Transsphenoidal approaches to the ventral midline skullbase were first proposed more than a century ago. Initiallythese approaches were restricted to the pituitary fossa,5,10,14

but with progressive evolution in biotechnology7,8 coupledwith increased anatomical understanding, the transsphe-noidal approaches were extended to regions beyond thesella turcica4,6,15 to include other entities in addition to pitu-itary tumors. The introduction of the operating microscopeby Hardy in the 1960s,9 coupled with Dott’s contribution offluoroscopy,14 provided the first critical navigation/visual-ization integration that formed the foundation of the workthat followed.

The addition of the endoscope,1–3,7,11–13 coupled with thecurrent sophisticated neuronavigation systems, builds onthis foundation. The expanded endonasal approach evolvedwhen these principles were then further augmented withthe concept of team surgery; that is, a neurosurgeon andotolaryngologist working simultaneously throughout allphases of the surgery (approach, resection, and reconstruc-

tion). Using the principles of the expanded endonasal ap-proach, we are now able to access the entire ventral skullbase, from the crista galli up to and through the odontoid,and we are able to address a diverse array of intra- and ex-tradural entities.

In this report we describe our experience over the past 7years, accessing the ventral skull base along a midline sag-ittal plane by using a fully endoscopic, completely trans-nasal approach. Our system of modular approaches is basedon specific anatomical corridors. For each module we willoutline the key anatomical principles and technical nu-ances, using illustrative case examples to highlight theseprinciples.

GENERAL APPROACH

Patient Positioning

Patients are positioned supine on the operating table inMayfield head holders, with the head in a neutral positionand slightly rotated to the right side. The patient positionremains the same for each approach. For more rostral orcaudal lesions, 45˚ or 70˚ endoscopes may be used. Themonitors used for image guidance and endoscopy are posi-tioned directly in front of the surgeons.

Neurosurg Focus 19 (1):E3, 2005

Expanded endonasal approach: the rostrocaudal axis. Part I.Crista galli to the sella turcica

AMIN KASSAM, M.D., CARL H. SNYDERMAN, M.D., ARLAN MINTZ, M.SC., M.D.,PAUL GARDNER, M.D., AND RICARDO L. CARRAU, M.D.

Departments of Neurosurgery and Otolaryngology, Minimally Invasive Neurosurgery Center, andCenter for Cranial Base Surgery, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania

Object. Transsphenoidal approaches have been used for a century for the resection of pituitary and other sellartumors. More recently, the standard endonasal approach has been expanded to provide access to other, parasellarlesions. With the addition of the endoscope, this expansion carries significant potential for the resection of skull baselesions.

Methods. The anatomical landmarks and surgical techniques used in expanded (extended) endoscopic approachesto the rostral, anterior skull base are reviewed and presented, accompanied by case illustrations of each segment (ormodule) of approach. The rostral half of the anterior skull base is divided into modules of approach: sellar/parasellar,transplanum/transtuberculum, and transcribriform. Case illustrations of successful resections of lesions with each mod-ule are presented and discussed.

Conclusions. Endoscopic, expanded endonasal approaches to rostral anterior skull base lesions are feasible and holdgreat potential for decreased morbidity. The effectiveness and appropriate use of these techniques must be evaluatedby close examination of outcomes as case series expand.

KEY WORDS • endoscopic surgery • skull base • endonasal approach •transsphenoidal approach

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Abbreviations used in this paper: ACA = anterior cerebral artery;ACoA = anterior communicating artery; AEA = anterior ethmoidalartery; CA = carotid artery; CSF = cerebrospinal fluid; ICA = inter-nal carotid artery; MR = magnetic resonance; OCR = opticocarotidrecess; PEA = posterior ethmoidal artery; SIS = superior intercav-ernous sinus.

The nose is prepared by placing pledgets soaked with0.02% oxymetazoline into each naris, followed by povi-done iodine solution applied over the nose and upper lip aswell as into each nares on a cotton tip applicator. Bilateral Exposure

Bimanual dissection forms the foundation of microneu-rosurgery and is also an absolute prerequisite for endoneu-rosurgery. To allow for bimanual dissection, a binasal ap-proach is strongly advocated for all expanded endoscopicapproaches. The procedure is initiated in the right nariswith the removal of the middle turbinate. For routine trans-sellar exposures for microadenomas, the middle turbinatemay be preserved. The posterior septum is disarticulatedfrom the rostrum of the sphenoid bone, which is then re-moved to create a bilateral opening in the sphenoid sinus.The medial turbinate of the left naris is generally lateralizedbut not resected. The natural sphenoid ostium on the left isopened and widened so that there is communication withthe previous sphenoidotomy on the right side, thus creatingwide bilateral sphenoidotomies. The lateral margins of thesphenoidotomies are extended to the level of the medialpterygoid plates.

