Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_4532_Библиотеки_им_академика_М_И_Перельмана
.pdf
Cerebrospinal Fluid Leak, Meningocele and Meningoencephalocele 95
In case of a cephalocele, signs and symptoms depend on its location. Transethmoidal cephaloceles
herniate into the nasal cavity and may be characterized by unilateral nasal obstruction; less frequently,
this is the heralding symptom of transsphenoidal
encephaloceles. Endoscopic evaluation may reveal
a smooth isolated polypoid mass coming from the
olfactory fossa (Fig. 7.1) or sphenoid sinus. In this
setting, removal or biopsy of the lesion is contraindicated unless appropriate radiologic evaluation has
been obtained. Fronto-ethmoidal and spheno-orbital
cephaloceles herniate into the soft tissues of the nose
region and of the orbit(s), respectively, and are characterized by swelling, proptosis, and hypertelorism.
In these cases, an association with facial deformities
and cleft palate is frequently observed (Mahapatra
and Suri 2002).
In a patient with persistent CSF leak, rarely nasal
endoscopy identifi es the site of CSF leakage. Watery
rhinorrhea and mucosal bulging at the olfactory fossa
is the most favorable situation suggesting a CSF leak
coming from a cephalocele. An unexpected sinonasal
neoplasm can also be detected by endoscopy.
Recurrent meningitis, even in the absence of rhinorrhea, should raise a suspicion of CSF leak. The
prevalence of meningitis and brain abscess is reported to be up to 40% in traumatic non-intermittent fi stulae, whereas their incidence greatly varies in
spontaneous leaks (Beckhardt et al. 1991; Eljamel
1994; Wa x et al. 1997).
7.3
Diagnosis
Physicians can be faced with two main different
scenarios: patients with persistent or intermittent
watery rhinorrhea highly suggestive for CSF leak
and patients who had one or more bouts of meningitis apparently without any specifi c cause. In the
fi rst situation, which is the most frequent, diagnosis
should include fi rst chemical methods to analyze the
nasal discharge in order to obtain confi rmation of
its nature, while in the second an immediate imaging examination and fl uorescein test are indicated
(Fig. 7.2).
Fig. 7.1. Meningocele of the left nasal fossa. Endoscopic evaluation with a 0°-angled rigid endoscope: an isolated bluish
polypoid mass (P) projecting from the left olfactory fossa is
visible. Nasal septum, NS; middle turbinate, MT
Fig. 7.2. Work-up in the case of suspected spontaneous or traumatic CSF leak. High resolution CT (HRCT)
Chemical methods for glucose, protein, or chloride
have been used for many years to confi rm CSF leak.
However, they are nowadays considered highly nonspecifi c (Oberascher and Arrer 1986) and beta-2
transferrin (B2T) assay has taken their place in the
confi rmation of CSF rhinorrhea diagnosis. B2T is a
polypeptide involved in ferrous ion transport: while
beta-1 transferrin is present in serum, nasal secretions, tears, and saliva, B2T has been demonstrated
in CSF, perilymph, and aqueous humor only. The reported sensitivity and specifi city for B2T test in the
diagnosis of CSF rhinorrhea is 100% and 95%, respectively (Nandapalan et al. 1996; Skedros et al.
1993). Furthermore, the procedure is absolutely noninvasive, the amount of fl uid necessary for analysis is
96
L. Pianta et al.
very small (0.5 ml), detection of B2T can be achieved
within 3 h, and contamination by other body fl uids
does not invalidate the method. Beta-trace protein
(BTP) is another brain specifi c protein that is produced mainly in the leptomeninges and the choroid
plexus; it is the second most abundant protein in CSF
after albumin. This protein has also been detected in
other body fl uids such as serum and perilymph at
much lower concentrations than in CSF. Recently, a
BTP nephelometric assay for the quantifi cation and
detection of CSF in nasal fl uid has shown sensitivity of 91.17% and specifi city of 100% (Bachmann et
al. 2000). Compared with B2T assay, BTP assay is less
time-consuming . Therefore, B2T and BTP assays are
nowadays considered the fi rst line test in confi rming
the diagnosis of CSF rhinorrhea.
