Abstract
Few reports have been made on the presentation and treatment of schwannomas originating in the sphenoid sinus due to their rarity. We report the case of a 60-year-old woman who presented with a cyst-like mass in the right sphenoid sinus on magnetic resonance imaging. Computed tomography showed a bone defect in the internal carotid artery (ICA) and enlargement of the round foramen on the affected side. A histopathological diagnosis of schwannoma was made, and endoscopic sinus surgery was performed. The anterior part of the tumor could be easily removed by aspiration; however, its adhesion to the ICA was remarkable, and its boundaries were unclear. Although partial paralysis of the maxillary nerve remained, no recurrence occurred for over 10 years. Careful evaluation should be performed to check for bone defects in the nerve to differentially diagnose schwannoma from cystic masses of the sphenoid sinus. Additionally, excision of masses similar to the presented case may expectedly be difficult because of unclear excisional margins and strong capsule adherence to important organs such as the ICA. Moreover, correct imaging, histopathological diagnosis, and appropriate informed consent are essential before surgery.
Keywords: Neurilemmoma, Endoscopic sinus surgery, Mucocele, Paranasal sinus, Carotid artery injuries
Introduction
Schwannomas in the head and neck region are often derived from the auditory nerve and rarely found in the nasal cavity or paranasal sinus. Schwannomas originating in the sphenoid sinus are quite rare such that only 9 reports (11 cases) have been published in English [1–9]. Extremely important organs surround the sphenoid sinus, such as the optic nerve and internal carotid artery; thus, surgeons are sometimes forced to choose between radical cure of the tumor and function preservation during surgery.
This case report presents the 10-year postoperative course of a sphenoid sinus schwannoma that was removed though endoscopic sinus surgery but had the risk of internal carotid artery damage from surgery. The clinical assessment, imaging, and differential diagnosis for this rare tumor in the sphenoid sinus are also discussed.
Case report
A 60-year-old woman presented with a headache for 2 months; however, magnetic resonance imaging (MRI) at a neurosurgery clinic revealed a mass in the right sphenoid sinus. Thus, she was referred to our department. No abnormal findings were observed in the otolaryngological areas, including bilateral nasal endoscopy results. Except for headache, the patient did not present with symptoms including pigment spots on the skin, enlarged lymph nodes or neurological symptoms, such as trigeminal neuropathy. No abnormalities were found in the blood tests as well.
A nonenhanced sinus computed tomography (CT) scan revealed a mass occupying the right sphenoid sinus (Fig. 1A and B). The mass appeared to have expansive enlargement and was posteriorly in contact with the internal carotid artery. A bone defect in the carotid canal was also observed (Fig. 1A, arrowhead). In the superior lateral direction to the skull base, bone defects and enlargement of the round foramen were detected (Fig. 1A). The maxillary and pterygoid nerves in the affected side could not be identified (Fig. 1B). On MRI, the tumor was depicted as a uniform mass of low intensity on T1-weighted images (Fig. 2A) and high intensity on T2-weighted images (Fig. 2B). Contrast-enhanced MRI showed that most of the tumor was not enhanced, except for the surrounding area and lower medial part (Fig. 2C).
Fig. 1.
Plain computed tomography images (bone conditions). (A), preoperative axial image; (B) preoperative coronal image, (C) postoperative axial image (10 years after surgery). Posterior to the tumor (T), bone defects in the carotid canal (ICA) was observed (arrowhead, Fig. 1A). Enlargement of the round foramen with bone defect was also observed. The maxillary nerve (V2) and vidian nerve (VN) in the affected side could not be identified (Fig. 1B). Osteogenesis (arrow) was observed postoperatively with no recurrence (Fig. 1C). Red circle, round foramen, O, oval foramen; S, spinous foramen.
Fig. 2.
Magnetic resonance images. (A) nonenhanced T1-weighted image (axial image); (B) nonenhanced T2-weighted image (axial image); (C) enhanced T1-weighted image (coronal image). The tumor (T) is cyst-like and hypointense on T1-weighted images and hyperintense on T2-weighted images. On contrast-enhanced magnetic resonance imaging, the tumor is mostly not enhanced, except for the surrounding and inferior medial parts of the tumor. ICA, carotid canal; ON, optic nerve.
Based on the imaging diagnosis, it was suspected to be a cyst with a wall partially thickened due to infection; however, the possibility of a tumor could not be disregarded. Since it was in the sphenoid sinus, where biopsy is difficult to perform in an outpatient setting, and the patient requested to be administered with general anesthesia, an endoscopic biopsy was performed 3 weeks after the first visit. After opening the sphenoid sinus, there was no fluid outflow, and a fragile solid yellowish-white tumor was observed (Fig. 3A). The results of the pathological diagnosis during surgery were: a bundle-like growth of spindle cells showing mild nuclear enlargement and varying in size was observed; malignant findings were not observed; and whether it was a neurogenic tumor could not be confirmed.
