Clinical case: Schwannoma of the nasal cavity
In this article, we describe a case of a woman who presented with progressive nasal obstruction, pain, and fullness, with intermittent epistaxis. Her final diagnosis was a schwannoma originating from the pterygopalatine ganglion. We will follow her journey from the history and admission, through imaging, histopathological examination, all the way to the interventions and management. We will also look at anatomical considerations that should be taken into account when dealing with such a clinical case.
|Nasopharynx||It is part of the pharynx, specifically the space superior to the soft palate at the back of the nose. It connects the nasal and oral cavities, which enables nasal breathing. The anterior aspect of the nasopharynx communicates through the choanae with the nasal cavity.|
|Drainage of the paranasal sinuses||
Frontal sinus -> frontonasal duct -> middle meatus
Ethmoidal air cells -> middle meatus (anterior and middle cells); superior meatus (posterior cells)
Sphenoid sinus -> sphenoethmoidal recess
Maxillary sinus -> middle meatus
|Choanae||Bony passageways between the nasal cavity and the nasopharynx|
After reviewing this case you should be able to describe the following:
- What is meant by the nasopharynx. How the nasopharynx relates to the other parts of the pharynx and the nasal cavity .
- The location and drainage patterns of the paranasal sinuses.
- What is meant by the choanae.
- The relative value of the CT and MRI scans to this case.
This article is based on a case report published in the Journal "Case Reports in Surgery" in 2015, by Caroline C. Jadlowiec, Beata E. Lobel, Namita Akolkar, Michael D. Bourque, Thomas J. Devers, and David W. McFadden.
- Case description
- Surgical and anatomical considerations
- Explanations to objectives
- Related diagrams and images
History and physical examination
A 52-year-old woman presented with a four-year progressive history of left nasal obstruction, pain, and fullness, with intermittent epistaxis. Her symptoms began when she had an upper respiratory tract infection with subsequent development of continuing mucous production. No other feature of her history was significant.
A nasoendoscopy exam through the left nostril revealed a very large mass (initially thought to be a polyp) completely obstructing the anterior part of the nasal cavity and thus limiting further examination.
A nasendoscopy through the right nostril showed the tumor occupying the left nasal cavity and nasopharynx, but the right side was clear. An examination of the eyes and the oral cavity was unremarkable.
CT images of the paranasal sinuses indicated complete opacification of the left frontal, ethmoidal, maxillary, and sphenoid sinuses and nasal cavity (Figures 1-3). The tumor significantly shifted the left lateral nasal wall so that it protruded into the maxillary sinus (Figure 2).
There was also hyperostosis (increased density) of the sphenoid and maxillary sinus walls (Figures 2–3). An MRI was done to provide a better estimation of the extent of the soft tissue mass than obtainable from CT mages. The MRI images showed that the mass occupied the entire left nasal cavity, extending into the choanae to completely fill the nasopharynx (Figures 4&5).
The mass measured 78×28×51mm (AP×ML× SI). The mass also filled the left anterior and posterior ethmoid air cells, obliterating all bony septations (Figure 3). The left maxillary sinus and frontal sinus were filled with mucus secretions secondary to the obstruction caused by the tumor (Figures 4&5).
In order to remove the tumor the patient was placed under general anesthesia in a reverse Trendelenburg position (head higher than feet). The superior aspect of the tumor was dissected off the anterior skull base. Clearance of the frontoethmoidal recess was by evacuation of mucous from the frontal sinus. Obstruction of the left maxillary sinus ostium was completed, followed by clearance of the maxillary sinus contents.
The nasopharyngeal component of the mass was easily removed. The floor of the sphenoid sinus was drilled because the sphenopalatine ganglion was believed to be the likely point of origin of the tumor. The patient was then extubated and had an uneventful postoperative recovery.
The tumor had been removed in two sections and both pieces were sent for histopathological examination. Both were found to be composed of Antoni-A and Antoni-B areas of variable cellularity, consistent with those of a schwannoma. Antoni-A and Antoni-B areas are characteristic morphological signs for schwannomas that pathologists observe on H&E stained slides. Antoni-A areas are very dense eosinophilic regions that are usually found next to Antoni-B areas, which are loose, hypocellular and pale.
As expected, immunoperoxidase stains for S100 and SOX10 were positive. S100 and SOX10 proteins are highly expressed in Schwann cells are commonly used to confirm the diagnosis of schwannomas by immunohistochemistry. There was no evidence of malignancy. Schwannomas are benign tumors. Their malignant counterparts are called Malignant peripheral nerve sheath tumors (MPNSTs).
Evolution and recovery
The patient had a very good response to surgery and at two-month follow-up, showed complete resolution of symptoms. Similarly, on follow-up nasendoscopy, there was no evidence of residual or recurrent disease.
Surgical and anatomical considerations
Differential diagnosis of unilateral nasal cavity tumors
Unilateral tumors in the nasal cavity associated with nasal obstruction, pain, fullness, and epistaxis are usually caused by benign disease processes such as polyps, cysts, and mucoceles. A unilateral tumor originating from the nasal cavity should also raise the suspicion of the rare esthesioneuroblastoma, a neoplasm originating from the olfactory neuroepithelium. Schwannomas within the nasal cavity and sinuses produce similar signs and symptoms, but are very rare.
