Author's Accepted Manuscript

Endoscopic Endonasal Surgery of the SphenoidSinus: Extended Approaches

Alejandro Vazquez MD, James K. Liu MD, JeanAnderson Eloy MD, FACS

PII: S1043-1810(14)00017-7DOI: http://dx.doi.org/10.1016/j.otot.2014.02.007Reference: YOTOT622

To appear in: Operative Techniques in Otolaryngology

Cite this article as: Alejandro Vazquez MD, James K. Liu MD, Jean Anderson Eloy MD,FACS, Endoscopic Endonasal Surgery of the Sphenoid Sinus: Extended Approaches,Operative Techniques in Otolaryngology, http://dx.doi.org/10.1016/j.otot.2014.02.007

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Endoscopic Endonasal Surgery of the Sphenoid Sinus: Extended Approaches

Alejandro Vazquez, MD1

James K. Liu, MD1,2,3 Jean Anderson Eloy, MD, FACS1,2,3

1Department of Otolaryngology – Head and Neck Surgery, Rutgers New Jersey Medical School, Newark, NJ 2Department of Neurological Surgery, Rutgers New Jersey Medical School, Newark, NJ

3Center for Skull Base and Pituitary Surgery, Neurological Institute of New Jersey, Rutgers New Jersey Medical School, Newark, NJ Corresponding Author: Jean Anderson Eloy, MD, FACS Associate Professor and Vice Chairman Director, Rhinology and Sinus Surgery Co-Director, Endoscopic Skull Base Surgery Program Department of Otolaryngology – Head and Neck Surgery Rutgers New Jersey Medical School 90 Bergen St., Suite 8100 Newark, NJ 07103 Phone: (973) 972-4588 FAX: (973) 972-3767 E-mail: jean.anderson.eloy@gmail.com ABSTRACT

Recent advances in surgical instrumentation and technique have allowed surgeons

unprecedented access to the sinonasal tract and skull base. In this report, we discuss our

experience with the various endoscopic endonasal approaches to the sphenoid sinus and

their role in addressing both intrinsic and extrinsic sphenoid sinus pathology.

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INTRODUCTION

The sphenoid sinuses are paired structures located within the body of the sphenoid

bone. They represent the most posterior of the paranasal sinuses, and are bounded

superiorly and posteriorly by the skull base. Similar to the other paranasal sinuses, the

sphenoid sinuses may be affected by a variety of intrinsic pathologic processes, such as

chronic bacterial rhinosinusitis, allergic fungal rhinosinusitis, mucoceles and

mucopyoceles, mycetomas, and neoplastic lesions. In addition, given their proximity to

the skull base, the sphenoid sinuses may be affected by extrinsic pathologic processes,

such as bony dehiscences of the skull base (resulting in cerebrospinal fluid leaks),

encephaloceles, and a variety of benign or malignant neoplasms. Even when not directly

involved, the sphenoid sinus may serve as a gateway to the skull base when addressing

extrinsic pathologies surgically. Approaches to the sphenoid sinus and surrounding

structures can be made difficult due to the intricate anatomy and surrounding anatomical

variants such as the Onodi cell1,2 and different degrees of sphenoid pneumatization.3

In this report, we discuss our experience with the various endoscopic endonasal

approaches to the sphenoid sinus and their role in addressing both intrinsic and extrinsic

sphenoid sinus pathology. Specifically, we have structured our discussion around the

different forms of approaching the sphenoid sinus; basic and extended sphenoidotomy

techniques; and transsphenoidal approaches to the skull base.

SURGICAL TECHNIQUES

Setup, Preparation, and Surgical Considerations

Patients are typically positioned supine with the head and neck in a neutral position. The

patient’s head is rotated slightly rightward. Prophylactic antibiotics (usually, intravenous

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cefazolin in non-allergic patients or clindamycin in patients allergic to penicillins) and

intravenous corticosteroids are administered. The eyes are covered with transparent film

dressing and kept in the operating field at all times. Pledgets saturated with

oxymetazoline hydrochloride are placed in both nasal cavities for decongestion and

vasoconstriction. If stereotactic navigation is to be utilized, the device components are set

up at this time as indicated by the manufacturer. At our institution, stereotactic navigation

during sinonasal and endoscopic skull base surgery is performed using the Brainlab®

ENT navigation system or the Medtronic StealthStation® S7®. Finally, the patient is

then draped in an aseptic fashion.