Fig. 3.
Nasal endoscopic findings. (A) posterior nasal cavity; (B) intra sphenoid sinus just in before of the internal carotid artery. The anterior part of the tumor is yellowish-white and brittle, and the posterior part is adhered as it approaches the internal carotid artery. T, tumor; U, uvula; E, posterior ethmoid sinus; ON, optic nerve.
A final diagnosis of schwannoma was obtained from a permanent pathological specimen. Endoscopic sinus surgery was performed under general anesthesia in combination with a navigation system 3 months after the first visit. The anterior part of the tumor was easily removed by aspiration; however, it became hard and fibrous as it approached the posterior wall of the sphenoid sinus (Fig. 3B). The capsule near the skull base and around the carotid canal was highly adherent. The tumor's adhesion to the carotid canal was severe, and it was difficult to separate. Consequently, resection was carefully performed because excessive resection has been associated with the risk of internal carotid artery damage and pseudoaneurysm formation after surgery.
Sensory partial paralysis of the right hard palate appeared immediately after surgery, and the second branch of the trigeminal nerve was confirmed to be the nerve of origin. Recurrence or abnormal findings in the internal carotid artery were not observed 10 years after the surgery (Fig. 1C).
Discussion
Schwannoma frequently occurs in the head and neck region in 25%-45% of the total cases, and approximately 70% are derived from the auditory nerve [10]. However, only approximately 2.9% of the head and neck neuroma occurs in the nasal and paranasal sinuses, in which the most common sites of occurrence are the nasal septum, maxillary sinus, and ethmoid sinus [11]. Only 9 reports (11 cases) in English [1–9] reported cases of tumors that can be clearly identified as having a sphenoid sinus origin. However, there have been reports of tumors that had progressed to the sphenoid sinus from the ethmoid sinuses [4,12] or pterygopalatine fossa [9,13], in multiple sinuses, and in which the primary site could not be identified [8,14].
Table 1 summarizes these 9 reports [1–9]. There was no sex or side predilection in the reports of sphenoid sinus schwannomas (Table 1). Symptoms included headache and vision loss, as well as diplopia and proptosis, all of which were characterized by gradual progression over several months (Table 1).
Table 1.
Summary of previous reports of sphenoid sinus schwannoma.
| No. | Author | Age(years)/Sex | Side | Presentation | Magnetic resonance imaging | Surgery | Sequelae | Follow-up period |
|---|---|---|---|---|---|---|---|---|
| 1 | Calcaterra et al., 1974 | 48/M | R | Diplopia, Paralysis on lateral gaze | (Only X-ray and internal carotid angiograms) | Frontotemporal approach and middle fossa approach (subtotal removal) | None | 2.5 years |
| 2 | Same as above | 32/M | R | Diplopia, Paralysis on lateral gaze | (Only X-ray and internal carotid angiograms) | Maxillary sinus approach | None | 6 months |
| 3 | Younis et al., 1991 | 63/F | R | Postnasal discharge, nasal obstruction | Iso to hyperintense on T2 | Extended lateral rhinotomy, external radiotherapy, and radon seed implants | None | 3 years |
| 4 | DiNardo et al., 1993 | 60/M | L | Diplopia, decreased VA | Cystic, hypo to hyperintense (heterogeneous) on T1/T2 | Endoscopic biopsy and transantral removal | None | 1 year |
| 5 | Sharma et al., 1997 | 18/F | R | Blurring of vision, proptosis, decreased VA | (Only CT) | Orbitofrontal flap craniotomy and medial orbitorhinotomy | None | 1 month |
| 6 | Srinivasan et al., 1999 | 71/M | R | Nasal obstruction | (Only CT) | Endoscopic resection | None | 6 months |
| 7 | Tanaka et al. 2004 | 68/M | L | Headache | Cystic, hypo to hyperintense (heterogeneous) on T1/T2 | Zygomatic extradural subtemporal approach | N/A | N/A |
| 8 | Wu et al., 2012 | 78/F | L | Unilateral nasal discharge (cerebrospinal fluid leak) | Cystic, hypo to hyperintense (heterogeneous) on T1/T2 | Endoscopic sinus surgery | None | 2 years |
| 9 | Forer et al., 2015 | 65/M | L | N/A | (Not listed) | Bilateral maxillary antrostomy and complete sheno-ethmoidectomy | None | 2 years |
| 10 | Same as above | 47/F | L | N/A | (Not listed) | Local excision (endoscopic) | None | 6 months |
| 11 | Dutta et al., 2018 | 22/M | L | Headache, decreased VA | Cystic, iso to hyperintense on T1/T2 | Pterional craniotomy with anterior ethmoidectomy | None | 6 months |
| Yoshida et al. (present case) | 60/F | R | Headache | Cystic, low to high (heterogeneous) on T1/T2 | Endoscopic sinus surgery | V2 palsy | 10 years |
CT, computed tomography; F, female; L, left; M, male; N/A, not available (not mentioned); R, right; VA, visual acuity.
