The extended transbasal approach

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Clinical Study

Advances in surgical management of malignancies of the cranial base: the extended trans-

basal approach

James P. Chandler1, Harold J. Pelzer2, Bernard B. Bendok,3 H. Hunt Batjer,3 and Sean A. Salehi31Department of Neurological Surgery, Northwestern University Feinberg School of Medicine and Center for CranialBase Surgery; 2Department of Head Neck Oncology and Otolaryngology, Northwestern Memorial Hospital;3Department of Neurological Surgery, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA

Key words: extended frontal, malignancies, orbitonasal osteotomy skull base, transbasal

Summary

The extended transbasal approach combines a bifrontal craniotomy with an orbital nasal and potentially a sphe-noethmoidal osteotomy to provide excellent access to malignancies of the anterior, middle and posterior skull base.

The approach enables the en bloc resection of tumors within the frontal lobes, orbits, paranasal sinuses andsphenoclival corridors without brain retraction and may obviate the need for transfacial access. We present our 7-year experience during which 29 patients underwent surgery with the extended transbasal exposure. In 25 patientsthe extended transbasal approach was used alone; in the remaining four it was combined with additional ap-proaches. With exception of two patients, all lesions were removed en bloc. Reconstruction was accomplished withthe use of pericranium and in some instances a temporalis muscle pedicle or a gracilis microvascular free flap. Therewere no mortalities associated with this approach. Seven patients experienced infections, four patients experiencedcerebral spinal fluid (CSF) leakage, two patients who had received adjuvant radiation experienced scalp necrosis,three patients experienced pneumocephalus, and 29 patients experienced cranial neuropathies, the majority of whichwere loss of olfaction. The average follow-up for our patients was 34 months with a range of 262 months.

Introduction

Malignancies of the sphenoclival corridor represent aunique surgical challenge to the cranial base surgeon.Historically, the approaches utilized to access this regionhave resulted in incomplete resections, cosmetic defor-mities, and significant morbidity and mortality [17].Recent technological advances including sophisticatedhead and neck imaging, neuronavigational systems, andimproved surgical instrumentation have resulted in abetter understanding of cranial base anatomy andopened the door to a variety of new approaches to thecranial base. The extended transbasal approach and itsmodifications have been previously described by severalauthors [1,823]. In this report, we detail the manner inwhich we have utilized this approach to successfullyresect lesions occupying the anterior, middle, and pos-terior cranial base with minimal morbidity and nomortality.

Materials and methods

Between January of 1996 and March of 2004, 29 pa-tients with tumors occupying the anterior, middle andposterior skull base underwent surgery utilizing the ex-tended transbasal approach. Patients ranged in age from14 to 69. Nineteen of the patients were male and 10female. Table 1 shows the histopathology of the surgi-cally resected lesions. Eleven of the tumors were high-grade malignancies and 18 were low grade. Nine pa-

tients received postoperative radiation and seven pa-tients received chemotherapy.

Preoperative evaluation

Extensive imaging studies were performed on all pa-tients including computerized tomography (CT) withbone windows and in some instances three-dimensionalreconstructions and magnetic resonance imaging (MRI)of the brain and face. The carotid artery anatomy andpatency were established by means of CT angiographyin three patients, MR angiography in eight patients, andfour patients underwent conventional cerebral angiog-raphy. In two patients, partial embolization was per-formed in advance of surgical resection. All patientswho had tumors encroaching on the optic apparatusunderwent visual field examination. The patients withfrontal lobe extension of tumor underwent a standardbattery of neuropsychological testing.

Operative technique

Following a standard endotracheal anesthetic technique,the head is positioned neutrally and secured in Mayfield3-point fixation. If appropriate, cranial nerve, somato-sensory evoked responses, and brainstem auditoryevoked responses are monitored. In situations wherethere are significant risks of carotid sacrifice, electroen-cephalography is available. In our early cases in whichwe anticipated dural section, a cerebrospinal fluid drain

Journal of Neuro-Oncology (2005) 73: 145152 Springer 2005DOI 10.1007/s11060-004-5173-6


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was placed prior to final positioning. All patients re-ceived broad-spectrum antibiotic prophylaxis. Mannitoland corticosteroids is administered in cases where sig-nificant brain infiltration and edema are present.

