Summary
Sinonasal tract and the skull base lesions in the pediatric population are rare and include a wide range of pathologies that originate from mesenchymal, neural, notochordal, vascular, and rarely, epithelial tissue. Although mostly benign, these lesions can grow to exert a mass effect and cause significant morbidity, thus requiring excision in most cases. Surgery of benign lesions in pediatric patients should be with maximal preservation of normal anatomy and critical neurological, neurovascular, and endocrine structures. Thus, endoscopic endonasal approach (EEA) is the optimal modality of treatment for sinonasal and skull base lesions in the pediatric population due to its minimally invasive nature. This chapter focuses on the endoscopic management of benign sinonasal and skull base lesions in children, and reviews the considerations unique to the pediatric population, the principal benign pathologies, the structure of the preoperative evaluation, and surgical techniques.
26 Endoscopic Sinus Surgery in Children for Benign Lesions
26.1 Introduction
Surgery of the sinonasal tract and skull base is a challenging task at any age. The skull base and the paranasal sinuses are characterized by a small and intricate anatomy situated in proximity to critical neurological and vascular structures. The challenge in accessing pathologic processes in these locations is even more pronounced in the pediatric population.
Once dominated solely by open approaches, 1 , 2 the modern field of sinonasal and skull base surgery is rapidly incorporating endoscopic techniques. Over the past decades, the role of the EEA has been constantly expanding to encompass a broader range of pathologies, pushing the limits of endonasal access toward more distant skull base locations in the coronal and sagittal planes. Although EEA was initially employed for adult sinonasal and skull base surgery, it has been adapted over time for use in pediatric patients as well, and its feasibility and safety in children have been established. 3 , 4 , 5 Furthermore, EEA is particularly advantageous in pediatric patients due to its minimally invasive nature compared to open approaches, providing direct access and optimal visualization without neural or vascular manipulation, thereby limiting the therapeutic sequelae of cosmetic deformity and functional deficiencies.
Pediatric lesions of the sinonasal tract and the skull base are rare and include a wide range of pathologies that originate from mesenchymal, neural, notochordal, vascular, and rarely, epithelial tissue. Although mostly benign, these lesions can grow to exert a mass effect and cause significant morbidity, thus requiring excision in most cases. In addition, pediatric skull base lesions commonly occur in the midline, making EEA the optimal modality of treatment.
This chapter focuses on the endoscopic management of benign sinonasal and skull base lesions in children, and reviews the considerations unique to the pediatric population, the principal benign pathologies, the structure of the preoperative evaluation, and surgical techniques.
26.2 Limitations and Special Considerations
The general principles of endonasal endoscopic surgery in the pediatric population correspond to those of adults; however, some critically important differences must be carefully considered. Since the sinonasal and skull base anatomy in children is dynamic, the surgeon encounters diverse stages of development, depending on the age of the patient. Furthermore, sinonasal and skull base lesions, especially those that are congenital, may distort the normal developing anatomy. An understanding of the surgical anatomy is imperative for safe surgical planning.
The age-dependent development and pneumatization patterns of the paranasal sinuses are critical issues to consider in EEA in children. Both the ethmoid and maxillary sinuses are present at birth. The maxillary sinuses expand between ages 0–3 and 6–12 years, and reach full adult size around age 18 years (▶ Fig. 26.1a). The ethmoid sinuses progressively develop in an anterior-to-posterior fashion until approximately age 12 years. The frontal sinus begins its development last, and becomes radiographically evident during the third year of life. It reaches the frontal bone only at age 5 years, and continues to expand throughout adulthood (▶ Fig. 26.1b). The sphenoid sinus is a structure of primary importance in endoscopic skull base surgery. It begins pneumatization at its anteroinferior aspect after age 2 years, and slowly proceeds posteriorly and superiorly throughout the first 10 to 15 years of life to aerate the sellae last (▶ Fig. 26.1c). The sphenoid anterior wall is fully pneumatized at age 6 to 7 years, but the clivus begins pneumatization after age 10 years. 6
Another potential limiting factor in endoscopic approaches in pediatric patients is the size of the pyriform aperture, which is significantly smaller in children under age 7 years compared with adults. However, it is considered to be an anatomic constraint only in the youngest patients (i.e., under 2 years old). 7 The intercarotid distance is an anatomic parameter that also must be considered, especially in cases of a non-pneumatized sphenoid sinus. It is known to be significantly narrower at the level of the cavernous sinus in patients up to 6 to 7 years old compared with adults, whereas at the level of the superior clivus no significant difference between children and adults was found. 7 The extent of the sphenoid sinus pneumatization, the size of the pyriform aperture, and the intercarotid distance limitations do not pose a contraindication for EEA in children, and can be safely overcome by an experienced team and with the use of an intraoperative navigation system.
