OPERATIVE NUANCES · 2017. 12. 15. · TRANSSPHENOIDAL SURGERY Although we concentrate on...

OPERATIVE NUANCES

TRANSSPHENOIDAL MICROSURGERY

Ivan Ciric, M.D.Division of Neurosurgery, EvanstonHospital, Northwestern UniversityMedical School, Evanston, Illinois

Sami Rosenblatt, M.D.Division of Neurosurgery, EvanstonHospital, Northwestern UniversityMedical School, Evanston, Illinois

Jin-Chen Zhao, M.D.Division of Neurosurgery, EvanstonHospital, Northwestern UniversityMedical School, Evanston, Illinois

Reprint requests:Ivan Ciric, M.D., Division ofNeurosurgery, Evanston Hospital,Northwestern University MedicalSchool, 2650 Ridge Avenue, Room4222, Evanston, IL 60201.Email: [email protected]

Received, January 2, 2002.

Accepted, March 6, 2002.

TRANSSPHENOIDAL MICROSURGERY IS a well-established neurosurgical procedurethat has become the standard of care in the management of the majority of pituitarytumors and a select group of other sellar lesions. The safety of the procedure dependson the surgeon’s adherence to certain anatomic concepts. Foremost among theseconcepts is the necessity of preserving the integrity of the arachnoid membranecovering the tumor dome and avoiding vascular injuries in the cavernous sinus. Theobjective of this article is to demonstrate the sequential steps of a transsphenoidalmicrosurgical procedure for the removal of a pituitary tumor in light of the anatomicconcepts discussed, with the goal of preventing complications and achieving the bestpossible outcome.

KEY WORDS: Anatomic concepts, Pituitary tumors, Technique, Transsphenoidal microsurgery

Neurosurgery 51:161-169, 2002 DOI: 10.1227/01.NEU.0000017719.06251.32 www.neurosurgery-online.com

The roots of transsphenoidal pituitarysurgical techniques can be traced to thelate 19th century (8). Cushing (7) also

used this approach to remove pituitary ade-nomas. The transsphenoidal microsurgicaltechnique was ushered in by Hardy in 1962(9). Transsphenoidal microsurgery is cur-rently a proven, well-established neurosurgi-cal procedure, as evidenced by the reports inthe literature that attest to its safety and effi-cacy (10, 14, 18, 24, 25). Nevertheless, compli-cations continue to be associated with thisprocedure (6, 15, 20). A review of the surgicaltechnique of transsphenoidal microsurgeryseems appropriate because it may contributeto further improvement in outcomes.

CONCEPTUAL NUANCES

The execution of a surgical procedure de-pends in large measure on the understandingof the surgical anatomy of the operative field.We consider the following three anatomicconcepts that are fundamental to the safe ex-ecution of a transsphenoidal microsurgicalprocedure:

1. The pituitary gland is an extra-arachnoidstructure.

2 The pituitary gland is strictly in the mid-line, with hazards to either side.

3. It is important to recognize the residualnormal anterior pituitary, especially dur-

ing operations to remove pituitarymacroadenomas.

First, the pituitary gland is an extra-arachnoidstructure (Fig. 1A) (6). Consequently, all pitu-itary adenomas originate in the extra-arachnoidspace. As they expand out of the sella, pituitaryadenomas distend the dural ring of the dia-phragma sellae. At the same time, they elevatethe arachnoid membrane of the diaphragmawithout penetrating it. Regardless of their sizeand shape, pituitary adenomas remain coveredby a layer of arachnoid that separates them fromthe subarachnoid space (Fig. 1B). A transsphe-noidal operation for the removal of a pituitaryadenoma should be executed with respect forthe preservation of the integrity of the arachnoidmembrane, which acts as a protective shieldbetween the surgical manipulation and the sub-arachnoid space, with its vital neurovascularstructures. Thus, the surgical dissection shouldbe performed along the tumor-arachnoid inter-face. Adherence to this simple anatomic conceptis responsible for good surgical outcomes aftertranssphenoidal microsurgery; when this con-cept is violated, however, many of the compli-cations associated with this procedure result (2,6, 15, 20).

