Childs Nerv Syst DOI 10.1007/s00381-006-0114-7
ORIGINAL PAPER
Endoscopic endonasal approaches to anterior skull base defects in pediatric patients Davide Locatelli & Federico Rampa & Ilaria Acchiardi & Maurizio Bignami & Andrea Pistochini & Paolo Castelnuovo
Received: 22 December 2005 # Springer-Verlag 2006
Abstract Introduction We studied 12 pediatric patients with congenital or acquired anterior skull base defects. All subjects underwent surgery owing to progressive symptoms. The endoscopic endonasal approach is a new method in the treatment of this pathology in children. Materials and methods Twelve children had surgery to correct anterior skull base defects: seven patients with a spontaneous anterior basal meningoencephalocele and five with posttraumatic cerebrospinal fluid (CSF) leakage. The defects were repaired using the endoscopic endonasal approach, which combined with the fluorescein diagnostic test, detects the exact location of the skull base defect. Different closure techniques were used to obtain a permanent graft, depending on the type, location, and size of the defect. An intraoperative fluorescein test confirmed the absence of CSF leakage after surgery. Results The follow-up period ranged from 3 to 72 months. Symptoms resolved in all patients after surgery and none of them experienced complications or recurrence of CSF leakage. Postoperative magnetic resonance scans showed
D. Locatelli (*) : F. Rampa : I. Acchiardi Department of Neurosurgery, IRCCS Policlinico S. Matteo, University of Pavia, 27100 Pavia, Italy e-mail:
[email protected] M. Bignami : P. Castelnuovo Department of Otolaryngology, Ospedale di Circolo, University of Insubria, Varese, Italy A. Pistochini Department of Otolaryngology, University of Sassari, Sassari, Italy
that the defect had successfully been repaired in all patients. Discussion The surgical treatment of skull base defects in children reduces life-threatening risks, which include infections, CSF leaks, and enlargement or trauma of the sac. The endoscopic technique minimizes surgical scars and has little impact on brain tissue. The endoscopic endonasal approach to the anterior skull base helps to preserve the physiology of the nose and sinuses and reduces the impact on the still developing splanchnocranium in pediatric patients. It ensures a definitive repair of the defect and requires a very short inpatient period. Keywords Endoscopy . Endonasal surgery . Meningocele . Rhinorrea . Skull base . Congenital defect . Cerebrospinal fluid leaks . Fistula
Introduction Anterior skull base defects in children can be congenital (meningoencephaloceles) or posttraumatic (skull base fractures). Anterior basal meningoencephaloceles are rare, representing 10–20% of all craniospinal dysraphisms [1] with an incidence of 1:5,000 live births, as reported by Suwanwela and Suwanwela [2]. Nasoethmoidal encephaloceles protrude through a defect between the nasal bone and nasal cartilage; the most common symptoms are progressive nasal obstruction with mouth breathing, snoring, and nasal discharge due to the projection of the herniated mass into the nasopharynx [1]. Transsphenoidal encephaloceles are associated with more serious abnormalities of the midline of the brain and sometimes involve vital structures [3, 4]. Posttraumatic cerebrospinal fluid (CSF) leaks in children, with an incidence of 0.2–0.3% of all head traumas in
Childs Nerv Syst Table 1 Symptoms presented by patients with congenital skull base defects Case
Age
Sex
Onset sign
Location of the skull defect
Side
MEP
Previous attempts to repair the CSF leak
FU
1 2 3 4 5 6 7
1 1 3 4 8 14 12
F M M F M F F
Nasal obstruction Nasal obstruction Nasal obstruction Nasal obstruction Recurrent meningitis (four episodes) Recurrent meningitis (three episodes) Recurrent meningitis (four episodes)
Cribriform plate Cribriform plate Cribriform plate Cribriform plate Cribriform plate Ethmoid Sphenoid, pterygoid
Left Left Right Right Left Right Left
Yes Yes Yes Yes Yes Yes Yes
No No No No No No Yes
19 12 38 69 12 30 13
FU Follow-up (months), MEP meningoencephalocele
childhood, are less common than in adults. The greater plasticity of the bone and the incomplete development of the paranasal sinuses mean that the traumatic event can be absorbed. Posttraumatic cerebrospinal fluid leaks occasionally cause intermittent rhinorrhea, and the only symptom may be recurrent episodes of meningitis. Early surgical repair is necessary to avoid the risk of infection and progressive breathing impairment in congenital meningoencephaloceles. We report our results on 12 children with anterior skull base defects, seven with congenital meningoencephaloceles and five with posttraumatic lesions and CSF leaks. All operations were performed using an endonasal endoscopic technique.
