Key-words:
Arachnoid cyst - cerebral spinal fluid leak - meningocele - skull base defect - spontaneous
rhinorrhea
Introduction
Cerebrospinal fluid (CSF) rhinorrhea is a well-documented phenomenon, with most cases
being attributable to causes such as trauma, neoplasms, postsurgical complications,
and congenital defects. Spontaneous CSF leaks are uncommon and the least understood
of these etiologies.[[1]] Spontaneous CSF rhinorrhea occurs with comorbidities such as obesity, middle- to
older-aged individuals, and increased intracranial pressures, and it is found to be
more common in females.[[2]] Frequently misdiagnosed by primary care as allergic rhinitis, literature reports
failure to treat this rare cause of CSF rhinorrhea, can increase the risk of meningitis
from 10% to 32%.[[3]] Present treatment options include transnasal endoscopic approaches but are limited
by the location of the defect, accessibility, and experience of the treating surgical
team. Open skull-based approaches are reserved for more complex defects and locations.[[4]],[[5]]
Case Report
A 57-year-old woman presented to her primary care physician with a 2–3-year history
of rhinitis, intermittent clear discharge, a chronic nonproductive cough, and recent
pneumonia. In recent few months, her cough had significantly worsened, she could not
sleep supine as this aggravated her symptoms, and more recently, while sitting, she
could feel clear drops running down her throat and spontaneously emerging from her
left nostril. She had a history of worsening headaches in the past 4 weeks and was
referred to the otolaryngologist for the evaluation of chronic allergic rhinosinusitis.
The patient underwent a nasal endoscopic evaluation and a left-sided lateral skull
base defect appeared to be the location of the CSF leak. Subsequent referral to neurosurgery
for evaluation and definitive surgical treatment was done, with meningitis workup
being negative. Further imaging included computed tomographic (CT) scan that revealed
an osseous defect between the roof of the left sphenoid sinus and the floor of the
left middle cranial fossa, immediately adjacent to the foramen rotundum [[Figure 1]]a, [[Figure 1]]b, [[Figure 1]]c. Magnetic resonance imaging ((MRI) revealed fluid buildup in the left sphenoid
sinus [[Figure 2]]a, [[Figure 2]]b, [[Figure 2]]c. The elevated risk of meningitis and worsening symptoms and signs required expedient
surgical intervention. Given the lateral location of the defect, we favored a left
anterior lateral skull base approach with an orbito-zygomatic osteotomy rather than
an endoscopic approach.
Figure 1: (a) Coronal unenhanced computed tomography image of the face demonstrating an osseous
defect within the roof of the left sphenoid sinus (red arrow) lateral to foramen rotundum
(blue arrow). Note the dehiscence of the inferior margin of foramen rotundum. (b)
Sagittal unenhanced computed tomography image of the face demonstrating an osseous
defect within the roof of the left sphenoid sinus (red arrow). (c) Axial unenhanced
computed tomography image of the face demonstrating an osseous defect within the floor
of the left middle cranial fossa (red arrow) adjacent to foramen rotundum (blue arrow).
Note the opacification of the left sphenoid sinus
Figure 2: (a) Coronal T1 FS image with gadolinium demonstrating fluid-filled structure (red
arrow) extending from the left middle cranial fossa into the left sphenoid sinus.
This was confirmed to be a meningocele during surgery. (b) Coronal T2 fat saturated
image demonstrating fluid extending from the floor of the left middle cranial fossa
into the left sphenoid sinus (red arrow). (c) Axial T2-weighted magnetic resonance
imaging at the level of the floor of the middle cranial fossa demonstrating fluid
within the left sphenoid sinus. Note the left trigeminal V2 branch within foramen
Rotundum (red arrow)
The vascularized pericranium was preserved along with the temporalis, and pericranium
used as a pedicle flap to cover the defect.[[6]] The foramen rotundum and the V2 component of the trigeminal nerve were identified,
with the defect being contiguous with them. The osseous defect demonstrated infiltration
of meningocele into the sphenoid sinus [[Figure 3]]a, which was later confirmed during the surgery. The nerve was visibly stretched
out and under tension with and overlying arachnoid cyst that was causing bowing and
displacement of the nerve [[Figure 3]]b. Two additional defects within the dura were visualized and the arachnoid meningocele
was observed to be contiguous with the sleeve of the trigeminal nerve. The arachnoid
cyst was incised, with CSF drainage followed by nerve decompression [[Figure 3]]c. The arachnoid cyst was resected under the microscope with a band of dura seen
across the foramen rotundum. A 2 cm × 2 cm Duragen with a slit in the center was created
and placed with the trigeminal nerve within the slit and then using the Duragen to
circumferentially cover the opening of the dura and trigeminal nerve as well as the
small punctate openings that were nearby. CSF flow appeared to decrease significantly.
