Endoscopic Trans-septal Frontal Sinusotomy 27

Contents

Introduction . . . . 251

Historical Perspective . . . . 252

Preoperative Planning . . . . 253

Anatomic Considerations . . . . 253

Operative Technique . . . . 253

Indications . . . . 257

Advantages . . . . 257

Disadvantages . . . . 257

Outcomes . . . . 257

Conclusions . . . . 258

References . . . . 259

Introduction

The successful surgical management of chronic fron- tal sinus disease remains a significant challenge for otolaryngologists. From an anatomic standpoint, the drainage pathway of the frontal sinus is hidden from direct view by a complex and variable pneumatiza- tion pattern of anterior ethmoid and frontal cells.

The close proximity to critical structures, including the lamina papyracea, anterior cranial fossa, and an- terior ethmoid artery, adds to the dilemma of effec- tive surgical treatment of these patients. The recent advances in endoscopic sinus surgery and image guidance have afforded direct visualization and easi- er access to the frontal recess and have made surgery feasible for chronic frontal sinusitis [4, 9, 14, 16, 18, 20].

Despite these advances, frontal sinus disease re- mains refractory in a subset of patients. This is typi- cally related to neo-osteogenesis resulting in com- plete or near-complete stenosis of the nasofrontal pathway.A common contributing factor to the frontal recess stenosis is resection of the middle turbinate [19]. The destabilized middle turbinate remnant with excoriated mucosa on its lateral surface lateralizes across the floor of the frontal sinus and compromises the frontal recess patency (Fig. 27.1) [19]. Standard endoscopic techniques are generally inadequate for treatment of chronic frontal disease in these patients.

In the past, they required external approaches such as frontal sinus obliteration or cranialization. These open techniques have the potential for significant morbidity. In 250 consecutive osteoplastic proce- dures, Hardy and Montgomery reported an operative complication rate of 19% and intraoperative cere- brospinal fluid (CSF) leak rate of 2.8% [7]. These difficult patients can now be successfully treated

Endoscopic Trans-septal Frontal Sinusotomy

Pete S. Batra, Donald C. Lanza

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Core Messages

쐽 Middle turbinate resection contributes to refractory frontal sinus disease after pri- mary sinus surgery

쐽 The trans-septal frontal sinusotomy tech- nique (TSFS) utilizes the relationship of the nasal septum to the midline floor of the frontal sinus

쐽 Safe completion of the TSFS procedure re- quires that the frontal sinus floor has an anterior-posterior diameter of at least 1.2 cm

쐽 When performing the TSFS procedure, all efforts are made to preserve sinus mucosa, especially in the frontal recess

with extended endoscopic approaches to the frontal sinus.

The novel technique of endoscopic trans-septal frontal sinusotomy (TSFS) augments management of refractory frontal sinus disease in this setting. TSFS is a unique endoscopic surgical approach that utilizes the relationship of the nasal septum to the midline floor of the frontal sinus. Like the Draf III or modi- fied Lothrop procedure, the trans-septal approach provides good access to the midline floor of the fron- tal sinus and permits but does not require intersinus septum removal [5, 6]. TSFS can be utilized even in circumstances where the severity of the stenosis pro- hibits cannulation of the frontal recess as a primary landmark.

Translocation of the nasal septum, especially in cases of a narrow nasal vault, allows for:

쐽 Improved visualization

쐽 Improved instrumentation

쐽 Minimizing the size of the planned septal perforation

In addition, TSFS also has several theoretical advan- tages over frontal sinus obliteration including:

쐽 Decreased morbidity

쐽 Improved cosmesis

쐽 Ease of endoscopic and radiographic surveillance postoperatively

Historical Perspective

An external approach to restore the communication between the nose and the frontal sinus began with the Lynch Howarth fronto-ethmoidectomy [13]. In 1914, Lothrop described a combined intranasal eth- moidectomy and external Lynch type approach to create a common nasofrontal communication by re- secting the floor of the frontal sinus, the intersinus septum, and the superior nasal septum [12]. Early at- tempts at intranasal approaches were largely aban- doned due to the inadequate visualization of the frontal recess and frequent treatment failures [3, 17].

In 1991, Draf described a median drainage ap- proach to the frontal sinus utilizing a combined mi- croscopic and endoscopic technique [5]. By using the operating microscope, the lateral bony walls were preserved, thus preventing medial collapse of the or- bital soft tissues with subsequent obstruction of the frontal recess. In 1995, Gross et al. described an ex- tended endoscopic approach to create a similar com- mon frontal opening [6]. In this procedure the frontal recess is cannulated and a posteriorly guarded drill is used to resect the frontal sinus floor from both sides.