The endoscope is then returned to the right naris and asmall portion (~ 1–2 cm) of the posterior nasal septum is re-sected. This represents the most critical step in the binasalapproach because it facilitates bilateral instrumentationwithout deviation of the septum into the path of the endo-scope and compromise of visualization (Video 1). The bi-lateral sphenoidotomies made via the binasal approachform the foundation of all subsequent expanded endoscop-ic approach modules. To optimize the available space, theendoscope is positioned superiorly at 12 o’clock, with thesuction entering into the 6-o’clock position in the rightnaris (Fig. 1). Dissecting instruments can be introduced in-to the nasal cavity through the left naris (Video 1).

Video 1. Principles of general bilateral exposure. (Clickhere to view with Windows Media Player and a broadbandconnection, here to view with a dial-up connection, or here toview with RealPlayer.)

The principle of this exposure is to create a single largerectangular cavity within the sphenoid sinus. This allowsfor the progressive placement of the endoscope closer tothe target, which is critical for visualization by allowing forthe delivery of divergent light (“flash-light” effect), close tothe target and its magnification. Close placement of theendoscope is also imperative in the event of bleeding to al-low for maneuverability of the equipment without soilingits lens, which can be a frustrating limitation when workingthrough a tight corridor.Resection Procedures

Intradural Endoneurosurgical Dissection Techniques. En-doneurosurgical tumor resection uses microneurosurgicaltechniques identical to those of internal debulking, capsularmobilization, and extracapsular dissection of neurovascularstructures, along with coagulation and capsule removal.These principles have stood the test of time, minimize mor-bidity, and are primary approaches for the removal of anytumor. It must be emphasized that these endoneurosurgicaldissection techniques are of critical importance and takeprecedence over the degree of tumor resection in all cir-cumstances.

Tumor debulking techniques are dependent on tumorconsistency. When feasible, a technique in which two suc-tion devices are used has proven to be the safest means fordebulking. For a right-handed surgeon, a suction device isused in the left hand to maintain gentle countertractionwhile a dissecting or debulking instrument is used in theright. Countertraction exerted with a grasping instrumentcan tear extracapsular vessels that will retract and bleed.For debulking of soft lesions, such as pituitary tumors, aNo. 6 or at most a No. 8 French suction is adequate. Mal-leable suctions allow for distal angulation to improve ac-cess. For firmer tumors, an ultrasonic aspirator can be used.Rarely, the tumor contents can be removed piecemeal intra-capsularly by using fine cup forceps or pituitary forceps.Internal debulking is continued until the capsule is mobile.

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Fig. 1. A: Photograph showing the right naris with the endo-scope and suction at the 12- and 6-o’clock positions, respectively.B: Photograph depicting the binasal approach with the endoscopistpassing the scope in the right naris. The dissecting surgeon uses thesuction in the right naris and a second instrument in the left naris,allowing for bimanual dissection.

Extracapsular dissection should be done sharply, or al-ternatively, with fine blunt endoscopic dissectors or smallsuction device (Video 2). Critical neurovascular structuresare then identified and protected. The capsule is coagulatedusing the appropriately shaped endoscopic bipolar cautery.Care should be taken to avoid thermal injury to importantneurovascular structures from heat dispersal during cauter-ization.

Video 2. Principles of endoneurosurgery. (Click here toview with Windows Media Player and a broadband connection,here to view with a dial-up connection, or here to view withRealPlayer.)

SPECIFIC MODULES

Pituitary and Sellar Surgery

Illustrative Case. This 64-year-old woman presented withprogressive visual loss. Neuroendocrine function wasfound to be intact. Admission MR imaging revealed a largepituitary macroadenoma (Fig. 2). The patient underwent anendoscopic tumor removal with preservation of the pitui-tary gland and recovery of visual function. This case is pre-sented to demonstrate the specific exposure required andthe sequence for the intrasellar dissection technique.

Technical Considerations.Exposure. Once the general exposure is achieved (see

General Approach, subhead Bilateral Exposure) and bilat-eral sphenoidotomies are completed, the exposure of thepituitary fossa can proceed. The sphenoidotomy is widenedto include the lateral recess of the sphenoid extending later-al to the carotid canal. The exposure is then extended ros-

trally to expose the posterior cells of the ethmoid sinus andto further define the planum–tuberculum junction. Finally,the floor of the sphenoid is reduced back to the level of theclivus. This is particularly important in the case of macroad-enomas with significant suprasellar extension. By reducingthe floor of the sphenoid, a greater caudal-to-rostral trajec-tory into the suprasellar space is created. Any intrasphe-noidal septations must then be reduced with care, becausethe paramedian septations often lead to the vertical canal ofthe ICA. The sphenoid sinus mucosa is removed and thevenous bleeding is controlled by irrigation with warmsaline.