Materials and methods We operated on 135 patients with anterior skull base defects between May 1995 and May 2004. Endonasal endoscopic repair was carried out in 121 cases, and a combined intracranial–extracranial approach was used in 14. The present study included 12 children, six males and six females, whose ages ranged from 1 to 18 years (mean age 8 years). Seven children, three males and four females, had a congenital meningoencephalocele, which was clinically revealed by nasal obstruction (four cases) or recurrent meningitis (three cases). The malformation involved the
cribriform plate in five cases, the ethmoid and the sphenoid sinus in one case, respectively (Table 1). Five children, three males and two females, sustained head injury and CSF leakage after being involved in a car accident (three cases), after being kicked by a horse (one case), and after heading a ball (one case). The lesion was confined to the ethmoid in one patient but was multiple in the remaining cases: two children had lesions in the ethmoid and cribriform plate, one in the ethmoid and the sphenoid sinus, and one in the ethmoid and the posterior wall of the frontal sinus. Rhinorrhea was the initial symptom in these children and was associated with headache in one case (Table 2). Two of these patients had previously been treated at other institutions: a 12-year-old girl for a meningoencephalocele in the sphenoid sinus and a 12-year-old boy for posttraumatic CSF leakage. Diagnostic tests included laboratory tests, endoscopic evaluation, computed tomography (CT) and magnetic resonance (MR) imaging studies. Beta-2-transferrin detection in fluid samples collected from the nose was used as a diagnostic test when active rhinorrhea was present [5]. We performed endoscopic endonasal evaluation to visualize CSF leaks or monolateral nasal obstruction, as well as to rule out any other nasal anatomical variations (Fig. 1). Spiral CT, with a bone and high-definition multiplanar reconstruction (MPR) algorithm, was performed with the
Table 2 Symptoms presented by patients with posttraumatic anterior skull base defects Case
Age
Sex
Etiology
Onset sign and symptom
Location of the skull defect
Side
Previous attempts to repair the CSF leak
FU
1 2 3 4 5
4 11 12 18 17
F M M M F
Horse kick Header Car accident Car accident Car accident
Rhinorrhea Rhinorrhea Rhinorrhea Rhinorrhea Rhinorrhea with headache
Ethmoid Ethmoid, cribriform plate Ethmoid, sphenoid sinus Ethmoid, cribriform plate Ethmoid, posterior wall of frontal sinus
Left Left Right Right Left
No No Yes No No
63 71 29 81 14
FU Follow-up (months)
Childs Nerv Syst Fig. 1 a T1 coronal MR study showing a congenital meningoencephalocele in the right nasal fossa, which dislocates the nasal structures. b Endoscopic appearance
patient in a supine position. This provided detailed studies in the axial, coronal, and sagittal planes, which localized the bony defect. CT cisternography was not performed. MRI with 3-mm slices was carried out with T1- and T2weighted sequences and in the fluid attenuated inversion recovery sequence when necessary. Contrast enhancement was used to better define the content of the sac in the event of masses projecting into the nasal cavity. All posttraumatic patients had a preoperative fluorescein test to confirm CSF leakage and, when possible, to pinpoint the lesion, in accordance with Stammberger [6]; we also took CSF samples for laboratory tests. All patients underwent endoscopic endonasal repair of the skull base defect. The surgical procedure was performed under general anesthesia and blood pressure was controlled. After inducing anesthesia, the intrathecal contrast was injected, following Stammberger’s guidelines, before graft placement in the definitive surgical position [6, 7].
