Congenital and Acquired Malformations of the Nose and Nasopharynx

Encephaloceles

An encephalocele is an extracranial herniation of cranial contents through a defect in the skull. When the encephalocele includes meninges only, it is termed a meningocele; if it includes both brain and meninges, it is termed a meningoencephalocele. Estimates of the incidence of these lesions vary considerably, ranging from 1 in 3000 to 1 in 30,000 live births in North America and Europe. The incidence in Asian populations is higher, with a reported incidence of 1 in 6000 live births. Encephaloceles have no familial tendency or gender predilection. Approximately 40% of affected patients have other associated anomalies.

Encephaloceles are divided into occipital, sincipital, and basal types ( Tables 5.1 and 5.2 ). Occipital encephaloceles are not discussed in this chapter because they occur outside the nose. Sincipital encephaloceles account for 25% of all encephaloceles and are further classified according to their location (see Table 5.1 ). Nasofrontal encephaloceles manifest as glabellar masses, causing telecanthus and inferior displacement of the nasal bones. Nasoethmoidal lesions manifest as dorsal nasal masses, causing superior displacement of the nasal bones and inferior displacement of the alar cartilages. Naso-orbital lesions manifest as orbital masses, causing proptosis and visual changes. Basal encephaloceles are less common, arising between the cribriform plate and the superior orbital fissure or posterior clinoid fissure. These manifest as intranasal masses ( Fig. 5.3 ) and may not present until later in childhood, when nasal obstruction and drainage ensues. Sincipital and basal encephaloceles appear as pulsatile bluish compressible lesions that transilluminate. Classically, these lesions expand with crying, straining, or compression of the jugular veins.

On histopathologic analysis, sincipital and basal encephaloceles have a glial component, with astrocytes surrounded by collagen, submucosal glands, and sometimes nasal septal cartilage or calcification. Although it may be difficult to differentiate between gliomas and encephaloceles, the presence of ependymal tissue is diagnostic of an encephalocele.

High-resolution computed tomography (CT) or magnetic resonance imaging (MRI) delineates encephaloceles and additionally helps to exclude associated anomalies such as agenesis of the corpus callosum and hydrocephalus. CT outlines the bony cartilaginous defect, whereas MRI provides complementary information regarding the soft tissue characteristics of the mass ( Fig. 5.4 ). MRI also differentiates meningoceles from meningoencephaloceles. Sagittal reconstructions and contrast enhancement are particularly advantageous for identifying an intracranial connection.

Once the diagnosis has been made, the management of encephalocele is surgical. Most authorities advocate intervention in the first few months of life to minimize the risk of meningitis and cosmetic deformity. As the intracranial connection is easier to identify in young patients, complete repair of the dural defect is easier to achieve. Prophylactic antibiotics are not necessary to prevent meningitis for patients awaiting surgery, as they are ineffective. Small lesions with minimal skull base defects may be managed endoscopically. Larger lesions require a combined approach with a craniotomy to resect condemned dura and cerebral tissue with concomitant endoscopic removal of the residual nasal tumor. The skull base defect can then be reconstructed using a pericranial flap or split-thickness calvarial bone graft. The most commonly encountered postoperative complications are cerebrospinal fluid (CSF) leak, meningitis, and hydrocephalus. Postoperative neurologic function should reflect the patient’s preoperative performance. Encephalocele recurrence rates of 4% to 10% have been reported.

Gliomas

Gliomas consist of heterotopic glial tissue that lacks a patent CSF communication to the subarachnoid space; however, 5% to 20% of gliomas maintain a fibrous affiliation (see Fig. 5.1 ). Nasal gliomas are rare benign masses that may be extranasal (60%), intranasal (30%), or combined (10%). They occur more commonly in males than females in a ratio of 3:2. Extranasal gliomas are smooth, firm, noncompressible masses that occur most commonly at the glabella, although they may arise along the side of the nose or the nasomaxillary suture line. Intranasal gliomas are pale polypoid masses that may protrude from the nostril. The nasal fossa on the involved side may be obstructed. Intranasal gliomas most often arise from the lateral nasal wall near the middle turbinate and occasionally from the nasal septum. Nasal gliomas may rarely extend into the orbit, frontal sinus, oral cavity, or nasopharynx. Because they lack a patent CSF connection, gliomas do not change in size with crying or straining and do not transilluminate. On histopathology, gliomas demonstrate fibrovascular and dysplastic neuroglial tissue, similar to nasal glial heterotopias, nasal cerebral heterotopias, or congenital nasal neuroectodermal tumors. Gliomas do not contain ependymal tissue, which differentiates them from encephaloceles.

Diagnostic evaluation should include nasal endoscopy to assess the location, origin, and extent of the nasal mass. CT scan is useful to assess the bony anatomy of the skull base, and MRI serves to define soft tissue connections to the CNS. As with encephaloceles, sagittal reconstructions and contrast enhancement are useful imaging adjuncts.

