Chapter( 6): Updates In Frontal Sinus Surgery

Endoscopic Management of Frontal Sinus CSF Leaks

Pathology of the frontal sinus represents one of the most

challenging areas for the sinus surgeon to reach endoscopically.

The use of 70° endoscopes and giraffe instruments allows excellent

access to the frontal recess, but postoperative 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 ( Yessenow and McCabe,1989) .

Etiology:

The underlying cause of a CSF leak will affect the management of

the subsequent repair.

CSF leaks are broadly classified into:

Spontaneous.

Traumatic (including accidental and iatrogenic trauma).

Tumor-related.

Congenital.

Spontaneous:Patients with no other recognizable etiology for their CSF

leak are deemed spontaneous. Most frequently these leaks occur in

obese, middle-age females who demonstrate elevated intracranial

pressure (ICP). In the frontal sinus, spontaneous leaks rarely occur

through the posterior table itself and are more likely to occur at

weaker sites of the skull base, such as the ethmoid roof or anterior

cribriform plate immediately adjacent to the frontal recess. They

are usually associated with meningoencephalocele in 70%

(Castelnuovo et al,2008).

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Trauma:Frontal sinus fractures represent approximately 5%-2% of

craniofacial injuries and have a high potential for late mucocele

formation, intracranial injury, and aesthetic deformity. Traumatic

disruption of the posterior table of the frontal sinus or frontal recess

with a dural tear can create an obvious CSF leak or present years

later with meningitis, delayed leak, or encephalocele. CSF leaks

usually begin within 48 hours, and 95% of them manifest within 3

months of injury ( Gerbino et al,2001).

Conservative, nonsurgical measures are often adequate for

injuries limited to the frontal recess and/or posterior table, but

severe fractures may require operative intervention due to a high

risk of subsequent mucocele formation. Here, operative intervention

addresses both the CSF leak and the potential for future mucocele

development, depending upon the anatomic site of the

defect( McCormack et al,1990).

Tumors related:

Anterior skull base and sinonasal tumors can create frontal

sinus CSF leaks directly through erosion of the posterior table or

frontal recess, or indirectly secondary to therapeutic treatments for

the tumor( Woodworth and Schlosser,2005).

Congenital:Since the frontal sinus is not present at birth, congenital

leaks of the frontal sinus proper do not exist. However, CSF leaks

may develop within or adjacent to the frontal recess, and congenital

defects often arise from the foramen cecum(Castelnuovo et

al,2008).

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Establishing the diagnosis and identifying the location 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

needed. In addition, the invasiveness of the test and risks to the

patient should be considered. The reported sensitivity and

specificity of any test should be interpreted with caution, as these

statistics are highly dependent upon the size of the defect, flow

rate of the leak, and the individual interpreting the test ( Kim et

al,2001).

Anatomic Site:

CSF leaks affecting the frontal sinus can be divided

anatomically into three general categories:( Kim et al,2001).

1. Those adjacent to the frontal recess:

Skull base defects located in the anteriormost portion of the

cribriform plate or the ethmoid roof just posterior to the frontal

recess do not directly involve the frontal sinus or its outflow tract,

but by virtue of their close proximity, the frontal recess must be

addressed. Endoscopic repairs may cause iatrogenic mucoceles or

frontal sinusitis if graft material, packing, or synechiae formation

obstructs the frontal sinus outflow tract(Castelnuovo et al,2008).

2. Those with direct involvement of the frontal recessA CSF leak that directly involves the frontal recess is one of

the most difficult sites to approach surgically, because the superior

extent of the defect may be difficult to reach endoscopically and the

inferior posterior extension of the defect may be difficult to reach

from an external approach( Woodworth and Schlosser ,2005).

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3. Those located within the frontal sinus proper

CSF leaks are within the frontal sinus proper involving the

posterior table above the isthmus of the frontal recess. The limits of

endoscopic approaches continue to expand with improved

equipment and experience. However, defects located superiorly or

laterally within the frontal sinus may still require an osteoplastic

flap with or without obliteration. Frontal trephination and an

endoscopic modified Lothrop procedure are adjuvant techniques

that are useful for unique cases( Woodworth and

Schlosser ,2005).