However, this anatomic concept does notnecessarily apply to craniopharyngiomas aswell. As a result of their developmental anat-omy, craniopharyngiomas can be completelyintrasellar and therefore completely extra-arachnoid; they can be partially intra- and

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partially extra-arachnoid; they can be completely intra-arachnoid, even interdigitating with the neuroepithelium ofthe infundibular region of the hypothalamus; or they can beintraventricular (5). Consequently, the possibility of a postop-erative cerebrospinal fluid (CSF) leak occurring in the wake ofa transsphenoidal microsurgical procedure performed to re-move a craniopharyngioma is considerably greater than oneperformed to remove a pituitary adenoma.

The second concept that the surgeon should keep in mind isthat the pituitary gland is strictly in the midline, with hazardsto either side. Veering off toward one side or the other beyondcertain limits during the approach—and especially duringsurgical maneuvers inside the sella—exponentially increasesthe risk of complications from transsphenoidal surgery (1, 3, 4,16, 21, 22) (Fig. 2).

The third anatomic concept worth remembering pertains tothe recognition of the residual normal anterior pituitary, es-pecially during operations to remove pituitary macroadeno-mas. As they expand, pituitary adenomas distend the residualnormal anterior pituitary to a point at which it is eventuallyrepresented by a thin layer of tissue surrounding the adenoma(6). This tissue can be recognized on the preoperative T1-weighted magnetic resonance imaging (MRI) scan as a thinlayer of increased signal intensity surrounding the pituitaryadenoma, which usually demonstrates decreased signal inten-sity. When the preoperative MRI study of a macroadenoma isexamined carefully, this layer can almost always be observed(Fig. 3). Recognition of this layer and its preservation willprevent a postoperative anterior pituitary insufficiency.

ENDOSCOPICTRANSSPHENOIDAL SURGERY

Although we concentrate on transsphenoidal microsurgeryof pituitary adenomas in this article, we also make severalcomments concerning endoscopic transsphenoidal surgery.Endoscopy is here to stay (11, 12). However, it will not replacemicrosurgery. The two techniques should viewed as beingcomplementary, not mutually exclusive. They both lead to thesame goal: they advance the surgeon to the sellar and supra-

FIGURE 1. Drawings illustrating anatomy. A, the pituitary gland is sit-uated below the diaphragma sellae, which is composed of the dural ringand the overlying arachnoid. B, as a pituitary tumor develops and grows,it distends the dural ring of the diaphragma sellae while it elevates thearachnoid of the diaphragma. The tumor remains beneath the arachnoidregardless of its size. The anterior and posterior arachnoid recesses can beseen.

FIGURE 2. Imaging studies in a patient with a growth hormone-secreting microadenoma. A, preoperative MRI scan; during surgery, theright carotid artery was injured in the cavernous sinus. B, postoperativeangiogram revealing balloon occlusion of the right cavernous carotid.

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sellar abnormality. Neither procedure should change how theneurosurgeon deals with the abnormality. Pituitary surgeonsshould be masters of both techniques and should use one orthe other as the situation demands.

Endoscopic imaging remains by and large monocular. Thus,the surgeon’s visualization of the operative field via endo-scopic imaging resembles what the neurosurgical assistantsees through the operating microscope. Advances are beingmade to improve endoscopic imaging by adding the thirddimension with a variety of binocular attachments. Also, hold-ers have been designed to secure the endoscope and therebyfree the surgeon’s hands for surgical manipulation. Theseinnovations are not yet available on a large-scale, commercialbasis, however. For the most part, such devices are used byonly a few pioneer endoscopic neurosurgeons.

PREOPERATIVE WORKUP

Each patient undergoes a thorough medical and endocrino-logical workup, a detailed description of which is beyond thescope of this article. In patients with endocrinologically con-firmed, pituitary-dependent Cushing’s syndrome whose MRIscans are inconclusive for a discrete microadenoma, a petrosalsinus sampling test is performed in conjunction withcorticotropin-releasing factor stimulation to search for an ad-renocorticotropic hormone gradient.