The recommended fl uorescein test protocol is
based on the employment of 1 ml of 5% sodium fl uorescein solution diluted with 10 ml of patient’s CSF.
The patient is put in Trendelenburg position and the
solution is slowly injected intrathecally through a
lumbar puncture (Stammberger 1991). Rare adverse
effects of intrathecal injection of fl uorescein have
been reported (temporary paresthesias of the lower
limbs, weakness of the extremities, dizziness, dysphasia, hemiparesis and status epilepticus) (Moseley et
al. 1978); however, the occurrence of these symptoms
seems to be related to the use of higher concentrated
solutions of the dye (Senior et al. 2001).
External approaches are still the mainstay in the
treatment of frontoethmoidal, spheno-orbital and
spheno-maxillary cephaloceles, while nasopharyngeal lesions may be amenable with a microendoscopic approach.
A large spectrum of materials can be used for duraplasty: abdominal fat, septal mucoperichondrium,
turbinate bone, temporalis muscle and fascia, cadaver pericardium, lyophilized dura, fascia lata, and
hydroxyapatite (Zweig et al. 2000).
Transnasal surgical repair involves mainly three
techniques: underlay, overlay and tobacco pouch
(Schick et al. 2001). The underlay technique is ideal
for defects located in the fovea ethmoidalis (Fig. 7.3).
Graft material (bone from the middle turbinate or
cartilage from the septum) is positioned between
the dura and the skull base or intracranially over the
dura. A free mucoperichondral graft, harvested from
the septum, is subsequently placed, as a second layer,
on the endonasal surface of the skull base to reinforce
the plasty.
7.4
Treatment Guidelines
Although most traumatic CSF fi stulas can spontaneously heal with conservative measures such as bed
rest, head supraelevation, administration of laxatives and antiemetics, and positioning of a lumbar
drainage, a surgical corrective procedure is recommended in case these measures fail within 10–15 days
(Hegazy et al. 2000).
Immediate surgical correction is instead indicated
in the case of traumatic fi stulas associated with intracranial lesions requiring craniotomy and in all cases
of iatrogenic leaks occurring during skull base surgery and sinus surgery (Hegazy et al. 2000).
Wi ga nd (1981) fi rst reported the endoscopic endonasal approach for CSF leaks occurring during microendoscopic sinus surgery for infl ammatory conditions. From this fi rst experience, microendoscopic
repair gained popularity and is now considered the
treatment of choice.
Fig. 7.3. Underlay technique. Coronal view of the anterior skull
base showing the repair of a defect in the fovea ethmoidalis
with “underlay technique.” Grafting material (autologous cartilage from nasal septum or bone from middle turbinate) is
positioned between the skull base and the dura. A mucosal
graft from nasal septum or middle turbinate is placed as a
second layer to reinforce the plasty
The overlay technique is generally employed for de-
fects located in the lamina cribra, where the presence of
olfactory phyla makes it diffi cult to dissect dura from
the adjacent skull base (Fig. 7.4). A free cartilaginous
or bony graft is fi rst placed on the extracranial surface of the skull base to close the bony gap; similarly
to underlay technique, duraplasty is then completed
Cerebrospinal Fluid Leak, Meningocele and Meningoencephalocele 97
with a second layer of free mucoperichondrium. This
technique can be also used in the lateral wall of extensively pneumatized sphenoid sinuses, where the leak is
usually coming from a defect in the fl oor of the middle
cranial fossa. In this setting, extensive drilling of the
pterygoid process is required to ensure an adequate
exposure (Casiano and Jassir 1999).
The tobacco pouch technique is an alternative procedure for sphenoid sinus defects: after careful removal of the entire mucosa investing the sinus, fascia
lata plus Gel foam or abdominal fat is positioned into
the sinus and then sealed by a mucoperichondral graft
(Weber et al. 1996; Schick et al. 2001) (Fig. 7.5).