In contrast to sinonasal surgery, endoscopic endonasal skull base procedures are a

collaborative effort between a skull base neurosurgeon and an otolaryngologist with

subspecialty training in rhinology and endoscopic sinus/skull base surgery. This dual-

surgeon approach permits the use of bimanual dissection techniques, the use of up to 4

instruments simultaneously (after binostril access is established), and dynamic,

anatomically-aware camera adjustments in real time.

Positioning in skull base surgery follows the same principles outlined above.

However, in this case, the patient’s head is placed in three-point fixation using a Mayfield

head holder. In addition to oxymetazoline, a solution of povidone-iodine is applied to the

nasal cavity and nose. Stereotactic navigation guidance is the norm, usually with fused

computed tomography (CT) and magnetic resonance (MR) images. Dedicated

intraoperative neurophysiologic monitoring by a clinical neurophysiologist is also carried

out routinely. When breaching the dura matter is anticipated, cefuroxime is administered

prophylactically.

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Endoscopic Endonasal Approaches to the Sphenoid Sinus

Three main endoscopic approaches to the sphenoid sinus exist: the transnasal (or

direct) route; the transethmoidal route; and the transseptal route.4 The fundamental goal

in all three is to safely identify the sphenoid ostium, which lies adjacent to the posterior

septum, approximately 1.5 to 2 cm superior to the choanal arch, and roughly 7 cm

posterior to the base of the columella.

Regardless of the approach, we favor the use of a 30-degree angled endoscope

over the perhaps more widely-used 0-degree endoscopes. In addition to allowing for

lateral, medial, superior or inferior visualization (depending on the direction in which the

beveled end is pointed), the slightly off-midline view provides some information about

the relative positions of structures to one another in the anterior-posterior dimension. This

grants the operator some degree of depth perception.

In the transnasal (or direct) approach, the sphenoid sinus is approached lateral to

the nasal septum and medial to the middle turbinate, through the sphenoethmoidal recess.

Here, the surgeon may choose one of two anatomic landmarks to guide the dissection: (1)

the superior turbinate or (2) the medial orbital floor if exposed through a prior maxillary

antrostomy. In the first option, the superior turbinate is identified after lateralization of

the middle turbinate. The sphenoid sinus ostium lies superomedial to the tail of the

superior turbinate, adjacent to the nasal septum, and may be identified by palpation using

a straight ball probe or a similar straight blunt instrument. In the second option, the

posterior aspect of the medial orbital floor is identified; a horizontal line is imagined

between this structure and the posterior nasal septum. This line provides a consistent

corridor to the middle one-third of the sphenoid sinus, which should contain the sphenoid

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sinus ostium in most cases. This method may prove useful when there is anatomic

distortion of the sphenoethmoidal recess and the superior turbinate cannot be adequately

identified.4,5

The transethmoidal approach begins with a total ethmoidectomy. Our preference

is to proceed sequentially in an anterior-to-posterior direction (in primary surgical cases),

beginning with the ethmoid bulla and continuing through the suprabullar air cells, basal

lamella, and posterior ethmoid air cells. This is carried out with a combination of forceps

and powered instrumentation. The dissection culminates with the identification of the

sphenoid sinus ostium in the region described previously.4,5

The transseptal approach has been advocated by some in cases where anatomic

distortion precludes use of a transnasal or transethmoidal approach.6 The origins of this

technique date back to 1910, when it was first described by Oskar Hirsch.7 The

endoscopic endonasal transseptal approach begins with a conventional endoscopic

septoplasty: first, a vertical incision is made immediately posterior to the limen nasi; next,

a perpendicular incision is made at the junction of the nasal cavity floor and the nasal

septum. The two are joined and, using a Cottle periosteal elevator, a posterosuperiorly-

based, L-shaped mucoperichondrial flap is elevated.5 Dissection in a sub-

mucoperichondrial (and later sub-mucoperiosteal plane) is carried posteriorly until the

sphenoid sinus ostium is encountered. A standard hemitransfixion incision may be used

in the place of an L-shaped flap technique. Known risks of the transseptal approach

include septal perforation, septal dislocation, synechia formation, nasal collapse or tip

deformity.