During the past 2 years, we have abandoned the use oftelevised fluoroscopy (10) for trajectory and instrument posi-tion control in favor of performing the operation with theassistance of MRI-based, computer-assisted frameless stereo-tactic guidance (Fig. 4). The advantages of frameless stereotaxyover televised fluoroscopy are many. First, whereas televisedfluoroscopy offers only a vertical orientation in a sagittalplane, frameless stereotaxy also provides for a horizontal ori-entation in the coronal plane, which is an important dimen-

sion, especially during operations in patients whose sellaranatomy is obliterated by the abnormality, during reopera-tions in patients with recurrent tumors, and when performingthe extended transsphenoidal approach, which requires nav-igation through a relatively narrow corridor between the twosupraclinoid carotid arteries. The use of frameless stereotaxyalso shortens operative time: the preoperative MRI scan can beobtained on any day before the operation by the use of exter-nal anatomic landmarks (e.g., tragus, outer and inner canthi,nasion, tip of the nose) as fiducials. In our experience withmore than 50 such cases, the accuracy of the use of anatomiclandmarks as fiducials has truly been impressive, with themargin of error around the sella being no more than 1 mm andwith the overall average margin of error being no more than2.1 mm for the entire series. Finally, the use of framelessstereotaxy as a navigational tool removes intraoperative radi-ation exposure.

PREOPERATIVE PREPARATION

During the operation, the patient lies comfortably supine.The back and the knees are elevated by approximately 15degrees. The head is tilted toward the left shoulder, with carebeing taken to account for the suppleness of the patient’s neck.Care is also taken not to cause an obstruction of the jugularoutflow on the left side and not to cause any stretch injury tothe right brachial plexus. In patients with microadenoma, thebridge of the nose is kept parallel to the operating room floor;in patients with macroadenoma, the head is inclined slightlymore toward the operating room floor. The patient’s head issecured in this position in relation to the operating table witha three-point fixation clamp. We prefer rigid fixation to having

FIGURE 3. MRI studies obtained from two patients with macroadeno-mas. A, sagittal T1-weighted MRI scan in a patient with a prolactin-secreting macroadenoma. B, coronal T1-weighted MRI scan in a patientwith a nonsecreting macroadenoma. The peripheral rim of enhancing tis-sue can be seen, in both cases representing residual distended anteriorpituitary.

FIGURE 4. MRI scans illustrating the anatomic landmarks (e.g., tragus,canthi, nasion) used as fiducials for MRI-based, computer-assisted frame-less stereotaxy.



the patient’s head lie on a head rest. The operating roomtable’s capabilities for changes in position during the opera-tion to adjust the field of view are used as needed throughoutthe procedure.

The nasal cavities and the surrounding facial skin are pre-pared with a povidone-iodine solution. Simultaneously, theright lower quadrant of the abdomen is prepared in a sterilemanner for harvesting an autologous fat graft. If a submucosalapproach is planned, the nasal mucosae are elevated on eitherside off the nasal septum by injecting approximately 10 to 12ml of 0.5% Xylocaine (Astra Pharmaceuticals, L.P., Wayne,PA) mixed with a 1:200,000 epinephrine solution. This maneu-ver facilitates submucosal dissection and decreases the poten-tial of bleeding. Such an injection is not administered, how-ever, when a direct transnasal approach is planned.

APPROACH TO THE SPHENOID SINUS(see video at web site)

The oldest of the modern approaches to the sphenoid sinus isthe ororhinoseptal approach, as popularized by Hardy (9, 10).The sublabial incision exposes inferior aspects of both nasalmucosal sacs and the septum in between. The rhinoseptal ap-proach is similar to the ororhinoseptal approach (14), except that

the incision ismade along thejunction of the skinand the beginningof the medial sep-tal mucosa of onenaris (Fig. 5A). Ineither instance, anipsilateral submu-cosal tunnel is de-veloped along thenasal septum as faras the sphenoidrostrum posteri-orly by creatingfirst a superior andthen an inferiortunnel before con-necting the twotunnels (Fig. 5B).

The nasal carti-lage is then weakened along its base with a shallow incisionmade with a no. 15-blade knife. This maneuver facilitates thedislocation of the cartilage together with the opposite mucosalsac toward the contralateral side as a single mucoperichon-drial flap. It prevents the formation of anterior nasal septumdefects. These defects tend to occur when the nasal mucosaeare lifted off the cartilaginous septum on either side, promot-ing the formation of bilateral opposing medial mucosal tearsthat more often than not fail to heal. As the nasal cartilage isdislocated to the contralateral side with a speculum, the junc-tion of the cartilage and the bony septum is seen (Fig. 6A). Thisjunction is then divided with a dissecting instrument that isalso used to create a posterior tunnel on the contralateral sideof the bony septum as far back as the sphenoid rostrum(Fig. 6B).