A review of the literature indicates high success
rates for microendoscopic procedures, varying from
75.9% to 97% after primary repair, up to 100% after revision surgery. These results are independent
Fig. 7.5. Tobacco pouch technique. Axial view of the skull
base showing the repair of a defect in the posterior wall of
a sphenoid sinus with “tobacco pouch technique.” A double
layer packing with fascia lata and abdominal fat or Gelfoam
is positioned into the sinus
a
b
Fig. 7.4a,b. Overlay technique. a Coronal view of the anterior
skull base showing the repair of a defect in the olfactory fossa
with “overlay technique.” Autologous cartilage or bone and
mucosal graft are positioned endonasally under the dural
defect. b Coronal view of the middle skull base showing the
repair of a defect in the lateral wall of a hyperpneumatized
sphenoid sinus with “overlay technique.” After drilling of the
pterygoid process a double layer plasty is positioned
from the surgical technique and grafting materials
(Dodson et al. 1994; Burns et al. 1996; Lanza et al.
1996; Castillo et al. 1999; Marshall et al. 1999;
Nachtigal et al. 1999; Mao et al. 2000; Zweig et al.
2000; Schick et al. 2001).
Important clues for a successful repair are represented by: precise location and exposure of the defect with adequate removal of the surrounding mucosa, removal of unstable bony fragments around the
breech, and use of an oversized graft (Gassner et al.
1999; Castelnuovo et al. 2001; Schick et al. 2001).
An elevated body mass index, a fi nding frequently
associated with spontaneous CSF leak (Schlosser
and Bolger 2003), has also been recently shown to
be related with failure of repair (Lindstrom et al.
2004).
Although some authors consider perioperative
antibiotic therapy unnecessary, or even contraindicated, for potential positive selection of resistant
bacteria, it is generally recommended for at least 48 h
after surgery to decrease the incidence of postoperative meningitis (Choi and Spann 1996; Nachtigal
et al. 1999; Hegazy et al. 2000; Zweig et al. 2000).
Some authors recommend the use of a lumbar
drainage and its maintenance for at least 72 h after surgery (Mccormack et al. 1990; Persky et al.
1991; Mao et al. 2000). According to more recent and
numerous series, its use should be limited to those
patients who have an associated hydrocephalus and/
or intracranial hypertension (Dodson et al. 1994;
Casiano and Jassir 1999; Hegazy et al. 2000).
98
L. Pianta et al.
The success rate of the microendoscopic approach
(superior to external techniques) and the low incidence of postoperative complications make it the
treatment of choice. External approaches are nowadays justifi ed in the case of repeated failures of microendoscopic techniques, multifocal fronto-basal
fractures, association with brain lesions requiring
craniotomy, and fi stulae not endoscopically treatable
(posterior wall of the frontal sinus).
7.4.1
Follow-Up
Although most CSF leak recurrences generally occur
within days or months after surgical repair, late recurrences have been described even after years. Periodic
endoscopic evaluations are therefore mandatory, while
BTP or fl uorescein tests and imaging techniques are
indicated in the case of suspicious symptoms such
as persistent rhinorrhea and meningitis. Patients with
intracranial hypertension should be considered at risk
for a recurrent lesion or a second meningocele at a
different site; periodic MR may therefore be indicated
for early detection of this occurrence.
directly demonstrating the leakage, as evidence of its
existence, to different – though not less challenging
– tasks.
As a direct consequence, there is less need to use
invasive “cisternographic” imaging techniques, which
have the purpose of tracking the fi stulous tract by
means of radiopaque or radioactive “markers” previously injected into the CSF. Therefore, nowadays, the
identifi cation of intra- and extracranial lesions possibly causing CSF leak and the detailed demonstration
of the anatomic/topographic features of the fi stula(e)
are the main objectives of imaging.
This information may be achieved by “plain” non-
invasive imaging techniques, aimed at identifying
lesions involving the skull base or to detect osseous/
dural defects. Interestingly, MR – the more recently
introduced imaging technique – enables the identifi cation of the fi stula by means of special sequences
that enhance the CSF signal (MR cisternography),
therefore providing fi ndings similar to those obtained
by invasive “cisternographic” techniques.