All surgery was performed with the patient lying on his back with his head slightly extended and turned to the right, facing the surgeon; head clamps were not used. The child’s face was cleansed and covered with a sterile cloth with a hole for the nose. Tampons soaked with topical anesthetic and vasoconstrictor drugs were inserted into both nostrils using bayonet forceps [8, 9]. The tampons were removed after 5 to 10 min, and local anesthetic drugs were then injected submucosally, under endoscopic vision, to facilitate the detachment of the nasal mucosa from cartilage or bone surface. The direct paraseptal endonasal approach was performed in five patients with a meningoencephalocele in the cribriform plate. In these cases, the middle turbinate had been pushed aside by the protruding mass and was thus conserved. A specific blade was used to separate the mucous membranes of the septal and lateral walls as far as the subperiosteal plane to reach the pedicle of the lesion. The extruding dural wall was dissected from the bone and mucoperichondrium, fully exposing the defect in the bone;
Table 3 Surgical repair of congenital anterior skull base defects Case
Location
MEP
Previous attempts to repair the CSF leak
Graft
Graft material
FU
1
Cribriform plate Cribriform plate Cribriform plate Cribriform plate Cribriform plate Ethmoid
Yes
No
Combined
19
Yes
No
Composite
Dural substitute + cartilage (underlay) and mucoperichondrium (overlay) Septal mucoperiostium + cartilage
Yes
No
Combined
Dural substitute + cartilage + septal mucoperiostium
38
Yes
No
Abdominal fat
69
Yes
No
Free simple Combined
Middle conca bone + dural substitute + mucosa of conche bullosa
12
Yes
No
Combined
30
No
Yes
Combined
Dural substitute + middle conca bone + dural substitute (underlay) and middle turbinate mucoperiostium (overlay) Dural substitute + cartilage (underlay) and mucoperichondrium (overlay)
2 3 4 5 6 7
Sphenoid, pterygoid
FU Follow-up (month)
12
13
Childs Nerv Syst Table 4 Surgical repair of posttraumatic anterior skull base defects Case
Location of the skull defect
Side
Graft
Graft material
Previous attempts to repair the CSF leak
FU
1
Ethmoid
Left
Combined
No
63
2
Ethmoid, cribriform plate Ethmoid, sphenoid sinus Ethmoid, cribriform plate Ethmoid, posterior wall of frontal sinus
Left
Composite
Middle turbinate mucoperiostium + middle conca bone Dural substitute + middle turbinate
No
71
Right
Combined
Middle turbinate + abdominal fat
Yes
29
Right
Combined
Dural substitute + middle turbinate
No
81
Left
Combined
(Obliterative technique) dural substitute, abdominal fat, and turbinate bone in the sphenoid Free simple graft of mucoperiostium from the middle turbinate in the pterygoid
No
14
3 4 5
FU Follow up (months)
the meningeal layer was then opened and the contents of the sac, if judged to be still functional, were replaced inside the skull base using an appropriate spatula. We used a combined graft to repair the defect in four cases and a free simple graft with abdominal fat in one patient (Table 3). An ethmoidectomy was carried out when the defect was localized in the ethmoid or if the defect involved both the cribriform plate and the ethmoid. The mucoperichondrium surrounding the defect was detached, and bipolar forceps were used to reinsert the meningeal protrusion. A combined graft was used in these cases (Table 4). The transethmoidal–pterygoidal–sphenoidal approach was used in one case to correct a meningoencephalocele of the lateral sphenoid sinus. The ethmoidectomy was combined with the excision of the middle turbinate and a wide antrostomy to identify the posterior wall of the mascellar sinus and the pterygoid that was finally drilled out to expose the lateral wall of the sphenoid sinus. An intraoperative fluorescein test confirmed the absence of CSF leakage in all cases. The grafts were then fixed into position with fibrin glue and held in place by hemostatic fibrillary sponges or Vaseline gauzes [10, 11]. Nasal packing was left in place for about 2 days. All patients underwent postoperative endoscopic evaluation and MR imaging 1 month after surgery. The MR test was performed under sedation (depending on the patient’s age), during which endoscopic endonasal evaluation was also performed.