This approach generates the desired single rectangularcavity and allows for the identification of key anatomicallandmarks (Fig. 3) as follows: the medial OCR, the carotidprotuberance within the parasellar space, the sellar face, cli-val recess, and the strut of bone over the SIS. The medialOCR represents the ventral surface of the medial clinoidand is the key anatomical landmark in this region. An entryat the level of the medial OCR will allow for simultaneousaccess to the carotid canal, optic canal, sella turcica, andmedial cavernous sinus. It is analogous to a “key hole” dur-ing a conventional pterional craniotomy.

The medial OCR does not need to be opened for the re-moval of pituitary tumors unless there is significant supra-sellar and lateral extension toward the opticocarotid cistern.Removal of the bone overlying the SIS is imperative for le-sions that extend into the anterior cranial fossa. Therefore,bone removal over the sellar face should extend laterallyover the medial portions of each cavernous sinus and ros-trocaudally to expose both the superior and inferior inter-cavernous sinus. It has been our experience that surgeons

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Fig. 2. A: Preoperative contrast-enhanced sagittal and coronalMR images. B: Postoperative contrast-enhanced sagittal andcoronal MR images. Notice the residual gland on the coronal im-age located at the level of the right OCR.

Fig. 3. Endoscopic view demonstrating the expanded endonasalapproach used to access the anterior skull base. The initial moduleexposes the sellar floor rostrally to the level of the SIS (dissector).The protuberance created by the parasellar ICA extends verticallyto meet the optic canal that is obliquely traveling from medial tolateral in a posterior to anterior direction. Medial to this junction isthe medial OCR, which represents the key anatomical landmark forall anterior base modules. This sellar module can be progressivelyextended in a rostral direction by performing wide bilateral eth-moidectomies to expose the planum sphenoidale and the cribriformplate sequentially.

who are novices at endoscopy fail to undertake an adequateexposure and are content with a smaller window. This elim-inates the primary advantage of endoscopic surgery, whichis to deliver divergent focal light and magnification thatfacilitates superior visualization and dissection.

Intrasellar Dissection. We prefer not to use curettes fortumor removal but instead to rely on the endoneurosurgicaltechniques described earlier. Although extracapsular dis-section for pituitary tumors is often not possible, debulkingusing two suctions or an expanded endonasal ultrasonic as-pirator in our opinion provides for a more controlled re-moval with improved and less traumatic separation of thetumor from the normal gland, stalk, and cavernous sinuscontents. It should be noted that the improved visualizationprovided by the endoscope does allow for extracapsulardissection in many cases.

As macroadenomas are resected, the diaphragma willdescend and obstruct visualization. Therefore, systematicintrasellar dissection is mandatory to optimize visualizationwhile protecting the normal gland. The dura mater is op-ened using a sickle knife in the center of the sellar face. Theopening is extended caudally and obliquely toward the 8-and 5-o’clock positions, creating the inferior flap of the o-pening. The superior flap is left intact to act as a retractorand hold the anterior face of the tumor overlying the dia-phragma (Fig. 4A). In the case of a macroadenoma, the tu-mor will herniate through this inferior opening. This portionof the tumor is removed in a posterior trajectory toward theclivus–dorsum junction. The resection should extend wide-ly from cavernous sinus to cavernous sinus laterally andposteriorly to the dorsum. Care should be taken because thebone is defective posteriorly in many macroadenomas, andthe basilar cistern can be transgressed. The pituitary stalk ismost commonly located in this position.

Once the posterolateral dissection is completed, the su-perior dura mater can now be opened, allowing access tothe superior portion of the tumor (Fig. 4B). The superolat-eral dissection along the cavernous–carotid recess can thenbegin. Each recess is dissected from a caudal-to-rostraldirection vertically. Before proceeding superiorly, the pos-terior junction of the cavernous–carotid recess should beexamined and the tumor posterior to the carotid genu in thecavernous sinus can be removed (see Cavernous Sinus Ex-tension). Often venous bleeding is encountered during this

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Fig. 4. Endoscopic views demonstrating the critical segments ofintrasellar tumor removal. A: The superior dural leaf is left intactto allow for the tumor (T) to herniate through the initial inferior (I)opening. The inferior portion of the tumor is then resected in a pos-terior direction toward the clival dorsal junction. B: The superiorleaf of the dura mater (DM) is opened with scissors (S) after theinferior portion of the tumor has been removed. C: Endoscopicview of the superior right margin. The diaphragma (D) is retractedmedially and the right optic nerve (O) can be seen through thediaphragma. The ICA in the cavernous sinus can be seen travelinglaterally to form the OCR. D: Following removal of the anteriorand superior portions of the tumor the diaphragma will descend.This is then gently retracted superiorly and the endoscope can bebrought directly into the cavity to examine the lateral margins. Inthis view the left ICA can be seen because the medial cavernoussinus wall has been eroded. Tumor in the posterior (P) segment ofthe cavernous sinus behind the ICA can then be removed.