Proper management of gliomas requires surgical extirpation using a multidisciplinary approach that involves both otolaryngology and neurosurgery. Delaying intervention may lead to infection or distortion of the septum or nasal bones. With cosmesis kept in mind, surgical access should provide exposure of the lesion and allow possible exploration of the skull base. For resection of extranasal gliomas, options include lateral rhinotomy, external rhinoplasty, and transglabellar, subcranial, bicoronal, and midline nasal approaches. Except in the case of large glabellar lesions, the external rhinoplasty approach provides adequate surgical exposure while minimizing the use of facial incisions. When a fibrous stalk is present that extends deep to the nasal bones toward the base of the skull, a nasal osteotomy is recommended to improve exposure. Following the stalk in its entirety is essential for assessing possible intracranial extension. As a result of advancements in surgical instrumentation, image guidance, and surgical techniques, most intranasal gliomas can be removed endoscopically. ^, Reported recurrence rates are between 4% and 10%.

Nasal Dermoids

Nasal dermoids are frontonasal inclusion cysts or tracts related to embryologic errors localized to the anterior neuropore. Congenital midline nasal masses occur in 1 in 3000 to 1 in 40,000 live births, and dermoids are by far the most common. Nasal dermoids account for 1% to 3% of all dermoids and approximately 10% to 12% of head and neck dermoids. Most dermoid cysts occur sporadically, with a slight male preponderance, ^, although familial associations have been reported. Nasal dermoids are typically isolated lesions, but 5% to 41% have associated anomalies, including aural atresia, pinna deformities, developmental delay, hydrocephalus, branchial arch anomalies, cleft lip and palate, hypertelorism, and hemifacial microsomia.

A nasal dermoid usually manifests as a midline pit or mass. In approximately 50% of cases, a dimple is present at or near the rhinion, along with a widened nasal bridge; however, the true spectrum of disease includes cysts, sinuses, or fistulas that may occur anywhere along the embryologic line from the nasal tip into the cranial space. Mass lesions are firm, lobulated, and noncompressible and may be associated with a sinus opening ( Fig. 5.5 ) with intermittent caseous discharge or infection. A protruding hair is pathognomic for a nasal dermoid, although it is seen in only a minority of patients. A lesion within the nasal septum may present as nasal obstruction. The incidence of intracranial extension ranges from 4% to 45%. Recurrent meningitis caused by organisms typical of skin flora may indicate an intracranial tract. Nasal dermoids do not enlarge with crying or straining and do not transilluminate.

Unlike teratomas, which contain all three embryonal germ layers, congenital dermoids contain only ectodermal and mesodermal embryonic elements such as hair follicles, sebaceous glands, and sweat glands. The presence of these elements in the wall of the cyst differentiates dermoids from simple epidermoid cysts. Keratin debris is another prominent feature on histologic examination, and dermoids lack the glial features of encephaloceles and gliomas.

CT and MRI provide complementary information in the radiologic evaluation of nasal dermoids. Thin-slice 1- to 3-mm CT scans with intravenous contrast are recommended to differentiate the dermoid from the surrounding nasal mucosa and to define the bony anatomy of the nose and anterior skull base. Findings unique to intracranial dermoids include a bifid crista galli ( Fig. 5.6 ) and an enlarged foramen cecum; when these structures are normal, intracranial extension is ruled out. Multiplanar thin-section contrast-enhanced MRI ( Fig. 5.7 ) is helpful to depict the soft tissue anatomy of the anterior skull base and to differentiate a dermoid (which does not enhance) from enhancing lesions such as hemangiomas and teratomas. High signal intensity on T1-weighted images is suggestive of an intracranial dermoid because the neonatal crista galli does not contain marrow fat.

As with other lesions of the congenital anterior neuropore, the management of nasal dermoids is surgical. Aspiration, incision and drainage, curettage, and subtotal excision are associated with high recurrence rates and are generally not advocated. It is critical to assess the degree of intracranial extension, and patients with suspected intracranial extension should be prepared for a combined intracranial-extracranial approach with a collaborating neurosurgeon. Extracranial access should fulfill four criteria: (1) excellent access to the midline, (2) access to the base of the skull, (3) adequate exposure for reconstruction of the nasal dorsum, and (4) an acceptable scar. Several different extracranial approaches have been described. The external rhinoplasty incision is the most widely used approach as it generally gives the best cosmetic result and allows access to the skull base and exposure of the nasal dorsum. However, the external rhinoplasty provides only limited access to lesions in the glabellar region; lateral rhinotomy and midline vertical incisions are preferred alternatives. Despite the possibility of a widened scar, glabellar lesions with a sinus opening require an elliptical incision to excise the ostium. A transglabellar subcranial approach, a paracanthal incision, or a bicoronal approach may be used for glabellar lesions without sinus tracts. For lesions that extend into the cranial cavity, frontal craniotomy is performed by a multidisciplinary team. A large frontal craniotomy is typically carried out through a coronal incision using a combined intracranial-extracranial approach; however, anterior small window craniotomies have been described. Some authors suggest that the tract may be adequately treated with suture ligation without craniotomy if frozen section analysis of the tract is negative for epidermal and adnexal structures at the skull base. ^{, ,} However, others have suggested that epidermal elements may be staggered along the tract such that a single biopsy site is inadequate to rule out intracranial extension. The overall recurrence rate after adequate excision is low; however, long-term follow-up is essential to diagnose the occasional late recurrence.