Before removing the inferior portion of the bony septum, itis advisable to separate sharply the bony septum from theperpendicular plate of the ethmoid to avoid applying traction

FIGURE 5. Photographs illustrating the rhinoseptal approach on the left.A, incision. B, developing the submucosal tunnel.

FIGURE 6. Photographs illustrating the surgical procedure. A, the nasalcartilage is dislocated toward the contralateral side, together with theopposite nasal mucosal sac. This maneuver displays the cartilage-bony sep-tum junction. B, a posterior submucosal tunnel is developed in the oppo-site, right side of the bony septum as well.

FIGURE 7. Photograph illustrating the bivalvespeculum locked in place anterior to the sphenoidrostrum.

FIGURE 8. Photographs illustrating the direct transnasal approach on the right.A, nasal mucosa visualized as it reflects from the bony septum over the rostrum ofthe sphenoid bone. B, nasal mucosa opened over the rostrum of the sphenoid. It isimportant that both sides of the rostrum be visualized.

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against the cribri-form plate, whichcould potentiallycause CSF leak.With the bony sep-tum removed, therhinoscope is re-placed with a bi-valve speculum,which is locked inplace anterior to thesphenoid rostrum.If the nasal mucosalsacs are redundantand thus obscurethe visualization ofthe sphenoid ros-trum, they can bedisplaced laterallywith a dissectinginstrument by ap-plying gentle com-pression against theposterior portion ofthe turbinates. Thismaneuver usuallyallows the specu-lum to be advancedfurther so that it canbe placed into con-tact with the sphenoid rostrum (Fig. 7). If the nasal mucosal sacs arestill redundant, their posterior portion can be shrunk by means ofbipolar or monopolar coagulation. A bloodless field usually indi-cates a proper submucosal trajectory; if bleeding occurs during theapproach, the surgeon more likely than not has veered off into thenasal cavity.

Our preferred approach is the direct transnasal approach. Theentire operative procedure is performed with the use of theoperating microscope. The bivalve speculum is advanced towardthe depth of the nose along a track, as assessed by performingintermittent spot checks with the stereotactic probe, until theregion of the mucosa that sweeps from the posterior bony sep-tum over the sphenoid rostrum is reached (Fig. 8A). At this point,the mucosa is opened with bipolar coagulation, and redundantmucosa also can be excised (Fig. 8B). After visualizing the ipsi-lateral side of the sphenoid rostrum, the surgeon should identifythe midline with the stereotactic probe and continue the dissec-tion of the nasal mucosa on the contralateral side of the sphenoidrostrum. It is important that the speculum lock into place oneither side of the sphenoid rostrum, at which point the operativeexposure is identical to that created in the submucosal ap-proaches (Fig. 7).

During the approach, care should be taken to avoid injur-ing the nasal mucosa inferolaterally so as to avoid injuringa branch of the sphenopalatine artery, which, even whencoagulated, can recanalize in the postoperative period, result-

ing in major epi-staxis. Our experi-ence has been thatpatients tolerate thedirect transnasalapproach betterand have a shorterconvalescence thanthey do when thetransnasal-submuc-osal approach isused, and that thedirect transnasalapproach is alsobetter than theororhinoseptal ap-proach. The directtransnasal approachis limited, however,by the width of thenares, which, if rel-atively small, maynot accommodate abivalve speculum.

In some patients,the anterior wall ofthe sphenoid si-nus—the sphenoidrostrum—can besturdy and thick,especially in pa-tients with acromegaly. Several techniques can be used to open thesphenoid sinus. For example, one can use a vertically biting instru-ment or a chisel to penetrate the sinus. When prominent, sphenoidsinus ostia also can be used to initiate the opening into the sinus.Throughout this procedure, frameless stereotactic guidance shouldbe used for vertical and horizontal orientation. After opening thesphenoid sinus, the surgeon should review the anatomy of thesphenoid sinus septa by MRI before they are removed. The insertionof the septum along the anterior sella wall may be a useful anatomiclandmark for the location of either a microadenoma or the medialextent of the cavernous sinus. The sphenoid sinus septa, along withthe sphenoid sinus mucosa, are then removed as completely aspossible. The removal of the sphenoid sinus mucosa prevents thepostoperative formation of a sphenoid sinus mucocele.