stage, and can be managed with packing. This should bedone prior to dissecting superiorly and risking a CSF leakto avoid the exchange of blood for CSF. Once the superiorlateral portion of the tumor in the sella turcica is removed,the medial OCR and angle between the optic nerve and CAas seen from inside the sella superolaterally should beexamined carefully bilaterally (Fig. 4C). This is one of thetwo sites most commonly found for retained tumor. Theother is under the anterior lip of the dura mater at the levelof the SIS directly beneath the sellar/tuberculum junction.To optimize visualization of this segment, the tumor alongthe anterior face overlying the diaphragma can be removed.This will allow the diaphragma to descend, opening up thesuperior angle between the dura mater at the level of theSIS and the anterior attachment of the diaphragma. Thedura can be coagulated, shrinking it back to the SIS. Thesemaneuvers in combination with removal of the overlyingbone will optimize visualization.

Final inspection of the sella turcica is undertaken in aclockwise fashion, starting inferiorly at 6 o’clock and usingangled endoscopes as required. At this stage, the diaphrag-ma should descend concentrically. In our experience, themost common position of the residual gland is as an apronplastered to the undersurface of the diaphragma. If the dia-phragma fails to descend concentrically, this is indicative ofretained tumor in the suprasellar space. Depending on thegoals of surgery, however, this may be an acceptable out-come. If the goals are optic decompression or staged sur-gery, then tumor removal should not be considered ade-quate until pulsations are visible in the diaphragma; in ourexperience this is a robust finding. If descent is not concen-tric and additional removal is needed, the diaphragma iselectively opened. With the aid of the endoscope, residualtumor in the suprasellar cistern can be removed until the op-tic nerves are directly visualized. During this resection, westrongly urge the use of endosurgical dissection techniquespreviously described as opposed to curettes, because smallsubchiasmatic and infundibular perforating vessels must bepreserved. If such suprasellar dissection is required then itis imperative to remove the bone overlying the medial OCRcompletely. This allows identification of the optic nerve andCA laterally and facilitates extracapsular dissection withoutthe need for excessive countertraction. These maneuverswill maximize the chance of preserving the perforating ves-sels (Video 3).

Video 3. Intrasellar resection technique. (Click here to viewwith Windows Media Player and a broadband connection, hereto view with a dial-up connection, or here to view withRealPlayer.)

Cavernous Sinus Extension. Once the superior and inferi-or margins of the cavity have been examined, the endo-scope can be place directly within the sella to examine themedial cavernous walls that form the lateral margins of thecavity. Visualization is improved in macroadenomas by thesellar expansion but can be augmented with angled endo-scopes if needed. The improved visualization facilitates theelective opening of the cavernous sinus to access tumorextension within the medial segment. The carotid siphon isusually anteriorly placed and the space between the poste-rior clinoid and the siphon represents an ideal entry point(Fig. 4D). Most often, the tumor creates a pathway throughthis space that can be pursued. The tumor posterior to the

CA can be removed using the two-suction technique. As anote of caution, if there is an opening in the diaphragma(intentional or inadvertent), great care should be taken toavoid the exchange of blood for CSF and to avoid a sub-arachnoid hemorrhage with its associated complications.

EXPANDED APPROACHES

Based on our pituitary experience we then proceeded toapply these principles to create a series of modular expand-ed approaches. The natural extension was rostrally to accessthe suprasellar cistern and anterior cranial base directlywithout going through the sella turcica. The transtubercu-lum/transplanum and transcribriform approaches are de-scribed next.

Transtuberculum/Transplanum Approach

Illustrative Case. This 40-year-old woman presented withprogressive visual failure (Fig. 5A). Admission MR imag-ing revealed a suprasellar meningioma with significant op-tic chiasm compression (Fig. 6A). Complete tumor resec-tion was achieved via an expanded endonasal approachtransplanum module (Fig. 6B). The patient was observedpostoperatively for 72 hours and discharged. On follow-upexamination, visual fields demonstrated a complete recov-ery (Fig. 5B). This case is presented to demonstrate theexposure required and the nuances of the intradural dissec-tion technique.

