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Endoscope-Assisted Transmaxillosphenoidal Approach to the Sellar and Parasellar Regions: An Anatomic Study
Accepted Manuscript Endoscope-Assisted Trans-Maxillo-Sphenoidal Approach to Sellar and Parasellar Regions: Anatomic Study Filippo Gagliardi, M.D., Ph.D., Carmine A. Donofrio, M.D., Alfio Spina, M.D., Michele Bailo, M.D., Cristian Gragnaniello, M.D., Ph.D., Alberto L. Gallotti, M.D., Samer K. Elbabaa, M.D., F.A.C.S., Anthony J. Caputy, M.D., F.A.C.S., Pietro Mortini, M.D. PII:
S1878-8750(16)30700-8
DOI:
10.1016/j.wneu.2016.08.034
Reference:
WNEU 4444
To appear in:
World Neurosurgery
Received Date: 1 June 2016 Revised Date:
8 August 2016
Accepted Date: 9 August 2016
Please cite this article as: Gagliardi F, Donofrio CA, Spina A, Bailo M, Gragnaniello C, Gallotti AL, Elbabaa SK, Caputy AJ, Mortini P, Endoscope-Assisted Trans-Maxillo-Sphenoidal Approach to Sellar and Parasellar Regions: Anatomic Study, World Neurosurgery (2016), doi: 10.1016/j.wneu.2016.08.034. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT ENDOSCOPE-ASSISTED TRANS-MAXILLO-SPHENOIDAL APPROACH TO SELLAR AND PARASELLAR REGIONS: ANATOMIC STUDY
[1]
Filippo Gagliardi, M.D., Ph.D., [1]Carmine A. Donofrio, M.D., [1]Alfio Spina, M.D.,
Michele Bailo, M.D., [2]Cristian Gragnaniello, M.D., Ph.D., [1]Alberto L. Gallotti, M.D.,
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[1]
[3]
Samer K. Elbabaa, M.D., F.A.C.S., [2]Anthony J. Caputy, M.D., F.A.C.S., and [1]Pietro
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Mortini, M.D.
[1] Department of Neurosurgery and Gamma Knife Radiosurgery, San Raffaele Scientific Institute, Vita-Salute University, Milan, Italy
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[2] Department of Neurosurgery, George Washington University, Washington DC, USA [3] Division of Pediatric Neurosurgery, Department of Neurological Surgery, Saint Louis University School of Medicine, Saint Louis, MO, USA
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Corresponding Author:
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Short title: Endoscope-assisted trans-maxillo-sphenoidal approach
Filippo Gagliardi, M.D., Ph.D.
Department of Neurosurgery and Gamma Knife Radiosurgery
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San Raffaele Scientific Institute Via Olgettina 60, 20132 Milano, Italy E-mail: [email protected] Phone: +39-02-26432396 Fax:
+39-02-26437302
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ACCEPTED MANUSCRIPT ABSTRACT
Objective. Anterolateral skull base surgery to sellar and parasellar region has always represented a technical challenge for neurosurgeons. The microscopic endoscope-assisted trans-maxillo-sphenoidal approach (MEMSA) affords a direct surgical corridor free from
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critical skull base structures. The aim of this study is to describe and critically evaluate its application to access the sellar and parasellar areas in terms of surgical exposure and operability.
Methods. Six cadaveric heads were examined. A stepwise dissection of the MEMSA
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was performed. Relevant anatomy and surgical technique have been critically described and comparatively reviewed. The operability score was applied for quantitative analysis of surgical operability.
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Results. MEMSA provides a wide bilateral surgical exposure and vascular control of the sellar, suprasellar, and parasellar regions, achieving the highest operability on the midline and the parasellar region. The approach can be tailored according to the lesion, easily widening the surgical corridor toward the contralateral pterygopalatine fossa. Anatomic knowledge of maxillary sinus landmarks is key to utilizing this approach. Favorable
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sphenoidal anatomy is the main limiting factor, making MEMSA an alternative surgical option to endoscopic endonasal routes, in case of their unfeasibility, and the approach of choice in selected cases of primarily sellar lesions widely extending contralaterally to the approached maxillary sinus.
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Conclusions. MEMSA is a safe and effective route, which provides access to the sellar, suprasellar and contralateral parasellar areas via a direct, minimally-disruptive surgical corridor. The preservation of nasal anatomy ensures the availability of preserved mucosal
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flaps for use with further reconstruction.
Key words: Trans-maxillo-sphenoidal approach; sella; skull base approach; pituitary
tumors.
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ACCEPTED MANUSCRIPT INTRODUCTION
Anterolateral skull base approaches to sellar and parasellar region have always represented a technical challenge for neurosurgeons, because of the extreme complexity of the critical neurovascular structures in this area.
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In the last two decades intrinsic surgical morbidity related to traditional trans-cranial and transfacial approaches has pushed the development of innovative microscopic and endoscopic, as well as endoscope-assisted microscopic, extracranial approaches to access the parasellar area1-4.
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Among the different surgical techniques, endonasal and sublabial transmaxillary approaches have gained an ever increasing consideration as elective surgical routes to access the sellar area and cavernous sinus, the anterolateral skull base, the middle/infratemporal
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cranial fossa, the pterygopalatine fossa, the parapharyngeal space, the orbital floor, the petrous bone as well as the middle third of the clivus4-15.
To date and to our knowledge, there are no studies in the literature, analyzing differences between microscopic and endoscopic trans-maxillo-sphenoidal approaches to the sellar region, with a critical comparative analysis on operability, as well as surgical exposure.
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The aim of this anatomic study is to describe and critically evaluate the surgical operability, considering the surgical freedom, the area of exposure and surgical field visualization of the endoscope-assisted microscopic trans-maxillo-sphenoidal approach
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(MEMSA).
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MATERIAL AND METHODS
Six cadaver specimens fixed with gluteraldehyde and injected with colored latex were
used for the anatomical dissections at the Ammerman Microsurgical Laboratory in Washington, DC (Department of Neurosurgery, George Washington University, Washington, DC). The heads were fixed in a Mayfield head-holder (Codman, Inc., Raynham, MA) and placed in surgical position, slightly rotated toward the contralateral side (20°) and extended of about 15°. The endoscopic equipment was placed behind the specimen, in front of the surgeon.
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ACCEPTED MANUSCRIPT Microsurgical dissections have been performed under the microscope (Zeiss OPM 1 FC, Carl Zeiss, Oberkochen, Germany) and with a rigid endoscope, 4 mm in diameter and 18 cm in length, with 0-, 30- and 45-degrees lenses (Karl Storz Inc., Culver City, CA, USA), using dedicated instruments. A high-speed drill has been used to perform bone drilling (Midas Rex, Medtronic, Fort
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Worth, TX, USA).