However, the success of this technique depends on the ability to cannulate the frontal recess, which is not always possible in cases of frontal recess stenosis.

TSFS builds on the concepts from these previous techniques and allows for entry into the medial fron-

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Fig. 27.1.Sagittal CT reconstruction demonstrating narrow an- terior-posterior dimensions of the frontal sinus

tal sinus floor where the bone is thinnest, especially in cases of extensive neo-osteogenesis that preclude identification and cannulation of the frontal recess.

Preoperative Planning

Symptomatic patients with complete or near-com- plete opacification of the frontal sinus(es) on CT im- aging are candidates for TSFS. They are considered refractory to maximal medical therapy. Each patient is given a comprehensive explanation of the advan- tages and disadvantages of the different surgical ap- proaches available to manage the frontal sinus dis- ease. Consent is also obtained for an external ap- proach when it was unclear whether the frontal sinus would be amenable to TSFS.

A detailed CT review is performed prior to consid- ering surgical intervention. Coronal and axial CT scans or triplanar views on an image-guidance sta- tion are evaluated to determine the pattern of frontal sinus pneumatization, the nature of agger nasi pneu- matization, presence of intersinus septal cells, frontal cells, and/or supra-orbital ethmoid cells, and frontal sinus mucocele formation. “Y-shaped” nasal septal attachment to the floor of the frontal sinus is sought.

Imaging is also evaluated for the presence of pneu- matized crista galli, the integrity of the skull base in the area of the proposed dissection, and the relation- ship of the middle turbinate to the frontal sinus.

The width and depth of the frontal sinus floor is estimated in either direct coronal or reconstructed sagittal planes on CT images.

쐽 An anterior-posterior diameter of at least 1.2 cm was considered requisite to safe endo- nasal drilling

쐽 A diameter less than this is considered a relative contraindication and limitation to successfully performing the TSFS given the currently available technology (Fig. 27.1).

Anatomic Considerations

The anterior-most aspect of the middle turbinate can be a helpful landmark in determining the position of

the frontal sinus relative to the cribriform plate when consideration is given to performing a drillout pro- cedure. Classic teaching holds that the anterior inser- tion of the middle turbinate lies adjacent to the crib- riform plate. In a radiographic study evaluating 35 coronal CT scans, only 13 of 35 (37%) patients had the superior insertion of the middle turbinate within the anterior 2 mm of the cribriform plate. In 22 of 35 (63%), the insertion of the middle turbinate was an- terior to the cribriform plate with 47% of these in- serting into the ascending process of the maxilla. Ad- ditionally, six of 35 patients (17%) had a superior in- sertion into the floor of the frontal sinus. Recogniz- ing these variations in the middle turbinate insertion can help the surgeon avoid inadvertent skull base in- jury. “Y-shaped” nasal septal attachment to the floor of the frontal sinus was noted in three patients. This unique configuration allows for entry into the frontal sinus through the superior nasal septum [1].

Operative Technique

All surgery is performed under general anesthesia.

The patient is positioned, prepped and draped as for routine endoscopic sinus surgery.Although this tech- nique was first applied without a computer-aided technique, it is now typically performed using image guidance. This helps confirm critical anatomic land- marks throughout a technically challenging proce- dure. At the outset of the procedure, the image guid- ance is properly registered and verified. Oxymetazo- line is instilled in each nasal cavity. Injections with 1% lidocaine with 1 : 200,000 epinephrine are per- formed bilaterally on the septum, lateral nasal wall (agger nasi region), and middle turbinate remnant. A bilateral greater palatine foramen block is also per- formed with the same agent. Because most of these patients have undergone previous endoscopic sinus surgery, the adjacent paranasal sinus disease, if present, is addressed first since superiorly created bleeding with TSFS can result in significant difficulty in performing the remainder procedures.

The septum may be endoscopically mobilized to one side for surgical access if necessary. The tech- nique for endoscopic septoplasty has been described [8]. A hemi-transfixion incision is made with an oph- thalmic crescent knife (Alcon Labs, Ft. Worth, TX) at

the mucocutaneous junction on the appropriate side of the septum. Bilateral inferior and unilateral (left) anterior tunnels are created by sub-perichondrial dissection. The quadrilateral cartilage is separated at the bony-cartilaginous junction, and the anterior septum is mobilized from the maxillary crest. Resec- tion of any deviated portions of septal cartilage and bone further improves surgical exposure. A high sep- tal perforation is then created.

Alternately, if space permits a septoplasty may be avoided and a 1.5–2 cm iatrogenic septal perforation is created just across from the leading edge of the middle turbinate/agger nasi region below the skull base. This permits further exposure, ventilation, fu- ture endoscopic inspection, and sinus debridement through the nasal cavity. The incisions for the perfo- ration are created utilizing an ophthalmic crescent knife. Through-cutting endoscopic forceps or a soft- tissue shaver is helpful in completing the perforation.