7.6.1
Integration of Imaging into the
Diagnostic Work-Up
7.5
Key Information to Be Provided by Imaging
Presence of intra- and extracranial pathology
possibly related to the CSF fi stula (empty sella,
paranasal sinuses diseases, skull or head and
neck tumors or infections) and/or contraindicating lumbar puncture possibly necessary for fl uorescein or contrast-medium injection (acute posttraumatic lesions, hydrocephalus, brain tumors)
Radiological confi rmation of the CSF leak
Side, site, size and possible number of the
fi stula(e)
“Nature” of the lesion primarily causing CSF rhi-
norrhea (bony dehiscence, meningocele, meningoencephalocele)
7.6
Imaging Findings
The development of highly accurate chemical methods to confi rm CSF leak has recently shifted the use
of imaging from its traditional primary purpose of
The use of imaging – as for the employment of either
fl uorescein test or BTP test – is dictated by the clinical
presentation of CSF leak that can be separated into
persistent or intermittent rhinorrhea vs. recurrent
meningitis (Fig. 7.2)
7.6.1.1
CSF Leak Associated with Persistent or Intermittent
Rhinorrhea
When persistent or intermittent watery rhinorrhea
suggests CSF leak, endoscopy is the fi rst line examination. An endonasal expansile lesion (cephalocele?
glioma?) may be detected or endoscopy may give
a negative result. In the fi rst case, BTP test is unnecessary, as CSF leak is assumed to be related to
the endonasal lesion. Additionally, having detected a
nasal mass, the main clinical issue is to defi ning its
relationship with intracranial structures. In this setting, MR is preferable to high resolution CT. In fact,
T2 and MR cisternographic sequences are superior
in demonstrating the uninterrupted CSF signal extending from the subarachnoid space into the mass,
or into paranasal sinuses/nasal cavity or into middle
ear, with or without brain tissue (Stafford et al.
1996) (Fig. 7.6).
Cerebrospinal Fluid Leak, Meningocele and Meningoencephalocele 99
a
Fig. 7.6a,b. Small spontaneous meningocele through the right cribriform plate. Coronal TSE T2 before (a) and after (b) surgi-
cal repair. a A small rounded fl uid collection (proved to be a meningocele at surgery) is seen under the right cribriform plate
(asterisk); both olfactory bulbs are clearly visible over the cribriform plate in this patient with a “deep” olfactory fossa (the left
one indicated by arrows). Subtle mucosal thickening in both maxillary sinuses, with retention cyst on the right side. b After
successful endoscopic repair with overlay technique, the CSF collection in the right olfactory cleft is no longer visible. Note the
post-surgical changes on the right side due to middle turbinectomy, uncinectomy, middle antrostomy, and ethmoidotomy
CT has a complementary role, related to its superior depiction of bony detail. At MR, the cephalocele
appears as a round “mass” with sharp margins, isointense to CSF in all sequences (meningocele) or containing some tissue isointense to brain parenchyma
(meningoencephalocele), protruding from the intracranial cavity into the nasal cavity or paranasal
sinuses. The lumen of the lesion is continuous with
the subarachnoid space and often has a constriction
in the portion passing through the bone defect (the
“neck” of the cephalocele) (Fig. 7.7). CT clearly shows
the sclerotic margins of the bone defect. Cerebral MR
may show the associated brain anatomy “distortion”,
presumably due to the effect of the brain pulsation in
utero, which “pushed” the pliable unmyelinated brain
outward through the defect (Truw it et al. 1996). The
result is a general tendency of the ventricles and subarachnoid spaces, which subtend the cephalocele, to
be stretched and elongated, “pointing” toward the
calvarial defect. This fi nding is usually observed in
patients with large occipital or parietal cephaloceles.