Technical Considerations.Extradural Exposure. Once the general bilateral approach

to the sphenoid is completed, the rostral exposure is initiat-ed by completing wide bilateral anterior and posterior eth-moidectomies (Fig. 3). The ethmoid septations are drilledflush with the anterior cranial base and laterally to the levelof the lamina papyracea, providing for a wide lateral expo-sure. For a transplanum approach, we try to minimize therisk of compromising olfaction by ensuring that the anteri-or margin of the exposure does not extend rostrally to thelevel of the PEAs and canals, and we leave the most rostralmargin of the nasal septum attached to the skull base.

Next, the planum sphenoidale is drilled from a rostral-to-caudal direction. Once the planum is eggshell thin it can begently fractured inferiorly by using a blunt dissector orKerrison rongeurs, if needed. The most rostral portion ofthe sellar floor can be opened to expose the SIS. To mobi-lize the SIS, the overlying bone strut is made eggshell thinby the drill and fractured inferiorly (alternatively, a 1-mm,45˚ Kerrison rongeur can be used). Mobilization of the si-nus will allow for subsequent direct access to the supra-sellar portion of the tumor in the parachiasmatic cisterns.Removal of this segment of the bone is adequate to allowfor direct access without the need to transect the SIS. Sinusbleeding can be controlled with microfibrillar collagen“sandwiches.” The ventral aspect of the medial clinoids,representing the medial OCR, is drilled away with a 3-mmhybrid bit, with copious irrigation to protect the opticnerves from thermal injury. It is not uncommon to find ve-nous bleeding from the SIS as it inserts laterally into thecavernous sinus directly under this bone. Using a 1-mmKerrison rongeur, the paraclinoid carotid canals can be re-moved in this region. This should be done by using only

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one third of the distal tip of the Kerrison positioned verti-cally in a parallel orientation to the underlying subclinoidcarotid canal. Removing the remainder of the medial cli-noid process is imperative to be able subsequently to accessthe OCR intradurally without having to retract the tumorand risk injury to the perforating artery. This point cannotbe overemphasized (Video 4).

Video 4. Planum exposure. (Click here to view withWindows Media Player and a broadband connection, here toview with a dial-up connection, or here to view withRealPlayer.)

Tumor Devascularization. It is not uncommon in anteriorskull base meningiomas to find a feeding artery arisingfrom the distal portion of the paraclinoid CA at the level ofthe medial OCR. This feeding vessel is coagulated to aid inthe devascularization of the tumor. Exposing and sacrific-ing the PEAs further accomplishes this goal. These arteriesare located approximately 5 to 7 mm anterior to the orbitalapex. The posterior ethmoidal canal is identified as itemerges from the lamina papyracea and courses toward thefovea ethmoidalis. The canal is unroofed to identify thePEA, which is then ligated. Care should be taken to preventthe proximal stump from bleeding and retracting into theorbit, resulting in a retrobulbar hematoma. The PEA is lig-ated using the technique described in the Transcribriformmodule to secure the AEA. At this point, a single midlineanterior base cavity has been created that extends from the

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Fig. 5. A: Preoperative visual field charts showing severe fielddeficits. B: Postoperative visual field charts showing visual re-covery.

Fig. 6. A: Preoperative postcontrast MR imaging with repre-sentative coronal (upper) and sagittal (lower) views demonstratinga suprasellar meningioma with critical relationships to the parasel-lar neurovascular structures. B: Postoperative postcontrast sagit-tal MR image demonstrating complete tumor removal and anatom-ical preservation of critical neurovascular structures.

planum/cribriform junction to the clival recess anteropos-teriorly and laterally between each lamina papyracea. Theexposed dura mater extending from the sella turcica to theanterior portion of the planum is then meticulously andtediously coagulated to provide further devascularization(Fig. 7A). The dura mater is opened widely in a cruciatefashion, taking care not to transgress the prechiasmatic cis-terns (Fig. 7B). Excessive exposure will allow normalbrain to herniate through the defect and obscure visualiza-tion. The anterior margin of the lesion is identified and thebrain/tumor interface marks the extent of the openingrequired. Additional bone and dura mater that interfereswith the exposure of this junction it should be removed atthis stage.

Intradural Dissection. Using the principles of endoneuro-surgical dissection, systematic extracapsular dissectionthrough the parachiasmatic cisterns is accomplished. Criti-cal neurovascular structures are identified. The first land-mark sought should be the paraclinoid CA as it emergesintradurally at the level of medial OCR, over which thebone should have already been adequately removed (Fig.8). The CA will lead to the optic nerve, which is locatedslightly superiorly. The optic nerve in turn can be followedwith circumferential extracapsular dissection to the chiasmand then to the contralateral optic nerve and CA. It bearsrepeating that to undertake extracapsular dissection safelyin this region, the capsule of the tumor must be thinnedenough to allow for gentle traction with no more than a No.4 or 6 French catheter used for suction. This will allow thearachnoid bands of the parachiasmatic cisterns to be underenough tension to facilitate sharp dissection (Fig. 9).Finally, care should be taken during the parachiasmatic dis-section, because the ACoA and in particular the recurrentartery of Huebner may be draped over the superior surface.

