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LETTER TO EDITOR
Year : 2011  |  Volume : 59  |  Issue : 6  |  Page : 924-926

Intraparenchymal schwannoma of brainstem in a pediatric patient


Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India

Date of Submission17-Aug-2011
Date of Decision25-Aug-2011
Date of Acceptance26-Oct-2011
Date of Web Publication2-Jan-2012

Correspondence Address:
Arun Tungaria
Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh
India
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DOI: 10.4103/0028-3886.91389

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How to cite this article:
Srivastav AK, Tungaria A, Kumar R, Sahu RN. Intraparenchymal schwannoma of brainstem in a pediatric patient. Neurol India 2011;59:924-6

How to cite this URL:
Srivastav AK, Tungaria A, Kumar R, Sahu RN. Intraparenchymal schwannoma of brainstem in a pediatric patient. Neurol India [serial online] 2011 [cited 2014 Oct 25];59:924-6. Available from: http://www.neurologyindia.com/text.asp?2011/59/6/924/91389


Sir,

Intracranial schwannomas account for 8-10% of all primary intracranial tumors, [1] and brainstem schwannomas have rarely been reported. [2],[3],[4],[5]

A 13-year-old boy was admitted with complaints of progressive left hemiparesis, ataxia and slurring of speech of 4 months duration and mild to moderate holocranial headache of 3 months duration. Family history revealed presence of multiple neurofibromas in his father, and detailed family screening could not be done. Neurological examination revealed slurred speech, left fifth, sixth, seventh and lower cranial nerve paresis, spastic left hemiparesis (grade 4/5) and bilateral cerebellar signs. His general physical examination was unremarkable. Cranial computed tomography (CT) showed a well-defined non-enhancing intra-axial cystic lesion in midbrain and pons with obstructive hydrocephalus [Figure 1]. Magnetic resonant imaging (MRI) revealed a lesion, hypointense on T1-weighted images and homogenously hyperintense on T2-weighted images. On gadolinium-DTPA administration, there was intense enhancement of the rim of the tumor with some solid part anterior and superior to the predominantly cystic part [Figure 2]. The patient underwent midline suboccipital craniectomy and, through a transvermian approach, partial excision of the lesion was performed. The lesion was subpial and the cyst wall was pinkish-white, vascular and firm having xanthochromic fluid inside. Part of the cyst wall was left behind as it was adherent to the normal brain stem, and there was no plane of cleavage. Partial resection of the solid part was done, as attempt to further dissection resulted in hemodynamic instability. Post-operatively, the patient had improvement in hemiparesis and ataxia and was discharged on day 7 of surgery. Post-operative MRI revealed residual enhancing cyst wall in midbrain with resolution of hydrocephalous [Figure 3]. Histopathology of the tumor tissue revealed spindle cells, with nuclear palisading and formation of Verocay bodies. Immunohistochemistry revealed positivity for S-100, vimentin and ki-67 [Figure 4]a and b. At 3-month follow-up, his hemiparesis and ataxia have improved as compared with the pre-operative status, and he is able to perform routine activities with minimal support. The patient was not offered radiation therapy and was advised to follow-up every 6 months.
Figure 1: Contrast-enhanced computed tomogram of the patient showed a well-defined intra-axial cystic lesion in the brainstem

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Figure 2: Magnetic resonance imaging of the patient showing intra-axial brainstem lesion hypointense on T1WI, hyper-intense on T2WI and peripheral contrast enhancement on post-gadolinium administration

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Figure 3: Post-operative contrast-enhanced T1-weighted magnetic resonance imaging of the patient

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Figure 4: (a) Histopathology of the tumor revealing spindle cells with nuclear palisading. (b) Immunohistochemistry positive for S-100

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Histogenesis of intraparenchymal schwannomas remains an enigma as Schwann cells are not normally present in the brain or spinal cord parenchyma. Most reported cases of intraparenchymal schwannomas are in the spinal cord, [6],[7] and cerebral intraparenchymal schwannomas are rare. [8],[9] To date, there have only been a few reports of brainstem schwannomas. [2],[3],[4],[5] While most reported patients of brainstem schwannomas were adults, our patient is a child, and another unique feature in our patient is the presence of multiple neurofibromas in his father. Radiological findings of intraparenchymal schwannomas include hypointense on T1-weighted images and inhomogeneously hyperintense on T2-weighted images. The solid portion and the wall enhance greatly after gadolinium-DTPA with distinct borders. Often, these lesions have a cystic component. [10] Intraoperative diagnosis of brainstem schwannoma using frozen-section specimens is difficult. [11] Conventional light microscopy can usually identify schwannoma easily. However, schwannomas in unusual sites are likely to be mistaken for various other tumors. Immunohistochemical findings are useful to confirm the diagnosis of schwannomas.