Cephaloceles may be isolated anomalies, but may
also be seen in conjunction with other congenital
brain malformations or as a part of a syndrome. The
radiologist must therefore also look for associated
anomalies, such as agenesis or hypogenesis of the
corpus callosum, Dandy-Walker malformation, or
malformations of cortical development (Naidich et
al. 1992).
Among lesions to be differentiated from cephaloceles is the so-called nasal glioma (heterotopic brain
tissue). It consists of a variable amount of dysplastic
brain tissue (especially glia cells, whereas neurons are
present in only about 10% of cases), located within
the nasal cavity or in the nasal subcutaneous tissue. It
is thought to result from the herniation of brain tissue
into a dural projection that normally extends through
the foramen cecum during the embryologic development. Regression of the more superior portion of this
dura projection leads to complete separation of the
nasal glioma from the intracranial contents. If inferiorly the dural projection remains adherent to the
skin of the nose and fails to involute, but no brain
tissue herniates through it; a dermal sinus tract is
present. It is usually suggested by a small dimple on
the surface of the nose. Along the path of the dermal
sinus tract (epi)dermoids may develop.
MR is clearly superior to CT in the evaluation of
nasal gliomas, because it directly shows the lack of
communication with the subarachnoid space, which
is the hallmark of cephaloceles. Furthermore, the
dysplastic brain tissue of nasal glioma appears hyper-
b
100
L. Pianta et al.
a
c
intense to gray matter in both T1- and T2-weighted
images (Fig. 7.8).
When no endonasal mass is detected by endoscopy, BTP test is indicated, its sensitivity for CSF leak
being more than 90% (Bachmann et al. 2000).
If post-traumatic rhinorrhea is investigated,
positivity of BTP will confi rm the diagnosis. In this
setting, high resolution CT is the fi rst line imaging
technique, having a reported sensitivity ranging from
50% up to 100% (Dietrich et al. 1993; Lloyd et al.
1994, Zapalac 2002). It is obtained without intrathecal or intravenous contrast agent administration,
using thin (1- or 2-mm) contiguous axial and coronal planes. Scans or multiplanar reconstructions are
orientated parallel and perpendicular to the anterior
cranial fossa fl oor, respectively. The whole skull base
needs to be examined, including the mastoid cells.
Because CSF leak is not directly detectable on
high-resolution CT, the identifi cation of a bony defect is indirectly taken as the possible site of the CSF
leak, even if the bone defect itself does not necessarily correspond to the site of dural tear (To ll e y et
al. 1992). However, bony dehiscences are not infrequent in the skull base (Tol l ey et al. 1991), having
b
Fig. 7.7a−c. Fronto-ethmoidal spontaneous meningocele in an
8-year-old girl. Coronal high resolution CT (a), TSE T2 in the
coronal (b) and sagittal (c) planes. a Bone defect in the left
cribriform plate (arrow), associated with soft-tissue density
in the left nasal cavity (asterisk). b The outpouching of CSF
in the left nasal cavity is clearly identifi ed as fl uid signal (hyperintense) on TSE T2 images (asterisk). Even if the signal
intensity of CSF is slightly brighter than that of nasal mucosa,
an infl ammatory polyp could be a differential diagnosis. c On
sagittal image, the direct communication between the fl uid
collection in the nasal cavity and the frontal subarachnoid
space is clearly depicted (arrow). There is no brain parenchyma extending into the endonasal CSF collection
been demonstrated in about 14% of ethmoid bones
(Ohnishi 1981). Similar dehiscences have been described in the sphenoid and, less commonly, in the
frontal sinus. As a consequence, a simple bony defect
cannot be considered a reliable sign of CSF fi stula.
Conversely, when a bony defect, located at the edge
between skull base and paranasal sinus/nasal cavity,
is associated with fl uid collection and/or mucosal
thickening within the adjacent sinus/nasal cavity, it
can be assumed to be located close to the dural breach
site (Fig. 7.9). By combining these fi ndings, the specifi city of high-resolution CT raised to 86% in a series
of 15 patients with traumatic (accident or iatrogenic)
fi stulae (Lloyd et al. 1994).