Schwannomas are benign tumors of peripheral nerve sheaths, and sinonasal schwannomas may originate from the ophthalmic or maxillary branches of the trigeminal nerve, or from sympathetic fibers from the internal carotid plexus, or from the sphenopalatine (pterygopalatine) ganglion. Most patients present with progressive nasal obstruction and pain, headache, and epistaxis but can occasionally complain of ptosis, proptosis, and diplopia. Because the majority of schwannomas have a focal origin and are mostly encapsulated, these tumors are commonly amenable to endoscopic resection.
The authors of this report speculated that the origin of this tumor was at the sphenopalatine ganglion (Figure 6). This ganglion is located within the same named fossa and is associated with sensory fibers of the maxillary nerve and parasympathetic fibers of the facial nerve. The parasympathetic fibers provide innervation to the mucous glands within the nasal cavity and nasopharynx, and also provide innervation to the lacrimal gland. The sensory fibers of the maxillary nerve provide sensation to the nasal cavity and nasopharynx. The maxillary nerve also passes through the sphenopalatine fossa on its way to becoming the infraorbital nerve.
Figures 2&3 show that some of the bones surrounding the tumor had increased density compared to the normal (contralateral) side. This resulted because this tumor secreted some growth factors that trigger new bone formation. BMPs (bone morphogenic proteins) are the most important ones but IGF, PDGF, FGF, TGF-b are some of the other growth factors that are secreted by tumor cells that can induce osteoblast growth and differentiation. Such hyperostosis is very common with prostate cancer and rare with schwannomas, but did occur here.
Explanations to objectives
Anatomy of the pharynx
The pharynx (Figure 9) is the part of the digestive system and is located posterior to the nasal and oral cavities and also posterior to the larynx (Figure 7). It is classically divided into nasal, oral, and laryngeal components: the (1) nasopharynx, (2) oropharynx, and (3) laryngopharynx (hypopharynx). The pharynx extends from the base of the skull inferiorly to the inferior border of the cricoid cartilage (about the C6 vertebral level), at which point it becomes continuous with the esophagus.
The pharynx is a fibromuscular tube lined by mucous membrane that is the common pathway for deglutition (swallowing) and respiration, and the two pathways cross each other in the pharynx. The nasopharynx is specifically the space superior to the soft palate at the back of the nose and connects the nasal cavity with the oral cavity (Figure 1), which enables nose breathing. The anterior aspect of the nasopharynx communicates through the choanae with the nasal cavity (Figure 8).
Anatomy of the paranasal sinuses
The frontal sinus is located posterior to the supraciliary ridges of the frontal bone, often extending dorsally into the orbital roof of the frontal bone, and is usually divided by a septum. Drainage is via the frontonasal duct, through anterior ethmoidal cells to the middle meatus (into upper portion of infundibulum, which is anterosuperior to the hiatus semilunaris; Figure 1).
The ethmoidal air cells are aggregations of thin-walled spaces (cells) in the ethmoidal labyrinth between the orbital and nasal cavities, arranged in 3 sets based on drainage. The anterior cells drain to the infundibulum of the middle meatus; the middle cells, drain on or above the ethmoid bulla in the middle meatus; the posterior cells drain into the superior meatus, with interconnections to the sphenoid sinus.
The sphenoid sinus is located in the body of the sphenoid bone, usually asymmetrically divided by a septum. The sphenoid sinus drains into the sphenoethmoidal recess.
The maxillary sinus (largest) is located in the body of the maxilla; roofed by floor of orbit; the lateral wall of nasal cavity is medial; alveolar process of maxilla is inferior; and, the sinus may extend into zygomatic bone. Drainage is into the semilunar hiatus of the middle meatus; an accessory opening is frequently found dorsal to the hiatus.
Anatomy of the choanae
The choanae (Figure 11) are the bony passageways between the nasal cavity and the nasopharynx (Figure 8). The conchae (turbinate bones) are the three convoluted delicate bony structures that protrude in the nasal cavity (Figures 1&8). They are covered with mucous membrane and serve to warm and moisten inhaled air. The inferior concha is a separate bone whereas the superior and middle conchae are part of the ethmoid bone.
Importance of MRI and CT scans in tumor diagnosis
MRI provides much better soft tissue resolution than CT, whereas CT provides better bony resolution. Thus, the hyperostosis of the bony walls of the nasal cavity is clearly seen on the coronal and axial CT images, but not on the comparable MRI images (Figures 2-5). However, the coronal and axial T2 weighted MRI images (fluid appears bright) show that the mass within the maxillary sinus is not the same as the mass within the nasal cavity and nasopharynx.
In the MRI images the maxillary sinus mass has a higher intensity than that of the tumor and therefore, as noted in the text, is not part of the tumor mass but rather is mucous that has been secreted in response to the tumor. This difference was not discernible in the CT images and this information informed the surgeons that they did not need to involve the maxillary sinus in their surgical extirpation but rather they just needed to drain the sinus.