Keywords
frontal sinus - skull base - cerebrospinal fluid leak - gunshot wounds
Introduction
Missile injuries of the anterior skull base usually occur during war or warlike situations;
however, in the United States, > 100 Americans die by suicide on an average day, and
∼ 50 of these suicides involve the use of firearms.[1] The anterior skull base is the most common region of the skull base injured by a
cranial missile. These missile injuries can result in cerebrospinal fluid (CSF) leaks.
Most CSF leaks can be broadly classified into traumatic (most frequent), nontraumatic
(tumors), spontaneous, and iatrogenic.[2] The clinical presentation usually is of unilateral clear rhinorrhea that can be
continuous or persistent. The patient can complain of a saltwater taste sensation;
fewer patients experience a sweet taste sensation. Also, the halo sign (clear ring
surrounding a central bloody spot on gauze) can be present.
High-resolution computer tomography (CT) is a vital diagnostic and planning tool in
patients with cranial and maxillofacial trauma. CT cisternography, radionuclide cisternograms,
magnetic resonance imaging (MRI), β-2 transferrin, and intrathecal fluorescein are
also part of the armament used in the diagnosis of CSF leaks. Some CSF leaks require
surgical treatment. The goals of surgery in patients with gunshot wounds to the head
are to evacuate a hematoma, achieve hemostasis, debride the wound, provide dural closure,
and repair the skull base. We present two cases of patients with CSF leak after gunshot
wound to the skull base.
Case Report
Case 1
A 16-year-old young man with a history of a self-inflicted gunshot wound with point
of entry through the mouth with a 3-cm exit wound on top of the head. He had copious
bleeding from the mouth and nose upon entry. Acute trauma life support protocol was
undertaken. No previous significant past medical history was reported. [Fig. 1] shows the preoperative images.
Fig. 1 (A) Noncontrast axial computed tomography consistent with a gunshot wound with entry
point at the left parasagittal midline hard plate (white arrow). (B) Fracture of the
inner table of both frontal sinuses with multiple fragments within the frontal sinuses
and along the interhemispheric fissure (white arrow). (C) The trajectory coursed cranially
through the left nasal cavity, left ethmoid air cells, left frontal lobe, and exited
through the left frontal bone. (D) Posterior intracranial view shows missile trajectory
entering through the skull base and exiting through the left frontal bone (arrow).
The patient underwent endoscopic reduction and debridement of a frontal sinus encephalocele
and CSF leak repair. An endoscopic modified Lothrop was performed to expose the lesion.
The bone fragments were debrided as well as the brain tissue within the cavity. A
large posterior table defect in the left frontal sinus was noted. The brain tissue
was covered with Duragen (Integra Lifescience Corporation, Plainsboro, New Jersey,
United States). The mucosa of the frontal sinus was removed, and abdominal fat was
packed to obliterate the cavity. A mucosal graft was not feasible due to the location
and extent of the defect.
To date the patient is without any complaints of clear rhinorrhea or a salty taste
sensation. Nasal endoscopy shows a bilateral patent frontal sinus recess with no evidence
of obstruction or drainage. Postoperative MRI shows complete frontal sinus obliteration
([Fig. 2]).
Fig. 2 (A) Sagittal magnetic resonance T1 fluid-attenuated inversion recovery scan shows
postoperative result of frontal sinus obliteration and frontal sinus encephalocele
repair. Bilateral frontal cortical and subcortical encephalomalacia from sequela from
gunshot wound injury (arrow, A and B). (B) Residual pneumatization of the left frontal
sinus (arrowhead, A and B). No evidence of frontal sinus mucocele formation.
Case 2
A 19-year-old female patient presented with a self-inflicted gunshot wound to the
right frontal lobe with right intracerebellar hematoma. Upon arrival, neurosurgeons
performed a first attempt to repair the frontal sinus floor with an inner table of
bone flap. They also used fibrin thrombin glue to seal the frontal skull base floor.
The bullet involved the frontal sinus, the posterior ethmoid, nasal septum, right
sphenoid sinus, and medial pterygoid plate with a major bullet fragment lodged into
the right, at C2-C3 vertebral level, without lesions of the cervical spine. Internal
carotid artery injury was excluded ([Fig. 3]).
Fig. 3 (A) Coronal head computed tomography (CT) shows the skull base fracture (arrow).
(B) Sagittal view of head CT shows bullet entry in the forehead through the anterior
and posterior walls of the right frontal sinus (arrow).
One month after discharge, the patient was complaining of right-sided clear rhinorrhea,
with no salty taste sensation in her mouth. Postfrontal craniectomy CT was done, and
the patient was scheduled for endoscopic CSF leak repair ([Fig. 4]).
Fig. 4 (A) Coronal view of status postfrontal craniectomy. Right anterior ethmoidal air
cells opacification (arrowhead) with fracture of ethmoid sinus roof (arrow). (B) Sagittal
view shows fracture at the ethmoidofrontal junction (arrow).
The surgical procedure was done after 15 mL of CSF was obtained. Then 0.1 mL of preservative-free
10% fluorescein was mixed with 10 mL of CSF and slowly injected intrathecally over
30 minutes. This was followed by slow infusion of 5 mL of pure CSF. Uncinectomy, antrostomy,
anterior and posterior ethmoidectomy, and sphenoidotomy were done. The skull base
was skeletonized working in a posterior to anterior direction. Due to multiple skull
base fractures, image guidance was used continuously. The sites of the CSF leak were
identified at the ethmoid frontal junction anteriorly and in the posterior ethmoidal
cells. Mucosa was dissected off the turbinate bone. Previous harvested abdominal fat
was positioned at the site of the leaks, which resulted in cessation of the fluorescein-identified
leak. Mucosal grafts were placed and positioned over the leak. Both grafts were supported
with Surgicel (Ethicon, Inc., Somerville, New Jersey, United States) followed by DuraSeal
(Confluent Surgical, Inc., Waltham, Massachusetts, United States). NexFoam (Hemostasis,
Saint Paul, Minnesota, United States) were placed to further support the graft, and
two Merocels (Medtronic, Mystic, Connecticut, United States) were placed in the right
nasal cavity. To date there is no evidence of CSF leak.