Results Seven children had congenital defects of the anterior skull base. On endoscopic endonasal evaluation, the four
children with monolateral nasal obstruction had a smooth, whitish-gray mass protruding into the nasal cavity. Of the three patients with recurrent meningitis, one had a small pulsating mass in the anterior portion of the olfactory groove, another did not present abnormalities, while the patient who had previously undergone surgery at another hospital had a pulsation in the pterygoid area, which synchronized with his heart beat. The five children with posttraumatic skull base lesions presented with monolateral rhinorrhea. On endoscopic endonasal evaluation, four patients were found to have a normal anatomy, while one patient had a meningoencephalocele. Beta 2 transferrin was tested in all patients with active rhinorrhea; all tested cases were positive. Complete imaging studies were performed in all cases: CT delineated bony structures while MR identified the content of the sac and checked for the presence of other brain abnormalities [12]. An intraoperative fluorescein test allowed us to pinpoint the leak in 11 of the 12 children [9]: endoscopic endonasal exploration was performed on all our patients. The direct paraseptal endonasal approach was used in five patients with a meningoencephalocele in the cribriform plate. An ethmoidectomy was carried out in one patient with a small ethmoidal meningoencephalocele and in five patients with posttraumatic CSF leaks (the defect was confined to the ethmoid in the 4-year-old girl, while the remaining four cases presented multiple defect sites). The transethmoidal– pterygoidal–sphenoidal approach was used in one patient with a meningoencephalocele of the lateral sphenoid sinus. Intraoperative fluorescein tests confirmed that the defect had successfully been repaired in all cases with no CSF leakage. None of our patients developed complications or required repeat surgery.
Childs Nerv Syst Fig. 2 a Preoperative T1 sagittal MR study of a congenital meningoencephalocele. b Postoperative T1 sagittal MR study after endonasal endoscopic repair
Mean hospitalization was about 1 week and mean duration of follow-up was 36 months, with a range of 12 to 72 months. Normal MRI confirmed the total resolution of symptoms (Fig. 2). An outpatient endoscopic endonasal evaluation 1 month after the operation revealed that the skull base defect had fully healed and that nasal mucosa had returned to normal (Fig. 3). Breathing had also normalized.
Discussion The diagnosis and treatment of anterior skull base defects is a challenging problem [8]: the clinical suspicion of meningoencephaloceles in children arises in the event of monolateral nasal obstruction, while rhinorrhea and recurrent meningitis may suggest the presence of CSF leakage. Endonasal evaluation is one of the first diagnostic tests we routinely perform, using 2.7-mm diameter endoscopes with 30° lenses. This procedure is easy to perform during the MRI study and avoids having to resedate patients; it allows us to evaluate the morphology of the nasal cavity and to directly visualize active rhinorrhea or the presence of a pulsating mass projecting into the nose.
Fig. 3 a Endoscopic endonasal repair of a meningoencephalocele. b Outpatient endoscopic evaluation after 3 months
The B2 transferrin dosage in the liquid sample collected from the nose has a sensitivity of 97.7% [13–15]; this test is rapid and requires just few milliliters of liquid [15–17]. One limit of this test is that rhinorrhea must be active, and even in cases of persistent rhinorrhea, it is not always easy to collect the fluid sample, especially from pediatric patients. Nowadays, spiral CT is the best imaging study for localizing skull base defects as it is possible to obtain very thin slices (0.5 mm) with a bone algorithm. The examination is very short so pediatric patients do not have to be anesthetized. High-definition MPR allows for a complete study in the axial, coronal, and sagittal planes in a supine position; cistern CT, with the patients lying face down, is used to localize the CSF leak in children with active rhinorrhea after dye injection. CT evaluation of the nasofrontal region is often difficult in the neonate because the anterior skull base is largely cartilaginous at birth. It is crucial to understand the CT appearance of this region in the normal neonate and infant. CT may be inadequate because small defects can be missed through the partial volume effect, while the detection of a small opening is not necessarily related to a connection between the nasal mass and the intracranial compartment. In difficult cases, acquisition of CT images