Once the suprachiasmatic dissection has been completedthe subchiasmatic sequence can begin. During this se-quence, several additional critical steps need to be specifi-cally performed to preserve critical structures during theextracapsular dissection. These are performed once ade-quate debulking in the respective regions has been accom-plished. Small subchiasmatic perforating vessels are oftendraped around the circumference of the tumor (Fig. 10).With adequate debulking and mobilization these can usual-ly be spared, and if present, the branches directly feedingthe tumor can be coagulated and sectioned (Fig. 11).

The infundibulum is most often adherent to the posteriormargin of the capsule and can easily be damaged during co-agulation of the base of the tumor at the tuberculum/sellarjunction. Bipolar cauterization should be avoided in thisspace until the stalk has been specifically identified (Fig. 12,Video 5).

Video 5. Intradural transplanum dissection. (Click here toview with Windows Media Player and a broadband connection,here to view with a dial-up connection, or here to view withRealPlayer.)

Transcribriform Approach

Illustrative Case. This 64-year-old woman presented withvisual failure, anosmia, and severe neurocognitive deficits.Preoperative MR imaging revealed a large olfactory groovemeningioma with severe bifrontal edema (Fig. 13A). Com-

puterized tomography angiography scans demonstratedsignificant vascular adherence of the second segments ofthe ACAs (A2) to the capsule of the tumor (Fig. 13B). Thepatient underwent a staged expanded endoscopic transcrib-riform surgery for tumor removal via a fully endoscopictransnasal approach Fig. (13C). Postoperatively the patientmade a complete visual recovery and her neurocognitivedeficits resolved completely. This case is presented to

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Fig. 7. A: Endoscopic view of the planum module once thebone removal has been completed. In the rostrocaudal axis theplanum sphenoidale (P), tuberculum (T), and sella turcica (S) canbe seen. The fold of the SIS between the tuberculum and sella isseen as well. The lateral extent of the opening is to the junction ofthe SIS as it merges with the cavernous sinus. This represents theregion of the medial OCR (mOCR). B: Endoscopic view show-ing the cruciate dural following cauterization and devasculariza-tion. The dura mater is opened from the planum inferiorly based onthe SIS. The suprasellar cistern (SC) can be seen and preserved.

demonstrate the exposure needed and the technique for dis-section of vascular structures from the tumor capsule.

Technical Considerations.

Extradural Approach. This module extends the rostral ex-tension of the previous approach to the level of the cristagalli. Following the transplanum module, the transcribri-form approach can be initiated by resecting the attachmentof the anterior portion of the nasal septum to the skull base.It is likely that olfaction has already been compromised bythe disease entity in question. The frontoethmoidal recess isidentified and the skull base is drilled from a rostral-to-cau-dal direction to mitigate the obscuring effects of drippingblood, thus optimizing visualization. The AEA is purpose-fully identified and sacrificed to provide for tumor devas-cularization (Fig. 14). If necessary, the back wall of the

frontal sinus can be accessed and/or removed via the fron-toethmoidal recess.

The olfactory sulcus extends on both sides of the cristagalli, from the cribriform plate rostrally to the anterior mar-gin of the planum caudally. To facilitate the drilling of thisbone all the overlying soft tissue must be removed. Thisconsists of the small branches of the ethmoidal arteries andthe olfactory filaments entering and exiting the crista galli,respectively. Coagulation of these vessels also further aidsin devascularization. The cribriform plate is removed bilat-erally, leaving the crista galli in the midline, which canextend for a variable depth into the intracranial cavity. Thecrista galli can be particularly prominent in the case of ol-factory groove meningiomas with secondary hyperostosis.Removal of the crista galli will involve additional drillinginternally, and then fracture once it has become eggshellthin (Fig. 15).

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Fig. 8. A: Endoscopic view following opening of the tubercu-lum and planum (P) dura mater. The tumor (T) can be seen oncethe suprasellar cistern is opened. B: Endoscopic view demon-strating extracapsular dissection of the tumor to identify the rightICA. Note that a small subchiasmatic perforating vessel (P) can beseen traveling from the ICA over the dome of the tumor to the un-dersurface of the chiasm. The dural leaf is coagulated using a pis-tol-grip bipolar (BP) to retract it from the field.