Fibrin glue was then used over this to get better hemostasis and a watertight CSF
seal. The vascularized pericranial flap was then rotated and used to cover the anterior
lateral middle fossa, including the foramen rotundum and defect. The pericranium was
held in place with sutures and fibrin glue [[Figure 3]]d. We inserted a lumbar drain for 48 h allowing CSF diversion and healing of the
defect. The patient was mobilized within the first 24 h with complete cessation of
the leak.
Figure 3: (a) Left middle fossa zygomatic approach. Extradural dynamic retraction of the anterior
middle fossa exposing the V2 nerve under tension existing through the foramen rotundum.
(b) Mobilization of the V2 nerve exposing the meningocele exiting through the foramen
rotundum into the sphenoid sinus. (c) Following the resection of the meningocele,
the V2 nerve is decompressed, and the enlarged foramen rotundum and dural deficit
are visualized. (d) After direct repair of the dura deficit, a vascularized pericranial
flap was rotated along the floor of the middle fossa
Discussion
There have been numerous papers demonstrating the common and unique etiologies of
CSF rhinorrhea, revealing most of these cases demonstrate brain herniation (82%),
arachnoid pits (63%), extensive pneumatization of the sphenoid sinus (91%), and an
empty sella (63%).[[7]] The most common anatomical locations for CSF leaks have been those with the thinnest
bone segments, namely the cribriform plate, tegmen, the ethmoidalis, and the sphenoid
sinus.[[5]],[[7]],[[8]] The most commonly documented osseous defect is through the lateral sphenoid sinus,
specifically through the Sternberg canal.[[9]] In fact, this report is the only documented occurrence of a meningocele protrusion
involving the foramen rotundum and maxillary nerve. The most common defect in the
sphenoid sinus is commonly associated with a compromised lateral pterygoid recess.
The diagnosis of spontaneous CSF leaks is clinical, with radiological investigations
to confirm the location and plan intervention. Radiological imaging using MRI and
CT help identify the anatomical location of the defect.
Various mechanisms leading to CSF leaks have been reported from blunt trauma to congenital
defects, and the speculative hypothesis of a ruptured arachnoid diverticulum within
the middle cranial fossa.[[10]] Elevated intracranial pressure is thought to lead to impaired CSF reabsorption
at arachnoid granulations, resulting in the development of arachnoid villi in locations
with little venous drainage, specifically, in the middle cranial fossa.[[11]] While the exact etiology in the case of our patient may be impossible to determine,
the presence of such arachnoid granulations may be the cause, supported by the intraoperative
identification of an arachnoid cyst at the site of the defect.
Regardless of the etiology, the surgical approach to repair skull base defects varies
by surgeon preferences and the anatomical challenges that are unique in each case.
High success rates have been reported utilizing endoscopic approaches (95%) along
with bone grafts in osseous defect restoration.[[5]],[[12]],[[13]] Alternatively, success is evident with the use of ventriculoperitoneal shunts to
divert CSF flow.[[14]] Transcranial skull-based approaches are advantageous in the ability to directly
visualize the intradural and extradural osseous defect, with the increased invasiveness,
possibly resulting in greater morbidity and longer hospital stay.[[4]] Given that spontaneous CSF leaks have the highest recurrence rate of any other
etiology, the best procedure for any case will likely depend on specific challenges
vary on a case-by-case basis.[[15]]
Conclusion
We report a case of spontaneous CSF rhinorrhea secondary to a congenital sphenoid
osseous defect involving the foramen rotundum and maxillary nerve, treated through
a direct open skull base approach with complete resolution. To the best of our knowledge,
this is the first documented case of this rare osseous defect and its direct treatment.
Patient consent
The patient/next of kin/guardian has consented to the submission of the case report
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Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms.
In the form, the patient has given her consent for her images and other clinical information
to be reported in the journal. The patient understands that name and initials will
not be published and due efforts will be made to conceal identity, but anonymity cannot
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