Exposed areas of bone or cartilage are minimized throughout the procedure.

The floor of the frontal sinus is identified by intra- operative surgical navigation or, alternately, by using surgical landmarks that are helpful in gauging the position of the frontal sinus relative to the cribriform plate. The midline position of floor of the frontal si- nus is typically localized posterior-superior to the most anterior-superior aspects of the septal bony- cartilaginous junction. This location is approximated adjacent to the most anterior remnant or root of the middle turbinate and the agger nasi (ascending pro- cess of the maxilla). This is considerably more anteri- or than the position of the naturally occurring fron- tal recess area. In patients with a Y-shaped septum at the floor of the frontal sinus, the midline floor of the frontal sinus has an appearance similar to that of the anterior wall of the sphenoid sinus that has been de- scribed during trans-septal sphenoid surgery. It ap- pears as the “prow of a ship”, albeit in a much nar- rower region (Fig. 27.2).

After careful inspection of the roof of the nasal vault, the frontal sinus is entered. The evolution of surgical instrumentation has permitted the use of angled drills with concurrent suction/irrigation (Fig. 27.3). Larger burrs can give a critical advantage while drilling around corners anteriorly, but may al- so pose a hazard by permitting inadvertent drilling the posterior table of the frontal sinus. Concurrent saline irrigation is essential to avoiding inadvertent

heat injury to bone and surrounding tissue. If straight drills are used without concurrent suction irrigation, irrigation can be applied through a 5 FR ureteral catheter with the help of an assistant and is positioned through the contralateral nares into the operative field. Alternatively, depending upon the thickness of the floor of the sinus, curetting may be sufficient to enter the frontal sinus (Fig. 27.4A).

After successful entry into the lumen of the frontal sinus, the opening can be enlarged further by drilling anteriorly and laterally. Depending on the extent of the disease, dissection can be carried laterally to in- clude the frontal recess. Note that the frontal recess is located posteriorly, and drilling directly across from one frontal recess to the other is not advised. This straight path of drilling will traverse the olfactory fossa and anterior cranial vault and place the patient at risk for CSF leak or even intracranial injury. All ef- forts are made to preserve the mucosa throughout the procedure, especially in the frontal recess. By re- ducing mucosal injury, bone exposure is minimized and risk of delayed stenosis is reduced.When drilling anteriorly, care must be taken to preserve the integ- rity of the radix. The inferior aspect of the intersinus septum may be resected in order to provide a com- mon outlet for both right and left frontal sinuses at the midline. In this fashion, a “neo-ostium” is created as illustrated in Figures 27.4B and 27.5.

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Fig. 27.2.Coronal CT scan demonstrating the “Y-shaped” bony attachment of the nasal septum to the floor of the frontal si- nus. Note presence of mucocele in the left frontal sinus

Fig. 27.3.

Sagittal illustration demonstrates drilling of the frontal sinus floor through a superiorly-created septal perforation (dotted line). Anterior dotted line represents the hemi-trans- fixion incision for the septoplasty

Fig. 27.4. ADemonstration of previous partial middle turbi- nate resection and lateralization in left nasal cavity and entry into the frontal sinus utilizing a frontal sinus curette in right

nasal cavity.BC-shaped “neo-ostium” created via TSFS. Note that the more lateral aspects including the frontal recess are more posterior than the midline opening

If septal dislocation was performed earlier, it is now corrected and the hemi-transfixion incision is closed with interrupted 4–0 chromic suture. The septal flaps are re-approximated using a running trans-septal

mattress-type closure with 4–0 plain gut suture on a Keith needle. Packing is not typically required.

In the postoperative period, maximal medical therapy is continued and meticulous debridement of blood and fibrin clots is initiated. It is performed on postoperative day 1, and then weekly for approxi- mately 6 weeks depending on the severity of the dis- ease and the appearance of the postoperative surgical bed [10]. Figure 27.6 demonstrates the healed endo- scopic appearance of the “neo-ostium” at 6 weeks.