However, precise location of the fi stula(e) may be
rather diffi cult, if not impossible, in the presence of
comminuted fractures, particularly when scar tissue
partially replaces the skull base or invests its endonasal interrupted surface. In this case, CT fi ndings may
indicate more than a single potential site of CSF leak,
therefore not enabling a suffi ciently tailored surgical
approach. MR may provide additional fi ndings, like
showing signal intensity consistent with CSF within
the scar tissue or across the interrupted skull base.
Cerebrospinal Fluid Leak, Meningocele and Meningoencephalocele 101
a
shows intermediate signal. e On off-midline sagittal plane, the nasal glioma (asterisk) appears bordered superiorly by the lateral
aspect of the crista galli (black arrows). A normal nasofrontal suture is present (white arrow)
d
cb
ed
Fig. 7.8a−e. Intranasal heterotopic brain
tissue (nasal glioma). Coronal (a−c) and
sagittal (d−e) TSE T2. a The mass (aster-
isk) arises from left olfactory fi ssure, the
left nasal cavity is completely occupied. b
The nasal glioma abuts the inferior surface of the cribriform plate (1) without
any connection with subarachnoid space.
Middle (2) and inferior (3) turbinates are
compressed. c The vertical lamina of the
middle turbinate limits the lateral aspect
of the nasal glioma. d On midline sagittal plane, the crista galli (black arrows)
In particular, MR cisternography has been proposed
as a non-invasive cisternographic technique. It consists of turbo spin echo sequences with fat-suppression (to null signal from bone marrow) that greatly
increase CSF signal intensity and suppress the background, providing heavily T2 images with detailed
anatomic information of the subarachnoid cisterns.
If necessary, a small number of images (usually between two and eight) may be compressed into composite images using maximum intensity projection
algorithms. Composite images may be useful to detect fi stulae with irregular and tortuous tracks (El
Gammal and Brooks. 1994). In detecting CSF fi stulae, MR cisternography yielded sensitivity of 87%,
specifi city ranging from 57% up to 100%, and accuracy of 78%–89% (El Gammal et al. 1998, Shetty et
al. 1998). Although MR cisternography may be added
Figure 7.9. Traumatic iatrogenic CSF fi stula, post-microendoscopic sinus surgery. Coronal high resolution CT at the level
of the olfactory fossa. A large bone defect is demonstrated to
involve the horizontal (short arrows) and the lateral lamella
(arrowhead) of the right cribriform plate. The right lamina
papyracea is not recognizable (long arrows). Note the absence
of the middle turbinate and ethmoid labyrinth on the right
side, due to previous endonasal surgery
to the diagnostic work-up, at present precise identifi cation of the fi stula(e) is made possible at surgery by
fl uorescein leakage detection, which is more accurate
than imaging techniques.
In fact, even fi stulae due to incomplete damage of
the meninges causing permeation rather than a complete breech are shown with this technique. The fl uo-
102
L. Pianta et al.
roscein tracer is administered via lumbar puncture,
and a special light fi lter is necessary to endoscopically
detect small fi stulae. In case of spontaneous fi stula,
a positive BTP test requires the patient to be investigated either by CT, adding the high resolution CT
technique to the standard examination of the head,
and by MR. Detection of paranasal sinuses or temporal bone hyperpneumatization will prompt the
accurate assessment of the whole skull base to rule
out bone dehiscences. The presence of an empty
sella with or without a fluid-like broad-based lesion on sphenoid walls may arouse the suspicion
of benign intracranial hypertension. In this setting, intermittent CSF leak may be associated with
other imaging findings suggesting idiopathic intracranial hypertension, as increased CSF amount
surrounding the optic nerves along their intraorbital course (Suzuki et al. 2001). Furthermore, any
fluid-like broad-based lesion hanging on the extracranial surface of the skull base may indicate a
cephalocele located beyond the limit of diagnostic
endoscopy (Stone et al. 1999).
