to reach the medial middle fossa (for lesions in Meckel’s cave, in particular), but an anterior approach through the greater wing of the sphenoid (transalisphenoid) has not been explored. In this study, the authors sought to assess the feasibility of and define the anatomical landmarks for an endoscopic anterior transmaxillary transalisphenoid (EATT) approach to Meckel’s cave and the middle cranial fossa. METHODS Endoscopic dissection was performed on 5 cadaver heads injected intravascularly with colored silicone bilaterally to develop the approach and define surgical landmarks. The authors then used this approach in 2 patients with tumors that involved Meckel’s cave and provide their illustrative clinical case reports. RESULTS The EATT approach is divided into the following 4 stages: 1) entry into the maxillary sinus, 2) exposure of the greater wing of the sphenoid, 3) exposure of the medial middle fossa, and 4) exposure of Meckel’s cave and lateral wall of the cavernous sinus. The approach provided excellent surgical access to the anterior and lateral portions of Meckel’s cave and offered the possibility of expanding into the infratemporal fossa and lateral middle fossa and, in combination with an endonasal transpterygoid approach, accessing the anteromedial aspect of Meckel’s cave. CONCLUSIONS The EATT approach to Meckel’s cave and the middle cranial fossa is technically feasible and confers certain advantages in specific clinical situations. The approach might complement current surgical approaches for lesions of Meckel’s cave and could be ideal for lesions that are lateral to the trigeminal ganglion in Meckel’s cave or extend from the maxillary sinus, infratemporal fossa, or pterygopalatine fossa into the middle cranial fossa, Meckel’s cave, and cavernous sinus, such as schwannomas, meningiomas, and sinonasal tumors and perineural spread of cutaneous malignancy. https://thejns.org/doi/abs/10.3171/2017.8.JNS171308 KEY WORDS anterior transmaxillary; transalisphenoid; Meckel’s cave; middle cranial fossa; skull base; surgical technique

eckel’s cave is a pouch of dural fold in the middle technology, many skull base pathologies can be treated cranial fossa. Inside the diverticulum dwells the effectively while potentially decreasing cosmetic and neu- trigeminal nerve as it emerges from the posterior rological morbidity. The endoscopic endonasal transptery- fossa,M the Gasserian ganglion, and part of the 3 branches goid approach to Meckel’s cave has been well described before they enter their respective foramina.22,32 Given the and has gained wide acceptance among skull base sur- simple contents of the structure, few types of pathology af- geons, and its clinical value has been proven.10,12,13,21,24 The fect the area. The most frequent tumor type that originates approach provides excellent access to the medial, anterior, from Meckel’s cave is trigeminal schwannoma;3,17 other and inferior aspects of Meckel’s cave, but it is limited and types include meningioma,17,23 epidermoid cyst,3,8,17,18 der- unsuitable for treating lateral or extended lesions.13 moid cyst,17 melanoma,7 and hemangiopericytoma.17 Noting that Meckel’s cave lies on the anterior slope of With advances in surgical anatomy and endoscopic the petrous apex, protected anteroinferiorly by the greater

ABBREVIATIONS EATT = endoscopic anterior transmaxillary transalisphenoid; ICA = internal carotid artery; ION = infraorbital nerve. SUBMITTED May 28, 2017. ACCEPTED August 8, 2017. INCLUDE WHEN CITING Published online February 2, 2018; DOI: 10.3171/2017.8.JNS171308. * H. Q. Truong and X. Sun contributed equally to this study.