The bone over the carotid tubercles may be missing (23); becauseof this possibility, the exenteration of the sphenoid sinus mucosacould be injurious to the underlying carotid arteries. We have notobserved this phenomenon in any of our patients. As the sphenoidsinus is exposed, it often seems that the exposure is inadequate ornarrow. In this event, shrinking the surrounding nasal mucosal veilswith bipolar or monopolar coagulation exposes just enough of theremaining anterior wall of the sphenoid sinus circumferentially forit to be removed with a fine, thin-lipped punch rongeur. A gain of1 or 2 mm in either direction is sufficient to enhance the ease of

FIGURE 9. Photographs of a pituitary macroad-enoma. A, pituitary macroadenoma. Note thatthe anterior arachnoid recess is not visualized—the result of compression by the tumor. B, photo-graph showing that the anterior arachnoid recesscan be seen clearly after tumor removal. Theresidual anterior pituitary is on the right.

FIGURE 10. Photographs illustrating pituitarymicroadenoma before (A) and after (B) excision.



operative manipu-lation in the sphe-noid sinus and sellaconsiderably.

It has been ourpractice to exposethe sphenoid sinusso that in every pa-tient we can visual-ize the clivus, theplanum, and bothcarotid tubercleslaterally. Becausethe bivalve specu-lum sometimes hasa tendency gradu-ally to dislodge in-feriorly as it islocked into placeanterior to the sphe-noid rostrum, itmaybe advanta-geous to advancethe speculum intothe sphenoid si-nus itself. Whenlocked into placein this position,the speculum is inline with the sellaas the target. Careshould be takennot to open the speculum too forcefully inside the sphenoidsinus, because too much force can result in a fracture of thesphenoid bone that may involve the optic nerve canals superolat-erally (19), with injury to the optic nerves. Conversely, the fracturemay be inferolateral, in which case it may result in a carotid arteryinjury (16).

We prefer to open the sella by removing the anterior sellarwall from just below the planum to the floor and from themedial border of one cavernous sinus to the medial border ofthe other. In microadenomas that are in a posterior position inthe anterior lobe, we may remove a portion of the sella floor inaccordance with the location of the microadenoma. Differenttechniques can be used to open the bony sella. If the anteriorsellar wall is relatively thick, one can use a chisel to initiate theopening. Conversely, if the sellar wall is paper-thin, a micro-hook or a microcurette can be used to begin opening the sella.The remainder of the opening is performed with fine, 2- or3-mm punch rongeurs. When the instruments are used, thesurgeon can lean them gently against the walls of the specu-lum to enhance the steadiness and the safety of the surgicalmanipulations. Generally speaking, the suction tip is usuallybrought into the speculum with the left hand (in right-handedsurgeons) from approximately the 10 o’clock position, with

the other instru-ments enteringthe speculum atapproximately the5 o’clock position.

An inspection ofthe dura of thesellar reveals in al-most every case asmall, centrally po-sitioned arterialvessel emanatingfrom the dura;however, varia-tions may occur.When opening thedura, it is probablybetter to open themiddle and infe-rior segments ofthe dura first so asnot to disturb apossible deep ante-rior arachnoid re-cess that, ifopened, could re-sult in a CSF fis-tula. In patientswith macroadeno-mas, such a recesscan be occluded by the adenoma (Fig. 9A), only to open as theadenoma is removed (Fig. 9B). We prefer to start with a cruciateincision and then to perform an excision of the four dural leaves.Additional exposure is then obtained by shrinking the peripheryof the dura opening by means of bipolar coagulation.

REMOVAL OF MICROADENOMAS

When removing a microadenoma that is visible either on thesurface or through a much-distended layer of normal pituitary,we usually look for a cleavage plane between the microadenomaand the residual normal anterior pituitary. This plane can eas-ily be established with a no. 11-blade knife and subsequently canbe developed with loop curettes and other dissectors, working inan alternating manner from opposite sides of the microadenoma(Fig. 10). We prefer the use of loop curettes to ring curettesbecause of the absence of any sharp edges in loop curettes thatcould prove injurious to the surrounding structures, such as thecavernous sinus and the overlying arachnoid.

When the microadenoma is not on the surface, the surgeonshould look for any change in the appearance of the overlyinganterior pituitary, such as discoloration or attenuated texture, beforemaking the incision along the surface between the changed and themore normal-appearing anterior pituitary. At times, it is necessaryto remove a small portion of the normal anterior pituitary to gainsufficient exposure for the complete removal of a microadenoma.

