Abstract
The anteromedial temporal region and the lateral wall of the sphenoid can be the site of an array of pathology including trigeminal schwannoma, encephalocele, cholesterol granuloma of the petrous apex, malignancy, infection, and sellar pathology extending to the lateral cavernous sinus. Approaches to this region are technically challenging and the existing approach requires sacrifice of all of the turbinates including the nasolacrimal duct, which can cause postoperative complications.
We describe a novel anatomical landmark between the periorbita and the periosteum of the pterygopalatine fossa (which is located at the inferolateral periorbital periosteal line [ILPPL]). The posterior one-third of the incision line lies between the foramen rotundum and the superior orbital fissure, which is proximal to the maxillary strut.
A 1.5-cm incision can divide the orbital and pterygoid contents and lead us to the posterior inferolateral orbital region, anteromedial temporal region, lateral wall of the sphenoid sinus, and lateral wall of the cavernous sinus.
A combined multiangled approach to the ILPPL will enable us to preserve all of the turbinates and the septum, and the nasolacrimal duct, allowing for the preservation of the physiological function and pedicled flaps, such as the middle turbinate, inferior turbinate, and septal membrane flap.
The ILPPL is a simple, effective, and novel landmark for the minimally invasive approach to the anteromedial temporal fossa.
Keywords: skull base, sinus cancer, cranial base, endoscopic sinus surgery, endoscopic skull base surgery
Introduction
The anteromedial temporal region and the lateral wall of the sphenoid sinus contain a complex set of neurovascular structures: the second and third divisions of the trigeminal nerve (V2 and V3), internal carotid artery, cavernous sinus, and temporal lobe. Diverse pathology can arise in this anatomically complex region, including trigeminal schwannoma, encephalocele, petrous apex cholesterol granuloma, malignancy with or without perineural spread, infection, and typical sellar pathology that extends to the lateral cavernous sinus. Approaches to this region are technically challenging because of the anatomic depth and the adjacent neurovascular structures. A perfect approach to this region has not been identified yet.
A transorbital approach has been previously described; however, the exposure is frequently inadequate and specialized instruments are required for orbital retraction. 1 Endoscopic transpterygoid approaches have also been reported, but these generally involve sacrifice of the piriform aperture, nasolacrimal duct (NLD), inferior turbinate, and/or the pterygopalatine fossa (PPF) neurovascular contents to gain surgical access. The aforementioned structures have important physiological function and sacrifice of these structures can result in facial deformity, alar collapse, NLD stenosis, palatal and facial numbness, dry eye, and/or empty nose syndrome. 2 3
The objective of this study is to report a novel technique to maximize surgical access to the anteromedial temporal fossa the and lateral sphenoid without sacrifice of these important structures. We describe a novel anatomic landmark between the periorbita and the periosteum of the PPF, which is located at the inferolateral periorbital periosteal line (ILPPL).
We previously reported the direct approach to the anterior and lateral part of the maxillary sinus (DALMA) 4 via an endoscopic modified medial maxillectomy (EMMM) that preserves the piriform aperture, NLD, and turbinates. 5 6 Combining these approaches and dividing the junction between the periorbita and the periosteum of the PPF lead us to the posterior inferolateral orbital region, anteromedial temporal region, lateral wall of the sphenoid sinus, and lateral wall of the cavernous sinus.
Therefore, the main goals of this study were to describe this novel landmark and elucidate the clinical implications.
Methods
Five cadaver heads were purchased through Science Care Inc. (Phoenix, AZ). An endoscopic endonasal approach (EEA) to the medial orbit and PPF was performed on all five cadaveric specimens at the University of North Carolina Surgical Skills Laboratory. It should be noted that only nine sides were dissected as one side on one of the specimens was not fit for the analysis because of the preexisting damage of the orbital and temporal regions. High-resolution cone beam computed tomography (CT) scans were performed on each of the specimens before and after dissection (J. Morita Mfg. Corp., Kyoto, Japan).