A bicoronal incision is performed from tragus totragus and potentially more laterally if a zygomatic os-teotomy is anticipated. In general, the incision is placedbehind the hairline or approximately 12 cm posterior tothe glabella. This generally allows for sufficient frontallobe exposure and the development of an adequatepericranial flap for purposes of reconstruction at the end

of the case. The length of the pericranial flap can beincreased with the use of traction posteriorly at the timeof skin incision. The scalp flap is mobilized forward withthe pericranium and swept above the temporalis fasciabilaterally to expose the frontozygomatic processes lat-erally and the superior orbital rim and nasion medially.If the supraorbital nerves and vessels complex resides ina foramen, a fine osteotome or Karresin punch is used to

create a window through which the nerves can bemobilized forward with the scalp flap. The periorbita isdissected superiorly from the orbital roof to a depth ofapproximately 22.5 cm, laterally to the point of theinferior orbital fissure and medially to the anterior eth-moidal foramina.

A series of burr holes are placed adjacent to the sag-ittal sinus anteriorly and posteriorly just adjacent to thecoronal suture. The bone flap should extend from thecoronal suture to as far frontal as can be achieved. Insome instances the frontal sinus may be deep necessi-tating osteotomes or a Gigli saw to take down its pos-terior wall. With the bone flap removed, the next step isto perform the orbitonasal osteotomy and potentially asphenoethmoidal osteotomy depending on the tumorsepicenter.

Orbitonasal and sphenethmoidal osteotomies

Resection of tumors with epicenters within the anteriorcranial fossa, including the orbitonasal and perinasalsinuses, oftentimes are enhanced with the addition of anorbitonasal osteotomy. After dissection of the perior-bita, the frontal dura (Figure 1) is elevated from theorbital roof working laterally towards the midline. Inthe midline, the dura will be tethered to the crista galliand cribriform plate (Figure 2a). The crista galli can beremoved with a narrow bone rongeur and the dura in-cised along the base of the cribriform plate with man-datory transection of anterior and posterior ethmoidalarteries and olfactory fibers. The dissection is carriedposteriorly to expose the planum sphenoidale and tu-

berculum sella (Figure 2b). Working laterally, the duraoverlying the optic foramina is exposed. The incisedmidline dura is primarily repaired in a meticulousfashion to eliminate the possibility of cerebrospinal fluidleakage (CSF). The preservation of olfactory fibers hasbeen described [23,24]; however, we have found thismaneuver to hinder our approach and not result inclinically significant preservation of olfaction. A recip-rocating saw is then used to perform strategic cuts on

Table 1. Tumor Pathology and Survival

Diagnosis # of

Cases

Status

Alive Dead

Low-Grade Malignancies

Atypical meningiomas 3 2 (42) 1 (36)Adenoid cystic carcinoma 3 3 (34)

Chordoma 4 3 (20) 1 (15)

Chondrosarcoma 2 2 (24)

Esthesioneuroblastoma 5 3 (37) 2 (16)

pituitary adenoma 1 1 (48)

Subtotal 18

High-Grade Malignancies

Aadenocarcinomas 7 3 (26) 4 (8)

Squamous cell carcinoma 3 1 (32) 2 (11)

Undifferentiated carcinoma 1 1 (28)

Subtotal 11

Total 29

Number in parenthesis denotes follow-up in months.

Figure 1. Schematic depicting exposure following bifrontal craniotomy, orbitonasal osteotomy. The upper quarter of the clivus remains on blind

spot.

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the exposed orbitonasal bar. The first cuts are per-formed across the supraorbital rim and orbital roof justmedially to the supraorbital foramina. Approximately2.5 cm of the orbital roof should be included in this cutso as to minimize the possibility of a postoperative en-ophthalmos. For more broad-based tumors these cutsmay be expanded to include the frontal zygomatic pro-cess and for lesions extending laterally into the infra-temporal fossa, a zygomatic osteotomy may be

considered. The next cut is across the superior aspect ofthe nasion just adjacent to the frontal nasal suture.Here, the saw is angled parallel to the plane of thecribriform plate and is directed towards the anteriorethmoidal foramina bilaterally. A narrow osteotome isthen used to perform a linear cut across the floor of theanterior cranial fossa inclusive of the midline cribriformplate. This same osteotome can then be used to gentlydisplace the orbitonasal bar. Once complete, pathologywithin the frontal lobes, orbits, midline nasal cavity and,potentially the maxillary sinus are completely accessible(Figure 2c).