FIGURE 11. Photographs of the pseudocapsule. A,pseudocapsule, a compressed layer of tissue consistingof admixture of adenoma and anterior pituitary tis-sue. B, after excision of pseudocapsule.

FIGURE 12. Pituitary macroadenoma. A, sche-matic. B, view through operating microscope.

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Once the microad-enoma has been re-moved, the surgeonshould inspect thetumor bed for thepresence of the so-called pseudocap-sule. The pseudo-capsule is acondensed layer oftissue along the sur-face of the adenomaand consists of amixture of ade-noma tissue andcompressed resid-ual normal anteriorpituitary (Fig. 11A).This layer is usuallydistinct and separa-ble from both themicroadenoma andthe residual normalanterior pituitary. Itis removed circum-ferentially to ensureendocrinologicalcure (Fig. 11B).

REMOVAL OF MACROADENOMAS

The removal of macroadenomas (Fig. 12) may be challenging,especially if they are sanguinous. Internal decompression of theintrasellar tumor component is probably the best first maneuver(Fig. 13). After hemostasis is reached at the major bleeding points,we prefer to separate the tumor from the dura of the sella floor,working toward both cavernous sinuses in an alternating manner.The dissection is then performed along the cavernous sinus wall

from the bottom upuntil the reflectionof the arachnoidmembrane of thediaphragma sellaeis observed supero-laterally on one orthe other side as itslopes toward thedural ring of thediaphragma sellae(Fig. 14). Recogni-tion of the arach-noid, which is usu-ally covered by athin layer of resid-ual normal anteriorpituitary, is a criticalpoint in the opera-tion. Failure toidentify the arach-noid and distin-guish it from thesurrounding supra-sellar tumor canlead to penetrationinto the subarach-noid space, with thepossibility of injur-ing the subarach-noid neurovascularstructures.

At this point,the decompressed and slack intrasellar portion of the tumor isexcised to gain maneuvering room for the removal of thesuprasellar tumor component. We do not use any intrathecaltechniques to deliver the residual suprasellar tumor into thesella. We may, however, ask the anesthesiologist to increase

FIGURE 13. Internal decompression of pitu-itary macroadenoma. A, schematic. B, viewthrough operating microscope.

FIGURE 14. The decompressed macroadenomais dissected away from the sella floor and leftcavernous sinus. The reflection of the arachnoidwhere it joins the dural ring of the diaphragmalaterally can be seen. A, schematic. B, viewthrough the operating microscope.

FIGURE 15. After being adequately decompressed, gentle traction can be applied against the slackened residue of the suprasellar tumor extension (A,schematic) while the tumor is dissected away from the arachnoid of the diaphragma sellae with a microsuction with perforations at the tip (B, view throughthe operating microscope) or with loop curettes (C, view through the operating microscope). The inverted arachnoid can be seen.



the intrathoracicpressure to causethe diaphragma sel-lae and the tumorbeneath it to de-scend into the sella.This event will notoccur unless the su-prasellar tumorcomponent is firstadequately decom-pressed. As the su-prasellar tumorcomes into view, itsfurther removal canbe facilitated by ap-plying gentle trac-tion against the tu-mor margin whiledissecting the tu-mor off the arach-noid and the thinlayer of residualnormal anterior pi-tuitary tissue at-tached to it (Fig. 15).The dissection usu-ally proceeds in alateral-to-medial di-rection from thepoint where the re-flection of thearachnoid meetsthe dural ring of the diaphragma sellae and toward the still elevateddome of the tumor. The dissection is performed with either a loopcurette or a microsuction device with perforations at the tip. As thetumor removal proceeds, the arachnoid of the diaphragma sellaegradually descends into the sella until it becomes completely in-verted toward the sella floor (Fig. 16).

In patients with large suprasellar tumor components in whom thearachnoid was significantly distended by the expanding tumor, theinversion of the arachnoid into the sella after the tumor is removedoccurs in a redundant fashion with several folds of arachnoidcrowding into the sella. These folds can be separated gently with amicrosuction tip to look for any residual tumor tissue and to accom-plish hemostasis. At no time should the arachnoid be penetrated.

