Frontal Sinus Cerebrospinal Fluid Leaks Chapter 17 145

Chapter 17 Frontal Sinus Cerebrospinal 17 Fluid Leaks

Bradford A. Woodworth, Rodney J. Schlosser

Contents Core Messages Introduction ...... 143 í Identification of a CSF leak etiology; Anatomic Site ...... 144 accidental trauma, surgical trauma, Etiology ...... 147 tumors, congenital, or spontaneous; Trauma ...... 147 is essential for successful repair Tumors ...... 148 Congenital ...... 148 í Anatomically, frontal sinus CSF leaks are Spontaneous ...... 148 divided into those located adjacent to the Diagnosis ...... 149 frontal recess, within the frontal recess, or Surgical Technique ...... 149 within the frontal sinus proper Endoscopic Approaches ...... 149 Extracranial Repair ...... 150 í Pre-operative evaluation may include beta- Intracranial Repair ...... 151 2 transferrin, radioactive/CT cisternogram, Adjuncts and Postoperative Care ...... 151 high-resolution CT, MRI, or intrathecal fluorescein and should be individualized for Conclusion ...... 151 the purposes of diagnosis and localization References ...... 151

í Frontal sinus CSF leaks adjacent to or within the frontal recess are typically amenable to endoscopic repair Introduction

í CSF leaks affecting the posterior table Pathology of the frontal sinus represents one of the within the frontal sinus proper may require most challenging and technically demanding areas external approaches, such as frontal tre- for the sinus surgeon to reach endoscopically. Cere- phine or osteoplastic flap. Combined endo- brospinal fluid (CSF) leaks in other parts of the sino- scopic and external techniques are useful nasal cavity have been repaired with relatively high for defects extending to the frontal sinus success rates using accepted endoscopic techniques outflow tract for nearly 20 years [7], yet little has been published regarding repair of frontal sinus defects. The use of í Severely comminuted posterior table frac- 70° endoscopes and giraffe instruments allows excel- tures may require craniotomy and cranial- lent access to the frontal recess, but postoperative ization of the frontal sinus stenosis, anatomic variants, and CSF leaks associated with the posterior table can make repair of these defects very challenging and pushes the limits of endoscopic repairs. Pertinent frontal sinus anatomy, etiologies of CSF leaks, preoperative imaging and considerations, and the technique and type of repair will be discussed. 144 Bradford A.Woodworth, Rodney J. Schlosser

Anatomic Site tal beak anteriorly, the orbit laterally, the attachment of the middle turbinate medially, and the face of the ethmoid bulla (if present) and ethmoid roof posteri- The complex anatomy and variability of the frontal orly. This anatomy is highly variable, and a number recess is described in great detail elsewhere in this of cells may alter this and encroach upon the frontal text, but in the most basic sense, the broadest boun- outflow tract if present, such as an agger nasi cell an- daries of the frontal recess are the internal nasofron- terolaterally or a suprabullar cell posteriorly.

Fig. 17.1. Coronal CT (A) and sagittal T2 weighted MRI (B) of patient with meningoencephalocele involving the posterior aspect of the frontal recess that was repaired endoscopically Frontal Sinus Cerebrospinal Fluid Leaks Chapter 17 145

CSF leaks affecting the frontal sinus can be divided ly, because the superior extent of the defect may be anatomically into three general categories: difficult to reach endoscopically and the inferi- or/posterior extension of the defect may be difficult í Those adjacent to the frontal recess to reach from an external approach (Figs. 17.1–17.3).If í Those with direct involvement of the frontal long-term frontal patency is questionable, then an recess osteoplastic flap with thorough removal of all muco- í Those located within the frontal sinus proper sa and obliteration is recommended. On the other hand, if the surgeon feels that frontal patency can be maintained, repair of the skull base defect without While most leaks are limited to one of these distinct obliteration can be performed (Fig. 17.4). sites, some defects encompass multiple anatomic ar- The final anatomic site for frontal sinus CSF leaks eas. is within the frontal sinus proper involving the poste- Skull base defects located in the anteriormost por- rior table above the isthmus of the frontal recess. The tion of the cribriform plate or the ethmoid roof just limits of endoscopic approaches continue to expand posterior to the frontal recess do not directly involve with improved equipment and experience. However, the frontal sinus or its outflow tract, but by virtue of defects located superiorly or laterally within the their close proximity, the frontal recess must be ad- frontal sinus may still require an osteoplastic flap dressed as described in the Surgical Methods section with or without obliteration. Frontal trephination of this chapter. Endoscopic repairs may cause iatro- and an endoscopic modified Lothrop procedure are genic mucoceles or frontal sinusitis if graft material, adjuvant techniques that are useful for unique cases packing, or synechiae formation obstructs the fron- (Fig. 17.5). The specific approach depends upon the tal sinus outflow tract. site and size of the defect, the equipment available, A CSF leak that directly involves the frontal recess and surgical experience. is one of the most difficult sites to approach surgical-

