Surgery of Anterior Skull Base Lesions in Children

Introduction

Congenital malformations of the nose and anterior skull base have an incidence of 1:20 000 to 1:40 000 births, thus representing a rare group of craniofacial pathologies. Meningo-(encephalo)celes are rare pathologies with an incidence of 1:3000 to 1:12 500 births.^1,2 Nasal glioma or fistulae, (epi)dermoid cysts, and meningo-(encephalo)celes develop in the third to fifth week of embryology as a result of neurogenic, ectodermal, and/or mesenchymal abnormalities. During the development of the anterior skull base, a temporary protrusion of the dura through the foramen caecum occurs with subsequent retrocession of the dura during obliteration of the foramen. If malformations of the foramen caecum occur, neurogenic pathologies like meningo-(encephalo)celes can emerge in the nasal cavity. Glia cells can also migrate into the prenasal cavity, forming gliomas with connection to the skull base. ³ As another example, ectodermal malformations such as dermoids, epidermoid cysts, and fistulas are typically found in the median or paramedian side of the nose and are caused by involvement of ectodermal structures during the meeting process of single parts of the face. ⁴

Furthermore, aneurysmal bone cysts are rare, highly vascularized formations that can be found in any skeletal part of the human body. When they manifest in the anterior skull base, which is extremely rare, the cyst is more aggressive and destructive than when located at other skeletal locations. It is postulated that aneurysmal bone cysts emerge through a bony trauma, causing an intraosseous arteriovenous shunt leading to local destruction ⁵ and requiring implicitly clear resection margins. ⁶

This article presents a case series of anterior skull base pathologies in children with a range of malformations that were surgically treated in an interdisciplinary setting.

Material and Methods

A retrospective analysis of our electronic patient record database was performed, searching for children with anterior skull base pathologies that were treated in our department. Cases were evaluated concerning the type of trauma, extension of destruction, and surgical procedure. Thirteen patients (8 males, 5 females) aging from 4 months to 12 years (median of 4.3 years) treated for malformations affecting the anterior skull base were retrospectively reviewed (Table 1). All patients underwent a slice imaging technique including magnetic resonance imaging (MRI) scan or computed tomography (CT) scan in the case of the aneurysmal bone cyst.

OPEN IN VIEWER

Table 1.

Clinical Data of All Patients.

Patient	Gender	Age	Pathology	Extension	Approach	Reconstruction	Treatments	Complications	Symptoms
1	M	2 y	Glioma	Intracranial, extradural	Transcutan + transnasal endoscopic	x	1	No	Unilateral nasal obstruction; app.
2	M	10 mo	Meningoencephalocele	Intracranial, intradural	Transcranial + transnasal endoscopic	GAP-CAS	1	No	Unilateral nasal obstruction
3	M	4 y	Fistula + nasal cyst	Intracranial, extradural	Transcutan + transnasal endoscopic	Onlay (Tachosil)	1	No	Secretion; swelling; infection; app.
4	F	5 y	Fistulae (2)	Intracranial, extradural	Transcutan + transnasal endoscopic	x	1	No	Secretion; swelling; infection; app.
5	F	1 y	Fistula	Intracranial, intradural	Transcutan + transnasal endoscopic	Onlay (Tachosil)	1	No	Secretion, cerebrospinal fluid leak; app.
6	M	6 mo	Fistula	Intracranial, intradural	Transcutan + transnasal endoscopic	Onlay (Tachosil)	1	No	Secretion; swelling; infection; app.
7	M	12 y	Fistula	Superficial	Transcutan	x	1	No	App.
8	M	1 y	Nasal cyst	Intracranial, extradural	Transcutan + transnasal endoscopic	x	1	No	Swelling, infection; app.
9	M	4 y	Nasal cyst	Intracranial, extradural	Transcutan + transnasal endoscopic	x	1	No	Swelling; infection; app.
10	M	1 y	Nasal cyst	Superficial	Transcutan	x	1	No	Swelling; infection; app.
11	F	4 mo	Nasal cyst	Intracranial, extradural	Transcutan + transnasal endoscopic	x	1	No	Swelling; app.
12	F	12 y	Nasal cyst	Superficial	Transcutan	x	2	Recurrence	App.
13	F	9 y	Aneurysmal bone cyst	Intracranial, intradural	Transcranial + transnasal endoscopic	GAP-CAS	1	No	Exophthalmus; diplopia

Abbreviation: App., Appearance.