EXTENDED TRANSSPHENOIDALAPPROACH

Until recently, craniotomy was thought to be the only alternativeto transsphenoidal microsurgery in patients with large and asym-metrically extending suprasellar tumor components and in patientswith a significantly constricted diaphragma sellae. Some of thesepituitary tumors, however, can be reached and successfully re-moved using an extended transsphenoidal microsurgical approach

(Fig. 17) (13, 17). Af-ter opening the an-terior sella wall upto the tuberculumsellae, the posteriorportion of the pla-num is drilled outwith the use of a mi-crodrill with a dia-mond burr. The in-tervening bone ofthe tuberculumsella is drilled outlast. Intracranialnavigation is usefulto open the dura atthe midline aboveand below the su-perior circular si-nus, which is thencoagulated and di-vided, again strictlyat the midline. The remaining dura can be shrunk with bipolarcoagulation. The surgeon thus gains access to the suprasellar spacealong a trajectory that allows for direct, unobstructed visualizationof the suprasellar tumor. The dissection of the tumor again proceedsalong the tumor arachnoid interface, with the goal always being tomaintain the integrity of the arachnoid membrane. When the pro-cedure is completed, there is copious inversion of the arachnoidmembrane into the created cranial base defect (Fig. 18).

CLOSURE

If definitive evidence of CSF escape during the operationexists, the inverted arachnoid and the defect in it should becovered with an autologous fascia graft removed from either thefascia lata or the abdominal fascia. The fascia is covered with alayer of autologous fat. If possible, the removed sella floor shouldbe reconstructed with a fragment of the bony nasal septum or therostrum of the sphenoid bone. This fragment should be placedbetween the dura and the bony openings of the sella. Bony

FIGURE 16. After complete tumor removal, thearachnoid of the diaphragma sellae inverts intothe sella. A thin layer of residual normal ante-rior pituitary is attached to the undersurface ofthe arachnoid. A, schematic. B, view throughoperating microscope.

FIGURE 17. Preoperative (A) and postoperative (B) MRI scans of a pituitaryadenoma removed by means of the extended transsphenoidal approach.

FIGURE 18. Photograph illustrating the copi-ous inversion of the arachnoid after the extendedtranssphenoidal approach.

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reconstruction is more difficult and often is not possible after theuse of an extended transsphenoidal approach. In such cases, a fatgraft also can be placed into the sphenoid sinus. Autologousfibrin glue can be used to hold the fat graft in place and seal allof the gaps around it. If evidence of significant CSF escape duringthe operation is found, especially during an extended transsphe-noidal approach, a lumbar subarachnoid drain should be placedin the patient for several days after the operation.

At the end of the procedure, after the bivalve retractor hasbeen removed, secure hemostasis is achieved along the nasalpassages, and the operative field is irrigated copiously with anantibiotic solution. In patients who undergo the ororhinosep-tal procedure and in those who undergo the submucosaltransnasal approach, the sublabial gingiva and the nasal mu-cosa, respectively, are sutured back into place with resorbablesuture material. The nasal cartilage is relocated back to themidline. It is usually not necessary to pack the nose. After theoral cavity is cleansed and the gastric contents are evacuated,the patient is awakened and extubated. Patients with acro-megaly, especially those with sleep apnea, should not beextubated before they are fully awake.

CONCLUSIONS

The outcome of a transsphenoidal operative procedure de-pends largely on the surgeon’s adherence to certain anatomicand surgical principles. We consider the following three prin-cipal notions to be important in the execution of transsphe-noidal microsurgical procedures to treat patients with pitu-itary adenomas. First, pituitary adenomas are extra-arachnoidlesions; therefore, a transsphenoidal microsurgical operationto remove a pituitary adenoma should be performed outsidethe arachnoid membrane without penetration into the sub-arachnoid space. Second, pituitary adenomas are largely mid-line lesions that are surrounded on both sides by importantneurovascular structures; therefore, the surgeon’s respect forthe midline and avoidance of far lateral approaches and tech-niques is associated with fewer complications. Third, pituitaryadenomas originate within the pituitary parenchyma, and, asthey grow, they distend the residual normal anterior pituitary.Consequently, the residual normal anterior pituitary invari-ably is situated on the surface of the adenoma.

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AcknowledgmentsWe thank Ania Pollack, M.D., and Frank LaMarca, M.D., for their valuable

contributions to this study.


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