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LETTER TO EDITOR
Year : 2011  |  Volume : 59  |  Issue : 5  |  Page : 786-788

Greater superficial petrosal nerve schwannoma: Report of two cases and literature review


1 Department of Neurosurgery, Postgraduate Institute of Medical Education and Research, Chandigarh, India
2 Department of Histopathology, Postgraduate Institute of Medical Education and Research, Chandigarh, India

Date of Submission19-Jul-2011
Date of Decision19-Jul-2011
Date of Acceptance25-Jul-2011
Date of Web Publication22-Oct-2011

Correspondence Address:
Alok Umredkar
Department of Neurosurgery, Postgraduate Institute of Medical Education and Research, Chandigarh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.86578

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How to cite this article:
Umredkar A, Singla N, Gupta SK, Radotra B. Greater superficial petrosal nerve schwannoma: Report of two cases and literature review. Neurol India 2011;59:786-8

How to cite this URL:
Umredkar A, Singla N, Gupta SK, Radotra B. Greater superficial petrosal nerve schwannoma: Report of two cases and literature review. Neurol India [serial online] 2011 [cited 2019 Jul 17];59:786-8. Available from: http://www.neurologyindia.com/text.asp?2011/59/5/786/86578


Sir,

Greater superficial petrosal nerve (GSPN) schwannomas are relatively uncommon tumors and involve the middle cranial fossa by anterior extension through the facial hiatus. [1],[2] We report two cases of GSPN schwannomas.

In the first case, a 51-year-female presented with headache and hearing loss in the left ear since 4 months. Neurological deficits included left-side lower motor facial palsy, decreased tear secretion, and sensori-neural hearing loss. Head computed tomography (CT) scan showed an iso- to hypodense mass in left middle cranial fossa abutting the petrous bone with erosion of the bone [Figure 1]a. Magnetic resonance imaging (MRI) scan demonstrated an extra-axial mass iso- to hypointense on T1 [Figure 1]b and iso- to hyperintense on T2-weighted images [Figure 1]c, with heterogenous enhancement [Figure 1]d and e. She underwent left temporal craniotomy and total excision. The tumor was totally extradural, eroding the anterosuperior surface of petrous bone. Histopathology showed a tumor composed of hypo- and hypercellular areas with focal areas of veroccay body formation, consistent with diagnosis of schwannoma [Figure 2]a. Repeat MRI at 6 months did not show any evidence of tumor recurrence [Figure 1]f. Her hearing improved but with no improvement in facial palsy at 1-year follow-up.
Figure 1: (a) Plain CT scan showing a hypodense rounded mass in the left middle fossa eroding the petrous bone in the first case. (b) T1-weighted MRI scan of the first case showing a heterogeneous hypointense rounded mass abutting petrous bone which was eroded. (c) T2-weighted MRI scan axial cut showing the same mass iso- to hyperintense with multiple cystic spaces in the first case. (d) The saggital section of contrast MRI scan of the first case showing the same tumor with dense heterogeneous enhancement. (e) Axial cut of contrast MRI showing the same tumor in the first case. (f) Post-op contrast MRI scan showing total excision of the tumor

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Figure 2: (a) Photomicrograph of the tissue specimen of case 1 showing a schwannoma composed of a prominent hypercellular area (antoni A) with some hypocelluar (antoni B) areas (hematoxylin and eosin; original magnification, ×100). (b) Microscopic examination of the specimen of case 2 showing a prominent hypocellular area (antoni B) with paleshading antoni A (hematoxylin and eosin; original magnification, ×100)

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In the second case, a 45-year-female was admitted for decreased hearing in the left ear and left facial paresis for the last 2 years. She had left sensorineural hearing loss, left facial palsy, and conjunctival congestion. Cranial contrast CT scan showed left temporal heterogeneously enhancing mass along the superior surface of petrous bone with erosion [Figure 3]a and b and MRI showed densely enhancing extraaxial mass occupying middle fossa suggestive of GSPN schwannoma [Figure 3]c- e. Gross total removal of the tumor was achieved by an extradural subtemporal approach. Histopathology showed a schwannoma [Figure 2]b. Postoperative CT scan showed complete excision [Figure 3]f and MRI done at 6 months showed no residual or recurrent tumor. She had improvement in the facial paresis, but not in hearing loss.
Figure 3: (a) Contrast CT scan of the second case showing a densely enhancing tumor occupying middle fossa with erosion of the petrous bone. (b) High resolution CT scan of temporal bone of the second case showing erosion of middle part of the left petrous bone. (c) The axial section of contrast MRI scan showing a densely enhancing tumor abutting petrous bone which was eroded partly in the second case. (d) The saggital section of contrast MRI scan of the second case showing the same tumor. (e) Contrast MRI scans of the second case showing the same tumor eroding petrous bone. (f) Post-op CT scan of the second case showing total excision with hematoma