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through the defect after intrathecal contrast administration may determine soft tissue continuity with the subarachnoid space; sagittal reconstruction of 1-mm images is optimal [12]. One-millimeter axial and coronal CT is performed. The coronal section has to be perpendicular to the hard palate to show the entire temporal bone and exclude a defect in the tegmen timpani or roof of the mastoid: in fact, CSF flow from the middle ear or the mastoid through the eustachian tube could simulate rhinorrhea. The CT pattern can indicate whether there is a protrusion of cerebral tissue into a meningeal sac or a tumor growing at the base. Highresolution, 3-mm, axial, coronal, and sagittal MRI in T1and T2-weighted sequences is mandatory to formulate a differential diagnosis. MRI is more sensitive than CT in detecting a continuity between the nasal and cranial cavities when there is a lesion with a very narrow neck; the examination is also valuable in differentiating herniated brain from inflammatory nasal masses, nasal gliomas, or nasal dermal sinus cysts [1]. The signal intensity of nasal gliomas is similar to that of both epidermoid tumors and brain tissue; therefore, anatomic factors are more important than signal characteristics in distinguishing between these malformations. Meningoceles have a typical low signal in T1 and a hyperintense signal in T2-weighted sequences. Meningoencephaloceles have a typical brain-like signal of the content in T2 sequences. Negative contrast enhancement (gadolinium DPTA) rules out tumors. During neuroradiological studies, the middle and posterior cerebral fossa are checked to exclude other congenital defects [18]. It is important to avoid any kind of biopsy during this diagnostic phase; in the event of encephaloceles, this manoeuvre could have serious consequences, namely, cerebral injury, infections or rhinorrhea [19, 20]. All outpatients with posttraumatic CSF fistulas had a preoperative fluorescein test: the fluorescein dyes the cerebrospinal fluid, which becomes directly visible through the endoscope, identifying the exact site of the leak. Identification is aided by the use of a blue optical filter system introduced into the light source for the endoscopic equipment [9]. The fluorescein test was unsuccessful in only one child with associated spinal trauma that may have limited the normal diffusion of the dye. The fluorescein test is essential to localize multiple CSF leaks. If the test is positive, then surgery is mandatory. The intraoperative fluorescein test was performed on all our patients, allowing us to visualize the exact site of the CSF rhinorrhea. No complications arose after injecting the dy,e and the test appeared to be safe if performed following the Graz school guidelines [7]. The direct paraseptal approach is performed in the event of a meningoencephalocele in the olfactory groove that lateralizes the middle turbinate; no other surgical procedure on the ethmoid is carried out in these cases. In fact, if the
space on the cribriform plate is large enough to position the graft, the middle turbinate is preserved and an autologous graft is harvested from the nasal septum. The first step in this surgical procedure is to reach and isolate the pedicle. We found that a small neck is easier to repair not only because of its size but also because the sac does not allow important parts of the overlying central structures to herniate. It is important to identify the correct layer to separate the dura from the bone and perform the anatomical dissection. The dura is often tightly adherent to the underlying mucosa. The dura mater must be detached thoroughly from the surrounding bone to fix the graft and prevent recurrences during the child’s growth. The intradural detachment of cerebral tissue adherence is obtained, and a dural substitute is positioned using the underlay technique under the bone (intracranially) and over the dura. Thanks to the submucous access, the endoscope makes it possible to dissect scarring tissue smoothly, minimizing impact on the brain and conserving nasal and sinus mucosa. An ethmoidectomy, with the excision of the middle turbinate, is performed when the ethmoidal roof has to be fully exposed to localize the CSF leak. This method is used mainly to repair posttraumatic CSF leaks. Traumatic CSF leaks involve multiple defect sites and the entrapment of the dura mater in the rim of the fracture. In these cases, the intraoperative fluorescein test is valuable to localize all the defects, and the ethmoidal roof has to be drilled with a diamond burr to completely expose the leak. The middle turbinate is generally excised and used to harvest the bone or the mucoperichondrial graft. The tear in the dura mater is fully exposed, and all mucosa must be carefully removed from the surrounding bone to fix the mucoperiosteum or mucoperichondrial graft (free simple graft) over the bone (overlay technique) and to prevent recurrences during the child’s growth. The transethmoidal–pterygoidal–sphenoidal approach