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Table of Contents    
BRIEF REPORT
Year : 2021  |  Volume : 69  |  Issue : 6  |  Page : 1747-1752

Cervico Medullary Junction “Intramedullary Schwannoma” Masquerading As Glioma: A Surprise During Surgery


1 Department of Neurosurgery, KEM Hospital, Mumbai, Maharashtra, India; Advanced Endoscopic Skull Base And Lateral Skull Base, Italy
2 Department of Neurosurgery, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India
3 Department of Pathology (Neuropathology Division), Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India
4 Department of Neurosurgery, Dr. Rajendra Prasad, Govt. Medical College, Tanda, Himanchal Pradesh, India

Date of Submission04-Jan-2021
Date of Decision16-Mar-2021
Date of Acceptance07-Jul-2021
Date of Web Publication23-Dec-2021

Correspondence Address:
Dr. Manjul Tripathi
Dept. of Neurosurgery & Gamma Knife Radiosurgery, Functional Neurosurgery, Oxford University; Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.333465

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 » Abstract 


Background: Intramedullary schwannomas (IS) at cervicomedullary junction (CMJ) are exceedingly uncommon. There is hardly any clinicoradiological marker for preoperative diagnosis and prognostication.
Case: We report a case of a 17-year-old boy with progressive spastic quadriparesis of six months duration. On radiology, there was a contrast-enhancing lesion expanding the cord extending from the medulla to C5 level. During surgery, the cord was expanded and the tumor was eccentric. Histopathology and immunohistochemistry were suggestive of schwannoma. In view of the ill-defined plane of separation from the normal neural tissue, only subtotal resection could be achieved.
Conclusion: Schwannoma should be considered as a remote differential of intramedullary lesions. The extent of resection should be tailored according to the plane of dissection and intraoperative neuromonitoring guidance. Though a masquerader, schwannoma carries better prognosis than rest of the pathologies.


Keywords: Cervicomedullary junction (CMJ), intramedullary schwannoma (IS), subtotal resection (STR)
Key Message: Intramedullary schwannoma at CMJ is very rare. It may come as a surprise during surgery. In contrary to the traditional belief, the plane of dissection during surgery may be variable. Prognosis is good if excised completely.


How to cite this article:
Dandpat SK, Tripathi M, Kaur G, Radotra BD, Joshi A, Mohindra S. Cervico Medullary Junction “Intramedullary Schwannoma” Masquerading As Glioma: A Surprise During Surgery. Neurol India 2021;69:1747-52

How to cite this URL:
Dandpat SK, Tripathi M, Kaur G, Radotra BD, Joshi A, Mohindra S. Cervico Medullary Junction “Intramedullary Schwannoma” Masquerading As Glioma: A Surprise During Surgery. Neurol India [serial online] 2021 [cited 2022 Jan 20];69:1747-52. Available from: https://www.neurologyindia.com/text.asp?2021/69/6/1747/333465




Spinal schwannomas are usually extramedullary in location. Primary intramedullary location of schwannoma is exceedingly unusual, as schwann cells are not present in central neuraxis. Intramedullary schwannoma (IS) accounts for 1.1% of spinal schwannoma and 0.3% of intraspinal tumors.[1] The association of ISs with neurofibromatosis (NF1 and NF2) is well documented.[2],[3] We report a case of IS clinicoradiologically mimicking as a glial tumor extending from medulla to the C5 segment of the spinal cord.


 » Case Top


A 17-year old boy presented with progressive spastic quadriparesis and paresthesia for six months. Gradually, he developed hoarseness of voice, poor respiratory effort, and urinary urgency. At presentation, he was wheel chair bound with spastic quadriparesis (modified Nurick grade IV). Gag reflex was weak and the rest of the neurological examination was within normal limits. There was no evidence of any phenotypic marker of neurofibromatosis in this case.


 » Imaging Top


Magnetic resonance imaging (MRI) of the craniovertebral junction and cervical spine showed a homogenously enhancing lesion extending from the medulla to the C5 level of spinal cord causing the expansion of the cord [Figure 1]a and [Figure 1]b. The lesion was well defined in the rostral part but poorly marginated in the cervical region. The bilateral nerve roots were normal. Our first differential diagnosis was astrocytoma with ependymoma as a remote possibility.
Figure 1: (a) Sagittal section T2 weighted MRI shows mild to moderate homogeneously enhancing intramedullary lesion extending from medulla to the C5 level of spinal cord causing expansion of the cord.; (b) Axial section of gadolinium-enhanced MRI shows the same as above. Bilateral nerve roots appear normal; (c) Intraoperative image after opening the dura revealed expanded cord and tumor on the right side depicted with solid blue arrow. Nerve roots are displaced dorsally (Blue arrow)