Fig. 9. A: Endoscopic view obtained after initial debulking ofthe tumor showing the technique for extracapsular sharp dissectionperformed using scissors to release the arachnoid bands (A) tether-ing the tumor capsule (T) to the chiasm (C) and frontal lobe (F).B: Endoscopic view showing the operating field after arachnoidalsharp dissection. Note the position of the ACoA (Acom) and the A1

segments (A1) of the ACAs. The tumor capsule has been sharplydissected from these vessels and the frontal lobe. Arachnoid bandstethering tumor to the chiasm can still be seen.

Resection of the crista galli and cribriform plate aug-mented with the transplanum module (if required) creates alarge single cavity along the anterior skull base. The ex-posed dura mater is thoroughly coagulated, which, in com-bination with the AEA and PEA ligations, is critical fordevascularization. This leaves the anterior falcine artery asthe primary residual supply to the tumor, in addition to anycortical vessels parasitized from the anterior circulation.

Intradural Dissection. Following coagulation, the duramater is opened on both sides of the falx individually. Themidline is kept intact intentionally because the tumor in thisregion is still vascularized. Internal tumor debulking issequentially performed on each side, exposing the freeedge of the falx bilaterally. At this point, the feeding ves-sels arising from the anterior falcine artery are coagulatedalong with the falx. The falx is transected to provide a sin-gle intradural working cavity. The tumor is debulked start-ing in the midline. The dura mater anterior to the brain/tu-mor interface is left intact to prevent herniation of the brain,

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Fig. 10. A: Endoscopic view showing a small subchiasmaticperforating vessel draped over the dome of the tumor. B: Endo-scopic view showing that after adequate debulking the tumor cap-sule (T) can be mobilized to separate this small subchiasmatic per-forating vessel (SP) by using endoneurosurgical techniques and topreserve it as it travels to the undersurface of the chiasm (C).

Fig. 11. Endoscopic views showing a small subchiasmatic per-forating vessel (SP) traveling to the undersurface of the chiasm (C).A: The initial position of the subchiasmatic perforating vesseldraped over the dome of the tumor (T) and adherent to the chiasmis depicted. Note the gentle countertraction being applied to theinferior portion of the tumor capsule to allow for mobilization.B: After initial debulking (D) of the tumor, the subchiasmatic per-forating artery is better visualized. C: The initial perforating ves-sel is entirely separate from the tumor capsule and supplies the chi-asm, and a small tumor feeding vessel (TV) supplying the tumor ina deeper plane can be seen. This view shows that this tumor vesselis coagulated and the chiasmatic perforating artery is preserved.

which will obscure visualization. During the extracapsulardissection of large tumors, there is very often subpial inva-sion of the lesion into the overlying cortex. Therefore, inthese cases a subpial dissection must be performed usingNo. 4 French catheters for suction and fine endoneurosur-gical bipolar cauteries under low heat. This dissection canproceed to the level of the interhemispheric fissure alongthe superior pole of the tumor. Care should be taken be-cause the A2 segments and the frontopolar artery will bedraped over the tumor surface (Fig. 16).

It is very useful after an initial adequate internal debulk-ing to proceed toward the parasellar space caudally (inferi-or pole). This will allow access to the parasellar cistern andidentification of key neurovascular landmarks described inthe Transtuberculum/Transplanum Approach section.Identification of the optic nerves and ACoA may greatly fa-cilitate the extracapsular dissection of the A2 segmentsalong the interhemispheric fissure from a preferred proxi-mal-to-distal direction. This provides proximal control dur-ing the vascular dissection along the capsule interface. The70˚ endoscope is invaluable for the most anterior and ros-tral dissection of the tumor. When this scope is needed, it isplaced at the 6-o’clock position and the suction is moved to12 o’clock, inverting the previous positions in the patient’sright naris (Video 6).

Video 6. Intradural transcribriform dissection. (Click here toview with Windows Media Player and a broadband connection,here to view with a dial-up connection, or here to view withRealPlayer.)

Staged tumor removal may be an excellent option, espe-cially for exceptionally large tumors in which circumferen-tial extracapsular dissection is not possible because ofgrowth along the sagittal or coronal planes (very “tall andwide tumors”). In these situations, pulsations from all seg-

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Fig. 12. Endoscopic view obtained after tumor resection. TheACoA (Acom) and the recurrent artery of Huebner (RAH) can beseen above the chiasm (C). A small perforating vessel (P) is pre-served and can be seen supplying the infundibulum (S). Also notethe preservation of the small perforating arteries on the undersur-face of the chiasm. The right ICA can also be seen.

