Introduction
The cerebrospinal fluid (CSF) corresponds to plasma's ultrafiltrate or to lymph, which
circulates throughout the subarachnoid space of the central nervous system (CNS) providing
physical support and balance for the brain and spinal cord, as well as contributing
to the homeostasis' maintenance of nervous tissues, removing molecules which are results
from metabolism and maintaining the chemical equilibrium of CNS. It is produced in
the plexus choroid of the ventricular system and drained in the arachnoid granulations
(structures that have an intimate relation with the dura mater's sinus).[1]
The CSF leak is the result of defects in the dura mater that enable part of the cerebrospinal
fluid to not be drained for arachnoid granulations but for the extracranial region.
Such involvement becomes potentially fatal due to the great capacity that this fistulation
has in taking microorganisms to the CNS and producing meningitis. It has been described
that 10 to 40% of patients with cerebrospinal fluid fistula develop meningitis.[2]
[3]
[4]
Revisions about the basis of dura mater defects' regeneration, which were followed
by experiments in the area have led to the conclusion that fibroblasts and connective
tissue that regenerate this meninge result in injuries near soft tissuesfrom adjacent
tissues (epidural space, fascia, muscle, and subcutaneous tissue). It was concluded,
therefore, that the dura mater's regeneration is inefficient when the defect is adjacent
to the bone, in contrast to dural injuries near soft tissues. This situation often
occurs at the base of the skull.[5]
The aim of this paper is to analyze the effectiveness of the endoscopic endonasal
surgical technique for treating cerebrospinal fluid fistulas, by comparing data from
literature and the authors' casuistry.
Materials and Methods
This is a retrospective study that included CSF leaks surgically treated, by endoscopic
approach, between 2001 and 2020. The population is constituted of 15 patients, five
males and ten females.
In addition, a thorough clinical history, a complete otorhinolaryngological examination,
clinical neurological evaluation, and endoscopic evaluation of the nasal cavity, complemented
by laboratory tests (glucose and beta-2 transferrin) and imaging tests such as Nuclear
Magnetic Resonance (NMR) and multi-slice Computed Tomography (CT) were carried out.
In particular, the hypodense fluorescein technique was used. This solution is obtained
by diluting 0.5cc of 5% fluorescein in 10ml of distilled water. The patient underwent
lumbar puncture at L3-L4 or L4-L5, after which an epidural catheter was inserted about
15cm into the patient's spine and fixed to the skin for 48 hours, to maintain mild
cerebrospinal fluid hypotension in the postoperative period. In addition to allowing
good visualization of the fistula site, the technique described avoids positioning
the patient in the Trendelenburg position, as is done in the hyperdense technique.
We used the following technique in our series:
-
The patient is placed in dorsal decubitus under general anesthesia.
-
ceftriaxone, 1g IV, is administered 1 hour before the procedure, as meningitis profilaxy.
-
Lumbar puncture at L3-L4, with the placement of an epidural catheter, for injection
of 5% fluoroscein diluted in 10 ml of double-distilled water, to obtain a hypodense
solution. It is important to notify you that immediately after the procedure, the
epidural catheter is removed. ([Figs. 1] and [2])
-
Localization of the lesion site with 30-degree or 45-degree endoscopes, in the case
of lamina crivosa or lateral lamella fistulas; an ethmoidectomy is necessary to better
localize the fistulous tract. Occasionally, it may be necessary to perform a resection
of the meatal aspect of the middle turbinate, which can be used to form a pedicled
flap of the middle turbinate itself. In septal deviations that make it difficult to
see the fistulas properly, septoplasty may be necessary.
-
Scarification of the surrounding mucosa in a perimeter of 5mm around the fistula to
make it easier to take the graft. Grafts of middle turbinate mucosa, septal mucosa,
fascia lata, or freeze-dried dura can be used. The use of Duragen, a dural substitute,
had a major role in sealing the dura-mater defects. In cases of larger ones, septal
cartilage can be used as a support to reinforce the anterior skull base. The use of
fibrin glue and Surgicel is important to completely seal off the flow of cerebrospinal
fluid.
-
Use of ceftriaxone, 1g, every 12 hours, for 5 days after surgery, for meningitis prophylaxis.
-
Hospital discharge 48 hours after surgery, after reviewing the nasal cavity with an
endoscope.
Figs. 1 and 2 The visualization of fluid fistula leak colored in green by the use of fluorescein
in the endoscopic view.
Surgical Techniques
Underlay Approach:
The Underlay technique involves the exact location of the fistula and scarification,
elevating the dura adjacent to the fistula site, which in most cases causes slight
bleeding due to the detachment of the dura. It is necessary to create a free area
to fit the graft, which will be positioned inside the inner edge of the hole, above
the defect in the anterior skull base. In the case presented, when using this technique
in ethmoidal fistulas with dural defects larger than 1cm, in addition to free flaps
of inferior turbinate, septal cartilage was also used to provide more support and
prevent recurrences. After positioning the flaps, fibrin glue and Surgicel were applied
to completely seal the defect.