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FIG. 1. Entry to maxillary sinus. A: Sublabial incision; the blue indicates the site of mucosal incision. B: Subperiosteal dissection–exposed anterior antral wall (AAW) and ION. C: The transantral approach provides access to the maxillary sinus (MS). D: Endoscopic view, via the transantral approach, of the posterior antral wall and the ION inside a bony canal. Figure is available in color online only. wing of the sphenoid, we investigated an anterior approach 1) entry into the maxillary sinus, 2) exposure of the greater to Meckel’s cave via an anterior transmaxillary corridor wing of the sphenoid, 3) exposure of the medial temporal through the pterygopalatine fossa, infratemporal fossa, and fossa, and 4) exposure of Meckel’s cave and the lateral wall the greater wing of the sphenoid. We suggest the new term of the cavernous sinus. Potential extension of the approach “transalisphenoid” for the procedure going through the to the infratemporal fossa and a combined transmaxillary greater wing of the sphenoid. In this article, we describe transpterygoid approach were also demonstrated. the details of this approach and discuss its potential advantages. EATT Approach Stage 1: Entry Into the Maxillary Sinus Methods The sublabial antrostomy (Caldwell-Luc procedure) We performed cadaveric studies in the Surgical Neuro- was used. The ipsilateral upper lip was retracted, and an anatomy Laboratory at the University of Pittsburgh. Five incision was made on the mucosa above the teeth (Fig. cadaver heads were used. Each of them was injected intra- 1A and B). Soft tissue anterior to the maxillary bone was vascularly with colored silicone (red for the arterial system elevated, and the infraorbital nerve (ION) was exposed and blue for the venous system). Surgical dissection was and protected. Entry into the sinus was allowed by using performed bilaterally using skull base neurosurgical endo- a chisel, Kerrison rongeurs, and a high-speed drill (Fig. scopic instruments, including 4-mm rod-lens endoscopes 1C). The maxillary sinus mucosa was removed, and the (0° and 30°) that were coupled to a high-definition camera posterior wall was exposed (Fig. 1D). and an AIDA HD system (Karl Storz GmbH and Co.). Vid- eos and still photos were taken during the dissections. Each Stage 2: Exposure of the Greater Wing of the Sphenoid specimen was scanned using thin-slice CT, and the Naviga- The posterior wall of the maxillary sinus was removed, tion System II (Stryker) was used for navigation. Two-hand and the pterygopalatine fossa was exposed. The periosteal and 3-hand techniques were used. After establishing this fascia and fat tissue were dissected carefully and removed. technique in the laboratory, we then applied it in 2 patients The ION was used as a landmark and guide to lead to the with tumors that involved Meckel’s cave, and we provide maxillary branch (V2) of the trigeminal nerve and fora- their illustrative clinical case reports later in the article. men rotundum. Contents of the infratemporal fossa, including pterygoid muscles, the maxillary artery, and the Results deep temporalis muscle, were then exposed (Fig. 2A). The endoscopic anterior transmaxillary transalisphenoid The ION was then mobilized from its groove on the (EATT) approach was divided into the following 4 stages: roof of the maxillary sinus. The infraorbital branch of the

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FIG. 2. Dissection steps in the transalisphenoid procedure. A: After removal of the posterior antral wall, contents of the pterygopalatine fossa (including the maxillary nerve [V2], the internal maxillary artery and its branches, the posterior superior alveolar artery [PSAA] running along the posterior superior alveolar nerve, the infraorbital artery [IOA], the descending palatine artery [DPA], the greater palatine nerve [GPN], and the sphenopalatine artery [SPA]) are exposed. The ION is dissected out of its bony canal (asterisk). B: The IOA and its 1–2 branches that connect to the intraorbital vasculature must be sacrificed to mobilize the ION superiorly and medially. The deep temporalis muscle (DTM) can be seen clearly. C: The internal maxillary artery (IMA) must be sacrificed to gain access to the infratemporal fossa, and the DTM and the upper head of the lateral pterygoid muscle (uLPM) are exposed. D: The DTM and uLPM are elevated subperiosteally to expose the greater wing of the sphenoid (GWS). The area of bone to be drilled is outlined by the yellow dashed line; the foramen rotundum (FR), pterygoid process (PP), foramen ovale, infraorbital fissure (IOF), and infratemporal crest (ITC) are used as landmarks. E: The GWS is drilled to paper-thin cortical bone; the IOF, V2, and mandibular nerve (V3) are used as its limitations. F: The temporal dura (asterisk) is exposed. The surgical corridor goes through the anterolateral triangle between V2 and V3. Figure is available in color online only.

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Unauthenticated | Downloaded 09/23/21 03:41 PM UTC H. Q. Truong et al. maxillary artery must be sacrificed to mobilize the nerve. After being released, the nerve can be pushed above the infraorbital fissure to provide a corridor to the upper part of the infratemporal fossa (Fig. 2B and C). The deep temporalis muscle was elevated subperiosteally and displaced laterally. The upper head of the lateral pterygoid muscle was elevated in the same manner and dissected along the lateral pterygoid plate and greater wing to expose the foramen ovale (Fig. 2D). Stage 3: Exposure of the Medial Middle Fossa Drilling of the greater wing of the sphenoid was then defined by using as landmarks the inferior orbital fissure anteriorly, the foramen rotundum medially, the foramen ovale posteriorly, and the infratemporal crest laterally (Fig. 2D). The surgical trajectory was confirmed with image guidance before advancing (Fig. 3). The lateral wall of the foramen rotundum should be drilled off to expose the posterior trunk of V2 for more mobility. The lateral border of the bony opening can be adjusted depending on extension of the lesion, although we found the infratemporal crest to be a reliable landmark. Lateral to the crest, the skull base slopes superiorly, which provides minimal additional access for the approach. The middle meningeal artery might be encountered and sacrificed if needed. After drilling the greater wing, the anterior dural