is used for defects in the lateral wall of the sphenoid sinus. We used this approach in one patient, who had previously undergone surgery at another hospital, to remove a left parasphenoidal CSF cyst, position a subdural–peritoneal drain, and carry out extracranial plastic repair of the skull base of the middle fossa. Two CSF leaks were detected after the pterygoid and anterior wall of the sphenoid sinus had been fully exposed: one in the paralateral left side of the sphenoid sinus, probably because the original graft onto the skull base of the middle fossa had shrunk, and one in the pterygoid due to abnormal pneumatization. After drilling the bone to expose the two defects, the leak in the sphenoid sinus was repaired with a dural substitute, abdominal fat, and turbinate bone, while the leak in the pterygoid was repaired with a free simple graft of mucoperiostium from the middle turbinate. We believe that the choice of graft is essential for a successful duraplasty. We generally use an autologous graft
Childs Nerv Syst
harvested from the nose to achieve a highly compatible duraplasty. The mucoperiostium, from the middle turbinate, and the mucoperichondrium, from the nasal septum, are fashioned and positioned to fit the defect. Particular care must be taken when implanting the graft: the mucosal part to the nasal cavity and the periosteum to the skull base. It is crucial not to obstruct the natural ostia of the paranasal sinuses so as to respect and preserve normal sinus function. Harvesting the graft from the nose avoids incising the abdomen to obtain abdominal fat. If the area in the olfactory groove is wide enough to position the graft, as in children with a meningoencephalocele in the cribriform plate that pushes the middle turbinate to one side, the middle turbinate is preserved. The graft taken from the nasal septum is then positioned with the underlay technique, and the mucoperichondrium is used as overlay. Different nasal tissues and other autologous tissue can be used to close the skull base in particular situations [7, 21, 22]. We fixed the grafts with fibrin glue and hemostatic sponges and did not observe any cases of graft displacement. The absence of fluorescein flow through the graft during the endoscopic test, using the Valsalva maneuver, reassures the surgeon that the fistula was effectively repaired. The main alternative to the endoscopic endonasal technique is the transcranial approach. A transcranial approach through a unilateral or bicoronal bone flap allows the neck of the protruding brain tissue to be isolated but requires a wider exposure with the retraction of one or both frontal lobes. The intracranial repositioning of the extruded tissue is difficult, and the repair of the dural defect requires a larger graft. It is also difficult to control the entire skull base defect without visualizing it directly. If an endonasal approach is not used, the meningocele sac has to be left in place, possibly causing breathing impairment and requiring a second surgical procedure. The limits of the extracranial endoscopic endonasal approach depend on the characteristics of the endoscope: loss of the third dimension in the surgical field and a long learning curve. Failure of an endoscopic approach may relate to the inability to successfully localize the defect, inadequate preparation of the defect area for the graft placement, the nature and amount of CSF leakage, the nature and size of the graft, as well as graft displacement or incomplete apposition of the graft to the skull base [23, 24]. The extension of the lesions can also be a limit for this approach: fractures extending cranially or laterally out of endoscopic view require a combined approach. A necrotic or fibrotic meningoencephalocele or a large CSF-filled sac may both be treated endoscopically: in the latter case by draining and reducing the dimension of the sac and by debriding the sac with its nonfunctional content in the former. Large hernias with facial deformities require combined transcranial endonasal approaches.
The goal of the endoscopic transnasal technique in pediatric patients with a transethmoidal defect is to ensure a stable duraplasty with minimally invasive surgery, avoiding craniotomy. This less invasive technique is well-tolerated by the child as clinical recovery is rapid and it requires only a short stay in hospital. Outpatient endoscopic evaluation, carried out 1 month after the surgical procedure, usually demonstrates that nasal mucosa has returned to normal without scars. In conclusion, in children, the endoscopic endonasal approach achieves the definitive repair of an anterior skull base defect and preserves the normal function of the nose and air sinuses with a very short inpatient period. It also reduces the impact on the still-developing splanchnocranium.
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