Onlay Approach:
In the Onlay technique, after locating the site of the lesion, the mucosa around the
fistula is scarified to a perimeter of 5mm. This increases the flow of cerebrospinal
fluid but allows the formation of a raw area that facilitates the adhesion of the
graft. After placing the graft, fibrin glue and Surgicel are applied to small defects.
In larger defects, free grafts of septal mucosa or inferior turbinate were used. In
the case of cribriform lamina fistulas, pedicled flaps of the middle turbinate were
used. In large fistulas formed by the resection of skull base tumors, we used fascia
lata, because as well as being resistant and malleable, it provides a more generous
amount of material when compared to grafts resected from the nasal cavity.
Results
A total of 15 patients formed our population. The current data was collected from
the period of December 2001 to December 2020. Among those, five patients were male
and ten female. The age of our population varies from 17 to 84 years (mean age 50.5
years). All the fistulas were spontaneous, with no related etiology. There were seven
patients presenting fluid nasoethmoid fistula situated on the fovea ethmoidalis, six
on the cribriform plate, one on the sphenoidal sinus roof, and one situated on the
sphenoidal sinus and cribriform plate, simultaneously. ([Table 1]) About their symptomatology, all patients presented with headache, rhinoliquorrhea,
and neck stiffness. ([Fig. 3]) Of the total, only five cases were presented with fever. Three cases were initially
diagnosed as meningitis, although, with further investigations, it was possible to
conclude that the spontaneous fistulas were responsible for their symptomatology.
Fig. 3 Visualization of rhinoliquorrhea in the physical examination.
Table 1
Baseline characteristics of population
|
Casuistry from 2001 to 2020
|
|
Total: 15 cases
|
|
Male Gender: 5
|
Female Gender: 10
|
|
Etiology:
|
|
Spontaneous
|
15
|
|
Location:
|
|
Fovea ethmoidalis
|
7
|
|
Cribriform plate
|
6
|
|
Esphenoidal Sinus Roof
|
1
|
|
Sphenoidal sinus and Cribriform plate
|
1
|
|
Recurrences: 2
|
|
Recurrent Meningitis: 2
|
During the endoscopic approach, there were no major complications and blood loss was
not reported. The mean time of the procedure was 1 hour and 45 minutes. Nine patients
proceeded with the underlay technique, and six underwent the onlay technique.
Only two patients presented post-operative complications such as meningitis. Those
were properly treated. At last, only two presented recurrences of the nasoethmoidal
fistula and were reoperated, through the endoscopic approach. To this date, no other
recurrences have been reported.
Discussion
The first description of a rhinogenic cerebrospinal fluid fistula was made by Galen
in 200 BC.[6]
[7] In 1826, Miller described a fistula located between the nasal cavity and the subarachnoid
space in a child with hydrocephalus with a history of intermittent nasal discharge
during a necropsy.[8] In 1889, Saint Clair Thompson reported a series of patients with spontaneous rhinogenic
CSF leak.[6]
[7]
The CSF fistulas can be classified as congenital or traumatic; however, when no apparent
cause is present, the fistula is described as spontaneous. Spontaneous CSF fistulas
are more common in patients with obesity and idiopathic intracranial hypertension
(ICH).[9]
The traumatic etiology is the main cause of cerebrospinal fluid leakage (80-90% of
cases), followed by iatrogenic (10%), spontaneous (3-4%), tumor, and inflammations.[10]
Spontaneous CSF fistulas are typically observed in the anterior and lateral regions
of the skull base, with the dura mater rupturing in areas over a pneumatized space.
The incidence of spontaneous CSF fistulas is higher in females (72%).[11]
Patients with spontaneous CSF leak often exhibit a thinning of the base of the skull.
This condition is more prevalent in middle-aged and older women, potentially due to
the fact that women have thinner bones, increasing their susceptibility to bone erosion.