Discussion
CSF is an ultrafiltrate of plasma produced by the choroid plexus that offers mechanical
and immunologic protection for the brain. CSF leaks occur when the skull and its underlying
dura are ruptured. A CSF rhinorrhea is defined as a fistula between the dura and the
skull base with CSF discharge through the nose.[3] About 70 to 80% of CSF leaks are secondary to trauma and evident within the first
2 days, first week, or within the first 3 months.[2]
[4] Energy deposited along the missile trajectory shatters the bone and lacerates soft
tissues, which makes it difficult to diagnose a CSF leak upon arrival.[5] Also, the surrounding edema associated with the trauma can conceal these leaks momentarily,
so CSF leaks can be revealed after this edema subsides or necrosis of the surrounding
tissues occurs.
The greatest concern with a CSF leak is the potential for meningitis, with a generally
accepted rate of 10%.[6] Approximately 35% of patients with recurrent meningitis have CSF leaks secondary
to trauma.[2] A missile traversing the face creates a communication between air-filled mucus-secreting
cavities and the subarachnoid spaces with wound contamination through the missile
entry point from oropharyngeal commensal staphylococcus, gram-negative or gram-positive
rods.[7] A 2006 Cochrane Review[8] concluded that no evidence indicates that prophylactic antibiotics reduce the risk
of meningitis in patients with skull base fractures with active CSF leak. However,
there are no data to apply this statement to patients with gunshot wounds to the head.
High-resolution CT is vital for the planning and prognosis of patients with a gunshot
wound to the head; it is also the preferred method to localize the site of a skull
base fracture. However, CT cisternography or MRI may be required to diagnose CSF rhinorrhea.
In the presence of a skull base fracture on CT and a clinical CSF leak, there is no
need for a further confirmatory test. In cases where a confirmatory test is needed,
the β-2 transferrin assay is the test of choice because of its high sensitivity and
specificity.[4]
[9]
Intrathecal fluorescein has been used to confirm and intraoperatively localize CSF
leaks.[2]
[4] The recommended dilution is 0.1 mL of 10% intravenous fluorescein in 10 mL of the
patient's own CSF that is infused slowly over 30 minutes. A yellow fluid leaking in
the nose should be visualized in the vicinity of the defect, and the use of a blue-light
filter makes the sensitivity even higher.
Most CSF leaks close spontaneously within 7 to 10 days. Patients with CSF leaks < 7
days have an 11% chance to develop meningitis versus 88% of those lasting > 7 days.
Surgical treatment is indicated when they last > 1 or 2 weeks.[10] Patients with increased intracranial pressure, such as those who experience intracranial
trauma, make hernias at points of weakness; these patients have a less successful
rate of CSF leak closure and more risk of developing meningoencephalocele.[4] Nonetheless, the success rate of surgical closure is ∼95% for CSF leaks associated
with trauma.[11]
In patients with a gunshot wound to the head, neurosurgical intervention is usually
required, so it is reasonable to repair an evident CSF leak. However, when intracranial
trauma is present, the associated significant brain edema makes an early repair likely
to fail because of elevated intracranial pressure.
In agreement with other authors,[12]
[13] we believe the use of a lumbar drain does not provide an additional benefit in the
treatment of CSF leaks associated with gunshot wounds to the head, especially because
of the risk of overdrainage and the resultant pneumoencephalos.
Endoscopic closure of CSF leaks was first described by Wigand in 1981, and to date,
it continues to be the preferred method of CSF leak closure because of its high success
rate (90–97%).[2]
[3]
[4]
[9]
[10]
[14] In cases of trauma, an open approach for repair of these lesions is still favored.
We present two cases where satisfactory endoscopic CSF leak repair was performed after
gunshot wound to the head. The primary goal of the repair is to separate the intracranial
from the extracranial spaces. In the cases presented, an endoscopic repair was favored
to minimize brain manipulation of an already severely injured brain. Cranial base
repair with fat and/or mucosa is utilized in other instances and highly successful.
Absorbable and nonabsorbable packing is routinely used to support the repair. We favor
the use of antistaphylococcal antibiotics in traumatic cases.
Postoperative recommendations are 30 degrees of head elevation, bed rest, stool softeners,
antiemetics, blood pressure management, and recommendations to refrain from sneezing,
nose blowing, coughing, and Valsalva maneuvers. Postoperative follow-up with CT scanning
is helpful.
Conclusion
Endoscopic closure of anterior skull base CSF leaks is now recognized as the treatment
of choice for most CSF leaks. In those cases resulting from firearm injuries, the
role of endoscopy is less clear. Many patients require transcranial procedures to
address intracranial injuries. Treatment should be decided by the severity of neurologic
deterioration throughout the emergency period and the existence or absence of associated
intracranial lesions. The risk of suppurative sequelae in patients with a missile
trajectory though the skull base are high, especially when the sinuses have been compromised,
so the timing for surgery should be decided with great care and with a multidisciplinary
approach. In selected patients in whom the primary concern is the repair of a CSF
leak and there is no need to address intracranial injuries, an endoscopic endonasal
repair can be safe and effective.