However, the presence of a high signal on T2 images within paranasal sinuses or mastoid cells or
adjacent to the skull base may be due to thickened
mucosa, mastoiditis or rhinosinusitis, and not necessarily to CSF accumulation. Therefore, a CSF fistula may be suspected whenever the high signal of
the fistulous tract appears to be in direct continuity with the intracranial subarachnoid space. This
point is relevant, as high signal intensities on T2
sequences are shown in up to 25% of patients examined by MR for non-sinonasal diseases (Moser
et al. 1991).
Indirect evidence of CSF fi stula is provided by a
low-lying gyrus rectus when the leak is located at the
cribriform plate area (“gyrus rectus sign”), probably
related to the negative pressure created by the fi stula
(Shetty et al. 1998).
Finally, unexpected intracranial or extracranial
tumors, hydrocephalus, or skull base infl ammatory
lesions may be demonstrated by CT or MR.
When BTP test, high resolution CT, and MR are all
negative, the diagnosis of CSF has to be considered
unlikely or spontaneous healing of the dural defect(s)
might have occurred during the diagnostic work-up.
In a series of 42 spontaneous and post-traumatic
CSF leaks examined by high-resolution CT, radionuclide cisternography, and CT cisternography, spontaneous resolution of CSF leakage within 1 month from
imaging studies was observed in all patients negative
at high resolution CT (29%) (Stone et al. 1999).
7.6.1.2
CSF Leak Presenting with Recurrent Meningitis
In this second group of patients, CSF leak is suspected because of recurrent meningitis in the absence of rhinorrhea. In this setting, the fi rst line approach entails both endoscopy and imaging. BTP is,
of course, unhelpful.
Endoscopy, CT and/or MR may succeed in demonstrating lesions both in post-traumatic and spontaneous fi stulae. Compared to patients with CSF leak
and rhinorrhea, the main difference consists in the
absence of imaging fi ndings of active leak (i.e., fl uid
collection within sinonasal cavities or focal mucosal
thickening adjacent to bone dehiscences or to skullbase fractures).
Being based on indirect fi ndings, high-resolution CT may be positive in inactive and active leaks
with similar rates because it does not depend on the
amount of CSF leakage at the time of investigation
(Fig. 7.10).
Recently, a three-dimensional (3D), heavily T2weighted sequence (3D CISS, constructive interference in steady state), has been proposed for CSF
fi stula detection (Jayakumar et al. 2001). 3D-CISS,
being heavily T2-weighted with better CSF-brainbone-air contrast, and allowing thinner (sub-millimeter) sections and multiplanar reconstructions,
seems to be ideally suited for the demonstration of
CSF leak (Fig. 7.11). Its very short TE enables a minimization of signal loss from magnetic susceptibility
effects at the air–bone interface. The main advantage
of this sequence is its ability to reduce artifacts from
CSF pulsations. Unfortunately, in CISS sequence fat
tissue appears moderately bright, so that anatomical details at the skull base/CSF interface may be obscured. Jayakumar et al. (2001) reported a sensitivity
of 100% in a series of six patients: larger series have
to be provided to establish the role of this promising
technique.
If both endoscopy and non-invasive imaging are
negative, the fl uorescein test is considered more useful than invasive cisternographic techniques, because
their sensitivity is insuffi cient in patients with inactive leak.
In the case of a positive fl uorescein test, endoscopy
may or may not precisely identify the fi stula, as the
defect can be located beyond diagnostic endoscopy
limits. Microendoscopic surgery with fl uorescein injection is indicated.
A negative fl uorescein test makes the diagnosis of
CSF leak unlikely.
Cerebrospinal Fluid Leak, Meningocele and Meningoencephalocele 103
a b
Fig. 7.10a,b. Traumatic (due to car accident) CSF fi stula. Coronal high resolution CT (a), with reformatted sagittal section (b).