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 » Operative Top


The posterior rim of the foramen magnum was removed and three-level laminoplasty (C1, C2, and C3) was performed. The spinal cord was expanded and the tumor was mainly on the right side of cord. Nerve roots were displaced dorsally [Figure 1]c. The tumor was firm and vascular. To our surprise, the frozen section was suggestive of schwannoma. Further tumor resection was performed with cavitron ultrasonic surgical aspirator (CUSA). Caudally, the plane between the tumor and cord parenchyma could not be appreciated and appeared to infiltrate the neural tissue, limiting the gross total resection. In view of poor respiratory efforts, the patient needed mechanical ventilation for prolonged duration but succumbed on the tenth post-operative day because of ventilator-associated pneumonia.


 » Histopathology Top


Histopathological examination revealed a mixed cellular morphology of both Antoni A and Antoni B type with verocay bodies. Extensive myxoid degeneration was also noted in some areas. Very occasional mitotic figures were noted [Figure 2]. On immunohistochemical analysis, the tumor was strongly positive for S100 suggestive of schwannomas. The sections were negative for EMA, Vimentin, and GFAP showing no evidence of any glial or ependymal component in the sample [Figure 3].
Figure 2: Histomorphology of Schwannoma showing both Antoni type A and B type of areas (a and b). Antoni A consisting of spindle-shaped cells and showing Verocay bodies, Antoni type B consisting of Schwann cells arranged haphazardly in very loose vacuolated reticular stromal tissue (100x) (a and b); Intranuclear pseudoinclusions (400x) (c); Extensive myxoid degeneration was noted in some areas (100x) (d); Perivascular accentuation of the tumor cells in some areas (100x) (e); Very occasional mitotic figure (black arrow) (400x), and (f) (Hematoxylin and Eosin)

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Figure 3: The immunohistochemical analysis suggestive of (a) diffuse expression of S-100 in tumor cells (IHC X 400); (b) The tumor cells are negative for EMA, (c) Vimentin, and (d) GFAP (IHC X 400 each) (EMA, epithelial membrane antigen; GFAP, glial fibrillary acidic protein; IHC, immunohistochemistry)

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 » Discussion Top


Historically, Kernohan is credited for the first published report of IS. in 1931.[4] Penfield also described a intramedullary lesion with characteristics of schwannoma in 1932.[5] To the best of our knowledge, totally 96 cases have been reported till date.[6],[7],[8] Among them, 50 cases were located in the cervical cord while five at the cervicomedullary junction (CMJ).[6],[8],[9],[10],[11],[12],[13],[14] The present case is the 6th case of IS at CMJ [Table 1].
Table 1: Literature review of cervical intramedullary schwannomas

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Cervical cord (63%) is the most commonly affected location, followed by thoracic (26%) and lumbar (11%) spine.[12] Though earlier studies have predicted male preponderance, recent studies show no predilection for any sex. The mean age of presentation of these tumors is 49.2 years.[15] The patients usually present with a long history in view of the slow-growing benign nature of the tumors. The average interval between the first symptom and the diagnosis is 28.2 months (range 6 months to 20 years).[16]

Intradural extramedullary schwannomas (IES) are encapsulated tumors arising from the dorsal root sensory ganglion. They characteristically present with radicular pain by virtue of its origin. In later stage, it may lead to pyramidal tract and sensory tract dysfunctions. Unlike ISs, IES are most commonly located in the cervical spine followed by lumbar spine. They show variable growth pattern of 2.3% annual rate. The pattern may be of unchanging, continuous slight growth, or initial slight growth followed by rapid growth, while meningioma is present with the continuous growth pattern. Intradural extramedullary meningioma shows constant growth at 7% annual rate.[40] Until now, all the reported cases of ISs show progressive symptoms, which warrant surgical excision at the time of initial detection. Among the common intramedullary tumors (ependymoma, astrocytoma, and hemangioblastoma), astrocytoma (grade II) shows rapid infiltrative growth, and symptoms of tract dysfunction are relatively early. Grade III or grade IV astrocytoma carry poor prognosis with survival of 15.5 months.[41] Ependymoma and hemangioblastoma are slow growing tumors. Hemangioblastomas are mesenchymal tumors originating from vasculature and grow in the dorsal portion of the cord. And, characteristically present with sensory tract dysfunction at early stage. Though back pain is present, radicular pain is rarely found in the aforementioned tumours. However, intramedullary tumor with root or radicular pain is a very characteristics clinical signature of ISs. Malignant transformation of intramedullary schwannoma has not been reported yet.