Craniofacial growth is another aspect unique to sinonasal and skull base surgery in the pediatric population. 8 Ossification of the skull base occurs throughout the first two decades of life, concluding with the fusion of the spheno-occipital synchondrosis, one of the primary skull base growth centers, between ages 12 and 16 years. 9 Disruption of the craniofacial growth center or tooth buds can have a long-term impact on subsequent development and may result in facial asymmetry and injury to permanent dentition. In contrast to traditional external approaches, EEA is believed to minimize the effect of surgery on facial growth, although long-term data are still lacking. Therefore, it is mostly recommended to preserve the normal anatomy as much as possible, especially in cases of benign lesions.
26.3 Preoperative Evaluation
A multidisciplinary collaborative team consisting of otolaryngologists, maxillofacial surgeons, neurosurgeons, pediatricians, and radiologists is required for the evaluation and treatment planning in any type of skull base lesion in children. An ophthalmologic evaluation is also necessary whenever the lesion is in proximity to the orbit or the optic nerve. However, a smaller team may be sufficient for purely intranasal benign lesions.
The clinical presentation of sinonasal and skull base lesions varies for each lesion and is dependent upon its location, extent, and compression on adjacent structures. Some lesions may present at birth, whereas others present later during childhood or adolescence. Clinical manifestations of sinonasal lesions include nasal obstruction, respiratory distress, rhinorrhea, or epistaxis. Lesions with skull base and intracranial involvement may present with a visible mass or facial deformity, headaches, visual disturbances, cranial nerve palsy, focal neurological deficiencies, seizures, and endocrinopathy if the sellar region is involved. Skull base defects with respiratory mucosa and intracranial communication may lead to recurrent meningitis.
A complete history, including the onset and progression of symptoms, is essential. The physical examination should include a thorough head and neck exam and a neurologic function assessment, although it can be challenging in young children due to their inability to cooperate. Nasal endoscopy is an essential part of the physical examination, but it may be limited in small children.
Preoperative imaging should consist of both computed tomography (CT) and magnetic resonance imaging (MRI) to provide complementary information critical for diagnosis, assessment of the lesion extent, and surgical planning. CT demonstrates bone anatomy, sinus size, and degree of pneumatization, whereas MRI better demonstrates the characteristics of the lesion and the surrounding soft tissue. Pediatric patients often require sedation during the MRI scan in order to obtain adequate images. A fine-cut CT angiography allows evaluation of the vasculature within and adjacent to the lesion, and it is used for intraoperative surgical navigation, often merged with MRI scan. The lack of sinus pneumatization in smaller children conceals the usual intraoperative anatomical landmarks, thus increasing the dependence on a navigation system. Angiography may be used for evaluation and preoperative embolization of highly vascular lesions.
A biopsy from the lesion should be considered only after a comprehensive review of imaging findings, and involved risks, such as bleeding from vascular lesions, or CSF leak and intracranial infection in cases of intracranial connection, must be evaluated beforehand. Some lesions do not require a biopsy and can be correctly diagnosed by imaging and clinical examinations. If a tissue diagnosis is indicated, the procedure should be done in the operating room.
26.4 Congenital Midline Lesions
Congenital midline nasal masses are rare benign lesions. Approximately 60% of them are dermoid cysts, while the others are gliomas or encephaloceles. Encephaloceles are discussed in Chapter 33.
26.4.1 Nasal Dermoid Cyst
Nasal dermoid cyst is the most common midline congenital nasal lesion. It is a benign tumor composed of ectoderm and mesoderm, and comprises approximately 4 to 12% of all head and neck dermoid cysts. 10 Nasal dermoid cysts usually presents at birth or in early childhood as a midline mass that may be located anywhere from the base of the columella, along the nasal dorsum, to the nasoglabellar region (▶ Fig. 26.2). It may cause a cosmetic deformity of the nose, resulting in nasal broadening that often appears similar to hypertelorism.