wall of the middle fossa was exposed, and the corridor was then continued by performing an interdural elevation in between the medial wall and floor of the middle fossa, namely, at the anterolateral triangle of the middle cranial fossa, as defined between V2 and the mandibular branch (V3) of the trigeminal nerve (Fig. 2F). A 3D reconstruction of a postprocedural CT image FIG. 3. Image guidance and postprocedural surgical corridor. A: In- (Fig. 4) showed the bony opening in relation to its sur- traprocedural image guidance using tip-extension function to show the rounding bony structures and the perspective of the surgi- direction of approach pointing to Meckel’s cave and the lateral cavern- cal corridor. The length and width of the bony opening ous sinus area. B and C: Postprocedural biaxial CT images showing were 2.17 and 1.48 cm, respectively. The slope of the tri- the surgical corridor and measurements of the bone opening of the geminal impression directly faced the surgical route of the greater wing. Figure is available in color online only. transalisphenoid approach. Stage 4: Exposure of Meckel’s Cave and Lateral Wall of the on both sides (Fig. 5D). This possibility should be kept in Cavernous Sinus mind while performing this surgery to avoid transecting The dorsolateral wall of Meckel’s cave can be dissected the nerve at the end of tumor removal. interdurally between the dura propria of the posterior fos- Surgical access and maneuverability were excellent in sa origin (inner layer) and the dura propria of the middle Meckel’s cave and laterally. However, we found limited fossa (outer layer).11,14,22 Because the dura of Meckel’s cave maneuverability in the upper and anterior cavernous sinus. continues as the epineurium of the trigeminal branches,22 Access was blocked by the maxillary strut, a bony bridge we found it easier to dissect along the cleavage at which between V2 and the superior orbital fissure. Although we could identify the trigeminal porus, or the mouth of Meck- V2 exits the medial temporal fossa at the foramen rotun- 22 dum to develop a safe interdural separation (Fig. 5A). The el’s cave, access to the posterior fossa was limited by the dural cover of Meckel’s cave was then opened, and the tentorium and petrous bone with the petrous carotid artery Gasserian ganglion was exposed (Fig. 5B and C). Access underneath it. to the lateral wall of the cavernous sinus was gained by With the foramen ovale opened and the trigeminal gan- continuing the dissection upward. The ophthalmic branch glion exposed, we found that the motor root of the trigemi- (V1) was found first. Then, the fourth cranial nerve and nal nerve, which is medial and anterior to the ganglion, carotid artery were identified at the upper border of V1, can be dissected out of the sensory branch, protected, and followed by the third cranial nerve located at the roof of preserved (Figs. 5C and 6C). the sinus (Fig. 5D). In 2 specimens, the trochlear nerve was found cross- Infratemporal Fossa Extension ing the operative field laterally (temporal dura near the Dissection of the infratemporal fossa was carried fur- tentorium) to medially (inner wall of the cavernous sinus) ther with removal of the lateral pterygoid muscle. The

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FIG. 4. Postprocedural 3D reconstruction. Upper: Superior view showing bony opening on the greater wing of the sphenoid anterior to the trigeminal impression on the left temporal fossa. Lower: Anterior view similar to the surgical trajectory showing the trigeminal impression through the bony opening. Dimensions of the bony opening are shown also. Figure is available in color online only. branches of the mandibular nerve were identified and ex- cave can be opened to provide access to its anteromedial posed (Fig. 6D). The buccal nerve was first identified be- part (Fig. 6B and C). The cavernous sinus can be accessed tween the 2 heads of the lateral pterygoid muscle; it then also, but this access is limited to the inferolateral portion. ran along the medial border of the deep temporalis muscle We found that the lingual process of the sphenoid bone, downward and forward. The deep temporalis muscle and between the carotid artery and Meckel’s cave, is a good masseteric branches were followed along the inferior sur- landmark for the exposure. face of the greater wing toward the temporomandibular joint. The lingual and mandibular nerves were found pos- Illustrative Cases terior and medial to the lateral pterygoid muscle, against the lateral plate of the pterygoid. Case 1: Squamous Cell Carcinoma of the Infratemporal Fossa With Perineural Spread Combination With the Transmaxillary Transpterygoid A 73-year-old male patient presented with a 1-year his- Approach tory of progressive right-sided midface pain and numbness. We also explored the possibility of combining the trans- Physical examination revealed decreased sensation over alisphenoid and transmaxillary transpterygoid approach- the right V2 distribution. CT imaging revealed a 3.6-cm es. The pterygoid base and lateral recess were drilled to lesion centered in the posterior wall of the maxillary sinus expose the Vidian nerve and gain access to the anterome- and infratemporal fossa, invading the pterygopalatine fos- dial part of Meckel’s cave, together with the anterior wall sa and foramen rotundum. MRI confirmed perineural ex- of the cavernous sinus and paraclival carotid artery, and tension of sinonasal malignancy along the maxillary nerve the Vidian nerve. In those with a well-pneumatized lateral to the level of Meckel’s cave and the Gasserian ganglion recess, the area is exposed spontaneously after drilling the (Fig. 7). An endoscopic transmaxillary transalisphenoid pterygoid process (Fig. 6A). The medial wall of Meckel’s and transmaxillary transpterygoid approach was recom-