Indications

쐽 Chronic frontal sinusitis after failed endoscop- ic sinus surgery, especially in the setting of “neo-osteogenesis” or middle turbinate resection

쐽 Frontal sinus mucocele formation (Fig. 27.7)

쐽 Inverted papilloma (Fig. 27.8)

쐽 Sinonasal malignancies

쐽 Fibro-osseous lesions

쐽 Trauma

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Fig. 27.6. Endoscopic appearance of healed “neo-ostium” at 6 weeks

Fig. 27.7.Coronal CT scan shows a complex, multi-septate fron- tal mucocele

Advantages

쐽 Functional restoration of frontal sinus drain- age

쐽 Utilizes inherent anatomic landmarks to facili- tate surgery

쐽 Allows for mucosal preservation

쐽 Allows for endoscopic and radiographic surveillance postoperatively

쐽 Improved cosmesis through avoidance of facial incisions

쐽 Decreased morbidity compared to open approaches

쐽 May resort to open approaches if required

Disadvantages

쐽 Requirement of endoscopic expertise

쐽 Need for specialized surgical instrumentation, including image guidance

쐽 Risk of inadvertent skull base injury and CSF leak

쐽 Possible bone loss at radix

쐽 Drill-related heat injury to nasal sill

쐽 Septal perforation with potential for chronic crusting

Fig. 27.8.

Coronal T1- weighted MRI with gado- linium demonstrates an extensive frontal sinus inverted papilloma

Outcomes

Retrospective analysis was performed to determine the incidence of drillout procedures in management of complex frontal sinus disease in a tertiary academ- ic-based rhinology practice (Cleveland Clinic Foun- dation). From May 1999 to April 2004, 207 endoscop- ic frontal sinus procedures were performed in 186 pa- tients. In this group, 161 patients (86.6%) were ad- dressed with endoscopic frontal sinusotomy. Twenty- five patients (13.4%) required 30 drill-out procedures for management of frontal sinus disease. The break- down of the procedures was as follows: TSFS, six pa- tients; Draf III, 17; Draf II, five; and Draf IB, two. The indications for the procedure included mucocele (11 cases), frontal sinusitis (two cases), invasive fungal sinusitis (two cases), mucosal melanoma (two cases), inverted papilloma (two cases), CSF leak (one case) and fibrous dysplasia (one case). Since the TSFS pro- cedure was only required on six occasions over a 5- year period, one must be cognizant that it is not a common procedure and is reserved for specific anat- omy and circumstances.

Of the six patients undergoing TSFS, three pa- tients (50%) were cured symptomatically, while two (33%) were improved and one (17%) was unchanged after the surgical intervention. Endoscopically, fron- tal patency was noted in five cases (83%). Two of these patients were noted to have partial stenosis of the “neo-ostium”; no patients required stenting to maintain patency. One patient (17%) had complete stenosis though CT demonstrated aeration of the frontal sinus. One intraoperative CSF leak was en- countered in a patient with a history of severe maxil- lofacial trauma secondary to a motor vehicle acci- dent. CT imaging demonstrated a multi-septate mu- cocele with posterior table erosion. The CSF was en- countered upon entering the frontal sinus and was not attributed to technical issues such as drill injury.

It was recognized and repaired intraoperatively uti- lizing fat, cartilage, and floor-of-nose mucosa with- out any long-term sequelae. The average follow-up was 16 months with a range from 3 to 37 months [2].

쐽 Lanza et al. reviewed 29 patients undergoing TSFS between 1995 and 1999. The male:female ratio was 21:8. All 29 patients were deemed

candidates for frontal sinus obliteration or cranialization. The main indication for TSFS was chronic frontal sinusitis in the setting of previously failed endoscopic surgery. Other in- dications for surgery were mucocele formation and nasofacial trauma. Twenty-four patients (83%) were available for telephone interview postoperatively. The mean follow-up period was 45 months (range 9–69 months). In this group, 18 of 24 (75%) reported at least 50% im- provement of symptomatology, while 14 of 24 (58%) reported 80% or greater improvement of their symptoms. Four (16.6%) patients underwent further frontal sinus surgery with three having frontal sinus obliteration [11, 15].

쐽 Complications included two CSF leaks, one unplanned anterior inferior septal perforation, and one patient with chronic crusting at the planned perforation in these cases. One leak was attributable to surgical trauma with a drill in a patient with narrow anterior posterior di- mensions, and the second occurred during de- bridement of scarred mucosa in a patient with history of severe trauma. Both CSF leaks were identified and repaired intra-operatively with- out further sequelae. Both patients with septal difficulties had prior septoplasty.

Conclusions

Endoscopic TSFS represents a novel surgical ad- vance in the management of patients with recalci- trant frontal sinus disease, especially in the setting of new bone formation. The approach utilizes the unique relationship of the nasal septum to the mid- line floor of the sinus. From an anatomic standpoint, it is best suited for patients with adequate anterior- posterior dimensions of the midline floor of the frontal sinus and a Y-shaped dorsal nasal septum.

Given the potential pitfalls of the technique, cumu- lative endoscopic experience, appropriate surgical instrumentation, and image guidance are requisite to performing successful TSFS.

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