Fig. 17.2. Endoscopic view of meningoencephalocele (from patient in Fig. 17.1) highlighted by fluorescein (A). Mucosa stripped from posterior aspect of frontal recess and septal bone graft placed into epidural space (B) 146 Bradford A.Woodworth, Rodney J. Schlosser

Fig. 17.3. Overlay mucosal graft (A) placed. Sialastic stent was placed for one week. Six month postoperative view (B) demon- strates successful repair and widely patent frontal sinus

Fig. 17.4. Coronal (A, B) and sagittal (C) CTs demonstrate a of the defect). This required a combined endoscopic and oste- traumatic skull base defect that involved the posterior table, oplastic approach frontal recess, and ethmoid roof (arrows in C depict the extent Frontal Sinus Cerebrospinal Fluid Leaks Chapter 17 147

Surgical Goals for Frontal CSF Leaks í Goal #1 – Successful repair of the skull base defect and cessation of the CSF leak. í Goal #2 – Long-term patency of the frontal sinus or a successful obliteration with meticulous removal of all mucosa within the frontal sinus. í Always be cognizant of both goals when de- ciding upon a specific surgical approach and repair for each skull base defect.

Etiology

The underlying cause of a CSF leak will affect the Fig. 17.4C management of the subsequent repair.

CSF leaks are broadly classified into:

í Traumatic (including accidental and iatrogenic trauma) í Tumor-related í Spontaneous í Congenital

These etiologies influence the size and structure of the bony defect, degree and nature of the dural dis- ruption, associated intracranial pressure differential, and meningoencephalocele formation. These factors greatly influence medical and surgical treatment and help predict long-term success.

Trauma

Frontal sinus fractures represent approximately 5%–12% of craniofacial injuries and have a high potential for late mucocele formation, intracranial injury, and aesthetic deformity [5, 8, 10]. Traumatic dis- ruption of the posterior table of the frontal sinus or Fig. 17.5. Isolated skull base defect in the lateral aspect of the frontal recess with a dural tear can create an obvious frontal sinus without involvement of the frontal recess. Such defects can be repaired via trephine while maintaining paten- CSF leak or present years later with meningitis, de- cy of the frontal recess layed leak, or encephalocele. Projectile injuries from 148 Bradford A.Woodworth, Rodney J. Schlosser