Wu et al.[15] compared the clinical symptoms of IS with astrocytoma and ependymoma. For IS, somatic and root pain were the predominant symptoms. Myelopathic features follow in the later stages of the disease. However, our case did not present with any somatic or root pain as initial symptoms, rather presented with spastic quadriparesis and paraesthesia.

The radiological diagnosis of IS is arduous and demands a high index of suspicion. It is difficult to differentiate astrocytoma or ependymoma from IS in an intramedullary lesion with cord expansion unless it has an exophytic component related to the nerve root, which hints toward IS. ISs are usually iso-hypointense on T1W1 and hyperintense on T2 weighted images. The enhancement with gadolinium depends on the macroscopic (solid and cystic) and histologic features of the tumor.[8] Thickened enhancing nerve root in continuity with the tumor is the only diagnostic feature of IS in MRI, but is rarely seen. Central enhancing lesion with polar cysts hints in favour of ependymoma. Astrocytomas are usually eccentric in location with an ill-defined margin due to its infiltrative properties and do not show uniform enhancement. In our case, the rostral part of the tumor was well defined but the lower part of the tumor margin was not well delineated. The review by Kodama et al.[32] mentioned that intense enhancement and well-delineated margins on contrast-enhanced T1-weighted images are the characteristic findings in ISs. However, it is not enough to differentiate it from an ependymoma or hemangioblastoma. Most of the IS tumors were in the cervical region, expanding the cord, accompanied by peritumoral oedema, cystic cavitation, and with an exophytic component in some cases [Table 2].
Table 2: Clinicoradiolgoical differentiation of intramedullary schwannomas from common pathologies

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The major question of the debate arises in the pathological evolution of IS as the schwann cells are not present in cord parenchyma. In 1957, Kernohan, McCarty, Riggs and Clary proposed that schwann cell proliferation originating from nerve fibers of the spinal arteries could be the possible origin of IS.[19] Ramamurthi et al. proposed that the migration of schwann cells (during the fourth gestational week) could be the source of these schwannomas.[42] In 1964, Mac Cormick and Wood stated that the neoplastic growth of schwann cells occurred near dorsal root entry zone where posterior nerve roots lose their sheath on entering the cord.[43] But the most acceptable theory was proposed by Rusell and Rubenstein in 1971. According to them, these tumors emerge from the transformation of neuroectodermal pial cells located in a “critical area” in the dorsal roots leading to a possible neoplastic growth of schwann cells.[44]

Radical excision should be the treatment of choice whenever possible. The majority of the cases reported in literature had a well-demarcated plane without adhesion to the surrounding neural tissue. However, some authors reported that ISs could be infiltrative and gross total resection (GTR) was not possible.[16],[21] Intraoperative frozen section report and its interpretation is of paramount importance for judicious decision. The role of adjuvant radiotherapy is controversial in literature. Modern technologies like image-guided radiotherapy or stereotactic radiosurgery or cyberknife have been used in recurrent or residual spinal cord tumor with better delivery of effective therapeutic dose to the target sparing the normal tissue. SRS is well established in spinal metastasis. However, in benign recurrent or residual spinal lesions, it has shown good tumor control.[45] Due to the limited data in intramedullary spinal lesions, the optimal spinal cord dose is yet to be clarified. Chemotherapy is not well studied in intramedullary spinal cord tumors. To minimize radiation-induced complications, stereotactic radiosurgery should be attempted for the residue as subsequent surgeries would be more problematic. Our case mimicked a glioma with clinicoradiolgoical features. The frozen section report of schwannoma encouraged us to attempt complete resection. However, as the tumor was infiltrating the cord, only STR could be achieved.

Neurophysiologic monitoring is an important tool in the surgery of intramedullary tumor. Its worth now remains uncontested but its availability is still an issue at many places in the world. The sensitivity and specificity of motor-evoked potentials for postoperative deficit is 100% and 90% respectively.[46] Due to unavailability, we could not use it in our case.


 » Conclusion Top


Cervicomedullary junction ISs are exceedingly rare tumors. ISs should be considered as a differential of intramedullary lesions when associated with the radiological features of intense contrast enhancement, well-defined margin, and thickened nerve root. Immunohistochemistry remains valuable in cases of pathological confusions. The extent of resection should be tailored according to the plane of dissection and intraoperative neuromonitoring guidance. Adjuvant radiosurgery should be considered for long-term progression-free survival.

Declaration of patient consent

The patient's brother has consented for the publication of this case report.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

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    Tables

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