For lesions based more posteriorly and medially

within the sphenoclival region, the addition of a sphe-noethmoidectomy should be considered. On completionof the orbital nasal osteotomy, the microscope isbrought into the field and the high-speed air drill with a

3 mm cutting burr is used to drill through the planumsphenoidale medially to expose the sphenoid sinus andthen more laterally to enter the ethmoid sinuses. Sinustrabeculations and mucosa are removed with a narrowpituitary rongeur. The optic nerves can then be unroo-fed utilizing a 23 mm diamond burr and microdissec-tors. Continuous irrigation is critical to minimize athermal optic nerve injury (Figure 3a). At this point theorbital apex contents are completely exposed. With

further drilling through the posterior wall of the sphe-noid cavity, sella dura is revealed. Working more cau-dally, the cancellous bone of the clivus can beprogressively removed to expose clival dura fromapproximately 510 mm inferior to the posterior cli-noids to the foramen magnum. In the depths of thisexposure the hypoglossal nerves may be skeletonized asthey course through the hypoglossal canal of the fora-men magnum and occipital condyle (Figure 3b).

Resection and reconstructionDural defects are closed primarily, or if necessary apericranial or fascia lata graft may be employed to en-sure a water-tight closure. Larger defects may requirecadaveric dura or bovine pericardium for reconstruc-tion. Exposed mucosa from the frontal, ethmoidal, and

Figure 2. Orbital frontal dura dissection with sectioning of olfactory fibers and ethmoidal vessels. (a) Dissection exposing planum sphenoidale.

(b) (Cadaveric dissection demonstrating) Orbitonasal osteotomy complete (c).

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sphenoid sinus is exonerated. Small portions of fat,typically harvested from the abdomen are then packedinto the above-mentioned sinus cavities. A generous

pericranial flap is then harvested and insinuated into thedepths of the exposure as far caudal as the margins ofthe bone resection. This flap serves as a barrier betweenthe sinus cavities and the brain, minimizing the risk ofpost-operative infection or spinal fluid leakage. Careshould be taken to preserve blood supply of the flap,which typically arises from the supraorbital vessel

complex. The dead space is then filled with fat and fibringlue or equivalent. More substantial defects whichcannot be adequately covered with pericranium due to

prior operations or poor tissue quality may require atemporalis, a muscle rotational flap, or a vascularizedfree flap. We have had success utilizing gracilis andrectus abdominus muscle for this purpose [25]. Theorbitonasal bone flap may then be secured with titaniumplates followed by replacement of the bifrontal crani-otomy. Central dural tack-ups are helpful in minimizing

Figure 3. Sphenoethmoidectomy complete, optic nerves skeletonized (a); : Completed dissection with exposure to foramen magnum (b).

Figure 4. Case 1. Preoperative frameless navigational axial, sagittal, and coronal T1-weighted MRI with gadolinium. Tumor extends onto right

temporal lobe, infratemporal fossa, and paranasal sinuses and is obstructing this patients nasopharynx. Right eye was blind at presentation.

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postoperative pneumocephalus and epidural hemato-mas. A subgaleal drain to gravity is left in place 48 h.

Illustrative cases

Case 1: Extensive cranial base esthesioneuroblastoma

This 16 year-old male presented with severe headaches,progressive right visual loss, a palpable right facial mass,and airway obstruction (Figure 5). He underwent atransnasal biopsy of the intranasal portion of his tumor,which confirmed for diagnosis of esthesioneuroblastoma.Given the apparent encasement of both carotid arteriesand the extremely vascular appearance of the lesion onMRI, an angiogram and embolization procedure wereperformed. An extended transbasal approach with the

addition of an orbitozygomatic osteotomy and temporalcraniotomy was utilized to achieve a gross total resection

of this lesion (Figure 6). Subsequent to the operation thepatient received radiation and chemotherapy. Four weeks

following the surgery he experienced a superficial woundinfection, which responded to intravenous antibiotics.Twelve months postoperatively he developed a recurrenceand expired 18 months following his initial operation.

Case 2: Extensive clival chordomaThis 41 year-old male presented to the emergency roomwith the worst headache of his life following blowing hisnose. A CT of the brain performed at that time dem-onstrated diffuse intracranial air and a very large sphe-noclival mass generating significant brain stemcompression and encasing both the basilar and bilateralcarotid arteries (Figure 7a and b). He was treated with

a transbasal approach with the addition of sphenoeth-moidectomy. The soft nature of the tumor facilitated a

Figure 5. Case 1. Frontal orbitotemporal exposure with extensive pericranial flap (a). Orbitonasal zygomatic osteotomy complete. Spheno-

ethmoidal region tumor excision. Note exposure of optic nerves (b).