Schwannomas require differentiation from plasmacytomas and malignant schwannomas [2], [3], which may have benign radiological features. Schwannomas can also be misdiagnosed as paragangliomas, which have rich vascularization and benign characteristics but also malignant potential [15]. However, sphenoid sinus schwannomas should also be differentiated from cysts because 6 of the 9 cases (cases 1, 2, 4, 7, 8, and 11), excluding 2 cases that did not describe the imaging details [8], were initially suspected to be cysts (Table 1). This may be due to the expanding tumor growth, and depiction of them as cyst-like masses in most MRIs (cases 3,4,7,8,11). Moreover, mucoceles can cause various neurological symptoms. Furthermore, the signal intensity of T1 and T2 depends on the viscosity and fluid content of the cyst, and their differentiation is important even if neurological symptoms are present. The imaging findings in this case were typical, and it was initially suspected to be a cyst. However, detailed evaluation of the CT images showed an enlarged round foramen and bone defects around the right maxillary nerve, which were considered as the most important points in this case for differentiating schwannoma on imaging. Furthermore, the tumor's anatomical relationship with important organs, such as the internal carotid artery and optic nerve, must be fully evaluated, and the extent of resection and treatment strategies must be determined. Distal segments of the internal carotid artery can be easily identified using ultrasound fusion imaging, which is a new promising imaging modality that combines live ultrasound investigations with preregistered images and can be safely repeated in follow-up examinations [16]. Preoperative biopsy is important for a correct histopathological diagnosis; however, pathological diagnosis of sphenoid sinus schwannoma from biopsy through intraoperative rapid pathological examination may be difficult.
Complete surgical resection is curative and remains the basis for treatment of benign schwannomas; however, only a few reports on the presentation and treatment of sphenoid sinus schwannomas have been made due to their rarity. Specific approaches for each specialty in neurosurgery and otolaryngology, such as lateral rhinotomy, Caldwell–Luc approach, midfacial degloving, and the endoscopic approach, are selected depending on the tumor location (Table 1) [17]. A few surgical complications in the primary sphenoid sinus have been reported (Table 1), including a report on the crucial complications of meningioma [4], [5], [6], [7]. Partial paralysis of the maxillary nerve remained in this case. We had the option to perform unification of the bilateral sphenoid sinus, which had been performed recently in surgery for tumors in the sphenoid sinus.
Conclusion
A schwannoma is a benign tumor with good long-term prognosis; however, the imaging diagnosis, treatment, and surgical procedures for a sphenoid sinus schwannoma may be more difficult to achieve than those for other sinuses. Even for cases wherein a cystic mass was present in the sphenoid sinus, careful evaluation should be performed to check whether bone defects of the nerve are present to differentially diagnose schwannoma. Moreover, excision may expectedly be difficult because of the tumor's unclear excisional margin and strong capsule adherence to important organs, such as the internal carotid artery.
Patient consent
I have obtained written informed consent for the submission and publication of our case report from the patient or their legal representatives.
Footnotes
Competing Interests: The authors have declared that no competing interests exist.
Acknowledgments: We gratefully acknowledge the work of past and present members of our laboratory. No funding was received for this work.