In women, skull thickness diminishes with age, in contrast to the observed trend in
men.[12]
In addition to a comprehensive clinical history and a detailed otorhinolaryngological
examination, a full clinical neurological evaluation and an endoscopic examination
of the nasal cavity are essential components of the diagnostic process. Laboratory
tests, such as glucose and beta-2 transferring, and imaging examinations, including
magnetic resonance imaging (MRI) and multi-slice computed tomography (CT), are also
crucial for complete assessment.[9]
Locating exactly the fistula is extremely important, seeing this precise identification
is paramount for therapeutic efficacy. One of the alternatives to be used is multi-slice
tomography that through three-dimensional reconstruction facilitates the detection
of the exact place of the lesion, allowing sagittal incisions to detect faults in
the roof of the sphenoid sinus.[13]
The accuracy of preoperative methods capable of locating the site of nasal congestion
is essential for surgical treatment.[14]
[15] Nasal congestion can develop in any of the paranasal sinuses: frontal, ethmoid,
or sphenoid. There is also a particular case called paradoxical, in which the CSF
exits into the middle ear through the auditory tube.[16]
Persistent rhinorrhea in patients with CSF leak is a medical condition that can lead
to meningitis in 19% of cases. In many cases, the treatment of choice is endoscopic
surgery for closure, which has been demonstrated to be an effective method of reducing
the risk of meningitis. The prophylactic use of antibiotics may also be an effective
method of reducing this risk.[10]
[17]
It is well established that ICH can result in spontaneous CSF rhinorrhea, given the
established link between this condition and the occurrence of ICH. Consequently, it
is recommended that ICH be managed with the use of Acetazolamide (AAZ), which was
the first non-mercurial diuretic to be introduced for clinical use in 1954. Subsequent
studies have demonstrated the efficacy of AAZ in the treatment of idiopathic intracranial
hypertension.[18]
[19]
AAZ is a low nanomolar inhibitor of carbonic anhydrase isoforms that are involved
in the secretion of CSF. Inhibition of the carbonic anhydrase isozymes II, IV, VA,
and XII in the brain and choroid plexus results in a reduction in CSF fluid secretion
and the maintenance of intracranial pressure. Despite the long-standing clinical use
of numerous sulfonamide/sulfamate carbonic anhydrase inhibitors, it appears that only
AAZ is currently employed in clinical practice for the treatment of ICH.[18]
[19]
Spontaneous fistulas and late installation after trauma or general surgery require
immediate surgery, due to the high recidivist rate.[20]
[21] Nevertheless, In the absence of a standard approach to the management of spontaneous
cerebrospinal fluid (CSF) leaks, the optimal course of action remains undetermined.[12]
Treatment decisions are made on a case-by-case basis, with consideration of several
factors. These include obesity (body mass index [BMI] > 30), the velocity of cerebrospinal
fluid (CSF) leakage, the magnitude of the skull base defect (>2 cm), a previous history
of CSF leaks, and the intricacy of the surgical repair. In light of these considerations,
the recommended course of action may entail lumbar drainage, cerebrospinal fluid diversion,
or the administration of medications to reduce intracranial pressure.[12]
Several techniques have been described for the treatment of cerebrospinal fluid rhinorrhea.
The initial technique was first described by Dandy (1926), who utilized a muscle and
fascia lata graft to repair a dural lesion following a frontal fracture trauma. Subsequently,
Wigand and Hosemamm (1985) devised an alternative technique utilizing solely the endoscopic
approach for the closure of these fistulas, employing mucoperiosteal flaps. Levine's
preferred method involves the use of pediculated flaps of the middle turbinate to
close the defects in the cribriform plate, effectively preventing the escape of cerebrospinal
fluid.[21]
Several types of graft are used and described in the literature for this kind of correction,
using conjunctive tissue grafts, such as fascia lata, temporal fascia, and muscle.
Furthermore, Herrera Caicedo addresses the use of septal cartilage, positioning it
between the dura mater and the previous skull base, underneath the defect, and it
has been demonstrated as a highly effective approach, especially in the more extensive
defects of the previous skull base.[22]
[23]
The contemporary surgical treatment for fistulas adheres to the methodology initially
proposed by Dandy. Nevertheless, the efficacy of this approach remains suboptimal.
Consequently, there is a need to develop a more efficacious method for the repair
of dura mater defects, frequently employing dural implants and biological or synthetic
sealants.[21]
In recent years, endoscopic surgery has become the technique of choice for the correction
of CSF leaks. Its less invasive nature, lower morbidity and mortality, better visualization
during the procedure, and higher success rate, with approximately a 90% success rate
in the first procedure, make it a safer method for surgical repair.[24] Other common approaches, such as transcranial and extracranial procedures, have
a 70% success rate, as well as possible significant morbidities such as permanent
anosmia.[15]
The "underlay" and "onlay" techniques are the most used. These techniques are also
used in combination to treat CSF leaks if there is a risk of neurological damage,
with the “onlay” being performed in repairs.[25]
Regarding CSF leak complications, the literature indicates that meningeal infections
are more prevalent among these patients. However, the incidence of these complications
is quite variable, and the relationship between their occurrence and the underlying
etiology is not particularly well-defined.[16] Another significant complication associated with this is occurrence of pneumocephalus,
which presents in the anterior portion of the skull base. This phenomenon is brought
about by contact between the nasal cavity and the intracranial cavity, which may result
in headaches and alterations in the level of consciousness.[8]
Conclusion
Based on what was presented in this article, the endoscopic surgical repair approach
proved to be satisfactory, with 2 recurrences out of 15 cases analyzed (86% success
rate in the first surgical intervention). This result is in line with the literature,
which reports a similar rate (approximately 90%).
About the prevalence, there was a statistically significant difference between males,
occurring majorly in female patients. As for the choice of techniques, it was not
possible to assess a clear relationship between the success of the repair and the
choice of endoscopic procedure used. The choice of Onlay or Underlay technique depends
on the size of the fistula to be repaired, and both have similar results when applied
properly.
