cerebrospinal fluid leaks
TRANSCRIPT
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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Chapter( 6): Updates In Frontal Sinus Surgery
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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Chapter( 6): Updates In Frontal Sinus Surgery
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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Chapter( 6): Updates In Frontal Sinus Surgery
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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Chapter( 6): Updates In Frontal Sinus Surgery
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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Chapter( 6): Updates In Frontal Sinus Surgery
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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