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FIG. 5. Exposure of Meckel’s cave and lateral wall of the cavernous sinus. A: Interdural dissection can be started conveniently at the dural cleavage (arrow), where V2 exits from the temporal lobe (TL). B: Complete interdural dissection–exposed dura propria layer that covers Meckel’s cave (MC) and the ophthalmic nerve (V1) superomedially. C: The dural layer is removed to expose the trigeminal ganglion (TG) and sensory roots (SR) of the trigeminal nerve. The superior petrosal sinus (SPS) is opened, bridging above the trigeminal porus (TP). The motor root (MR) of the trigeminal nerve can be seen anteromedial to the SR near the foramen ovale. D: Different dissection shows the possibility of the trochlear nerve (CN IV) crossing from the temporal dura near the anterior petroclinoid fold to the medial wall of the cavernous sinus to join with V1. The oculomotor nerve (CN III) and cavernous segment of the ICA (asterisk) can be exposed also. Figure is available in color online only. mended in an attempt to achieve gross-total resection and D). The nerve was transected just before entering Meckel’s symptomatic improvement before adjuvant therapy. cave to avoid a CSF leakage. Normal-looking nerve fibers Surgery via a sublabial transmaxillary approach was were identified at the transection level, but microscopic tu- performed. Soft, well-circumscribed, and vascularized mor infiltration was still present. Nasal mucosa was har- tumor was found protruding into the maxillary sinus. vested and used as a free graft to cover the exposed portion Pathological sampling and debulking were done to pro- of the middle fossa dura (Video 1). vide access to the pterygoid bone and greater wing of the VIDEO 1. Video summary of case 1. Copyright Department of sphenoid. Given the small size of the tumor in the middle Neurosurgery, University of Pittsburgh. Published with permission. cranial fossa, which created less space for maneuverability, Click here to view. a combined transalisphenoid and transpterygoid approach The patient recovered well after surgery, had no addi- was chosen. The tumor was resected from the ION and fol- tional neurological deficit, and experienced relief of his lowed posteriorly to expose the Vidian nerve, infraorbital fissure, infratemporal crest, and foramen rotundum, which severe preoperative pain. Postoperative MRI revealed com- were widened by the tumor (Fig. 8A and B). The base of the plete macroscopic removal of the tumor. Pathological ex- pterygoid and greater wing of the sphenoid bones around amination revealed the lesion to be a squamous cell carci- the foramen rotundum were drilled off to expose the dura noma, and the patient underwent adjuvant radiation therapy. of the middle cranial fossa. With good exposure and a wide working space, interdural dissection was performed Case 2: Middle Fossa Invasion of a Juvenile between the temporal lobe dura and the tumor-filled max- Nasopharyngeal Angiofibroma illary nerve toward the trigeminal ganglion (Fig. 8C and An 11-year-old boy presented with bilateral nasal ob-

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FIG. 6. Extension of the approach to the infratemporal fossa and medial aspect of Meckel’s cave. A: The combined transalisphenoid and transpterygoid approach was performed through the transantral corridor. In this case, a well-pneumatized lateral recess (yellow dashed line) provides an excellent view of the anterior cavernous and paraclival ICA (pICA). B: After bone removal and interdural dissection, Meckel’s cave can be accessed from both sides of the trigeminal ganglion. The lingula of the sphenoid (LoS) can be used as a landmark for the transpterygoid approach in this combination. C: Exposure of the anteromedial aspect of the trigeminal ganglion with its relevant structures, the abducens nerve (AN) with its accompanying sympathetic branches of the internal carotid plexus (asterisk), and the cavernous ICA (cICA). The motor root can be exposed and dissected, which leads to the trigeminal porus (arrow). The lingula of the sphenoid was removed to show the petrolingual fissure. D: Overview of possible extension of the approach. Branches of V3 can be seen, as can the lingual nerve (LN), inferior alveolar nerve (IAN), buccal nerve (BN), masseteric nerve (MN), and branches to the deep temporalis muscle (DTB). The tip of the dissector is pointing to the arcuate eminence of the temporal bone. Figure is available in color online only. struction, recurrent sinusitis, and minor epistaxis for ap- formed. The first stage of surgery was carried out through proximately 6 months. He also was experiencing right- endonasal and transmaxillary endoscopic approaches on sided hearing loss and constant tingling on his right cheek both sides to remove the large portion of tumor in the nasal (V2 distribution). Physical examination confirmed right- cavity, pharynx, and sphenoid sinus and debulk the tumor sided hearing loss with middle ear effusion but intact sen- in the cavernous sinus and infratemporal fossa. The sur- sation to light touch throughout the trigeminal branches. gery was staged because of significant blood loss. The sec- MRI revealed a markedly enhancing bulky mass centered ond stage was performed 1 week later for total removal of in the area of the right pterygopalatine fossa with exten- the tumor. Residual tumor around the right internal carotid sion into the right posterior nasal cavity, nasopharynx, artery (ICA) at the foramen lacerum and at the petrous right cavernous sinus, right infratemporal fossa, and right bone and anterior wall of the cavernous sinus was dissect- middle fossa with compression of the right temporal lobe ed and removed in piecemeal fashion. Meckel’s cave was (Fig. 9). Endoscopic surgery in which endonasal and bi- opened medially, and V3, V2, and the ION were identified lateral transmaxillary approaches were combined for total and carefully dissected. A transalisphenoid procedure was removal of the tumor with the possibility of staged surgery performed to remove tumor at the superior orbital fissure was offered. Endovascular embolization of the right inter- near the apex and middle fossa lateral to Meckel’s cave to nal maxillary artery and ascending pharyngeal artery was the lateral sphenoid wing. Minor CSF weeping was ob- performed to reduce blood loss. served when the residual tumor was peeled en bloc from A bilateral sublabial transmaxillary procedure was per- the temporal dura. Angled (45° and 70°) scopes, together

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FIG. 8. From laboratory to the operating room, cadaveric correlation to surgery. A and B: Endoscopic views of the greater wing of the sphenoid showing landmarks. InfraT. Crest = infratemporal crest; yellow line indicates the inferior orbital fissure. B: View after removal of tumor in the pterygopalatine fissure, showing an enlarged V2 filled with tumor. C and D: Views after bone drilling showing interdural dissection of V2 toward Meckel’s cave. Figure is available in color online only.