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SURGICAL TECHNIQUE
The surgical technique of MEMSA can be divided into three main anatomical steps:
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the maxillary/antral, the sphenoidal, and the sellar/parasellar phase.
Maxillary phase
A sublabial transverse incision is made on the mucosa and periosteum at the buccogingival sulcus, extending from the ipsilateral superior canine to the third molar (Figure 1), as described for the Caldwell-Luc approach16.
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The upper lip is retracted and soft tissues are dissected maintaining a subperiosteal plane to expose the anterior wall of the maxillary sinus (MS), up to the level of the infraorbital foramen (IOF) superiorly and the anterior projection of the zygomatic arch laterally (Figure 2).
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At this point, the infraorbital nerve (ION) and artery (IOA) are identified and reflected superiorly. An osteotomy of about 2 x 2 cm is performed lateral to the superior aspect of the canine jugum to access the MS. After peeling away the sinus mucosa, it is possible to identify
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the course of ION and IOA, which emerge from the junction between the roof, the posterior and the lateral walls of the antrum. The nerve and the artery run along the roof, into the infraorbital canal (IOC). The origin of the ION is a critical landmark of the pterygo-maxillary fissure, through which the pterygopalatine fossa communicates with the infratemporal fossa17, 18
. The medial wall of MS can be divided in two parts, keeping as landmark the
horizontal line running at its junction with the inferior nasal turbinate. The superior portion corresponds to the middle nasal meatus and presents the maxillary ostium (MO), which opens inside the hiatus semilunaris, while the inferior portion corresponds to the inferior nasal meatus (Figure 3 and 4). 4
ACCEPTED MANUSCRIPT Sphenoidal phase An osteotomy is performed to remove the superior portion of the medial wall of the MS at the junction with the roof (Figure 4), keeping the IOC and the MO as landmarks for surgical orientation, to avoid the opening of the pterygopalatine fossa, which is not routinely
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performed, except for lesions extending into the infratemporal fossa. The IOC represents the supero-lateral limit of the surgical corridor within the sinus, while the MO should be kept as the medial landmark. The opening of the MS might be extended to the MO, mostly through the posterior fontanelle, in order to improve sinusal pneumatization, and to avoid further
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recirculating phenomena, which may cause chronic sinusitis.19
The intra-nasal portion of the surgical corridor runs above and behind the middle turbinate, toward the sphenoidal sinus (SS). Before performing the sphenoidotomy, if needed,
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the nasal mucosa, lining the rostrum sphenoidalis, might be elevated in a submucosal fashion, in order to preserve the vascular peduncle, for harvesting a nasoseptal flap, which runs just inferiorly to the sphenoid ostium. It has to be noticed, that in case of patient’s unfavorable nasal anatomy, the intra-nasal corridor might be enlarged by performing a posterior ethmoidectomy and by removing the most posterior aspect of the middle turbinate.
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At this point the lateral wall of the SS is opened and the sphenoidal mucosa and septa are removed, exposing the sellar floor, on the midline, the carotid prominences inferolaterally, the optic canals superolaterally and the opticocarotid recesses.
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Sellar and parasellar phase
Drilling the bone allows exposure of the sellar floor, the carotid prominences, the pituitary gland, the medial wall of the contralateral cavernous sinus and internal carotid
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artery, as well as the petrous apex together with the vidian nerve, and the apex of the contralateral pterygopalatine fossa (Figure 5). At this point, the degree of pneumatization of the sphenoid sinus is the main limiting
factor in surgical maneuverability. Furthermore, it should be considered, that the bone of the carotid prominence might vary in thickness, being thinner at its anterior part as compared to its posterior aspect, in particular the thinnest segment is located just below the tuberculum sellae20. Another crucial point is represented by sphenoid bone septa anatomy18. In some cases, septa might have a direct insertion into the bone covering the internal carotid artery (ICA).
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. Final surgical exposure on the side of the approach comprises the gyrus rectus, the
olfactory and optic nerves, the chiasm, the C4 segment of the ICA, while contralaterally the contralateral rectus gyrus, olfactory and optic nerves, the ICA from C4 to C2, the contralateral
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vidian nerve together with the medial wall of the contralateral cavernous sinus are exposed (Figure 6-9).
Endoscope assistance with 0°, 30° and 45° angled optics enables to reach visualization of the pituitary stalk together with the superior pituitary artery and the diaphragma sellae on
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the midline (Figure 9), the neurovascular structures of the cranial aspect of the pterygopalatine fossa (i.e. V2 and V3) as well as the vidian nerve and the pterygopalatine
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ganglion to the greater palatine nerve (Figure 6).
ANTHROPOMETRIC MEASUREMENTS AND OPERABILITY SCORE
The mean value of the measurements were recorded and served as the basis for the
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final tabulated data. (Table 1).
Anatomical areas exposed by the surgical approaches were calculated using ImageJ 1.37a software (National Institute of Health).
Operability score was calculated as reported in a previous study22 (Table 2) (Figure
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10).
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DISCUSSION
Among the different surgical routes developed over the last decade to access the sellar
and parasellar area, the transmaxillary corridor gained an increasing interest 4-14. The most utilized transmaxillary approaches are the endoscopic ipsilateral sublabial, the endoscopic ipsilateral endonasal, the endoscopic contralateral endonasal, the microscopic sublabial trans-maxillo-sphenoidal, and the microscopic sublabial transmaxillary approach4-6, 9, 23-25
. In particular, the endoscope-assisted trans-maxillo-sphenoidal approach (MEMSA)
allows for exposing the sellar and parasellar regions to reach tumors, especially pituitary 6
ACCEPTED MANUSCRIPT adenomas, which have unilaterally invaded the contralateral cavernous sinus and parasellar area, as well as the cranial aspect of pterygopalatine fossa. The advantages of this approach are related to the surgical corridor, free from critical neurovascular structures, and the strength of both types of visualizations via the microscope and endoscope, which can be easily applied during surgery2, 4, 5, 7, 9, 12, 23-25.
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The surgical corridor runs behind the choana and does not involve the nasal cavity or the pterygopalatine fossa. In this way, the extra-nasal route leaves intact the nasal anatomy, preserving mucosal flaps for further reconstruction. Both the middle turbinate and the septum are usually preserved; in case of large lesions with wide lateral extension, the surgical
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corridor can be enlarged through a small posterior septostomy, preserving the vascular pedicle for harvesting a nasoseptal flap, if needed, as well as through a posterior ethmoidectomy and the resection of the most posterior aspect of the middle turbinate14, 23, 26.
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The parasellar area can be approached without opening the pterygopalatine fossa, through a straight surgical corridor, which reduces significantly the risks of neurovascular damages, such as the maxillary and sphenopalatine arteries, the maxillary and vidian nerves and the pterygopalatine ganglion14, 17, 26.