bullets, shotgun blasts, or shrapnel can result in sig- Tumors nificant comminution of the skull base, and are more likely to involve intracranial injury. CSF leaks usually begin within 48 hours, and 95% of them manifest Anterior skull base and sinonasal tumors can create within 3 months of injury [15]. Although over 70% of frontal sinus CSF leaks directly through erosion of traumatic CSF leaks close with observation or con- the posterior table or frontal recess, or indirectly sec- servative treatment, a 29% incidence of meningitis ondary to therapeutic treatments for the tumor. Per- has been reported in long-term follow-up when sistent tumor following resection and repair will managed nonsurgically [1]. continue to erode the skull base and contribute to Conservative, nonsurgical measures are often ade- frontal sinus CSF leaks. Creating a watertight seal quate for injuries limited to the frontal recess and/or between the sinonasal and intracranial cavities after posterior table, but severe fractures may require op- tumor removal can be difficult. If the tumor is ap- erative intervention due to a high risk of subsequent proached intracranially, a pericranial flap is often mucocele formation.Here,operative intervention ad- used to create a barrier. CSF leaks may still occur due dresses both the CSF leak and the potential for future to tears in the flap that occur during elevation, devas- mucocele development,depending upon the anatom- cularization, and necrosis, or from inadequate cover- ic site of the defect. Other considerations include the age. Posterior table defects and frontal sinus floor de- overall health of the patient, associated intracranial fects (after cranialization) may still be present and or intraorbital injuries, and other skull base or facial contribute to CSF leak. Prior chemotherapy or radia- fractures. These additional issues influence surgical tion creates significant healing difficulties due to treatment and approach. poor vascularity of the wound bed. Functional endoscopic sinus surgery (FESS) and neurologic surgery are the two most common sur- geries leading to iatrogenic skull base defects. Signif- Congenital icant defects can result from powered instrumenta- tion if they occur during bone resection near the Since the frontal sinus is not present at birth, congen- skull base.A CSF leak can occur in the posterior table ital leaks of the frontal sinus proper do not exist. of the frontal sinus or frontal recess during routine However, CSF leaks may develop within or adjacent frontal sinusotomy. The posterior table may be less to the frontal recess, and congenital defects often than 1 mm thick, and is much thinner than the ante- arise from the foramen cecum [14].These patients of- rior table.An expansile mucocele or tumor can create ten have a low, funnel-shaped skull base that can dehiscences along the posterior table that are more make repairs more challenging. susceptible to iatrogenic CSF leak during instrumen- tation. More aggressive surgical techniques for man- aging frontal sinus disease, such as the endoscopic Spontaneous Lothrop/Draf procedures and osteoplastic flaps, car- ry a risk of iatrogenic CSF leak as high as 10% [13]. Patients with no other recognizable etiology for their CSF leak following neurological surgery can occur CSF leak are deemed spontaneous. Most frequently during frontal craniotomy if the superior or lateral these leaks occur in obese, middle-age females who recess of the frontal sinuses are entered with removal demonstrate elevated intracranial pressure (ICP) of the bony plate. Individuals with extensive pneu- [12]. In the frontal sinus, spontaneous leaks rarely oc- 17 matization are at higher risk. CSF leaks in the lateral cur through the posterior table itself and are more recess are often impossible to repair endoscopically likely to occur at weaker sites of the skull base, such and may require an osteoplastic flap or trephine ap- as the ethmoid roof or anterior cribriform plate im- proach. Placement of grafts over defects limited to mediately adjacent to the frontal recess. The elevated the lateral recess via a frontal trephine may preserve CSF pressures seen in this subset of patients leads to the frontal recess and avoid the need for frontal oblit- the highest rate (50%–100%) of encephalocele for- eration. mation, and the highest recurrence rate following Frontal Sinus Cerebrospinal Fluid Leaks Chapter 17 149 surgical repair of the leak (25%–87%), compared to less than 10% for most other etiologies [4, 6, 11]. We í MRI/MR cisternography recommend adjuvant therapies to treat documented – Advantages: Excellent soft tissue (CSF/brain elevation of the ICP as described in the Adjuncts Sec- vs. secretions) detail, noninvasive tion of this chapter. – Disadvantage: Poor bony detail í Intrathecal fluorescein – Advantages: Precise localization, blue light Diagnosis filter can improve sensitivity – Disadvantages: Invasive; skull base expo- Establishing the diagnosis and identifying the loca- sure required for precision localization tion of a CSF leak in a patient with intermittent clear nasal drainage and no history of head trauma can be difficult. Pre-operative tests should be based upon the clinical picture and the precise information need- Surgical Technique ed, rather than following a rigid algorithm. In addi- tion, the invasiveness of the test and risks to the patient should be considered. The reported sensitivity Endoscopic Approaches and specificity of any test should be interpreted with caution, as these statistics are highly dependent upon Defects located inferiorly in the posterior table, with- the patient population studied,size of the defect,flow in the frontal recess itself, or those immediately adja- rate of the leak, and the individual interpreting the cent to the frontal recess are generally amenable to test. endoscopic repair, thereby minimizing the potential complications of other extracranial or intracranial procedures. The technique for endoscopic manage- Techniques for Diagnosing ment generally outlines those previously described and Localizing CSF Leaks [12].We typically inject intrathecal fluorescein (0.1 cc í Beta-2 Transferrin of 10% fluorescein in 10 cc of CSF injected over 10 minutes) and place a lumbar drain at the begin- – Advantages: Accurate, noninvasive ning of each case. This aids with intra-operative lo- – Disadvantages: Nonlocalizing calization of the defect and confirmation of a water- í High-resolution coronal and axial CT scan tight seal at the conclusion of the case. To obtain ade- – Advantages: Excellent bony detail quate exposure, a total ethmoidectomy, maxillary an- – Disadvantages: Inability to distinguish CSF trostomy, and frontal sinusotomy, as well as partial from other soft tissue; bony dehiscences middle turbinectomies or an endoscopic modified may be present without a leak Lothrop may be indicated. The extent of dissection í Radioactive cisternograms should be limited to that required for each individu- – Advantages: Localizes side of the leak, iden- al defect. tifies low volume or intermittent leaks Using 0°, 30°, and 70° nasal endoscopes, any ence- – Disadvantages: Localization imprecise phalocele present is ablated with bipolar cautery to the skull base. If the encephalocele extends under í CT cisternograms surrounding mucosa or nasal bones,dissection of the – Advantages: Contrast may pool within fron- entire encephalocele is unnecessary and may lead to tal sinus; good bony detail potential complications such as nasal stenosis. We – Disadvantages: Invasive, may not detect have shown that these submucosal extensions atro- intermittent leaks phy and the mucosa returns to normal after ablation of the intracranial communication and repair of the bony skull base defect [14]. 150 Bradford A.Woodworth, Rodney J. Schlosser