A 0- and 70-degree endoscope (4 mm diameter and 18 cm length) coupled with a high-definition camera and monitor (Karl Storz Endoscopy, Tuttlingen, Germany) was used to obtain the endoscopic view. Video images were recorded and stored using an AIDA system (Karl Storz Endoscopy). A high-speed drill (Stryker Co., Kalamazoo, MI) with a straight handpiece and 4-mm coarse diamond burrs were used for the osseous dissections.
The lengths of the ILPPL and maxillary strut were endoscopically measured. Exposure of the orbital fat and pterygopalatine fat after incision was also evaluated with palpation of the globe. The area of drilling was compared using pre- and postoperative CT.
Results
Video 1 Right-sided cadaver dissection.
Following a sphenoethmoidectomy, a concurrent EMMM and DALMA was performed. 4 5 Through the DALMA port and prelacrimal port, the lateral aspect of the maxillary sinus could be accessed with a 0-degree endoscope and straight instruments. The posterior bony wall of the maxillary sinus was removed without sacrificing any branches of the internal maxillary artery including the sphenopalatine artery or descending palatine artery, infraorbital nerve, inferior and middle turbinates, piriform aperture, and NLD ( Fig. 1a ).
Fig. 1.
Right side of the specimen viewed using a 0-degree endoscope. ( a ) Line structure is seen between the periorbita and periosteum of the pterygopalatine fossa ( white dot ). ( b ) Posterior one-third of the line remains; exposure of the great sphenoidal wing is inadequate ( white circle ). ( c ) Maxillary strut ( white arrow ) located between the superior orbital fissure and foramen rotundum ( white circle ); the vidian artery is seen ( white square ). ( d ) Orbital ( white circle ) and pterygopalatine surfaces ( white square ) of the great sphenoidal wing are clearly visualized. ( e ) Temporal dura and inferior orbital nerve (white circle) are identified. ( f ) Interior ( white square ) and middle turbinates ( white circle ) are preserved.
Using a diamond drill and Kerrison rongeurs, the lamina papyracea and the remaining posterior walls of the maxillary sinus were removed to expose the periorbita and the PPF.
An incision between the periorbita and the periosteum of the PPF was performed extending anterior from the maxillary strut ( Fig. 1a–c ). After incision of the ILLPL, the periosteum could be elevated up to the infraorbital surface ( Fig. 1b ) and down to the posterior wall of the PPF ( Fig. 1d ).
The posterior one-third of the incision line lies between the foramen rotundum and the superior orbital fissure, which is proximal to the maxillary strut ( Fig. 1b–d ); the zygomatic nerve (ZN) runs just below this region and is divided during the noted incision. The root of the V2 nerve and foramen rotundum was identified easily, with wide exposure of the greater wing of the sphenoid and superior orbital fissure.
After entering the orbital floor, the lateral part of the superior orbital fissure was easily detected and could be drilled out and removed completely ( Fig. 1e ).
After drilling, the greater wing of the sphenoid, anteromedial temporal fossa, floor of the temporal fossa, V3 nerve, lateral aspect of the sphenoid, lateral aspect of the cavernous sinus, and the posterior lateral area of the orbit were accessible transnasally using a 0-degree endoscope ( Fig. 1e ).
After the dissection, the lateral nasal wall with intact inferior, middle, and superior turbinates could be reconstructed by interrupted suture ( Fig. 1f ; Video 1 ).
The length of the ILPPL, vertical length of the maxillary strut, and orbital fat exposure after incision were measured ( Table 1 ). The average length of the ILPPL was 17.75 ± 1.75 mm. The average vertical height of the maxillary strut was 4.59 ± 1.8 mm. Exposure of the orbital fat and pterygopalatine fat after incision was absent.