The orientation of the surgical corridor provides a straight route to the contralateral
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parasellar area, optimizing local surgical operability and endoscope maneuverability. Application of endoscopy enables to optimize the surgical exposure, critically widening the surgical exposure toward the cranial aspect of the contralateral pterygopalatine fossa, and increasing the surgical control on the ICA from C4 to C2 segment. Utilization of the
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endoscope optimizes the surgical control, by a targeted magnification and illumination, and by enabling the surgeon to look “around the corner” in otherwise blind areas. Surgical exposure might be influenced by the degree of sphenoid sinus
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pneumatization18, 21, 27. The conchal sphenoid type represents a historical theoretical limitation for trans-sphenoidal approaches, because the lack of pneumatized spaces might limit the view on the anatomical landmarks that is overcome by the concurrent use of high speed drills and neuronavigation21, whereas pre-sellar and sellar sphenoid pneumatization provide a better maneuverability. The post-sellar type represents the best sphenoid pneumatization type for this approach; the extension of the sphenoid sinus below the sellar floor and posterior to the tuberculum sellae, allows accessing easily the infra-sellar area and the lateral aspect of the sphenoid to reach the foramen rotundum and the vidian canal14,
21, 27
. In the present study,
among the specimens used for anatomical dissection, we have not observed any case of absence of pneumatization; it is widely known that this morphological condition is not 7
ACCEPTED MANUSCRIPT favorable for surgical dissection, because of the absence of intra-sinusal anatomical landmarks, as well as because of the significant limitation in terms of surgical maneuverability.21, 27 MEMSA provides for both endoscopic and microscopic approach a direct angle of view of the surgical field on the parasellar area, improving surgical control on critical regional
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neurovascular structures; on the contrary purely anterior approaches do provide the same surgical visualization thanks to the application of angled-lens endoscopes, nevertheless without significantly improving the local operability, as provided by a direct corridor.
Besides the assessment of surgical exposure, a critical aspect to take into consideration in planning the surgical approach is indeed the concepts of surgical freedom. According to
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our previous published report22, the surgical freedom, or operability, is described as the ability to execute surgical maneuvers on the visualized area, and is related to three
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independent variables: I) the angle of attack, II) the maneuverability arc and III) the depth of the surgical field, that are all influenced in endoscopic surgery by the pivot point. This point represents the fixed pivot between the tip and the base of the endoscope, where the direction of movement is changed and the movement of the proximal end of the endoscope to one direction results in a movement of the distal end to the opposite direction22, 23, 28.
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The straight corridor to a paramedian target such as the parasellar area, as provided by the MEMSA, critically improves surgical maneuverability as compared to midline anterior approaches, by significantly widening the maneuverability area for both microscopic and endoscopic techniques24.
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There are only few studies in the literature comparing endoscopic transmaxillary approaches to the anterolateral cranial base with microscopic and endoscopic approaches to the cavernous sinus and sella turcica in terms of operability and visualization2, 4, 23. To our
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knowledge there are no studies that analyze surgical operability of MEMSA, by applying a dedicated score system, such as the operability score, when critically analyzing technical advantages of the approach as well as its surgical limitation. Elhadi et al.23 and Wilson et al.4 demonstrated that the endoscopic sublabial
transmaxillary approach provides greater surgical freedom than endoscopic ipsilateral and contralateral endonasal transmaxillary approaches for anterolateral skull base targets, although these approaches offer comparable area of exposure. In another study, Elhadi et al.2 reported that the endoscopic binostril transsphenoidal approach provided the greatest surgical freedom in the sellar region when compared to the endoscopic
uninostril
transsphenoidal,
the
microscopic
sublabial
and
endonasal 8
ACCEPTED MANUSCRIPT transsphenoidal approaches, concluding that the microscopic sublabial, transsphenoidal approach offers the greatest area of exposure. They also demonstrated that the microscopic sublabial transsphenoidal approach provides the most versatile exposure of the sella and cavernous sinus. The endoscopic endonasal transsphenoidal approach permits a very good exposure of the cavernous sinus, while the endoscopic trans-ethmoid-pterygoid-sphenoidal
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approach achieves the best maneuverability in the lateral compartment of the cavernous sinus.2
The MEMSA combines the described advantages of microscopic sublabial transsphenoidal and endoscopic binostril transsphenoidal approaches to the sella and cavernous sinus and the endoscopic sublabial transmaxillary approach to the anterolateral
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skull base, in terms of surgical freedom and area of exposure2, 4, 23.
Moreover, MEMSA provides a great deal of surgical freedom, because working
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through the maxillary sinus, a natural route with a large volume working space, increases both the maneuverability arc and the area; the straight corridor significantly improves the angle of attack, maintaining the same depth of surgical field as compared to other purely anterior approaches. On the other hand, MEMSA provides an excellent area of exposure of the sellar and contralateral parasellar regions, especially enhanced by the endoscope assistance, which,
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as previously stated, helps through the magnification and illumination visualizing otherwise blind corners, such as sphenoidal sinus recesses as well as the cranial aspect of the contralateral pterygo-palatine fossa.
The direct and straight surgical corridor improves the instruments maneuverability on
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parasellar area as compared to standard endonasal microscopic and endoscopic approaches. The wide working space provided by this anatomic route reduces possible conizing effects and allows accomplishing with ease the two or four hands endoscopic techniques. The
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increased surgical freedom limits the sword fighting and instrument collisions, optimizes the microdissection and target visualization, as well as the good area of exposure improves the feasibility of surgery2. Ultimately, the application of endoscopy, significantly improves the capacity to “look around corners” widening the surgical exposure, even through the magnification and targeted illumination. On the other hand, one of the main surgical limitations of the approach is the reduced control on the ipsilateral parasellar region, which restricts the main indication of MEMSA to sellar lesions with unilateral parasellar extension. As mentioned above, the degree of SS pneumatization represents a further limitation of the approach, as it happens for any other type of transsphenoidal route, although the application of endoscopy has signficantly 9
ACCEPTED MANUSCRIPT improved surgical maneuverability even in unfavorable anatomical conditions. Moreover, the presence of intra-nasal pathologies, which involve anatomical structures located along the surgical corridor (e.g. tumors, chronic sinusitis or previous sinusal surgeries), might limit the indications for MEMSA. With regard to surgical exposure, the sella turcica and the middle third of the clivus on
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the midline, as well as the contralateral medial aspect of the cavernous sinus and optic canal are directly and completely visualized and are easy to work in. Contralateral C3 and C4 ICA segments are directly exposed with a good surgical maneuverability, whereas the intra-petrous portion (C2) of contralateral ICA, particularly its horizontal segment, might be visualized and
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surgically controlled based on the degree of SS pneumatization, even if operability might be strictly limited.
Ipsilaterally, the cavernous sinus, as well as C4 segment of the ICA can be well
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visualized, particularly with the application of endoscopic angled optics. Nevertheless, operability might be limited in this area, because of the unfavorable angle of attack and the consequent limitation of maneuverability.