Surgical Goals for Frontal CSF Leaks:

Goal 1: Successful repair of the skull base defect and cessation

of the CSF leak. Goal 2: Long-term patency of the frontal sinus

Techniques for Diagnosing and Localizing CSF Leaks:

Beta-2 Transferrin(Skedros et al,1993).

Advantages: Accurate, noninvasive

Disadvantages: Non-localizing

High-resolution coronal and axial CT scan

Advantages: Excellent bony detail

Disadvantages: Inability to distinguish CSF from other

soft tissue; bony dehiscences may be present without a

leak

Radioactive cisternograms:

Advantages: Localizes side of the leak, identifies low

volume orintermittent leaks

Disadvantages: Localization imprecise

CT cisternograms:

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Chapter( 6): Updates In Frontal Sinus Surgery

Advantages: Contrast may pool within frontal sinus; good

bony detail

Disadvantages: Invasive, may not detect intermittent leaks

MRI cisternography:

Advantages: Excellent soft tissue (CSF/brain vs.

secretions) detail, noninvasive

Disadvantage: Poor bony detail

Intrathecal fluorescein:

Advantages: Precise localization, blue light filter can

improve sensitivity

Disadvantages: Invasive; skull base exposure required

for precision localization(Lioyd et al,2008).

Surgical Technique:

Defects located inferiorly in the posterior table, within the

frontal recess itself, or those immediately adjacent to the frontal

recess are generally amenable to endoscopic repair, thereby

minimizing the potential complications of other extracranial or

intracranial procedures(Schlosser and Bolger ,2002).

Injection intrathecal fluorescein (0.1 cc of 10% fluorescein

in 10 cc of CSF injected over 10 minutes) and place a lumbar

drain. This aids with intraoperative localization of the defect, blue

light can be helpful for easier identification. To obtain adequate

exposure, a total ethmoidectomy, maxillary antrostomy, and

frontal sinusotomy, as well as partial middle turbinectomies or an

endoscopic modified Lothrop may be indicated(Placantonakis et

al,2007).

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Fig.6.32: surgical repair of a frontal sinus CSF leak. (A) A large encephalocele fills the frontal sinus. Note fluorescein CSF flowing out of the f s. (B) The encephalocele is removed and the dimensions of the defect and distance from the anterior ethmoid roof are measured. (C) A nasoseptal flap is placed onto the posterior table after underlay repair graft and Surgisus. (D) Postoperative view of well-healed nasoseptal flap repair on the posterior table with a widely patent frontal sinus at 1 year(Hadad et al,2006).

An inlay or onlay free tissue graft may be used to patch the

site of injury.Fascia lata,temporalis muscle, abdominal fat, septal or

middle turbinate mucosa or composite grafts, periosteum, and

perichondrium are suitable grafting tissues(Meco et al,2008).

Epidural inlay graft:

the dura is elevated around the edges of the defect using a small

elevator and the graft is inserted between the dura and the bone of

the skull base.

Subdural inlay graft:

the dura may be separated from the brain and the inlay graft may

be placed in the subdural space.

Onlay graft:

When an inlay graft is not possible due to technical difficulties

or because the leak involves a linear fracture that does not expose

the dural defect, or because dissection of the duramay risk

neurovascular structures, the graft is placed as an onlay over the

defect, outside the cranial cavity(Purkey et al,2009).

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Chapter( 6): Updates In Frontal Sinus Surgery

Bath Plug graft:

Free muscle or fat grafts can also be used as a dumbbell graft.

Fibrin glue,platelet rich serum, or other biologic glue may be used

to increase the adhesiveness of the muscle or fascia graf t. The graft

is supported in place with layers of Gelfoam,followed by a sponge

packing or bacitracin-impregnated gauze. Gelfoam prevent

adherence of the packing to the graft,thus preventing accidental

avulsion of the graft when the packing is removed 3 to 7 days after

the surgery( Banks et al,2009).