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A key step in any sphenoidotomy approach is confirming the presence of an air-

filled cavity beyond the presumed ostium. In a well-pneumatized sinus, the posterior

walls of the sphenoid sinus lies approximately 9 cm away from the base of the columella.

Blind dissection, particularly in a lateral direction (where the internal carotid artery and

optic nerve travel) can lead to complications and should be avoided.

Surgical Management of Intrinsic Sphenoid Sinus Pathology: Basic and Extended

Techniques

Simmen and Jones have proposed a classification scheme for sphenoidotomy

procedures. In their system, a type I sphenoidotomy involves identification of the

sphenoid ostium without further instrumentation; a type II sphenoidotomy entails

enlargement of the ostium inferiorly to one-half the height of the sphenoid sinus, and

upward to the skull base; and a type III sphenoidotomy involves extension to the floor of

the sinus and laterally to the so-called “vital structures” (i.e., intrasphenoid carotid artery

and optic nerve).8 While this concise scheme adequately describes the spectrum of

dissection required to address most sphenoid sinus disease, it fails to address the unique

surgical challenges presented by certain disease processes and/or anatomic variations.

One such situation is the presence of a pathologic process within the lateral recess

of the sphenoid sinus. In some cases, lateral recess pathology (e.g., a mucocele,

mycetoma, or skull base dehiscence resulting in cerebrospinal fluid leak) may be

addressed by extending an ipsilateral sphenoidotomy laterally. In these cases, the use of a

70-degree endoscope and other angled instrumentation (e.g., bipolar cautery device) may

be sufficient to address the problem.9 However, visualization and surgical access may be

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inadequate in the case of a very well-pneumatized lateral recess. Such cases may call for

the enhanced access that a contralateral corridor may afford or a transpterygoid approach.

In a bilateral extended sphenoidotomy, the bilateral sphenoid sinuses are accessed

and the ostia opened as described previously. Resection of the sphenoid sinus rostrum

and intersinus septum is then carried out. Care should be taken when resecting the

intersinus septum, as it often attaches to the anterior wall of the carotid canal; for this

reason, clean resection techniques (without pulling or twisting) are paramount. These

steps may be performed with a 30-degree endoscope as well. However, in cases with

excessive pneumatization of the lateral sphenoid recess, to achieve maximal lateral

visualization of the contralateral lateral sphenoid recess, a 70-degree endoscope is

occasionally necessary.

The endoscopic endonasal transpterygoid approach (EETP) may be also used to

access the lateral recess of the sphenoid sinus.10 This approach evolved as an endoscopic

alternative to sublabial and transfacial approaches to the pterygopalatine fossa,11 but has

since been recognized as a versatile corridor to several key structures and spaces, among

them the petrous apex, Meckel cave, infratemporal fossa, cavernous sinus, and lateral

nasopharynx.12-15

First, the uncinate process and natural ostium of the maxillary sinus are identified.

The maxillary sinus ostium is widened posteriorly toward the posterior fontanelle of the

maxillary sinus. Once the dissection reaches the level of the posterior maxillary sinus

wall, a transethmoidal sphenoidotomy is performed as previously described. A wide

sphenoidotomy is paramount for maximal maneuverability; however, care should be

taken to preserve the septal branch of the sphenopalatine artery if the need for a pedicled

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nasoseptal flap is anticipated during reconstruction. This vessel travels just inferior to the

sphenoid sinus ostium. Next, the mucosa of the posterior and superior maxillary sinus

walls is elevated using a Cottle or Freer periosteal elevator; in a similar fashion, the

lateral nasal wall mucosa is elevated. A wedge-shaped projection of bone is thus exposed,

representing the lateral and medial pterygoid plates in their respective positions. Medially,

the sphenopalatine artery is identified posterior to the crista ethmoidalis as it exits the

sphenopalatine foramen (Figure 1). Preservation of this blood vessel is preferred, but is

sometimes not possible. Using powered instrumentation (i.e., a high-speed drill) or