Fig. 13. A: Preoperative MR images demonstrating a largeolfactory groove meningioma. Note the significant bifrontal edemaas seen on the axial fluid-attenuated inversion-recovery (flair)sequence. On the coronal view note the edema reaching verticallyto the level of the corpus callosum and its horizontal extent to thelevel of the midorbit. Also note the hyperostosis of the anteriorbase of the tumor on the coronal view. B: Computerized tomog-raphy angiography demonstrating the adherence of the second seg-ments of the ACA (A2) on the surface of the tumor (T). C: Post-operative MR images obtained at the 2-year follow-up visit. Notethe significant resolution of the bifrontal edema as seen on the axialfluid-attenuated inversion-recovery sequence. The postcontrast T1-weighted sequence does not reveal evidence of tumor recurrence orresidual lesion.

ments of the tumor cavity following initial debulkingshould be observed. If this occurs, the tumor will likelymigrate in from all directions to fill the cavity created. Thefirst stage is not terminated until such complete pulsationsare seen.

DISCUSSION

In this report we have outlined our 7-year experience indeveloping a modular approach to the ventral skull basefrom the sella turcica to the crista galli by using a fully en-doscopic and completely transnasal approach. We havedemonstrated that the modular approaches are based on spe-cific anatomical corridors and have outlined the key an-atomical principles and technical nuances for each region.

Starting with the approach to the pituitary, we have de-tailed a general binasal exposure of the sphenoid sinus and

sella turcica. Use of endoneurosurgical techniques necessi-tates a wide sphenoid opening, which becomes the standardapproach for all the expanded modules. Extending anteri-orly, we have outlined the feasibility of dealing with intra-and extradural lesions of the planum and cribriform re-gions.

The importance of maintaining strict microneurosurgicaltechniques in all endoneurosurgical cases has been empha-sized. The specific approaches and instrument modifica-

Neurosurg. Focus / Volume 19 / July, 2005

Expanded endonasal approach. Part I. Crista galli to sella turcica

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Fig. 14. A: Endoscopic view using a 70˚ scope showing thekey relationships along the left olfactory sulcus. The cribriformplate (CP) is seen medially and the AEA is also seen. This arterycan be seen as it emerges from the orbit after the lamina papyraceahas been removed. B: The periorbita (PO) can be seen laterallyand a hemoclip (HC) is applied just at the level at which the AEAemerges from the periorbita.

Fig. 15. Endoscopic view using a 70˚ scope after clip ligation ofthe AEAs bilaterally. The cribriform plate over the olfactory sulcus(OS) has been removed bilaterally. The crista galli (C) is drilledfrom an inferior to superior direction as it penetrates the anteriorskull base.

Fig. 16. Endoscopic view using a 70˚ scope showing the rela-tionship of the tumor capsule to the second segment of the ACA(A2) as it courses through the interhemispheric fissure (F). Notethe small arachnoid bands (AB) attaching the A2 to the tumor cap-sule. Once the tumor has been separated from adjacent structures,a Teflon pledget (TP) is placed to maintain the position. Theseshould be removed at the end of the surgery after tumor resection.

tions that allow for endoscopic bimanual dissection, in-ternal debulking, capsular mobilization, and extracapsularsharp dissection have been outlined and form the backboneof the expanded endonasal approaches.

CONCLUSIONS

The goal of this report is to demonstrate the feasibility ofthe endoscopic approaches to the anterior skull base. Wehave provided the technical and anatomical nuances anddetailed the endoneurosurgical techniques. Also, the im-portant outcome studies are underway to determine theclinical efficacy of this work.

References

1. Cappabianca P, Alfieri A, Colao A, et al: Endoscopic endonasaltranssphenoidal surgery in recurrent and residual pituitary ade-nomas: technical note. Minim Invasive Neurosurg 43:38–43,2000

2. Cappabianca P, Cavallo LM, Colao A, et al: Endoscopicendonasal transsphenoidal approach: outcome analysis of 100consecutive procedures. Minim Invasive Neurosurg 45:193–200, 2002

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11. Jho HD: Endoscopic transsphenoidal surgery. J Neurooncol-ogy 54:187–195, 2001

12. Jho HD, Carrau RL: Endoscopic endonasal transsphenoidalsurgery: Experience with 50 patients. J Neurosurg 87:44–51,1997

13. Jho HD, Carrau RL, Ko Y, et al: Endoscopic pituitary surgery:an early experience. Surg Neurol 47:213–223, 1996

14. Rosegay H: Cushing’s legacy to transsphenoidal surgery. JNeurosurg 54:448–454, 1981

15. Zada G, Kelly DF, Cohen P, et al: Endonasal transsphenoidalapproach for pituitary adenomas and other sellar lesions: anassessment of efficacy, safety, and patient impressions. J Neu-rosurg 98:350–358, 2003

Manuscript received June 8, 2005.Accepted in final form June 28, 2005.Address reprint requests to: Amin B. Kassam, M.D., University

of Pittsburgh School of Medicine, 203 Lothrop Street, Suite 500,Pittsburgh, Pennsylvania 15213. email: kassamab@upmc.edu.

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