Performing the standard microscopic transsphenoidal technique, also using curved curettes and aspirators, the portion of the adenoma invading the cavernous sinus can be
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removed, although with limitation in terms of angle of attack and maneuverability arc, even by applying endoscopy, which increases surgical visualization as well as vascular control by magnification and illumination12. In contradistinction, the MEMSA allows full exposure of the tumor and direct visualization of the intracavernous tract of the ICA during tumor
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removal. In this way, tumors invading the cavernous sinus through its medial wall are approached infero-medially following the direction of tumor growth, sparing the cranial nerves, which run on the opposite side. Surgical control on the midline is comparable to
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anterior approaches in each aspect. The MEMSA as well as other sublabial transmaxillary approaches have theoretical
low rates of complications. The described risks are: facial numbness or paresthesias, facial asymmetry, tooth devitalization and oro-antral or cerebrospinal fluid (CSF) fistulas19, 29. To significantly reduce the probability of complications, it is critical to tailor a small anterior maxillotomy, keeping in mind the anatomical landmarks within the sinus, and protecting the ION during the subperiosteal dissection of soft tissues. Furthermore, as discussed before, in case of CSF fistulas MEMSA makes available nasal mucosal flaps for the reconstruction.
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ACCEPTED MANUSCRIPT CONCLUSION
This anatomic study demonstrates that the endoscope-assisted trans-maxillosphenoidal approach (MEMSA) is feasible and safe, ensuring wide surgical maneuverability
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and surgical exposure of the sellar, suprasellar and contralateral parasellar regions. It is indicated in case of tumors, that have invaded the cavernous sinus contralaterally to the approached MS, taking advantage of a wide natural corridor running through the MS and
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combining the advantages provided by microscope and endoscope.
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ACCEPTED MANUSCRIPT COMPLIANCE WITH ETICAL STANDARD
Conflict of interest
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The authors report no conflict of interest.
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stereotaxy:
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ACCEPTED MANUSCRIPT LEGEND FOR FIGURES
Figure 1. Gingival incision.
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Figure 2. Maxillotomy.
Figure 3. Maxillary phase.
Abbreviations list: G: gingiva; M: maxilla; MO: maxillary ostium; MS: maxillary
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sinus; NM: nasal mucosa; SL: superior lip; VM: vestibular mucosa.
Figure 4. Maxillary sinus landmarks. Drilling area of the maxillary sinus wall (red dotted line) and surgical enlargement of the maxillary ostium (blue dotted line).
ostium; PW = posterior wall.
Figure 5. Sphenoidal phase.
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Abbreviations list: IOC: infra-orbital canal; LW: lateral wall; MO = maxillary
Abbreviations list: G: gingiva; M: maxilla; MS: maxillary sinus; LICA: left internal
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carotid artery; LON: left optic nerve; MCD: middle clival dura; OC: optic chiasm; RICA: right internal carotid artery; SD: sellar dura; VM: vestibular mucosa.
Figure 6. Sellar phase. Endoscopic view.
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Abbreviations list: CB: clival bone; III: third cranial nerve; LICA: left internal carotid artery; LO: left olfactory nerve; LON: left optic nerve; LRG: left rectus gyrus; MCD: middle clival dura; OC: optic chiasm; RICA: right internal carotid artery; RO: right olfactory
nerve.
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nerve; RON: right optic nerve; RRG: right rectus gyrus; SD: sellar dura; VI: sixth cranial
Figure 7. Sellar phase. Endoscopic view of suprasellar compartment.
Abbreviations list: CB: clival bone; LICA: left internal carotid artery; LO: left olfactory nerve; LON: left optic nerve; LRG: left rectus gyrus; OC: optic chiasm; PS: pituitary stalk; RICA: right internal carotid artery; RO: right olfactory nerve; RON: right optic nerve; RRG: right rectus gyrus; SD: sellar dura.
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Figure 9. Sellar phase. Endoscopic view of suprasellar compartment at higher magnification.
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Abbreviations list: DS: diaphragma sellae; LICA: left internal carotid artery; LON: left optic nerve; LRG: left rectus gyrus; OC: optic chiasm; PS: pituitary stalk; RICA: right internal carotid artery; RO: right olfactory nerve; RON: right optic nerve; RRG: right rectus
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gyrus; SD: sellar dura.
Figure 10. Schematic drawing resembling operability scores. The blue area corresponds to the further exposure obtained by the endoscope. list: MEMSA:
microscopic endoscope-assisted
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Abbreviations
trans-maxillo-
sphenoidal approach; TATSR: traditional anterior transsphenoidal route (trans-septal
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microscopic or endoscopic approach).
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MAC
Mean
Mean
Mean
PG
49.3
60.0°
49.5°
OC
52.3
61.7°
45.5°
Ipsilateral ON
44.7
50.3°
35.5°
Ipsilateral ICA
39.7
49.7°
29.3°
Ipsilateral CS
37.8
32.8°
Controlateral ON
59.0
60.0°
Controlateral ICA
55.2
Controlateral CS
57.8
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Depth (mm)
19.8°
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51.2°
60.5°
55.7°
60.8°
60.3°
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Abbreviations list: CS: cavernous sinus; ICA: internal carotid artery (C3 segment); ON: optic nerve; MAC: maneuverability arc; OC = optic chiasm; PG: pituitary gland; SAA: surgical angle of attack; SD: standard deviation.
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MAC
OS
PG
1
1
1
3
OC
0
1
1
2
Ipsilateral ON
1
0
Ipsilateral ICA
1
0
Ipsilateral CS
1
0
Controlateral ON
0
1
Controlateral ICA
0
1
Controlateral CS
0
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Depth
1
0
1
0
1
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0
1
2
1
2
1
2
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Abbreviations list: CS: cavernous sinus; ICA: internal carotid artery (C3 segment); ON: optic nerve; MAC: maneuverability arc; OC = optic chiasm; PG: pituitary gland; SAA: surgical angle of attack.
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ACCEPTED MANUSCRIPT HIGHLIGHTS •
This study critically evaluates MEMSA surgical operability on sellar/parasellar area
•
MEMSA
is
feasible
and
safe,
combining
advantages
provided
by
•
MEMSA
provides
wide
surgical
sellar/parasellar area
maneuverability
and
exposure
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MEMSA is indicated in sellar tumors, invading the controlateral parasellar area
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•
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microscope/endoscope on
ACCEPTED MANUSCRIPT ABBREVIATIONS LIST
ICA: internal carotid artery; IOA: infraorbital artery; IOC: infraorbital canal; IOF: infraorbital foramen; ION: infraorbital nerve; MEMSA: microscopic endoscopeassisted trans-maxillo-sphenoidal approach; MO: maxillary ostium; MS: maxillary
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sinus; SS: sphenoidal sinus.