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Using 0°, 30°, and 70° nasal endoscopes skull base defect is

identified, A nasoseptal flap based on the posterior septal artery

was used in the majority of cases.16 Free grafts were used when the

septum was involved, with tumor and nasoseptal flap reconstruction

of frontal sinus defects was not attempted until mid-2008(Martin et

al,2008).

The flap is created from an anterior hemitransfixion incision

to maximize length. The inferior and superior incisions are

typically completed using radiofrequency coblatio technology

The flap is raised with a suction elevator and displaced into

nasopharynx. For reconstruction involving the cribriform plate and

medial posterior table, the flap is draped vertically from the medial

aspect of the choana(Fortes et al,2007).

When defects are laterally-based, the mucosa of the medial

orbital wall is removed and the flap is rotated and positioned along

the orbital wall and over the defect in the frontal sinus. A Draf III

procedure (ie, bilateral resection of the frontal sinus floor) was

performed when necessary for skull-base resection and improved

access to the posterior table(Virgin et al,2011).

The skull-base defect was metic meticulously prepared

following tumor/encephalocele removal. Closure of the defect

involved placement of a variety of grafts(Hadad et al,2006).

the graft site is prepared by removing a cuff of normal

mucosa around the bony defect. This not only provides an area of

adherence for the graft but also contributes to osteoneogenesis and

osteitic bone formation. This thickens the bone around the defect

and aids bony closure, if a bone graft is used, between the graft and

recipient bed( Bolger and McLaughlin,2003).

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The choice of grafts is often of personal preference, but

may include alone or in combination the following: bone ,cartilage

, mucosa , fascia and alloplastic materials These grafts are

typically free grafts, rather than pedicled. Bone (or cartilage in

select cases) grafts for large skull base defects can provide

structural support for herniating dura or brain that may displace

the overlay fascia or mucosa graft. Bone grafts are also useful in

smaller defects when the patient has a spontaneous leak and

elevated intracranial pressures. This elevated pressure contributes

to disruption of the soft tissue graft and is responsible for the

higher failure rates in this category. Mastoid cortex, parietal

cortex, septal, and turbinate bone are all acceptable bone grafts. If

a mucosal graft is used, septal or turbinate bone may be a more

suitable option(Schick et al,2001).

Regardless of the choice of graft, the bone is shaped to

match the bony defect and placed in an underlay fashion in the

epidural space. Care must be taken to avoid enlargement of the

existing bony defect or entrapment of mucosa in the epidural space

that may lead to an intracranial mucocele. A fascia or mucosal graft

is then placed in an overlay fashion over the skull base defect and

supported with gelfoam and intranasal packs. Non absorbable

packing is typically removed 5-7 days postoperatively( Banks et

al,2009).

Even with meticulous dissection and wide exposure of the

frontal recess, the potential for obstruction of the frontal recess by

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Chapter( 6): Updates In Frontal Sinus Surgery

grafts or packing material is high. To avoid this, a soft silastic

frontal stent for can be placed one week. Careful debridement and

cleaning every week for several weeks will lessen the incidence of

scarring and make future surveillance easier( Banks et al,2009).

Adjuncts and postoperative care:

Lumbar drains are a useful adjunct in the management of

frontal sinus CSF leaks. They allow lowering elevated intracranial

pressure in patients with a spontaneous etiology. These patients will

have increased pressure postoperatively due to overproduction

against a closed defect. A lumbar drain is used in selected patients

who will have elevated intracranial pressure postoperatively, and

left in place for 2-3 days( Leng et al,2008).

Acetazolamide is a diuretic that can be a useful adjunct in

patients with elevated CSF pressures. It can decrease CSF

production up to 48%( Carrion et al,2001).

Patients are instructed to avoid heavy lifting, nose blowing,

and excessive straining. Patients are also prescribed pain

medications and stool softeners(Kountakis ,2005).

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