Once the skull base defect is identified, the graft foam and intranasal packs. The graft at the skull base site is prepared by removing a cuff of normal muco- may be augmented with fibrin glue if desired.Nonab- sa around the bony defect. This not only provides an sorbable packing is typically removed 5–7 days post- area of adherence for the graft but also contributes to operatively. osteoneogenesis and osteitic bone formation. This Even with meticulous dissection and wide expo- thickens the bone around the defect and aids bony sure of the frontal recess, the potential for obstruc- closure, if a bone graft is used, between the graft and tion of the frontal recess by grafts or packing materi- recipient bed [2]. al is high. To avoid this, we often will place a soft Si- lastic frontal stent for one week. Careful debridement The choice of grafts is often of personal preference, and cleaning every week for several weeks will lessen but may include alone or in combination the follow- the incidence of scarring and make future surveil- ing: lance easier (Fig 2 and 3).

í Bone Extracranial Repair í Cartilage í Mucosa í Fascia Defects in the posterior table of the frontal sinus are often not amenable to a strict endoscopic approach. í Alloplastic materials Leaks that are particularly difficult to repair are those that extend to the isthmus of the frontal sinus These grafts are typically free grafts, rather than ped- outflow tract. It is this site where the skull base tran- icled. Bone (or cartilage in select cases) grafts for sitions from the horizontal (axial) orientation of the large skull base defects can provide structural sup- ethmoid roof/cribriform plate to the vertical (coro- port for herniating dura or brain that may displace nal) orientation of the posterior table. This area often the overlay fascia or mucosa graft. Bone grafts are al- requires a combined approach, since it is at the limit so useful in smaller defects when the patient has a of an external osteoplastic approach from above and spontaneous leak and elevated intracranial pres- an endoscopic approach from below (Fig 4).A frontal sures. This elevated pressure contributes to disrup- trephine can provide access to the superior limits of tion of the soft tissue graft and is responsible for the the defect, and endoscopes may be utilized through higher failure rates in this category. Mastoid cortex, the trephine as well as from below, but if meticulous parietal cortex, septal, and turbinate bone are all ac- removal of mucosa from the entire frontal sinus with ceptable bone grafts.We prefer to use septal bone for subsequent obliteration is needed, an osteoplastic small, flat defects and mastoid cortical bone for larg- flap, rather than a trephine, is recommended. er, curved defects. Otolaryngologists are more famil- Posterior table defects that are superior to the si- iar with the temporal bone than the parietal bone, nus outflow tract can be repaired with an external, and this can be harvested at the time of temporalis extracranial approach using a traditional osteoplas- fascia harvest if needed. If a mucosal graft is used, tic flap with or without frontal sinus obliteration. At- septal or turbinate bone may be a more suitable op- tempts at repairing a posterior table defect without tion. This spares an external incision and can easily obliteration is not recommended for defects in the be harvested from the operative field. frontal sinus, unless the defect is sufficiently superior Regardless of the choice of graft, the bone is or lateral to the sinus outflow tract to allow repair 17 shaped to match the bony defect and placed in an without compromising the frontal recess. A well- underlay fashion in the epidural space. Care must be pneumatized frontal sinus with a defect in the lateral taken to avoid enlargement of the existing bony de- recess can be repaired via an osteoplastic flap or fect or entrapment of mucosa in the epidural space trephine without compromising the frontal recess that may lead to an intracranial mucocele.A fascia or (Fig 5). mucosal graft is then placed in an overlay fashion The specific technique for raising osteoplastic over the skull base defect and supported with gel- flaps is described elsewhere. After elevating the oste- Frontal Sinus Cerebrospinal Fluid Leaks Chapter 17 151 oplastic flap with direct access to the frontal sinus, The optimal timing, dosing, and long-term benefits preparation of the recipient bed and grafting is per- of this approach have not been proven, but it may re- formed in a similar fashion as endoscopic manage- duce the risk of developing subsequent skull base de- ment if the surgeon feels the frontal sinus outflow fects in patients with elevated CSF pressures. We pe- tract is not compromised, and the frontal drainage riodically monitor electrolytes in any patient placed pathway will be left open. Fat obliteration should be on long-term diuretic therapy. performed if there is a question about the feasibility of a patent drainage pathway after repair. After all mucosal remnants are stripped and meticulously Conclusion

