Intraosseous schwannoma in the clivus mimicking chordoma treated with endoscopic endonasal surgery: A case report
- Department of Neurosurgery, University of Tsukuba, Tsukuba,
- Department of Neurosurgery, Dokkyo Medical University, Shimotsuga,
- Department of Otolaryngology, University of Tsukuba, Tsukuba,
- Department of Diagnostic Radiology, Toranomon Hospital, Tokyo, Japan.
Hiroyoshi Akutsu, Department of Neurosurgery, Dokkyo Medical University, Shimotsuga, Japan.
DOI:10.25259/SNI_473_2022Copyright: © 2022 Surgical Neurology International This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-Share Alike 4.0 License, which allows others to remix, transform, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms.
How to cite this article: Takaaki Ishikawa1, Hiroyoshi Akutsu2, Takuma Hara1, Shuho Tanaka3, Tomohiko Masumoto4, Eiichi Ishikawa1. Intraosseous schwannoma in the clivus mimicking chordoma treated with endoscopic endonasal surgery: A case report. 05-Aug-2022;13:346
How to cite this URL: Takaaki Ishikawa1, Hiroyoshi Akutsu2, Takuma Hara1, Shuho Tanaka3, Tomohiko Masumoto4, Eiichi Ishikawa1. Intraosseous schwannoma in the clivus mimicking chordoma treated with endoscopic endonasal surgery: A case report. 05-Aug-2022;13:346. Available from: https://surgicalneurologyint.com/?post_type=surgicalint_articles&p=11758
Background: Intraosseous schwannomas are extremely rare and they have not yet been reported to occur in the clivus. We report a schwannoma in the clivus mimicking chordoma and review intraosseous schwannomas of the skull.
Case Description: A 62-year-old man presented with gradually worsening hoarseness with dysphagia and atrophy of the left tongue, trapezius muscle, and sternocleidomastoid muscle. Magnetic resonance imaging showed that the tumor was mainly located in the clivus, and a computed tomography (CT) scan revealed an osteolytic lesion with expansion of the clivus and preservation of the bony cortex. Endoscopic endonasal surgery was performed to diagnose and treat symptoms. The tumor was subtotally removed without any complications. The histopathological findings revealed typical schwannoma, which showed Antoni A and Antoni B patterns positive for S100 protein. Based on the preoperative imaging, intraoperative and histopathological findings, the tumor was considered to be an intraosseous schwannoma in the clivus, and no recurrence was observed after 1 year of postoperative follow-up.
Conclusion: Even though the intraosseous schwannoma in the clivus is uncommon, it should be considered as a differential diagnosis if an expansive lesion without destruction of the cortical bone is shown on CT as well as iso-hyperintensity on T2-weighted magnetic resonance imaging.
Keywords: Clivus, Endoscopic endonasal surgery, Schwannoma
Schwannomas comprise 8.6% of central nervous tumors in the Unites States,[
Here, we present the first case, to the best of our knowledge, of a schwannoma located in the clivus that was treated with endoscopic endonasal surgery (EES). We discuss the preoperative radiological diagnosis, origin, and treatment of this tumor.
A 62-year-old man presented with a 5-year history of gradually worsening hoarseness. He was referred to our department, because magnetic resonance imaging (MRI) revealed a mass lesion in his clivus. His medical history included diabetes mellitus and hyperlipidemia, and he had no remarkable family history. Neurological examination revealed dysphagia and atrophy of the left tongue, trapezius muscle, and sternocleidomastoid muscle. There were no abnormal laboratory findings, including blood counts or alkaline phosphatase levels. Laryngoscopy revealed paresis of the left vocal cord. MRI showed that the tumor was of moderately high intensity, accompanied by cystic components on T2-weighted images and heterogeneous enhancement mainly in the peripheral area with gadolinium (Gd) on T1-weighted images [
Preoperative magnetic resonance imaging. Axial T2-weighted (a) and T1-weighted images with gadolinium enhancement (b) images show that the tumor is isointense with cystic components and is enhanced mainly in the peripheral area. The tumor is mainly in the clivus, and the small part of the tumor protrudes toward the brainstem around the left hypoglossal canal (the left hypoglossal canal: b,c, and e, white arrow). Axial (c and d) and coronal (e) bone window computed tomography images show destruction of the hypoglossal canal and jugular foramen (d and e, white dot arrow). The clival bone itself is expanded due to the tumor invasion (c and d), and the bony cortex is preserved in most parts (d, arrowhead).