Kerrison rongeurs, the pterygoid plates are removed from a medial to lateral direction and

the pterygopalatine fossa is exposed. The contents of the pterygopalatine fossa include

the internal maxillary artery, descending palatine artery, posterosuperior alveolar artery,

pterygopalatine ganglion, and infraorbital nerve (Figure 2).16 These structures must be

retracted laterally while resecting the medial pterygoid plate and sphenoid process of the

palatine bone. Once this step is completed, the lateral recess of the sphenoid sinus should

come into view.10

Surgical Management of Extrinsic Sphenoid Sinus Pathology: The Transsphenoidal

Corridor

The concept of surgical corridors is central to endoscopic skull base surgery.

According a the classification system proposed by Schwarz, et al, four corridors exist:

transnasal, transsphenoidal, transethmoidal and transmaxillary.17 Of these, perhaps the

most commonly used is the transsphenoidal, as it provides access to the sella turcica for

the removal of pituitary lesions.18 In addition to the sella turcica, extended

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transsphenoidal dissection techniques can provide access to the suprasellar cistern, upper

clivus and medial cavernous sinus.17

Regardless of the approach, several key sphenoid landmarks must be identified

prior to transgressing the skull base. These include the sella turcia (superiorly) and clivus

(inferiorly); the tuberculum sellae and planum sphenoidale (anterosuperiorly); the carotid

and optic protuberances (paired lateral structures), and the opticocarotid recess (the space

between the latter two structures).

Two transsphenoidal corridor approaches are used in the management of sellar

lesions: the conventional transsellar approach, and an extended approach which entails

dissection of the planum sphenoidale and tuberculum sellae. The endoscopic endonasal

transsellar approach is appropriate when direct access to the sella turcica is desired. In

theory, this approach is feasible through a unilateral extended sphenoidotomy provided

that the target lesion is sufficiently small and directly within the sella. However, in most

cases, a bilateral extended sphenoidotomy (as described above) is required. The result of

such a sphenoidotomy should be a panoramic view of the sphenoid sinus cavity, making

identification of the aforementioned structures relatively straightforward (Figure 3).

Using a high-speed diamond drill, the anterior wall of the sella is gradually thinned.

Bimanual technique allows the surgeon to hold a double-barrel suction-irrigating

instrument in one hand and the drill in the other; meanwhile, the camera is held and

dynamically maneuvered by a second surgeon. Dissection is restricted to the space

flanked by the carotid protuberances bilaterally and continues until dura is exposed

(Figure 4).

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The endoscopic endonasal transplanum transtuberculum approach provides

access to the suprasellar cistern. This approach is useful as a means of addressing

pituitary lesions with suprasellar extension, craniopharyngiomas or other retrochiasmatic

lesions. The tuberculum strut and medial opticocarotid recesses are thinned using a

curved high-speed diamond drill. Irrigation is key in maintaining the translucency of the

bone and also in preventing thermal injury to the optic nerve. Once sufficiently thinned,

bone remnants are removed using an up-angled curette. The sellar bone is removed first,

followed by the bone of the planum sphenoidale. Anteriorly, the limit of planum

dissection is the posterior cribiform plate. Removal of the opticocarotid recesses follows,

which facilitates exposure of the optic nerves and carotid arteries as they course through

the opticocarotid cisterns (Figure 5).12,19,20

The endoscopic endonasal transclival approach permits access to the upper one-

third of the clivus. Depending on the site of the pathology, the approach may begin in a

similar fashion to the transsellar dissection, as the pituitary gland must often be retracted

in order to reach lesions with posterior clinoid process extension.21,22 It is then carried

inferiorly along the face of the clivus. Extent of resection is dictated by the pathologic

process in question. In other variation where the upper clivus is not involved, bilateral