drilled with a diamond burr, underlay bone and overlay fascia grafts are placed as needed to close the t defect. Bilateral obliteration for relatively small frontal sinuses or involvement of both posterior tables is Frontal sinus CSF leaks are a difficult entity to man- recommended. Finally, the mucosa of the frontal age. When possible, endoscopic repair will provide recess is stripped and abdominal fat packed in the the least morbidity, but the location and size of the sinus. defect as well as the etiology often dictate custo- mized management. Achieving the best possible results for patients with CSF leaks depends on a Intracranial Repair thorough understanding of the underlying pa- thophysiology and fundamental principles of medi- Large defects in the posterior table, as seen in severe cal and surgical treatment. facial trauma or tumors, may benefit more from repair via a craniotomy with cranialization of the frontal sinus and pericranial flap. This approach provides excellent exposure of the defect and allows better access for removal of the mucosa, but does require a References craniotomy and retraction on the frontal lobe with possible sequelae such as anosmia, intracranial hem- 1. Bernal-Sprekelsen M, Bleda-Vazquez C, Carrau RL (2000) orrhage or edema, epilepsy, and memory and con- Ascending meningitis secondary to traumatic cerebrospi- centration deficits [9]. nal fluid leaks. Am J Rhinol 14(4) : 257 2. Bolger WE, McLaughlin K (2003) Cranial bone grafts in cerebrospinal fluid leak and encephalocele repair: A pre- liminary report. Am J Rhinol 17(3) : 153–158 Adjuncts and Postoperative Care 3. Carrion E, Hertzog JH, Medlock MD, Hauser GJ, Dalton HJ (2001) Use of acetazolamide to decrease cerebrospinal Lumbar drains are a useful adjunct in the manage- fluid production in chronically ventilated patients with ment of frontal sinus CSF leaks. They can aid a ques- ventriculopleural shunts. Arch Dis Childhood 84(1) : 68–71 4. Gassner HG, Ponikau JU, Sherris DA, Kern EB (1999) CSF tionable diagnosis with the preoperative injection of Rhinorrhea: 95 consecutive surgical cases with long term intrathecal fluorescein and allow lowering elevated follow-up at the Mayo Clinic. Am J Rhinol 13 : 439–447 intracranial pressure in patients with a spontaneous 5. Gerbino G, Roccia F, Benech A, Caldarelli C (2000) Analy- etiology. These patients will have increased pressure sis of 158 frontal sinus fractures: Current surgical management and complications. J Craniomaxillofac Surg 28(3): postoperatively due to overproduction against a 133–139 closed defect. We prefer to use a lumbar drain in se- 6. Hubbard JL, McDonald TJ, Pearson BW, Laws, ER Jr (1985) lect patients who will have elevated ICPs postopera- Spontaneous cerebrospinal fluid rhinorrhea: Evolving tively, and we generally leave the drains in place for concepts in diagnosis and surgical management based on 2–3 days. the Mayo Clinic experience from 1970 through 1981. Neu- rosurgery 16 : 314–321 Acetazolamide (Diamox) is a diuretic that can be a 7. Mattox DE, Kennedy DW (1990) Endoscopic management useful adjunct in patients with elevated CSF pres- of cerebrospinal fluid leaks and cephaloceles. Laryngo- sures. It can decrease CSF production up to 48% [3]. scope 100 : 857–862 152 Bradford A.Woodworth, Rodney J. Schlosser

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