study reports, suggested the endoscopic extradural supraorbital approach, which shares a similar corridor but might avoid the risk of complications and suboptimal cosmesis. FIG. 7. Case 1. Preoperative MR images. A: Preoperative axial view shows that the tumor occupies and displaces the pterygopalatine fossa No clinical application of this approach has been reported. and extends to the infratemporal fossa and through the sphenopalatine The corridor lateral to Meckel’s cave provides excel- foramen and foramen rotundum. B: Preoperative coronal view confirms lent access to the entire middle cranial fossa and upper that the extension is along V2. C and D: Respective postoperative axial part of the posterior cranial fossa by transecting the ten- and coronal views showing complete removal of V2 extension of the torium, but the important advantage of the corridor is the tumor. possibility it provides for combining it with transpetrosal approaches for complete removal of tumors that span the middle and posterior cranial fossae.4,5,9,13,17,20,23,27,32,33 How- with angled dissectors, were deployed to completely re- ever, the tradeoff is the risk of morbidity that might remove residual tumor in the middle cranial fossa. A fat sult from temporal lobe retraction and injury to the vein graft was used to prevent CSF leakage (Video 2). of Labbe, middle ear structures, facial nerves, and the pe- 9,13 VIDEO 2. Video summary of case 2. Copyright Department of trous ICA. Neurosurgery, University of Pittsburgh. Published with permission. Several approaches for reaching Meckel’s cave endo- Click here to view. scopically have been developed. The classification by 15 The patient recovered well after the surgery, although Komatsu et al. includes 3 transcranial routes (the extra- he experienced right V2 hypoesthesia and transient sixth- dural supraorbital, extradural subtemporal, and retrosig- nerve palsy. Postoperative imaging revealed total removal moid approaches) and the endonasal transpterygoid and of the tumor (Fig. 10). Pathological results confirmed the transmaxillary transpterygoid approaches. Among those tumor to be a nasopharyngeal angiofibroma. approaches, the endonasal transpterygoid approach has been applied clinically and resulted in reasonably good outcomes.10,12,13,21,24,25,29,34 However, because the route is Discussion slightly medial to Meckel’s cave, the approach provides Standard transcranial and endoscopic endonasal ap- limited access to lesions that are located or extend later- proaches share territory at Meckel’s cave.13 The antero- ally in the middle cranial fossa.13 lateral corridor approaches, with the pterion as an entry The EATT approach creates a corridor anterior to point, provide good access to the lateral and upper cavern- Meckel’s cave and the medial middle cranial fossa. By go- ous sinus; however, to gain access to the anterior compo- ing through the greater wing of the sphenoid, this approach nents of Meckel’s cave, the trajectory must dissect through provides surgical access directly anterior to Meckel’s cave, the anteromedial and anterolateral triangles. For lesions and the lesion is in line with the surgical corridor. This located posteriorly inside the cave, the ganglion must be approach provides a better opportunity for microsurgical traversed.9,13,32 These approaches also confer a risk of mor- dissection of the tumor and neural tissue and, hence, pres- bidity that results from brain retraction and temporalis ervation of function. The approach involves an interdural muscle elevation.16 Komatsu et al.,15,16 in their anatomical dissection technique, as shown in Video 1, so it is com-

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FIG. 10. Case 2. Postoperative images. A–C: Immediately postopera- FIG. 9. Case 2. Preoperative images. A and B: MR and CT images, re- tive MR images showing total removal of tumor. D: Postoperative sagit- spectively, showing markedly enhancing tumor occupying the sphenoid tal CT image demonstrating the surgical corridor (yellow dashed lines) and nasal cavity, extending into the pterygopalatine and middle cranial from the antrostomy to middle cranial fossa. Figure is available in color fossa. C and D: Coronal MR images at different levels show the exten- online only. sion of tumor into the right parapharyngeal space, infratemporal fossa, and middle cranial fossa. limited access to the posterior fossa because of the depth of the approach and depth of the trigeminal porus. In the pletely extradural in regard to the temporal lobe. It also