The origin of these tumors remains unclear. [1],[2],[3],[4],[5],[6],[7],[8] Intracranial schwannomas arise only from the sheath of cranial nerves other than the olfactory and optic nerves. Of the cases reported to date, these tumors have been reported to arise from the intracerebral parenchyma and the floor of the skull. They are primarily located in the midline and periventricular structures. [12] However, the reported intraprenchymal schwannomas from brainstem are almost equally distributed along the brainstem. [2],[3],[4] Several theories have been proposed to explain the possible origin of these tumors. One theory suggests a developmental origin; tumors arise from aberrant Schwann cells in the central nervous (CNS) parenchyma. Russel and Rubinstein [13] suggested that transformation of the mesenchymal pial cells into ectodermal Schwann cells account for their presence in the CNS parenchyma. Other authors have proposed that the tumor arises from proliferation of Schwann cells in the perivascular nerve plexus. Schwann cells exist within the perivascular nerve plexuses around large arteries in the subarachnoid space. Similar nerve plexuses accompany intrinsic arteries of the spinal cord parenchyma. [14] However, it is not clear whether these structures exist deep within the brain parenchyma. It has been proposed that a developmental abnormality occurs during the closure of the neural tube in the fourth gestational week, resulting in a hamartomatous foci of Schwann cells from which intraparenchymal schwannoma can arise. [15] Ramamurthy and colleagues had hypothesized that such neoplasms arise from neural crest cells that could possibly have been displaced into the developing spinal cord early in embryonic life. [16] Because of the very rare occurrence of these tumors and paucity of clinical and experimental evidence, there is no accepted theory regarding the origin of these tumors. However, we believe that the plausible explanation of brainstem schwannoma is probably from Schwann cells in the root entry zone of cranial nerves (seventh cranial nerve in our case), which may grow preferentially into the subpial space of brainstem. Moreover, in the background of positive family history in our patient, chance association of intraparenchymal schwannomas with genetic alteration in NF-1 cannot be ruled out.

 
 » References Top

1.Russell DS, Rubinstein LJ. Pathology of Tumours of the Nervous System, 5 th ed. Baltimore: William and Wilkins; 1989. p. 537.  Back to cited text no. 1
    
2.Jiangkai Lin, Hua Feng, Fei Li. Intraparenchymal schwannoma of the medulla oblongata. J Neurosurg 2003;98:621-4.  Back to cited text no. 2
    
3.Tanabe M, Miyata H, Okamoto H. Brainstem schwannoma: Case report. Neurol Med Chir (Tokyo) 1996;36:880-3.  Back to cited text no. 3
    
4.Eum SW, Kim BR, Park JY. Atypically located brainstem Schwannoma. J Korean Neurosurg Soc 1999;28:97-101.  Back to cited text no. 4
    
5.Sharma V, Newton G. Schwannoma of the medulla oblongata. Br J Neurosurg 1993;7:427-42.  Back to cited text no. 5
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6.Ross DA, Edwards MS, Wilson CB. Intramedullary neurilemomas of the spinal cord: Report of two cases and review of literature. Neurosurgery 1986;19:458-64.  Back to cited text no. 6
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7.Beskonakli E, Cayli S, Turgut M, Bostanci U, Seçkin S, Yalçinlar Y. Intraparenchymal schwannomas of central nervous system: An additional case report and review. Neurosurg Rev 1997;20:139-44.  Back to cited text no. 7
    
8.Casadei G, Komori T, Scheithauer BW, Miller GM, Parisi JE, Kelly PJ. Intracranial parenchymal schwannoma: A clinicopathological and neuroimaging study of nine cases. J Neurosurg 1993;79:217-22.  Back to cited text no. 8
    
9.Huang PP, Zagzag D, Benjamin V. Intracranial schwannoma presenting as a subfrontal tumor: Case report. Neurosurgery 1997;40:194-7.  Back to cited text no. 9
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10.Luo B, Sun G, Zhang B, Liang K, Wen J, Fang K. Neuroradiological findings of intracranial schwannomas not arising from the stems of cranial nerves. Br J Radiol 2004;77:1016-21.  Back to cited text no. 10
    
11.Kuhn JR, Neely JG, Pollay M. Cystic cerebellar schwannoma. Otolaryngol Head Neck Surg 1985;90:570-2.  Back to cited text no. 11
    
12.Li J, Hu B, Zou Y. Intracranial schwannomas not arising from the stems of cranial nerves. J Clin Neurol 1999;12:46-7.  Back to cited text no. 12
    
13.Russel DS, Rubinstein BJ. Pathology of tumors of the nervous system. Baltimore, MD: Williams and Wilkins; 1977.  Back to cited text no. 13
    
14.Adelman LS, Aronson SM. Intramedullary nerve fiber and Schwann cell proliferation within the spinal cord (schwannosis). Neurology 1972;22:726-31.  Back to cited text no. 14
[PUBMED]    
15.Vailati G, Occhiogrosso M, Trocooli V. Intramedullary thoracic schwannoma. Surg Neurol 1979;11:60-62.  Back to cited text no. 15
    
16.Ramamyrthy B, Anguli VC, Iyer CG. A case of intramedullary neurinoma. J Neurol Neurosurg Psychiatry 1958;21:92-4.  Back to cited text no. 16
    


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