Figure 6. Postoperative day 2 CT of brain.

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gross total resection. Clival dura from the foramenmagnum to mid pons was resected (Figure 7c and d).The vertebral-basilar complex and abducens nerves werepreserved with the resection. Postoperatively, the patientexperienced a small amount of CSF rhinorrhea, whichpersisted despite attempts of resolution with lumbardrainage and ultimately required a ventricular perito-neal shunt. He remains disease-free 8 months postop-eratively.

Results

The patients in this series were followed for an averageof 34 months with the range of 262 months. Themalignancies treated in the disease status at follow-upare indicated in Table 1. There were 18 patients (62%)with low-grade malignancies and 11 (38%) with high-grade malignancies. At the most recent follow-up, 15patients (83%) with low-grade malignancies and 5patients (45%) with high-grade malignancies weredisease-free or with stable disease. The postoperativehospitalization ranged from 314 days.

Complications

Postoperative complications are listed in Table 2. Fourpatients experienced cerebral spinal fluid leakage, one inthe immediate postoperative and the remaining in adelayed fashion. In two instances spinal fluid leak was

Figure 7. Case 2. Admission computerized tomography (CT) scan demonstrating marked pneumocephalus (a). T1-weighted magnetic MRI

following gadolinium administration revealing large nonenhancing sphenoclival mass with brainstem compression (b). T2-weighted MRI image

demonstrating cavernous carotid encasement and erosion of right petrous apex and clivus (c). Postoperative axial T1-weighted MRI with

gadolinium (d).

Table 2.

Complications # of Cases

CSF leak 4 (14%)

Partial flap necrosis 2 (7%)

Infections

Superficial wound 4 (14%)

Cerebritis 1 (3%)

Epidural abcess 2 (7%)

Cranial nerve dysfunction

Olfactory 29 (100%)

Optic 2a (7%)

Abduces 0 (0%)

Pneumocephalus 3 (10%)

a One patient presented with visual loss which persisted postopera-

tively, and the second underwent anucleation due to the extent of

orbital involvement.

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controlled with 45 days of lumbar drainage. All of thepatients experiencing CSF leak had significant intra-dural extent of their tumor, necessitating primary duralrepair or grafting. In one instance due to the low clivalposition of our dural resection, a primary closure couldnot be achieved. This patient ultimately required aventricular peritoneal shunt. In our early experience,lumbar drains were routinely placed in many patients atrisk for CSF leakage; however we found this strategy toresult in an increased incidence of pneumocephalus andneurologic changes secondary to overdrainage. We nowonly place drains in patients demonstrating CSF leakagepostoperatively.

There were seven patients who developed woundinfections. In each of these instances, the tumors werequite large and the operations long. Four patientsexperienced superficial wound infections, which wereeffectively treated with local wound care and intrave-nous antibiotics. Two patients experienced epiduralabscesses and required surgical evacuation, irrigation,and debridement. The bone flaps, both craniotomy andosteotomy, were not removed and the patients weretreated with a six to eight week course of appropriateIV and oral antibiotic therapy. In one case of a giantesthesioneuroblastoma infiltrating the frontal lobes,there were clinical and radiographic findings suspiciousfor cerebritis. This was not confirmed by tissue sam-pling; however, it was treated with a 6-week course ofintravenous antibiotics. The patient responded favor-ably both clinically and radiographically.

Cranial nerve injuries may occur with this operation[21]. All patients undergoing a true transbasal approachwill experience loss of olfaction.In the vast majority of thecases olfaction had been lost preoperatively. There wasone patient who presented with right eye blindness, whichpersisted postoperatively, and another patient withsquamous cell carcinoma who underwent an anucleationprocedure as a significant tumor burden within the orbitwas encountered at the time of surgery.

Significant pneumocephalus was apparent in three pa-tients. All were treated successfully with cessation oflumbar drainage in one patient and flatbed rest withoxygenation in two others. Oftentimes pneumocephalusoccurs in combination with CSF leak. This was noted tobe the case in two of our patients.