S1878-8750(16)30700-8
DOI:
10.1016/j.wneu.2016.08.034
Reference:
WNEU 4444
To appear in:
World Neurosurgery
Received Date: 1 June 2016 Revised Date:
8 August 2016
Accepted Date: 9 August 2016
Please cite this article as: Gagliardi F, Donofrio CA, Spina A, Bailo M, Gragnaniello C, Gallotti AL, Elbabaa SK, Caputy AJ, Mortini P, Endoscope-Assisted Trans-Maxillo-Sphenoidal Approach to Sellar and Parasellar Regions: Anatomic Study, World Neurosurgery (2016), doi: 10.1016/j.wneu.2016.08.034. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT ENDOSCOPE-ASSISTED TRANS-MAXILLO-SPHENOIDAL APPROACH TO SELLAR AND PARASELLAR REGIONS: ANATOMIC STUDY
[1]
Filippo Gagliardi, M.D., Ph.D., [1]Carmine A. Donofrio, M.D., [1]Alfio Spina, M.D.,
Michele Bailo, M.D., [2]Cristian Gragnaniello, M.D., Ph.D., [1]Alberto L. Gallotti, M.D.,
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[1]
[3]
Samer K. Elbabaa, M.D., F.A.C.S., [2]Anthony J. Caputy, M.D., F.A.C.S., and [1]Pietro
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Mortini, M.D.
[1] Department of Neurosurgery and Gamma Knife Radiosurgery, San Raffaele Scientific Institute, Vita-Salute University, Milan, Italy
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[2] Department of Neurosurgery, George Washington University, Washington DC, USA [3] Division of Pediatric Neurosurgery, Department of Neurological Surgery, Saint Louis University School of Medicine, Saint Louis, MO, USA
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Corresponding Author:
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Short title: Endoscope-assisted trans-maxillo-sphenoidal approach
Filippo Gagliardi, M.D., Ph.D.
Department of Neurosurgery and Gamma Knife Radiosurgery
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San Raffaele Scientific Institute Via Olgettina 60, 20132 Milano, Italy E-mail: [email protected] Phone: +39-02-26432396 Fax:
+39-02-26437302
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ACCEPTED MANUSCRIPT ABSTRACT
Objective. Anterolateral skull base surgery to sellar and parasellar region has always represented a technical challenge for neurosurgeons. The microscopic endoscope-assisted trans-maxillo-sphenoidal approach (MEMSA) affords a direct surgical corridor free from
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critical skull base structures. The aim of this study is to describe and critically evaluate its application to access the sellar and parasellar areas in terms of surgical exposure and operability.
Methods. Six cadaveric heads were examined. A stepwise dissection of the MEMSA
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was performed. Relevant anatomy and surgical technique have been critically described and comparatively reviewed. The operability score was applied for quantitative analysis of surgical operability.
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Results. MEMSA provides a wide bilateral surgical exposure and vascular control of the sellar, suprasellar, and parasellar regions, achieving the highest operability on the midline and the parasellar region. The approach can be tailored according to the lesion, easily widening the surgical corridor toward the contralateral pterygopalatine fossa. Anatomic knowledge of maxillary sinus landmarks is key to utilizing this approach. Favorable
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sphenoidal anatomy is the main limiting factor, making MEMSA an alternative surgical option to endoscopic endonasal routes, in case of their unfeasibility, and the approach of choice in selected cases of primarily sellar lesions widely extending contralaterally to the approached maxillary sinus.
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Conclusions. MEMSA is a safe and effective route, which provides access to the sellar, suprasellar and contralateral parasellar areas via a direct, minimally-disruptive surgical corridor. The preservation of nasal anatomy ensures the availability of preserved mucosal
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flaps for use with further reconstruction.
Key words: Trans-maxillo-sphenoidal approach; sella; skull base approach; pituitary
tumors.
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ACCEPTED MANUSCRIPT INTRODUCTION
Anterolateral skull base approaches to sellar and parasellar region have always represented a technical challenge for neurosurgeons, because of the extreme complexity of the critical neurovascular structures in this area.
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In the last two decades intrinsic surgical morbidity related to traditional trans-cranial and transfacial approaches has pushed the development of innovative microscopic and endoscopic, as well as endoscope-assisted microscopic, extracranial approaches to access the parasellar area1-4.
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Among the different surgical techniques, endonasal and sublabial transmaxillary approaches have gained an ever increasing consideration as elective surgical routes to access the sellar area and cavernous sinus, the anterolateral skull base, the middle/infratemporal
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cranial fossa, the pterygopalatine fossa, the parapharyngeal space, the orbital floor, the petrous bone as well as the middle third of the clivus4-15.
To date and to our knowledge, there are no studies in the literature, analyzing differences between microscopic and endoscopic trans-maxillo-sphenoidal approaches to the sellar region, with a critical comparative analysis on operability, as well as surgical exposure.
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The aim of this anatomic study is to describe and critically evaluate the surgical operability, considering the surgical freedom, the area of exposure and surgical field visualization of the endoscope-assisted microscopic trans-maxillo-sphenoidal approach
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(MEMSA).
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MATERIAL AND METHODS
Six cadaver specimens fixed with gluteraldehyde and injected with colored latex were
used for the anatomical dissections at the Ammerman Microsurgical Laboratory in Washington, DC (Department of Neurosurgery, George Washington University, Washington, DC). The heads were fixed in a Mayfield head-holder (Codman, Inc., Raynham, MA) and placed in surgical position, slightly rotated toward the contralateral side (20°) and extended of about 15°. The endoscopic equipment was placed behind the specimen, in front of the surgeon.
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Worth, TX, USA).
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SURGICAL TECHNIQUE
The surgical technique of MEMSA can be divided into three main anatomical steps:
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the maxillary/antral, the sphenoidal, and the sellar/parasellar phase.
Maxillary phase
A sublabial transverse incision is made on the mucosa and periosteum at the buccogingival sulcus, extending from the ipsilateral superior canine to the third molar (Figure 1), as described for the Caldwell-Luc approach16.
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The upper lip is retracted and soft tissues are dissected maintaining a subperiosteal plane to expose the anterior wall of the maxillary sinus (MS), up to the level of the infraorbital foramen (IOF) superiorly and the anterior projection of the zygomatic arch laterally (Figure 2).