sphenoid sinusotomies can be performed to expose the clival recesses. Resection of the

clival bone is subsequently undertaken from a craniocaudal direction (Figure 6). During

the clival dissection, care must be taken to avoid the internal carotid arteries, which run

parallel to one another and may be separated by as little as 11 mm. Similarly, the sixth

cranial nerves run paramedian at the clival level and may be separated from one another

by as little as 15 mm.21,23

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Endoscopic endonasal transcavernous approaches are also possible. McCoul, et

al, have described two techniques: a transsellar (“transsphenoidal transsellar”) and a

parasellar (“transethmoidal transsphenoidal parasellar”) approach.24 The transsellar

approach usually follows a standard endoscopic endonasal transsellar resection of a

pituitary tumor that has invaded the medial cavernous sinus. The parasellar approach

follows a transethmoidal sphenoidotomy and addresses primary pathologies of the medial

cavernous sinus.

CONCLUSION

In the age of endoscopic sinonasal and skull base surgery, the sphenoid sinus

plays a central role, both as an end-target in itself as well as a gateway to the skull base.

Endoscopic endonasal approaches represent minimal-access alternatives to the more

conventional transcranial surgery. In many cases, endoscopic endonasal procedures have

come to replace their open predecessors. An understanding of sphenoid sinus anatomy

and the different techniques available is key to addressing intrinsic and extrinsic

pathology of the sphenoid sinus.

DISCLOSURES

The authors report no proprietary or commercial interest in any product mentioned or concept discussed in this article.

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14. Gore MR, Zanation AM, Ebert CS, Senior BA. Cholesterol granuloma of the petrous apex. Otolaryngologic clinics of North America 2011; 44:1043-1058.

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16. Fortes FS, Sennes LU, Carrau RLet al. Endoscopic anatomy of the pterygopalatine fossa and the transpterygoid approach: development of a surgical instruction model. Laryngoscope 2008; 118:44-49.

17. Schwartz TH, Fraser JF, Brown S, Tabaee A, Kacker A, Anand VK. Endoscopic cranial base surgery: classification of operative approaches. Neurosurgery 2008; 62:991-1002; discussion 1002-1005.

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18. Jho HD. Endoscopic pituitary surgery. Pituitary 1999; 2:139-154. 19. Liu JK, Christiano LD, Patel SK, Tubbs RS, Eloy JA. Surgical nuances for

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23. Aktas U, Yilmazlar S, Ugras N. Anatomical restrictions in the transsphenoidal, transclival approach to the upper clival region: A cadaveric, anatomic study. Journal of cranio-maxillo-facial surgery : official publication of the European Association for Cranio-Maxillo-Facial Surgery 2012.

24. McCoul ED, Anand VK, Schwartz TH. Endoscopic approaches to the cavernous sinus. Operative Techniques in Otolaryngology - Head and Neck Surgery 2011; 22:263-268.

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FIGURE LEGENDS Figure 1. Cadaveric dissection showing initial approach to the pterygopalatine fossa through the posterior fontanelle of the left maxillary sinus (30-degree endoscope). Figure 2. Cadaveric dissection showing anatomic structures within the left pterygopalatine fossa (yellow circle) and infratemporal fossa (30-degree endoscope). Figure 3. Cadaveric dissection demonstrating 30-degree endoscopic panoramic view of the sphenoid sinus after bilateral extended sphenoid sinusotomies. Note the presence of two separate, non-midline instersinus septi. R, right; L, left; OC, optic canal. Figure 4. Cadaveric dissection demonstrating 30-degree endoscopic view of the sellar floor dura after sellar bone removal with a high-speed drill. R, right; L, left; OC, optic canal. Figure 5. Intraoperative photograph after resection of the sellar floor, bony tuberculum sellae, and the planum sphenoidale, with exposed sellar and planum dura (30-degree endoscope). R, right; L, left; OC, optic canal. Figure 6. Intraoperative photograph after resection of clivus for a clival chordoma (30-degree endoscope).

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Fig 1

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Fig 2

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Fig 3

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Fig 4

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Fig 5

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Fig 6