On the left side, the posterior aspect of the fovea ethmoidalis is not visible (arrows): a soft tissue density is clearly demonstrated
(arrowhead) strictly adjacent to the large bone defect
a
c
Fig. 7.11a−e. Small traumatic (due to
car accident) meningocele through the
right cribriform plate. Coronal TSE T2
d
e
the CSF possibly present in the ethmoidal cells from the thickened mucosa and/or sinus secretions. Only the left olfactory bulb
is seen (arrow). b On coronal CISS sequence – 0.7 mm of thickness, obtained at the same level as (a) − the small meningocele
(white arrows) shows the same signal as intracranial CSF, brighter than mucosal thickening. The contralateral olfactory bulb is
demonstrated (black arrow). c−e The CISS sagittal reformatted sections show the small meningocele “neck” (arrows)
(a); coronal (b) and sagittal (c−e) images
from a CISS sequence. a The hyperintense signal of CSF appears to continue
with the hyperintense signal within the
right ethmoid cells, through a presumed
bone defect in the right cribriform plate,
raising the suspicion of a meningocele.
However, it is impossible to distinguish
b
104
L. Pianta et al.
7.6.2
Invasive Imaging Techniques
In the past, several invasive “cisternographic” nuclear
medicine and radiologic techniques have been developed to confi rm and locate the site of CSF leaks. Since
“cisternographic techniques” rely on demonstrating
the passage of some “marked” CSF through the bone/
dural defect, their sensitivity strictly depends on the
amount of CSF crossing the defect at the time of the
examination. Nowadays they are indicated in very
few cases.
Among invasive techniques, radionuclide cis-
ternography has been the fi rst to successfully detect the site of CSF rhinorrhea (Crow et al. 1956).
Unfortunately, most CSF leaks are intermittent, causing its accuracy to reduce from approximately 70%
in patients with active leaks to 28% in patients with
inactive leaks (Eljamel et al. 1994).
CT cisternography has been considered one of
the most reliable techniques in CSF fistula detection, although the rate of positive studies has been
quite variable in large reported series, ranging from
36%–40% in inactive leaks, and up to 81%–92% in
active leaks (Manelfe et al. 1982; Colquhoun
1993; Eljamel et al. 1994). It requires intrathe-
cal injection of contrast agent (usually via lumbar
puncture). A few minutes after contrast agent injection, thin CT slices (1–3 mm) are obtained, with
both soft tissue and bone algorithms, preferably in
the coronal plane (Drayer et al. 1977). Not to miss
any potential CSF leakage site, scans should extend
from the anterior frontal sinus wall to the posterior surface of the petrous bone. In fact, CSF rhinorrhea due to leakage through the petrous bone
into the middle ear and then, via Eustachian tube,
into the nasopharynx – where the CSF may emerge
via the nasal cavity – has been reported (Shetty
et al. 1997). CT cisternography may directly demonstrate the contrast agent passage through bony
and dural defects and/or the pooling of the contrast agent within nasal cavity or paranasal sinuses
(Fig. 7.12).
Positive fi ndings consist of direct demonstration of
contrast agent passage through the bone/dural defect
or of bone defect(s) associated with contrast agent
pooling within ipsilateral sinus. Equivocal fi ndings
entail detection of bone defect(s) and/or the presence
of contrast agent within the ipsilateral nasal pledget.
Negative fi ndings require no extracranial contrast
agent or bone defect demonstrated (Manelfe et al.
1982).
a
Fig. 7.12a,b. Multiple traumatic CSF fi stulae due to fractures of the anterior skull base fl oor. CT cisternography, coronal sec-
tions (a,b). a Contrast agent fl ows from the right frontobasal subarachnoid space into the ethmoid cells through the right fovea
ethmoidalis fracture (black arrows). The superfi cial lining of the mucosa investing nasal structures is hyperdense (arrowheads)
due to layering and absorption of contrast agent leaking from the fi stula. On the left side, a thicker collection of contrast agent
fi lls a cleft in the middle turbinate (white arrow). These fi ndings prompt a careful examination of the CT scan set, looking for
other CSF fi stulae. b A more posterior coronal section discloses a fovea ethmoidalis fracture on the left side (arrows), with leak
of a small amount of contrast agent into the ethmoidal cells
b
Соседние файлы в папке Библиотека им академика М.И. Перельмана