re- case of dumbbell-shaped tumors, we do not know whether quires minimal brain retraction, given that working space the trigeminal porus can be expanded enough to allow safe is created by the tumor. surgical intervention.1 In contrast to the endoscopic endonasal transpterygoid The EATT approach can conveniently be combined approach, this approach offers excellent surgical access with the transantral transpterygoid approach to provide to the anterior, lateral, and posterior portions of Meckel’s better access to the anteromedial aspect of Meckel’s cave cave. The lateral limit is the line of the temporomandibu- and more surgical freedom when needed. The transantral lar joint, as can be seen in Video 2. By going through the transpterygoid and endonasal transpterygoid approaches pterygopalatine and infratemporal fossa, this approach were described and compared by Van Rompaey et al.28 In avoids the cavernous sinus and the associated risk of inju- that study, they concluded that the 2 approaches provide ry to the carotid artery and abducens nerve. Although the similar workable access to Meckel’s cave. The authors also carotid artery can be encountered posteriorly when going advocated the minimally invasive aspect of the transantral through Meckel’s cave, the petrolingual ligament can serve approach for avoiding the removal of sphenoid sinus, the as a landmark for recognizing and avoiding the artery. The posterior third of the nasal septum, the middle and lower majority of schwannomas, the most common pathology in turbinates, and the medial wall of the maxillary sinus.28 Meckel’s cave,17 have been shown in previous study re- The authors also suggested that the transantral approach ports to be well defined from neighboring structures and could be expanded to cover the whole lateral skull base, to displace rather than engulf those structures.15,17,30 This but they did not provide any further description, especially approach can preserve the dura propria of the lateral wall for how to approach the lateral aspect of Meckel’s cave. In and, thus, avoid injury to the cranial nerves and ICA. contrast to Van Rompaey et al., we do not see the need to Other than trigeminal schwannomas limited to Meckel’s expose and dissect the paraclival carotid artery for Meck- cave, the stand-alone EATT approach can be a competitor el’s cave lesions. We suggest using the lingula of the sphe- for the endoscopic endonasal transpterygoid approach to noid bone to limit the bony exposure medially, because epidermoid/dermoid cysts or melanomas in Meckel’s cave. the lingula will continue laterally with the petrolingual The decision should be more affirmative when imaging ligament, which provides a natural separation between can delineate the tumor to be medial or lateral to the gan- Meckel’s cave and the petrous carotid artery. glion. The transalisphenoid approach, in our opinion, offers Important to note is that the EATT approach offers the least invasive route for treating perineural spread of multicompartmental access to the middle fossa and the malignancy that involves trigeminal nerves, especially the infratemporal and pterygopalatine fossae. Therefore, it V2 and V3 branches, such as squamous cell carcinomas, provides wide surgical intervention for tumors that span basal cell carcinomas, melanomas, and adenoid cystic those 3 compartments. This approach, however, provides carcinomas.2,26,31 The approach can follow the maxillary

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Unauthenticated | Downloaded 09/23/21 03:41 PM UTC H. Q. Truong et al. nerve from its cutaneous portion through the maxillary 3. Beck DW, Menezes AH: Lesions in Meckel’s cave: variable sinus and pterygopalatine fossa to the Gasserian ganglion. presentation and pathology. J Neurosurg 67:684–689, 1987 The mandibular nerve can also be followed from the Gas- 4. Chen LF, Yang Y, Yu XG, Gui QP, Bu B, Xu BN, et al: Op- erative management of trigeminal neuromas: an analysis of a serian ganglion to the mandible with infratemporal fossa surgical experience with 55 cases. Acta Neurochir (Wien) dissection. Other possible routes of perineural spread, such 156:1105–1114, 2014 as the greater and lesser palatine nerves, Vidian nerve, and 5. Day JD, Fukushima T: The surgical management of trigemi- pterygoplalatine ganglion,26 can be addressed also. Inter- nal neuromas. Neurosurgery 42:233–241, 1998 esting to note is that the microsurgical counterpart of the 6. DeMonte F, Hanna E: Transmaxillary exploration of the approach for malignant maxillary nerve perineural spread intracranial portion of the maxillary nerve in malignant peri- was described in 2007 by DeMonte and Hanna,6 who also neural disease. Technical note. J Neurosurg 107:672–677, predicted the endoscopic application of the surgical route 2007 and advocated its advantages. 