Table 1. Measurement of the vertical length of the maxillary strut, length of the inferior lateral periorbital periosteal line (ILPPL), and orbital fat exposure after incision of the ILPPL.
| No. | Side | Vertical length of the maxillary strut (mm) | Length of the ILPPL (mm) | Orbital fat exposure after incision of the ILPPL |
|---|---|---|---|---|
| 1 | Right | 7.98 | 16 | – |
| Left | 4.45 | 18 | – | |
| 2 | Right | 5.45 | 16 | – |
| Left | 4.34 | 19 | – | |
| 3 | Right | 3.03 | 16 | – |
| 4 | Right | 4.47 | 21 | – |
| Left | 2.43 | 18 | – | |
| 5 | Right | – | 18 | – |
| Mean ± SD | 4.59 ± 1.8 | 17.75 ± 1.75 |
Discussion
Endoscopic transorbital approaches (ETOAs) have been described to access V2 and V3 schwannomas and lateral sphenoid encephaloceles, especially located lateral to Sternberg's canal; however, with such approaches, it can be difficult to access the posterior and inferior aspects of pathology due to the angle of the approach and anatomic limitations of the corridor. One report evaluated 50 cases of the trigeminal schwannoma to evaluate the optimal indications and clinical outcomes of ETOAs for trigeminal schwannomas, based on the classification by Samii. 7 They concluded that tumors involving the infratemporal fossa (type D3) can be successfully removed using an ETOA alone or in combination with an EEA. 8 Our endonasal approach may be an optimal approach instead of an ETOA or even in combination with an ETOA.
The addition of the endonasal approach provided wide access to the infratemporal fossa and the middle cranial fossa. However, the addition of the endonasal approach comes with additional morbidity. 1 9 The corridor we describe in this study is less invasive but provides similar access.
A 17.75-mm incision of the ILPPL extending from and including the maxillary strut allows direct approach to the floor of the temporal fossa, the medial region of the superior orbital fissure, the V2 and V3 nerves, and the lateral sphenoid sinus without sacrificing any turbinate, neurovascular structure, the piriform aperture, or NLD. Moreover, most orbital approaches result in fat exposure that requires concurrent management as it interferes with the surgical field. Incision of the ILPPL avoids such exposure.
Approaching the superior orbital fissure requires an additional posterior 5-mm incision that sacrifices the ZN. Since the ZN is comprised of parasympathetic fibers to the frontal branch of the trigeminal nerve, which innervate the lacrimal gland and conjunctiva, this procedure may lead to dry eyes. However, once the ZN is sacrificed, the contents of the superior orbital fissure and V2 nerve can be further displaced and the anteromedial temporal fossa clearly visualized leading to minimized risk of additional injury. 10
The EMMM combined with the DALMA approach provided two working ports affording a multiangled access, thereby allowing us to insert one or two instruments in addition to the endoscope ( Fig. 2a–f ). Additionally, such a multiangled approach enabled us to reach laterally with preservation of normal anatomic structures and physiological function. Such an approach also allowed preservation of an array of pedicled flaps, such as the middle turbinate, inferior turbinate, and nasoseptal flaps.
Fig. 2.
Cone beam computed tomography (CT) findings pre- and postprocedure. ( a ) Coronal, before surgery. ( b ) Coronal, after surgery; the lateral orbital wall is removed, while the infraorbital nerve is preserved. ( c ) Coronal, after surgery, with an illustration; the area in yellow is surgically accessible. ( d ) Axial, before surgery. ( e ) Axial, after surgery; anteromedial wall of the temporal fossa is removed. ( f ) Axial, after surgery; the area in white can be reached through the DALMA port; the inferior medial area in yellow can be reached through the nose. DALMA, direct approach to the anterior and lateral part of the maxillary sinus.
Although the approach has quite limited indications, the ILPPL is a simple, effective, and novel landmark for the minimally invasive approach to the anteromedial temporal fossa.
Acknowledgments
We are grateful to Crystal A. Lincoln, Manager of the University of North Carolina Neurosurgery Skills Laboratory, for support on the cadaver research.
Conflict of Interest None declared.
These authors contributed equally to this article.
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