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At this point, the infraorbital nerve (ION) and artery (IOA) are identified and reflected superiorly. An osteotomy of about 2 x 2 cm is performed lateral to the superior aspect of the canine jugum to access the MS. After peeling away the sinus mucosa, it is possible to identify
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the course of ION and IOA, which emerge from the junction between the roof, the posterior and the lateral walls of the antrum. The nerve and the artery run along the roof, into the infraorbital canal (IOC). The origin of the ION is a critical landmark of the pterygo-maxillary fissure, through which the pterygopalatine fossa communicates with the infratemporal fossa17, 18
. The medial wall of MS can be divided in two parts, keeping as landmark the
horizontal line running at its junction with the inferior nasal turbinate. The superior portion corresponds to the middle nasal meatus and presents the maxillary ostium (MO), which opens inside the hiatus semilunaris, while the inferior portion corresponds to the inferior nasal meatus (Figure 3 and 4). 4
ACCEPTED MANUSCRIPT Sphenoidal phase An osteotomy is performed to remove the superior portion of the medial wall of the MS at the junction with the roof (Figure 4), keeping the IOC and the MO as landmarks for surgical orientation, to avoid the opening of the pterygopalatine fossa, which is not routinely
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performed, except for lesions extending into the infratemporal fossa. The IOC represents the supero-lateral limit of the surgical corridor within the sinus, while the MO should be kept as the medial landmark. The opening of the MS might be extended to the MO, mostly through the posterior fontanelle, in order to improve sinusal pneumatization, and to avoid further
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recirculating phenomena, which may cause chronic sinusitis.19
The intra-nasal portion of the surgical corridor runs above and behind the middle turbinate, toward the sphenoidal sinus (SS). Before performing the sphenoidotomy, if needed,
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the nasal mucosa, lining the rostrum sphenoidalis, might be elevated in a submucosal fashion, in order to preserve the vascular peduncle, for harvesting a nasoseptal flap, which runs just inferiorly to the sphenoid ostium. It has to be noticed, that in case of patient’s unfavorable nasal anatomy, the intra-nasal corridor might be enlarged by performing a posterior ethmoidectomy and by removing the most posterior aspect of the middle turbinate.
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At this point the lateral wall of the SS is opened and the sphenoidal mucosa and septa are removed, exposing the sellar floor, on the midline, the carotid prominences inferolaterally, the optic canals superolaterally and the opticocarotid recesses.
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Sellar and parasellar phase
Drilling the bone allows exposure of the sellar floor, the carotid prominences, the pituitary gland, the medial wall of the contralateral cavernous sinus and internal carotid
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artery, as well as the petrous apex together with the vidian nerve, and the apex of the contralateral pterygopalatine fossa (Figure 5). At this point, the degree of pneumatization of the sphenoid sinus is the main limiting
factor in surgical maneuverability. Furthermore, it should be considered, that the bone of the carotid prominence might vary in thickness, being thinner at its anterior part as compared to its posterior aspect, in particular the thinnest segment is located just below the tuberculum sellae20. Another crucial point is represented by sphenoid bone septa anatomy18. In some cases, septa might have a direct insertion into the bone covering the internal carotid artery (ICA).
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. Final surgical exposure on the side of the approach comprises the gyrus rectus, the
olfactory and optic nerves, the chiasm, the C4 segment of the ICA, while contralaterally the contralateral rectus gyrus, olfactory and optic nerves, the ICA from C4 to C2, the contralateral
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vidian nerve together with the medial wall of the contralateral cavernous sinus are exposed (Figure 6-9).
Endoscope assistance with 0°, 30° and 45° angled optics enables to reach visualization of the pituitary stalk together with the superior pituitary artery and the diaphragma sellae on
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the midline (Figure 9), the neurovascular structures of the cranial aspect of the pterygopalatine fossa (i.e. V2 and V3) as well as the vidian nerve and the pterygopalatine
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ganglion to the greater palatine nerve (Figure 6).
ANTHROPOMETRIC MEASUREMENTS AND OPERABILITY SCORE
The mean value of the measurements were recorded and served as the basis for the
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final tabulated data. (Table 1).
Anatomical areas exposed by the surgical approaches were calculated using ImageJ 1.37a software (National Institute of Health).
Operability score was calculated as reported in a previous study22 (Table 2) (Figure
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10).
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DISCUSSION
Among the different surgical routes developed over the last decade to access the sellar
and parasellar area, the transmaxillary corridor gained an increasing interest 4-14. The most utilized transmaxillary approaches are the endoscopic ipsilateral sublabial, the endoscopic ipsilateral endonasal, the endoscopic contralateral endonasal, the microscopic sublabial trans-maxillo-sphenoidal, and the microscopic sublabial transmaxillary approach4-6, 9, 23-25
. In particular, the endoscope-assisted trans-maxillo-sphenoidal approach (MEMSA)
allows for exposing the sellar and parasellar regions to reach tumors, especially pituitary 6
ACCEPTED MANUSCRIPT adenomas, which have unilaterally invaded the contralateral cavernous sinus and parasellar area, as well as the cranial aspect of pterygopalatine fossa. The advantages of this approach are related to the surgical corridor, free from critical neurovascular structures, and the strength of both types of visualizations via the microscope and endoscope, which can be easily applied during surgery2, 4, 5, 7, 9, 12, 23-25.
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The surgical corridor runs behind the choana and does not involve the nasal cavity or the pterygopalatine fossa. In this way, the extra-nasal route leaves intact the nasal anatomy, preserving mucosal flaps for further reconstruction. Both the middle turbinate and the septum are usually preserved; in case of large lesions with wide lateral extension, the surgical
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corridor can be enlarged through a small posterior septostomy, preserving the vascular pedicle for harvesting a nasoseptal flap, if needed, as well as through a posterior ethmoidectomy and the resection of the most posterior aspect of the middle turbinate14, 23, 26.
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The parasellar area can be approached without opening the pterygopalatine fossa, through a straight surgical corridor, which reduces significantly the risks of neurovascular damages, such as the maxillary and sphenopalatine arteries, the maxillary and vidian nerves and the pterygopalatine ganglion14, 17, 26.
The orientation of the surgical corridor provides a straight route to the contralateral
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parasellar area, optimizing local surgical operability and endoscope maneuverability. Application of endoscopy enables to optimize the surgical exposure, critically widening the surgical exposure toward the cranial aspect of the contralateral pterygopalatine fossa, and increasing the surgical control on the ICA from C4 to C2 segment. Utilization of the
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endoscope optimizes the surgical control, by a targeted magnification and illumination, and by enabling the surgeon to look “around the corner” in otherwise blind areas. Surgical exposure might be influenced by the degree of sphenoid sinus
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pneumatization18, 21, 27. The conchal sphenoid type represents a historical theoretical limitation for trans-sphenoidal approaches, because the lack of pneumatized spaces might limit the view on the anatomical landmarks that is overcome by the concurrent use of high speed drills and neuronavigation21, whereas pre-sellar and sellar sphenoid pneumatization provide a better maneuverability. The post-sellar type represents the best sphenoid pneumatization type for this approach; the extension of the sphenoid sinus below the sellar floor and posterior to the tuberculum sellae, allows accessing easily the infra-sellar area and the lateral aspect of the sphenoid to reach the foramen rotundum and the vidian canal14,
21, 27
. In the present study,
among the specimens used for anatomical dissection, we have not observed any case of absence of pneumatization; it is widely known that this morphological condition is not 7
ACCEPTED MANUSCRIPT favorable for surgical dissection, because of the absence of intra-sinusal anatomical landmarks, as well as because of the significant limitation in terms of surgical maneuverability.21, 27 MEMSA provides for both endoscopic and microscopic approach a direct angle of view of the surgical field on the parasellar area, improving surgical control on critical regional
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neurovascular structures; on the contrary purely anterior approaches do provide the same surgical visualization thanks to the application of angled-lens endoscopes, nevertheless without significantly improving the local operability, as provided by a direct corridor.