References
- 1.Calcaterra TC, Rich JR, Ward PW. Neurilemoma of the sphenoid sinus. Arch Otolaryngol. 1974;100(5):383–385. doi: 10.1001/archotol.1974.00780040395016. [DOI] [PubMed] [Google Scholar]
- 2.Younis RT, Gross CW, Lazar RH. Schwannomas of the paranasal sinuses. Case report and clinicopathologic analysis. Arch Otolaryngol Head Neck Surg. 1991;117(6):677–680. doi: 10.1001/archotol.1991.01870180113022. [DOI] [PubMed] [Google Scholar]
- 3.DiNardo LJ, Mellis MG. Cystic schwannoma of the sphenoid sinus and skull base. Ear Nose Throat J. 1993;72(12):816–818. doi: 10.1177/014556139307201212. [DOI] [PubMed] [Google Scholar]
- 4.Sharma MC, Mahapatra AK, Gaikwad SB, Sarkar C. Solitary giant skull base schwannomas – Report of four cases. Surg Neurol. 1997;48(4):382–387. doi: 10.1016/s0090-3019(97)00004-9. discussion 387. [DOI] [PubMed] [Google Scholar]
- 5.Srinivasan V, Deans JAJ, Nicol A. Sphenoid sinus schwannoma treated by endoscopic excision. J Laryngol Otol. 1999;113(5):466–468. doi: 10.1017/s0022215100144238. [DOI] [PubMed] [Google Scholar]
- 6.Tanaka C, Kurita H, Shiokawa Y, Terado Y, Saito I. Schwannoma involving the sphenoid sinus. Acta Neurochir. 2004;146(10):1159–1160. doi: 10.1007/s00701-004-0342-0. [DOI] [PubMed] [Google Scholar]
- 7.Wu SW, Chen WL, Chen WL, Chen MK. Transnasal endoscopic resection of vidian nerve schwannoma accompanied by sphenoid mucopyocele and oculomotor palsy: A case report. B-ENT. 2012;8(3):207–211. [PubMed] [Google Scholar]
- 8.Forer B, Lin LJ, Sethi DS, Landsberg R. Endoscopic resection of sinonasal tract schwannoma: presentation, treatment, and outcome in 10 cases: presentation. Ann Otol Rhinol Laryngol. 2015;124(8):603–608. doi: 10.1177/0003489415572339. [DOI] [PubMed] [Google Scholar]
- 9.Dutta G, Singh D, Singh H, Singhal G, Saran RK. Atypical presentation of cystic schwannoma of the sphenoid sinus: a nonsolitary mass with osseous, intracranial and cavernous sinus invasion. Pan Afr Med J. 2018;31:233. doi: 10.11604/pamj.2018.31.233.16515. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10.Das Gupta TK, Brasfield RD, Strong EW, Hajdu SI. Benign solitary schwannomas (neurilemmomas) Cancer. 1969;24(2):355–366. doi: 10.1002/1097-0142(196908)24:2<355::aid-cncr2820240218>3.0.co;2-2. 10.1002/1097-0142(196908)24:2≤355::aid-cncr2820240218≥3.0.co;2-2. [DOI] [PubMed] [Google Scholar]
- 11.Cakmak O, Yavuz H, Yucel T. Nasal and paranasal sinus schwannomas. Eur Arch Otorhinolaryngol. 2003;260:195–197. doi: 10.1007/s00405-002-0540-4. [DOI] [PubMed] [Google Scholar]
- 12.Kasliwal MK, Yerramneni VK, Sai Kiran NA, Suri A, Mahapatra AK, Sharma MC, et al. Giant sphenoethmoidal nasopaharyngeal schwannoma with anterior skull base extension managed by a total anterior transbasal approach. Neurol India. 2007;55(4):429–431. doi: 10.4103/0028-3886.33309. [DOI] [PubMed] [Google Scholar]
- 13.El Amri G, Malinvaud D, Laccourreye O, Bonfils P. Cystic lesions of the pterygoid process. Eur Ann Otorhinolaryngol Head Neck Dis. 2014;131(1):61–63. doi: 10.1016/j.anorl.2013.03.005. [DOI] [PubMed] [Google Scholar]
- 14.Zhou H, Xing G, Gao X, Wang J, Chen F, Lu L, et al. Schwannoma of the sinonasal tract and the pterygopalatine fossa with or without intracranial extension. ORL J Otorhinolaryngol Relat Spec. 2015;77(2):61–69. doi: 10.1159/000374122. [DOI] [PubMed] [Google Scholar]
- 15.Chervenkov L, Doykova K, Hilendarov A, Pazardzhikliev D. Carotid bifurcation paraganglioma. Rentgenologiya i Radiologiya. 2020;59(4):365–368. [Google Scholar]
- 16.Peycheva MV, Chervenkov L, Harizanova Z, Ahmed-Popova F, Zahariev ZI. Ultrasound fusion imaging system in neurology practice. Folia Med (Plovdiv) 2022;64(4):667–671. doi: 10.3897/folmed.64.e64271. [DOI] [PubMed] [Google Scholar]
- 17.Kodama S, Okamoto T, Suzuki M. Ancient schwannoma of the nasal septum associated with sphenoid sinus mucocele. Auris Nasus Larynx. 2010;37(4):522–525. doi: 10.1016/j.anl.2009.09.015. [DOI] [PubMed] [Google Scholar]