To define the histological diagnosis, treat the patient’s symptoms, and decompress his brain stem, EES was performed using intraoperative MRI. A rapid pathological diagnosis was planned to determine the radicality of resection depending on the tumor malignancy. Nerve integrity monitoring (NIM, Medtronic, Minneapolis, MN, USA) was used to localize the lower cranial nerves (IX, XI, and XII). After dissection of the nasal septal mucosa and wide sphenoidotomy with drilling of the anterior wall, septum, and inferior wall of the sphenoid sinus, the upper part of the tumor was exposed. The tumor seemed to have no typical feature of chordoma or chondrosarcoma, rather of schwannoma. Rapid pathology of a specimen from this part of the tumor revealed no malignant findings and features of typical schwannoma. Considering the intraoperative findings and pathological result, not radical but maximum safe resection was intended. Subsequently, a left transmaxillary-transpterygoid approach with dissection of the nasopharyngeal mucosa was performed to expand the surgical field laterally and caudally. The left Vidian nerve and artery were cauterized and cut, and the contents of the left pterygopalatine fossa were lateralized to facilitate resection of the left medial pterygoid plate. The nasopharyngeal mucosa was incised in an inverted U-shape, dissected, and caudally reflected with a monopolar electrocautery to expose the lower clivus. The bone overlying the left paraclival carotid artery was removed, and the fibrocartilaginous tissue attached to the internal carotid artery (ICA) and Eustachian tube around the foramen lacerum was disconnected to enable mobility of these structures [
Intraoperative findings of transmaxillary-pterygoid approach combined with translacerum approach. (a) Intraoperative endoscopic view showing the area around the left internal carotid artery (ICA) at the foramen lacerum. (b) The cancellous bone of the clivus is replaced by the grey-yellowish tumor. (c) Cranial nerve IX, X, or XI (white arrow) is seen at the rostral margin of the tumor around the jugular foramen.
The histopathological findings revealed typical schwannoma, which showed spindle cells arranged in a palisading pattern with Verocay bodies (Antoni A) and a small number of tumor cells dispersed in edematous stroma (Antoni B). The tumor cells were positive for S100 protein, and the prevalence of Ki-67 positive cells was <1%. Based on the histology, preoperative MRI, and intraoperative findings, the tumor was considered an intraosseous schwannoma in the clivus.
Postoperative MRI showed subtotal resection of the tumor with successful decompression of the brain stem with a small residual tumor lateral to the occipital condyle [
Intraosseous schwannomas are rare, because there are very few sensory nerves in bone,[
Origin of the tumor
Intraosseous schwannomas frequently occur in the mandible, sacrum, long bone, and vertebrae.[
Schwannomas rarely arise and extend into the clivus, and if they arise there, they mimic chordoma, which frequently arises in the clivus, as observed in our patient. The radiological differential diagnoses of clivus lesions include chondrosarcoma, fibrous dysplasia, multiple myeloma, and metastatic tumors in addition to chordoma. Chondrosarcoma frequently arises along the petro-occipital fissure and petrous bone,[
Treatment and prognosis
In our patient, intraosseous schwannomas in the clivus were successfully resected using an endoscopic endonasal transmaxillary-transpterygoid approach without any complications. Most of the reported cases of intraosseous schwannomas in the skull have been treated through craniotomy, except for one case that was treated with radiation as the first line of treatment [
Only one previously reported case with a high proliferation index (Ki-67 index, 10%) showed recurrence after surgery, and stereotactic radiation therapy was performed.[
Here, we report a case of intraosseous schwannoma in the clivus mimicking clival chordoma. The tumor was subtotally resected without any complications with EES using the transmaxillary-transpterygoid and translacerum approaches. Although an intraosseous schwannoma in the clivus is extremely rare, it should be included as one of the differential diagnoses of clivus lesions if the lesion is expanding the bone while preserving the cortex on CT images or is not hyperintense on T2-weighted MR images.
The authors certify that they have obtained all appropriate patient consent.
There are no conflicts of interest.
We wish to thank the help given by Hiroyoshi Kino and Masahide Matsuda for discussing operative technique and anatomy of the area around the clivus. The authors thank Bryan J. Mathis for excellent narration of operative video and the Editage (www.editage.jp ) for English language editing.
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