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A schwannoma originating from the GSPN is a rare type of facial nerve schwannoma comprising 0.8% of all petrous bone lesions. [1] It was first described by Woodruf et al. in 1981. [3] Only 13 patients with schwannomas originating from the GSPN had been reported in the literature [Table 1]. [1],[2],[3],[4],[5],[6],[7],[8],[9] As GSPN contains the parasympathetic fibers to lacrimal gland, decreased tear secretion is major clue to the diagnosis of GSPN schwannoma. [2],[8] The common presenting symptoms of GSPN schwannoma were facial palsy, hearing disturbances due to inner ear destruction, headache, and burning pain and redness of eye [Table 1]. In our report also, both patients had facial palsy, sensorineural hearing loss, and decreased tear secretions, and a Schirmer test was positive.
Table 1: Cases with greater superficial petrosal nerve schwannoma

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CT scan is valuable for showing bony details such as erosion of the petrous bone or enlargement of the internal auditory meatus; facial canal and facial hiatus are better delineated by CT scan. [1],[8] MRI is more useful in detecting GSPN schwannomas and their relation with the facial nerve. MRI characteristics include mildly hypo- or hyperintense to gray matter on T1-weighted images and hyperintense on T2-weighted images, with marked contrast enhancement. [3] Differential diagnosis includes facial nerve and trigeminal schwannomas, primary cholesteatoma, meningioma, and bony tumor of petrous bone. [2],[3] The surgical excision through the middle fossa approach remains the first line treatment. [1] In both our patients, as the tumor was restricted to GSPN, the continuity of facial nerve was not disturbed. In both the patients, total tumor excision was done with no intervening nerve graft.

Due to relative rarity of this tumor, preoperative diagnosis may be misleading unless one is aware of the clinical and radiological presentation. The clinical presentation depends on the size of the tumor. The early signs include decreased tear secretion followed by facial nerve palsy. The presence of an extra-axial enhancing mass on the anterior aspect of the middle part of petrous bone with underlying bony erosion along with the clinical presentation should help in the early diagnosis. Early diagnosis and surgical treatment of GSPN schwannoma may preserve the function of facial and acoustic nerves.

 
  References Top

1.Aihara N, Yamada K, Matsuda F, Murakami S. Neurinoma of the greater superficial petrosal nerve developed acute facial palsy: case report and review of the literature. Skull Base 2001;11:77-80.  Back to cited text no. 1
[PUBMED]  [FULLTEXT]  
2.Amirjamshidi A, Hashemi SM, Abbassioun K. Schwannoma of the greater superficial petrosal nerve. J Neurosurg 2010;113:1093-8.  Back to cited text no. 2
[PUBMED]  [FULLTEXT]  
3.Ayberk G, Ozveren MF, Uzum N, Tosun O, Akcay EK. Cellular schwannoma of the greater superficial petrosal nerve presenting with abducens nerve palsy and xerophthalmia: case report. Neurosurgery 2008;63: E813-4.  Back to cited text no. 3
[PUBMED]  [FULLTEXT]  
4.Dolenc VV, Korsic M. Middle cranial fossa schwannoma of the facial nerve. Br J Neurosurg 1996;10:519-23.  Back to cited text no. 4
[PUBMED]    
5.Furlow LT. The neurosurgical aspects of seventh nerve neurilemmoma. J Neurosurg 1960;17:721-35.  Back to cited text no. 5
[PUBMED]  [FULLTEXT]  
6.Kleinsasser O, Friedmann G. On neurinoma of the nervus facialis. Zentralbl Neurochir 1959;19:49-59.  Back to cited text no. 6
[PUBMED]    
7.Kumon Y, Sakaki S, Ohta S, Ohue S, Nakagawa K, Tanaka K. Greater superficial petrosal nerve neurinoma. Case report. J Neurosurg 1999;91:691-6.  Back to cited text no. 7
[PUBMED]  [FULLTEXT]  
8.Schmidinger A, Deinsberger W. Greater superficial petrosal nerve schwannoma. Acta Neurochir (Wien) 2005;147:659-63.  Back to cited text no. 8
[PUBMED]  [FULLTEXT]  
9.Tremble GE, Penfield W. Operative exposure of the facial canal. With removal of a tumor of the greater superficial petrosal nerve. Arch Otolaryngol 1936;23:573-9.  Back to cited text no. 9
    


    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

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