7. Falavigna A, Borba LA, Ferraz FA, Almeida GC, Krindges Júnior JV: Primary melanoma of Meckel’s cave: case report. Angiofibromas are benign tumors that originate at the Arq Neuropsiquiatr 62 (2A):353–356, 2004 medial aspect of the pterygopalatine space but can extend 8. Furtado SV, Hegde AS: Trigeminal neuralgia due to a small through the inferior orbital fissure and gain access to the Meckel’s cave epidermoid tumor: surgery using an extradural middle cranial fossa through the superior orbital fissure. corridor. Skull Base 19:353–357, 2009 The floor of the middle cranial fossa can be eroded, and 9. Inoue T, Rhoton AL Jr, Theele D, Barry ME: Surgical ap- large intracranial tumors can involve the lateral cavern- proaches to the cavernous sinus: a microsurgical study. Neu- ous sinus. As shown in Video 2, the transalisphenoid ap- rosurgery 26:903–932, 1990 proach, by following the course of the tumor, provides 10. Jacquesson T, Berhouma M, Picart T, Jouanneau E: Total removal of a trigeminal schwannoma via the expanded endo- optimal access to the tumor both medial and lateral to the scopic endonasal approach. Technical note. Acta Neurochir orbital apex. (Wien) 157:935–938, 2015 Dural reconstruction should be a concern with the 11. Janjua RM, Al-Mefty O, Densler DW, Shields CB: Dural re- transantral approach, because a vascularized nasal septal lationships of Meckel cave and lateral wall of the cavernous flap, which has been found to be very effective for CSF sinus. Neurosurg Focus 25(6):E2, 2008 leak prevention,19 is not available with this approach. We 12. Jouanneau E, Simon E, Jacquesson T, Sindou M, Tringali S, suggest multilayered free-graft reconstruction and possi- Messerer M, et al: The endoscopic endonasal approach to the bly a lumbar drain for CSF diversion, because the arach- Meckel’s cave tumors: surgical technique and indications. World Neurosurg 82 (6 Suppl):S155–S161, 2014 noid space around the Gasserian ganglion is connected to 13. Kassam AB, Prevedello DM, Carrau RL, Snyderman CH, the posterior fossa. Gardner P, Osawa S, et al: The front door to Meckel’s cave: The transalisphenoid approach requires subperiosteal an anteromedial corridor via expanded endoscopic endonasal elevation of only a part of the lateral pterygoid and deep approach—technical considerations and clinical series. Neu- temporalis muscles. Significant reduction in mastication rosurgery 64 (Suppl 1):ons71–ons83, 2009 power and postoperative pain while chewing are not ex- 14. Kawase T, van Loveren H, Keller JT, Tew JM: Meningeal pected. The ION is kept intact macroscopically during the architecture of the cavernous sinus: clinical and surgical im- dissection, but hypesthesia can result. Clinical validation plications. Neurosurgery 39:527–536, 1996 15. Komatsu F, Komatsu M, Di Ieva A, Tschabitscher M: Endo- is needed, however, to confirm and put forth the general scopic approaches to the trigeminal nerve and clinical con- indications for this approach. sideration for trigeminal schwannomas: a cadaveric study. J Neurosurg 117:690–696, 2012 Conclusions 16. Komatsu F, Komatsu M, Inoue T, Tschabitscher M: Endo- scopic supraorbital extradural approach to the cavernous The EATT approach is technically feasible and offers sinus: a cadaver study. J Neurosurg 114:1331–1337, 2011 excellent surgical access to the anterior and lateral por- 17. Muto J, Kawase T, Yoshida K: Meckel’s cave tumors: relation of Meckel’s cave, and the possibility of expansion tion to the meninges and minimally invasive approaches for toward the infratemporal fossa and lateral middle fossa. surgery: anatomic and clinical studies. Neurosurgery 67 (3 It can complement the current repertoire of surgical treat- Suppl Operative):ons291–ons299, 2010 ment for Meckel’s cave lesions and could be ideal for le- 18. Ohta H, Ottomo M, Nakamura T, Yokota A: [A case of epidermoid tumor inside the Meckel’s cave.] No Shinkei Geka sions that are located lateral to the trigeminal ganglion in 25:943–947, 1997 (Jpn) Meckel’s cave or extend from the maxillary sinus, infra- 19. Ong YK, Solares CA, Carrau RL, Snyderman CH: New temporal fossa, or pterygopalatine fossa into the middle developments in transnasal endoscopic surgery for malignan- cranial fossa, Meckel’s cave, and cavernous