Besides the assessment of surgical exposure, a critical aspect to take into consideration in planning the surgical approach is indeed the concepts of surgical freedom. According to
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our previous published report22, the surgical freedom, or operability, is described as the ability to execute surgical maneuvers on the visualized area, and is related to three
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independent variables: I) the angle of attack, II) the maneuverability arc and III) the depth of the surgical field, that are all influenced in endoscopic surgery by the pivot point. This point represents the fixed pivot between the tip and the base of the endoscope, where the direction of movement is changed and the movement of the proximal end of the endoscope to one direction results in a movement of the distal end to the opposite direction22, 23, 28.
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The straight corridor to a paramedian target such as the parasellar area, as provided by the MEMSA, critically improves surgical maneuverability as compared to midline anterior approaches, by significantly widening the maneuverability area for both microscopic and endoscopic techniques24.
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There are only few studies in the literature comparing endoscopic transmaxillary approaches to the anterolateral cranial base with microscopic and endoscopic approaches to the cavernous sinus and sella turcica in terms of operability and visualization2, 4, 23. To our
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knowledge there are no studies that analyze surgical operability of MEMSA, by applying a dedicated score system, such as the operability score, when critically analyzing technical advantages of the approach as well as its surgical limitation. Elhadi et al.23 and Wilson et al.4 demonstrated that the endoscopic sublabial
transmaxillary approach provides greater surgical freedom than endoscopic ipsilateral and contralateral endonasal transmaxillary approaches for anterolateral skull base targets, although these approaches offer comparable area of exposure. In another study, Elhadi et al.2 reported that the endoscopic binostril transsphenoidal approach provided the greatest surgical freedom in the sellar region when compared to the endoscopic
uninostril
transsphenoidal,
the
microscopic
sublabial
and
endonasal 8
ACCEPTED MANUSCRIPT transsphenoidal approaches, concluding that the microscopic sublabial, transsphenoidal approach offers the greatest area of exposure. They also demonstrated that the microscopic sublabial transsphenoidal approach provides the most versatile exposure of the sella and cavernous sinus. The endoscopic endonasal transsphenoidal approach permits a very good exposure of the cavernous sinus, while the endoscopic trans-ethmoid-pterygoid-sphenoidal
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approach achieves the best maneuverability in the lateral compartment of the cavernous sinus.2
The MEMSA combines the described advantages of microscopic sublabial transsphenoidal and endoscopic binostril transsphenoidal approaches to the sella and cavernous sinus and the endoscopic sublabial transmaxillary approach to the anterolateral
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skull base, in terms of surgical freedom and area of exposure2, 4, 23.
Moreover, MEMSA provides a great deal of surgical freedom, because working
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through the maxillary sinus, a natural route with a large volume working space, increases both the maneuverability arc and the area; the straight corridor significantly improves the angle of attack, maintaining the same depth of surgical field as compared to other purely anterior approaches. On the other hand, MEMSA provides an excellent area of exposure of the sellar and contralateral parasellar regions, especially enhanced by the endoscope assistance, which,
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as previously stated, helps through the magnification and illumination visualizing otherwise blind corners, such as sphenoidal sinus recesses as well as the cranial aspect of the contralateral pterygo-palatine fossa.
The direct and straight surgical corridor improves the instruments maneuverability on
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parasellar area as compared to standard endonasal microscopic and endoscopic approaches. The wide working space provided by this anatomic route reduces possible conizing effects and allows accomplishing with ease the two or four hands endoscopic techniques. The
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increased surgical freedom limits the sword fighting and instrument collisions, optimizes the microdissection and target visualization, as well as the good area of exposure improves the feasibility of surgery2. Ultimately, the application of endoscopy, significantly improves the capacity to “look around corners” widening the surgical exposure, even through the magnification and targeted illumination. On the other hand, one of the main surgical limitations of the approach is the reduced control on the ipsilateral parasellar region, which restricts the main indication of MEMSA to sellar lesions with unilateral parasellar extension. As mentioned above, the degree of SS pneumatization represents a further limitation of the approach, as it happens for any other type of transsphenoidal route, although the application of endoscopy has signficantly 9
ACCEPTED MANUSCRIPT improved surgical maneuverability even in unfavorable anatomical conditions. Moreover, the presence of intra-nasal pathologies, which involve anatomical structures located along the surgical corridor (e.g. tumors, chronic sinusitis or previous sinusal surgeries), might limit the indications for MEMSA. With regard to surgical exposure, the sella turcica and the middle third of the clivus on
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the midline, as well as the contralateral medial aspect of the cavernous sinus and optic canal are directly and completely visualized and are easy to work in. Contralateral C3 and C4 ICA segments are directly exposed with a good surgical maneuverability, whereas the intra-petrous portion (C2) of contralateral ICA, particularly its horizontal segment, might be visualized and
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surgically controlled based on the degree of SS pneumatization, even if operability might be strictly limited.
Ipsilaterally, the cavernous sinus, as well as C4 segment of the ICA can be well
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visualized, particularly with the application of endoscopic angled optics. Nevertheless, operability might be limited in this area, because of the unfavorable angle of attack and the consequent limitation of maneuverability.
Performing the standard microscopic transsphenoidal technique, also using curved curettes and aspirators, the portion of the adenoma invading the cavernous sinus can be
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removed, although with limitation in terms of angle of attack and maneuverability arc, even by applying endoscopy, which increases surgical visualization as well as vascular control by magnification and illumination12. In contradistinction, the MEMSA allows full exposure of the tumor and direct visualization of the intracavernous tract of the ICA during tumor
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removal. In this way, tumors invading the cavernous sinus through its medial wall are approached infero-medially following the direction of tumor growth, sparing the cranial nerves, which run on the opposite side. Surgical control on the midline is comparable to
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anterior approaches in each aspect. The MEMSA as well as other sublabial transmaxillary approaches have theoretical
low rates of complications. The described risks are: facial numbness or paresthesias, facial asymmetry, tooth devitalization and oro-antral or cerebrospinal fluid (CSF) fistulas19, 29. To significantly reduce the probability of complications, it is critical to tailor a small anterior maxillotomy, keeping in mind the anatomical landmarks within the sinus, and protecting the ION during the subperiosteal dissection of soft tissues. Furthermore, as discussed before, in case of CSF fistulas MEMSA makes available nasal mucosal flaps for the reconstruction.