Results

Glioma

A 2-year-old male presented with nasal obstruction of the right side and a right supraalar nasal mass, which was present at birth (Figure 1A). An initial surgical treatment via an endonasal approach was performed elsewhere at the age of 11 months, resulting in the diagnosis of a nasal glioma. The MRI revealed a nasal mass connecting to the falx cerebri (Figure 1B).

OPEN IN VIEWER

Figure 1.

(A) A 2-year-old boy with a nasal glioma of the nasal dorsum. (B) Sagittal magnetic resonance imaging section shows a fine connection to the falx cerebri.

An open septorhinoplasty with resection of the recurrent nasal glioma and reconstruction of the internal part of the nose with a double composite graft harvested from the external ear was performed. The pedicle reaching the falx cerebri was endoscopically resected and the skull base sealed with TachoSil (Takeda, Berlin, Germany).

Meningoencephalocele

Patient 2 was a 10-month-old female who presented with a left unilateral nasal obstruction and the initial diagnosis of a nasal foreign body. Endoscopically, a solid pale mass was detected with complete occlusion of the left nasal cavity. An MRI scan was performed showing a meningoencephalocele penetrating the left anterior skull base and advancing into the nasal cavity (Figures 2A and 2B).

OPEN IN VIEWER

Figure 2.

(A) Sagittal and (B) coronal magnetic resonance image showing a menigoencephalocele with extension to the nasal cavity. (C and D) A craniotomy combined with an endoscopic transnasal approach for tumor removal was performed.

A combined transcranial and transnasal approach was chosen. After resection of the meningoencephalocele, the defect in the left anterior skull base was closed with the GAP-CAS technique using calvarian split bone and a divided galea-periost flap in a sandwich technique with 1 part of the myofascial flap of the galea frontalis torn to the nasal cavity, between the bone graft with the other part of the galea flap on the upper side (Figures 2C and 2D).^7,8

The patient showed an uneventful postoperative recovery and was without recurrence in a 5-year follow-up.

Nasal Fistula

Out of 5 cases with nasal fistulas aged between 6 months and 12 years (3 males, 2 females) at diagnosis, 3 patients presented with a solitary nasal fistula, 1 patient with 2 simultaneous nasal fistulas, and 1 patient with a nasal fistula combined with a cyst. All nasal fistulas were primarily located at the nasal dorsum. In 3 cases, no penetration of the skull base was visible as the nasal fistula ended blindly at the anterior skull base. In 2 cases, the fistula penetrated the skull base with involvement of the dura mater. The complaints of the patients included secretion from the opening of the fistula in 4 cases as well as recurrent swelling and infections in 3 cases. In 1 case, a rhinoliquorrhea was apparent particularly during periods of increased intracranial pressure (eg, during crying). In all cases, the cranial origin of the fistulas could be delineated. In 1 case, the surgical resection was performed via an external approach, while in all other cases the resection was performed via a combined transcutan-endoscopic navigated approach. In 2 cases, a leakage of the dura mater occurred after resection of the fistula. The defect was covered by TachoSil, without necessity of bony reconstruction. Neither major complications nor recurrences developed in any case during a follow-up time of at least 5 years.

As an example, a 4-year-old male with a nasal fistula resulting in a small opening at the tip of the nose (Figure 3A) presented after a few months of recurrent infections with cloudy secretion through the opening without any signs of rhinorrhea, fever, or meningitis. An MRI scan revealed a nasal fistula combined with a nasal cyst connected to the falx cerebri (Figure 3B). An open septorhinoplasty with resection of the fistula and dermoid sinus was performed (Figure 3D). The fistula was located between the bony and cartilage portions of the nose. A paramedian osteotomy was necessary to expose the fistula up to the anterior skull base. Adherence to the dura mater was visible. Under microscopic visualization, separation from the dura mater and subsequent extirpation of the duct were possible (Figure 3C). Although no leakage of the dura was visible, a TachoSil reinforcement of the dura was performed as a precaution. Postoperatively, no deformities of the nasal tip were visible except a discrete scar.

OPEN IN VIEWER

Figure 3.

(A) A nasal fistula on the tip of the nose. (B) The sagittal picture of magnetic resonance image shows a fistula reaching to the falx cerebri. (C) An open septorhinoplasty with resection of the fistula was performed. (D) Endoscopic view on the dura mater after resection of the fistula.