sinus, such as cies of the sinonasal tract and adjacent skull base. Curr Opin schwannomas, meningiomas, and sinonasal tumors. Otolaryngol Head Neck Surg 18:107–113, 2010 (Erratum in Curr Opin Otolaryngol Head Neck Surg 18:221, 2010) 20. Ramina R, Mattei TA, Soria MG, da Silva EB, Jr., Leal AG, References Neto MC, et al: Surgical management of trigeminal schwan- 1. Al-Mefty O, Ayoubi S, Gaber E: Trigeminal schwannomas: nomas. Neurosurg Focus 25(6):E6, 2008 removal of dumbbell-shaped tumors through the expanded 21. Raza SM, Donaldson AM, Mehta A, Tsiouris AJ, Anand VK, Meckel cave and outcomes of cranial nerve function. J Neu- Schwartz TH: Surgical management of trigeminal schwanno- rosurg 96:453–463, 2002 mas: defining the role for endoscopic endonasal approaches. 2. Amit M, Eran A, Billan S, Fridman E, Na’ara S, Charas T, et Neurosurg Focus 37(4):E17, 2014 al: Perineural spread in noncutaneous head and neck cancer: 22. Sabancı PA, Batay F, Civelek E, Al Mefty O, Husain M, Ab- new insights into an old problem. J Neurol Surg B Skull dulrauf SI, et al: Meckel’s cave. World Neurosurg 76:335– Base 77:86–95, 2016 341, 266–267, 2011

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23. Samii M, Carvalho GA, Tatagiba M, Matthies C: Surgical multiple fossae: surgical methods and review of the literature. management of meningiomas originating in Meckel’s cave. J Neurosurg 91:202–211, 1999 Neurosurgery 41:767–775, 1997 34. Zhang QH, Chen G, Kong F, Guo HC, Li MC: [Endoscopic 24. Shin SS, Gardner PA, Stefko ST, Madhok R, Fernandez- endonasal surgery of trigeminal schwannoma extending Miranda JC, Snyderman CH: Endoscopic endonasal approach into the infratemporal fossa.] Zhonghua Wai Ke Za Zhi for nonvestibular schwannomas. Neurosurgery 69:1046– 48:1454–1458, 2010 (Chinese) 1057, 2011 25. Simal Julián JA, Miranda Lloret P, García Piñero A, Botella Asunción C: Full endoscopic endonasal suprapetrous approach to Meckel’s cave. Acta Neurochir (Wien) 156:1623– Disclosures 1626, 2014 26. Singh FM, Mak SY, Bonington SC: Patterns of spread The authors report no conflict of interest concerning the materi- of head and neck adenoid cystic carcinoma. Clin Radiol als or methods used in this study or the findings specified in this 70:644–653, 2015 paper. 27. Van Rompaey J, Bush C, Khabbaz E, Vender J, Panizza B, Solares CA: What is the best route to the Meckel cave? Ana- Author Contributions tomical comparison between the endoscopic endonasal ap- Conception and design: Truong, Sun. Acquisition of data: Truong, proach and a lateral approach. J Neurol Surg B Skull Base Sun, Celtikci. Analysis and interpretation of data: Truong, Sun, 74:331–336, 2013 Celtikci, Borghei-Razavi. Drafting the article: Truong. Critically 28. Van Rompaey J, Suruliraj A, Carrau R, Panizza B, Solares revising the article: Fernandez-Miranda, Sun, Wang, Snyderman, CA: Meckel’s cave access: anatomic study comparing the Gardner. Reviewed submitted version of manuscript: Fernandez- endoscopic transantral and endonasal approaches. Eur Arch Miranda, Truong, Wang, Snyderman, Gardner. Approved the final Otorhinolaryngol 271:787–794, 2014 version of the manuscript on behalf of all authors: Fernandez- 29. Wang X, Zhang X, Hu F, Yu Y, Gu Y, Xie T, et al: Image- Miranda. Administrative/technical/material support: Celtikci, guided endoscopic endonasal transmaxillary transpterygoid Borghei-Razavi. approach to Meckel’s cave. Turk Neurosurg 26:309–314, 2016 Supplemental Information 30. Wanibuchi M, Fukushima T, Zomordi AR, Nonaka Y, Fried- Videos man AH: Trigeminal schwannomas: skull base approaches Video 1. https://vimeo.com/237562099. and operative results in 105 patients. Neurosurgery 70 (1 Video 2. https://vimeo.com/237562216. Suppl Operative):132–144, 2012 31. Warren TA, Nagle CM, Bowman J, Panizza BJ: The natural history and treatment outcomes of perineural spread of ma- Previous Presentations lignancy within the head and neck. J Neurol Surg B Skull Portions of this work were presented in abstract poster form at the Base 77:107–112, 2016 27th Annual Meeting of the North American Skull Base Society, 32. Yasuda A, Campero A, Martins C, Rhoton AL Jr, de Oliveira held in New Orleans, LA, March 3–5, 2017. E, Ribas GC: Microsurgical anatomy and approaches to the cavernous sinus. Neurosurgery 62 (6 Suppl 3):1240–1263, Correspondence 2008 Juan C. Fernandez-Miranda: University of Pittsburgh Medical 33. Yoshida K, Kawase T: Trigeminal neurinomas extending into Center, Pittsburgh, PA. [email protected].

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