Dermoid cyst is a noncompressible and nonpulsatile mass that does not transilluminate. It does not enlarge when the patient cries, and it has a negative Furstenberg sign (no enlargement with compression of the jugular veins). Nasal dermoid cyst can present with a cutaneous pit that secretes sebaceous material and may become intermittently infected (▶ Fig. 26.3). Hair protruding through a cutaneous pit over the nasal dorsum is pathognomonic for a nasal dermoid cyst.
Intracranial extension through the anterior skull base is reported to occur in 5% to 45% of the cases, and it is usually located at the foramen cecum or crista galli. 11 Although the great majority remains extradural, intradural extensions with involvement of brain parenchyma have also been reported.
MRI and CT studies provide complementary information and both contribute in making the diagnosis, determining the extent of the lesion and planning the surgery. Since dermoid cyst is a nonenhancing lesion, it can be distinguished from the enhancing nasal mucosa and other lesions, such as teratomas and hemangiomas, with the use of contrast material. The demonstration of a bifid crista galli and enlarged foramen cecum on a CT scan is suggestive of intracranial involvement (▶ Fig. 26.4); however, these findings are not pathognomonic. MRI is preferred in delineating soft tissue and determining whether there is intracranial extension. 12 Complete surgical resection is imperative since recurrence rates of 50 to 100% are reported when the cyst or its sinus tract have not been completely resected. 13
26.4.2 Glioma
Nasal glioma is a benign congenital lesion of the craniofacial region composed of heterotropic mature neuroglial tissue. It is believed to be derived from either a nasal encephalocele which has lost its intracranial connection or from entrapped neuroectodermal tissue after the closure of the skull base. Nasal gliomas are present at birth, but may be identified only later in life, depending upon their size and location. Gliomas may manifest extranasally (60%), intranasally (30%), or both (10%). 14 Extranasal gliomas are typically located in the region of the glabella, but they can also extend down to the nasal tip. Intranasal gliomas are most frequently located in the nasal cavity, but they have been found in other locations, such as the nasopharynx and the pterygopalatine fossa. Within the nasal cavity, they usually arise from the lateral wall adjacent to the middle turbinate, and less frequently from the nasal septum. 15 Intranasal gliomas may present with nasal obstruction and respiratory distress. Nasal gliomas are firm, noncompressible masses, and, in contrast to encephaloceles, they are nonpulsatile, they do not expand with crying or straining, and they are negative on the Furstenberg test.
Nasal gliomas have a fibrous stalk extending toward the base of skull with an underlying bony defect in 10 to 25% of cases. MRI is used to evaluate whether there is an intracranial connection. Surgical excision should be performed as early as possible to minimize the risks of complications, such as distortion of the nasal anatomy. Total resection that includes the stalk is imperative not only to decrease recurrence rates (4–10%), but also to minimize the risks of CSF leak and subsequent meningitis. 16 Extranasal gliomas are usually managed by external approaches, while intranasal gliomas are increasingly managed by transnasal endoscopic approach.
26.5 Middle Skull Base Lesions
26.5.1 Pituitary Adenoma
Pituitary adenomas are relatively rare in the pediatric population, representing 3% of all intracranial neoplasms in children. In comparison to adults, pituitary adenomas in children are more predominantly functional, with prolactinomas being the most frequent adenoma subtype, followed by adrenocorticotropin hormone (ACTH)- and growth hormone (GH)-secreting adenomas. Other secreting adenoma subtypes and nonfunctioning adenomas are much less common, and account for only 3 to 6% of all pituitary tumors in children. 17
Clinical manifestations are usually related to the hormone secreted by the functioning adenoma. Prolactinomas mostly present during puberty with amenorrhea, and less commonly with growth arrest, delayed puberty, or galactorrhea in males. ACTH-secreting adenomas usually present at the onset of puberty, and may manifest as growth arrest, Cushingoid appearance, weight gain, hypertension, hyperglycemia, and psychiatric changes. GH-secreting tumors often present in prepubertal children and infants with precipitous growth, acromegaly, or headaches. Symptoms related to a mass effect, such as visual disturbances and focal neurologic signs, may also be present; however, they are more typical of nonfunctioning macroadenomas that dominate adult disease. 18
Surgical resection is indicated for most pituitary adenomas, with the goals of surgery being total resection with preservation of endocrine and CNS function. Prolactinoma can be managed medically.
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