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This anatomic study demonstrates that the endoscope-assisted trans-maxillosphenoidal approach (MEMSA) is feasible and safe, ensuring wide surgical maneuverability
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and surgical exposure of the sellar, suprasellar and contralateral parasellar regions. It is indicated in case of tumors, that have invaded the cavernous sinus contralaterally to the approached MS, taking advantage of a wide natural corridor running through the MS and
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combining the advantages provided by microscope and endoscope.
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Conflict of interest
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The authors report no conflict of interest.
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ACCEPTED MANUSCRIPT REFERENCES
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Fraioli B, Esposito V, Santoro A, Iannetti G, Giuffre R, Cantore G. Transmaxillosphenoidal approach to tumors invading the medial compartment of the cavernous sinus. J Neurosurg. 1995;82:63-69.
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Kassam AB, Gardner P, Snyderman C, Mintz A, Carrau R. Expanded endonasal approach: fully endoscopic, completely transnasal approach to the middle third of the
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clivus, petrous bone, middle cranial fossa, and infratemporal fossa. Neurosurg Focus. 2005;19:E6. 15.
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tomography analysis of the carotid artery and sphenoid sinus pneumatization patterns. Am J Rhinol. 2004;18:203-208.
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qualitative analysis of the working area obtained by endoscope and microscope in various approaches to the anterior communicating artery complex using computed tomography-based
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a
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Matheny KE, Duncavage JA. Contemporary indications for the Caldwell-Luc
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procedure. Curr Opin Otolaryngol Head Neck Surg. 2003;11:23-26.
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stereotaxy:
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ACCEPTED MANUSCRIPT LEGEND FOR FIGURES
Figure 1. Gingival incision.
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Figure 2. Maxillotomy.
Figure 3. Maxillary phase.
Abbreviations list: G: gingiva; M: maxilla; MO: maxillary ostium; MS: maxillary
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sinus; NM: nasal mucosa; SL: superior lip; VM: vestibular mucosa.
Figure 4. Maxillary sinus landmarks. Drilling area of the maxillary sinus wall (red dotted line) and surgical enlargement of the maxillary ostium (blue dotted line).
ostium; PW = posterior wall.
Figure 5. Sphenoidal phase.
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Abbreviations list: IOC: infra-orbital canal; LW: lateral wall; MO = maxillary
Abbreviations list: G: gingiva; M: maxilla; MS: maxillary sinus; LICA: left internal
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carotid artery; LON: left optic nerve; MCD: middle clival dura; OC: optic chiasm; RICA: right internal carotid artery; SD: sellar dura; VM: vestibular mucosa.
Figure 6. Sellar phase. Endoscopic view.
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Abbreviations list: CB: clival bone; III: third cranial nerve; LICA: left internal carotid artery; LO: left olfactory nerve; LON: left optic nerve; LRG: left rectus gyrus; MCD: middle clival dura; OC: optic chiasm; RICA: right internal carotid artery; RO: right olfactory
nerve.
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nerve; RON: right optic nerve; RRG: right rectus gyrus; SD: sellar dura; VI: sixth cranial
Figure 7. Sellar phase. Endoscopic view of suprasellar compartment.
Abbreviations list: CB: clival bone; LICA: left internal carotid artery; LO: left olfactory nerve; LON: left optic nerve; LRG: left rectus gyrus; OC: optic chiasm; PS: pituitary stalk; RICA: right internal carotid artery; RO: right olfactory nerve; RON: right optic nerve; RRG: right rectus gyrus; SD: sellar dura.
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ACCEPTED MANUSCRIPT Figure 8. Schematic drawing, illustrating the surgical exposure of the internal carotid arteries.
Figure 9. Sellar phase. Endoscopic view of suprasellar compartment at higher magnification.
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Abbreviations list: DS: diaphragma sellae; LICA: left internal carotid artery; LON: left optic nerve; LRG: left rectus gyrus; OC: optic chiasm; PS: pituitary stalk; RICA: right internal carotid artery; RO: right olfactory nerve; RON: right optic nerve; RRG: right rectus
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gyrus; SD: sellar dura.
Figure 10. Schematic drawing resembling operability scores. The blue area corresponds to the further exposure obtained by the endoscope. list: MEMSA:
microscopic endoscope-assisted
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Abbreviations
trans-maxillo-
sphenoidal approach; TATSR: traditional anterior transsphenoidal route (trans-septal
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microscopic or endoscopic approach).
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MAC
Mean
Mean
Mean
PG
49.3
60.0°
49.5°
OC
52.3
61.7°
45.5°
Ipsilateral ON
44.7
50.3°
35.5°
Ipsilateral ICA
39.7
49.7°
29.3°
Ipsilateral CS
37.8
32.8°
Controlateral ON
59.0
60.0°
Controlateral ICA
55.2
Controlateral CS
57.8
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19.8°
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51.2°
60.5°
55.7°
60.8°
60.3°
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Abbreviations list: CS: cavernous sinus; ICA: internal carotid artery (C3 segment); ON: optic nerve; MAC: maneuverability arc; OC = optic chiasm; PG: pituitary gland; SAA: surgical angle of attack; SD: standard deviation.
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MAC
OS
PG
1
1
1
3
OC
0
1
1
2
Ipsilateral ON
1
0
Ipsilateral ICA
1
0
Ipsilateral CS
1
0
Controlateral ON
0
1
Controlateral ICA
0
1
Controlateral CS
0
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1
0
1
0
1
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0
1
2
1
2
1
2
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Abbreviations list: CS: cavernous sinus; ICA: internal carotid artery (C3 segment); ON: optic nerve; MAC: maneuverability arc; OC = optic chiasm; PG: pituitary gland; SAA: surgical angle of attack.
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ACCEPTED MANUSCRIPT HIGHLIGHTS •
This study critically evaluates MEMSA surgical operability on sellar/parasellar area
•
MEMSA
is
feasible
and
safe,
combining
advantages
provided
by
•
MEMSA
provides
wide
surgical
sellar/parasellar area
maneuverability
and
exposure
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MEMSA is indicated in sellar tumors, invading the controlateral parasellar area
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•
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microscope/endoscope on
ACCEPTED MANUSCRIPT ABBREVIATIONS LIST
ICA: internal carotid artery; IOA: infraorbital artery; IOC: infraorbital canal; IOF: infraorbital foramen; ION: infraorbital nerve; MEMSA: microscopic endoscopeassisted trans-maxillo-sphenoidal approach; MO: maxillary ostium; MS: maxillary
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sinus; SS: sphenoidal sinus.