Nasal Cyst/Dermoid

Five patients (3 males, 2 females) in age ranging from 4 months to 12 years presented with recurrent swelling and infections of nasal cysts located between the eyebrows, nasal base, supraorbital region, and the nasal dorsum in 2 cases. One patient had a recurrence after extirpation at the age of 1 year (alio loco). In all cases, MRI was performed to evaluate the extension of the nasal cyst. A connection to the frontal sinus was present in 2 cases, and a connection to the falx cerebri could be demonstrated in a single case. In all cases, an uncomplicated resection for complete removal was performed (in 3 cases transcutaneous-transnasaly, in 2 cases transcutaneous only; see Table 1).

As an example, a 1-year-old male presented with a small dehiscence on the nasal dorsum with excretion of sebaceous material including hairy structures. Recurrent infections were observed, the last one associated with an immense swelling and redness of the forehead (Figure 4A). The MRI scan confirmed the diagnosis of a nasal cyst with connection to the falx cerebri (Figure 4 B). A surgical resection of the cyst via an external approach was performed. The nasal cyst was separated from the frontal bone and the falx cerebri and extirpated. No complications were noticed after surgical treatment (Figure 4C), and no recurrences were visible in the long-term follow-up.

OPEN IN VIEWER

Figure 4.

(A) Infected dermoid sinus on the forehead with an opening on the back of the nose. (B) Magnetic resonance imaging scan in a coronal view: the dermal sinus was visible in the central forehead. (C) Intraoperative external approach and resection of the pathology.

Aneurysmal Bone Cyst

A 9-year-old female presented with a left-sided exophthalmus and beginning diplopia without a previous history of surgery or physical trauma. A CT scan revealed a mass in the left ethmoidal sinus with extension into and destruction of the left lamina papyracea as well as the anterior skull base (Figure 5A). The histological result of the initial endoscopic biopsy was inconclusive. However, due to the progressive growth, a transcranial subtotal resection was performed. Taken together, the histological results and early recurrence led to the final diagnosis of an aneurysmal bone cyst. Consequently, a combined transcranial-transnasal resection was performed (Figure 5B). The integrity of the orbital cavity was maintained, and the anterior skull base defect was covered by the GAP-CAS technique, as described previously.^7-9 There were no postoperative complications regarding vision and orbital mobility.

OPEN IN VIEWER

Figure 5.

(A) Computed tomography scan, coronal view: the aneurysmatic cyst is visible with destruction of the left anterior skull base and lamina papyracea as well as the orbital roof with displacement of the left orbita. (B) Intraoperative view with reconstruction of the anterior skull base by the GAP-CAS technique.^7,8

Regular follow-up was performed in all cases, and a median follow-up time of more than 4 years was reached without detection of recurrence.

Discussion

Unilateral nasal obstruction, meningitis, or rhinoliquorrhea in childhood may be indicative for various pathologies including nasal fistula, dermoids, gliomas, and meningoencephaloceles. Nevertheless, differential diagnosis also needs to consider more common pathologies, such as foreign bodies or ordinary infection. If symptoms persist over time, precise endoscopy and customized imaging technique may be combined to determine diagnosis and extent of the lesion. Congenital pathologies, such as nasal gliomas, can also be diagnosed prenatally by ultrasonic investigation, allowing an adequate preparation for postnatal surgical intervention. ¹⁰ A complete and safe resection of the pathology is mandatory.

Nasal gliomas occur extranasal (60%), intranasal (30%), and combined (10%), showing a male dominance of 3:1. ¹¹ An association with hypertelorism is a common finding. The intranasal appearance is similar to a nasal polyp. Nasal gliomas are benign structures but grow locally aggressive. Imaging is mandatory to demonstrate extension and a potential connection to the anterior skull base. Therapy options include transnasal (endoscopic) and transcranial approaches or a rendezvous treatment. In 10% of cases, a recurrence can occur if the resection was incomplete, as seen in case No. 1. ³

If an intracranial and intradural extension is present, reconstruction of the dura is mandatory for avoiding cerebrospinal fluid (CSF) leakage, meningitis, and brain prolapse. Besides the onlay-technique (avital tissue), this article describes the GAP-CAS (sandwich)-technique (vital tissue).^9,12 The onlay-technique is used for defects with no possibility of an underlay technique (eg, because of high risk of nerve/vessel injuring), which is commonly seen in the region of lamina cribrosa (fila olfactoria) or the sphenoid sinus. ¹³ For leakages with greater extension and with higher complexity, the GAP-CAS technique enables a sufficient closure of the anterior skull base^7,9 and was used in the current series in a case of a meningoencephalocele and an aneurysmal bone cyst.