Discussion

Malignancies along the sphenoclival corridor and asso-ciated nasal sinuses represent a unique surgical chal-lenge. Oftentimes these tumors may extend into thebrain or brainstem. Standard anterior approaches,including the transfacial, transmaxillary, transsphenoi-dal, and transoral may fail to yield enough exposure toachieve gross total resection. The concept of gainingbetter access to these lesions through removal of theorbital rims was introduced initially by Frazier in 1913[26]. In 1972 Derome et al. described the transbasalapproach for removal of sphenoid ethmoidal tumors[13]. Since that time there have been several reports froma variety of authors detailing the addition of osteoto-

mies to gain better access to tumors and fractures of thecranial base [1,3,6,8,14,17,18,21,23,2729]. In particular,Raveh et al. have authored reports in the literaturedetailing his anterior subcranial approach for skull basetumors and fractures without the addition of a bifrontalcraniotomy [17,18]. Sekhar was the first to introduce theconcept of a bifrontal craniotomy with addition oforbital nasal and sphenoid ethmoidal osteotomies [21].All of these techniques are relatively similar and must betailored to the epicenter of the lesion and the surgeonsexperience. The ultimate goal in cranial base surgery formalignant disease is appropriate access to achieve grosstotal resection with minimal damage to neural vascularstructures. In some instances this may require theaddition of a transfacial or subtemporal infratemporalapproach to the extended transbasal approach as de-tailed in this report [11,20,28].

Until more recently, aggressive approaches to anteriorcranial base lesions were treated primarily with transfa-cial and transmaxillary approaches whichwhile providingfor reasonable surgical access, may be associated with ahigh incidence of postoperative infection, CSF leakage,cosmetic deformity, and unacceptable mortality [2,4,7,11,12]. The extended transbasal approach is specificallywell suited for lesions with epicenters in the sphenoclivalregion extensive into the frontal lobe paranasal sinus andorbits. It is a cosmetically sound approach yieldingexcellent visualization of the anterior cranial fossa con-tents without brain retraction and creates an excellentwindow for primary dural repair or reconstruction ifwarranted [29]. Malignancies in the nasal and paranasalsinuses can be accessed through this approach; however,lesions confined to these sinus cavities may be moreappropriately treated by transmaxillary or transfacialapproaches. Similarly, lesions confined to the sphenoidsinus or clivus may be better accessed through a trans-sphenoidal or transoral route [13,12,22]. When appro-priate, the wide exposure offered by the extendedtransbasal approach affords the safest opportunity forpreservation of the carotid arteries, optic, and abducensnerves.

Bilateral loss of olfaction is a mandatory consequenceof this approach. Patients must be counseled carefullypreoperatively as loss of olfaction is oftentimes associ-ated with transient disturbances in taste and can in factsignificantly affect the patients lifestyle. In two patientswe attempted to preserve olfaction as described bySpetzler et al. [23,24]; however, postoperatively the pa-tients reported anosmia. The majority of the patientswith lesions amenable to this particular approach havelost all or a substantial part of olfaction prior to surgery.

Despite appropriate antibiotic prophylaxis, infectiondid occur in our patients. The risk factors for infectioninclude prolonged operative time, exposure of nasal andparanasal sinuses to exposed brain and prior radiation.All of our patients received either unasyn or combina-tion Vancomycin and Gentamicin prior to incision.Antibiotics were continued for a minimum of 72 h orlonger if drains remained in place. We found the risk ofinfection could be minimized by first resecting extra-dural disease and then, following a complete instrumentchange, preceding forward with intradural tumor

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resection. The importance of a water-tight primary duralclosure or dural repair cannot be overemphasized.

Important anatomic limits exist with this approach.In general, the lateral extent of the approach is limitedby the optic nerves, cavernous sinuses, carotid arteries,petrous apexes, and the hypoglossal canals [21,23,27].The rostral extent of the exposure along the clivus is just inferior to the base of the posterior clinoid pro-cess (Figure 1). Thus, tumors extending superior tothe posterior clinoid involving in the petrous apexes orcavernous sinus may require the addition of a morelateral approach such as a petrosal craniotomy orsubtemporalinfratemporal technique [11,20].

This relatively novel approach lends itself to a widevariety of application and obviates the need for many ofthe traditional more aggressive anterior cranial baseapproaches. However, the approach requires a veryclear knowledge of cranial base anatomy and an abilityto deal with all potential complications. Our resultssuggested this approach can be utilized alone to treat thevast majority of sphenoclival malignancies with minimalcomplications and good short immediate results. Fur-ther long-term results are needed.

Acknowledgment

We wish to thank Angela L. Park for her assistance inpreparation of this manuscript.

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Address for offprints: James P. Chandler, MD, Department of Neu-

rological Surgery, 233 E. Erie St., Suite 614, Chicago, 60611 Illinois,

USA; Tel.: 312-695-0491; Fax:+312-695-0225; E-mail: jchan-

[email protected]

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The extended transbasal approach