Meningo(encephalo)celes present as herniations filled with CSF and brain tissue. In 40% of cases, additional malformations like hydrocephalus, brain anomalies, or hyperteleorism are found. Four subtypes of their relation to the anterior skull base are known. Most common are transethmoidalceles, followed by the sphenoethmoidal ones, whereas transsphenoidal and sphenoorbitalceles are rare. In addition, Gerhardt et al ¹⁴ described a fifth subtype, the sphenomaxillar meningonecephaloceles. In frontoethmoidal celes, an extranasal expansion through a defect between the ethmoidal sinus and the frontal bone is possible. The origin of the defect is the crista galli, which can be connected to the orbita, the foramen caecum, or the os nasale.

Symptoms vary depending on the origin. A facial deformity is often the first symptom of extranasal encephaloceles. The intranasal manifestation can cause rhinoliquorrhea, recurrent meningitis, and nasal obstruction. ¹⁵ In the head-down position, as well as during periods of raised intracranial pressure, an enlargement of the structure may occur and has been demonstrated in 1 of our patients (case No. 2). Imaging by CT reliably determines the bone defect of the skull base, ¹⁶ whereas MRI gives information on associated brain abnormalities. ¹⁷ In children, the use of CT should be restricted, and generally, an MRI is sufficient, even in skull base pathologies. A biopsy of the suspected meningo(encephalo)cele is contraindicated. Intranasal encephaloceles are often treated within the first year of life with a combined transcranial and transnasal endoscopic approach, frequently ensuring good results. A sole intranasal approach may be incomplete, thus leading to persistent rhinoliquorrhea and meningitis. ¹⁸ In the presented case, a combined transcranial and transnasal approach was chosen, enabling a complete resection with tight sealing of the skull base using GAP-CAS (sandwich) technique as described earlier.^7,8

Nasal (dermoid) cysts are benign tumors of germ cells and are the most common lesions of the nasal midline. Most of the time, they are located close to the midline of the face and attract attention through recurrent infections, which occurred in all of the presented cases. An erosion of the cartilage or nasal bone is seen during development. ⁴ Nasal cysts are frequently associated with nasal fistulas, as in 1 of 5 presented cases in the current article. Imaging is obligatory to demonstrate the involvement of central structures. ¹⁹ Complete extirpation is necessary to prevent further infections and deformities or even episodes of meningitis with cerebral involvement.^20-22

Aneurysmal bone cysts are benign, vascular, and expansive lesions. An association with fibrous dysplasia, giant cell tumors, or osteoblastoma is described. ²³ Most common locations are the metaphysis of long bones ²³ ; the affection of the skull base is extremely rare.^24,25 The imaging technique of choice is a CT scan demonstrating multiple blood-filled cysts with thin walls. ²⁶ Eventually a CT-angiography can be helpful to detect and evaluate arteriovenous malformations. However, occasionally, as shown in the current case, no definite statement on the nature of the entity is possible even after biopsy taking. Pathogenesis of aneurysmal bone cysts remains unclear. Beside congenital condition, a physical trauma is suggested, causing an intraossal arteriovenous shunt. ⁵ However, there are clear cases without any recognizable traumatic event prior to diagnosis, as shown in the current case. The treatment of choice is complete resection; however, recurrences are frequent. ²² Besides surgical intervention, radiation and embolization might be considered in case of inoperable or recurrent tumors. ²³

Anterior skull base pathologies are rare, challenging, and best managed by an interdisciplinary team. Although the reconstruction techniques in practice are similar to those performed in adults, the developing geometry of the craniofacial skeleton in children provide unique surgical challenges. A systematic approach with an interdisciplinary setting (ENT, neurosurgery) and the right diagnostic imaging modality are critical for an efficient handling of these cases. We would like to propose an algorithm for a systematic approach to skull base lesions in children (Figure 6).

OPEN IN VIEWER

Figure 6.

Systematic approach to children with suspected anterior skull base pathologies, beginning with specific symptoms/complaints and ending with therapeutic procedures. Red marked boxes: multidisciplinary setting required; poss, possible.

Conclusion

Congenital malformations of the anterior skull base have to be considered if space-occupying lesions in the facial midline with (unilateral) nasal obstruction, recurrent meningitis, and/or rhinoliquorrhea occur. A multidisciplinary setting including an (pediatric) ENT and neurosurgeon is of advantage for planning combined transcranial and transnasal endoscopic surgical approaches with the best functional and aesthetic results.