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| CASE REPORT |
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| Year : 1997 | Volume
: 43
| Issue : 1 | Page : 14-5 |
Intraparotid facial nerve schwannoma.
HK Shah, C Kantharia, AS Shenoy
Department of General Surgery and Pathology, Seth GS Medical College, Parel, Mumbai.
Correspondence Address:
H K Shah
Department of General Surgery and Pathology, Seth GS Medical College, Parel, Mumbai.
 Source of Support: None, Conflict of Interest: None  | Check |
PMID: 0010740706 
Intraparotid facial nerve schwannoma are uncommon. Preoperative diagnosis of parotid tumour as schwannoma is difficult when facial nerve function is normal. A rare case of solitary schwannoma involving the upper branch of the facial nerve is described and the literature on the subject is reviewed.
Keywords: Adult, Case Report, Facial Nerve Diseases, pathology,surgery,Female, Human, Neurilemmoma, pathology,surgery,Parotid Neoplasms, pathology,surgery,
How to cite this article:
Shah H K, Kantharia C, Shenoy A S. Intraparotid facial nerve schwannoma. J Postgrad Med 1997;43:14 |
A schwannoma is an ectodermal benign encapsulated tumour arising from Schwann cells[1]. Neurogenic neoplasms of the facial nerve are uncommon[2]. Schwannoma of the acoustic or VIIIth nerve are the well described[2]. Very few originate from the facial nerve and in the majority of these cases, the tumour involves the intratemporal seventh nerve[3]. The following case is presented because it appeared as a non-symptomatic parotid tumour with normal seventh nerve function and intraoperatively as a cystic tumour involving the upper branch of facial nerve.
A 30-year-old female presented with a six month history of a gradually enlarging left parotid mass. She denied any facial weakness, twitching or pain. Examination revealed a 3 x 4 cm cystic non-tender mobile mass over the masseter muscle. Facial nerve function as well as the remainder of head and neck examination was normal. Intraoperatively, the parotid gland was normal. A cystic swelling of 3x4 cm was located at the anterior part of parotid gland. The main trunk of the facial nerve was normal and was dissected anteriorly. Extreme peripheral and upper branches had become incarcerated into the mass. Electrical stimulation of the mass elicited facial motion. The mass was removed and a superficial parotidectomy was performed. Postoperatively, the patient developed facial weakness of upper half of the face, which improved partially in a week. Histological examination revealed a benign schwannoma [Figure - 1]. Three months postoperatively, facial nerve function improved significantly.
Benign schwannoma is a slow growing encapsulated tumour arising from the neuroectodermal sheath of Schwann. Approximately 25-30% of all reported schwannomas occur in the head and neck and most of these in the eighth nerve[2]. Among 802 parotid tumours Eneroth[4] could demonstrate two cases with neurogenic origin and in a review of 700 parotidectomies Nussbaum[5] found only one case of neurilemmoma of the facial nerve.
Neurilemmomas of the facial nerve may arise from its extratemporal or intratemporal course. The main symptoms are usually of facial weakness or paralysis[1],[3]. Much attention has been given to intratemporal seventh nerve neurilemmomas. In our case, the tumour was involving the upper branch of the facial nerve with normal facial nerve function.
The difficulty in establishing a correct preoperative diagnosis has been pointed out by Conley and Janecka[6] because this tumour is infrequent and generally unsuspected. Preoperative facial nerve paresis or paralysis was found in 20% of all cases[6]. This is remarkable because it is well known that facial nerve paresis or paralysis is associated with a malignant parotid tumour.
Neurogenic tumours should be suspected intraoperatively when they are inseparable from the nerve and electrical stimulation of the tumour elicits facial movement. Surgical resection remains the definitive treatment although benign tumours associated with normal facial function may be carefully followed with serial electroneurography and computerized tomography when electrical testing reveals minimal evidence of progressive neural degeneration[7].
On gross examination, the tumour is well encapsulated. The cut surface is relatively homogenous, glistening, tan or gray with irregular yellow areas and variable cystic degeneration. The tumour is often adherent to the nerve. Microscopically, the tumour shows two patterns, Antoni Type A i.e. cells are spindle shaped, compactly arranged with long oval nuclei oriented with their long axis parallel to each other (nuclear palisading) and Antoni Type B i.e. with less cellular areas, reticular, with cells showing vacuolation and xanthomatous change. The blood vessels show hyalinised walls.
Preservation of facial nerve function is of paramount importance when dealing with these benign tumours. Occasionally, the schwannoma is mistaken for fibrosarcoma on frozen section[8] and unwarranted radical surgery is performed. For this reason the surgeon should await the permanent section before proceeding with a radical procedure. Rarely, sacrifice of the nerve may be necessary to achieve complete resection. Such a surgery may be followed by nerve grafting with the hypoglossal nerve or greater auricular nerve[6].
We thank the Dean of Seth GS Medical College, Dr. PM Pai for her permission to publish the hospital data.
| :: References | |  |
| 1. |
Kettel K. Neurinoma of the facial nerve. Arch Otolaryngol 1946; 44:253-261.  |
| 2. | Putney FJ, Morran JJ, Thomas GK. Neurogenic tumours of the head and neck. Laryngoscope 1964; 74:1037-1059. |
| 3. | Horn KL, Cromley RL, Schndler RA. Facial neurilemmomas. Laryngoscope 1981; 91:1326-1331. |
| 4. | Eneroth CM, Hamberger CA. Principles of treatment of different types of parotid tumours. Laryngoscope 1974; 84:1732-1740. |
| 5. | Nussbaum M, Cho HT, Som ML. Parotid spaces tumors of non-salivary origin. Ann Surg 1976; 184:10-12. |
| 6. | Conley J, Janecka I. Neurilemmoma of the facial nerve. Plast Reconstr Surg 1973; 52:55-60. |
| 7. | Sullivan MJ, Babyak JW, Kartush JM. Intraparotid facial neurofibroma Laryngoscope 1987; 97:219-223. |
| 8. | Ross DB, Byars LT, Ackerman LV. Neurilemmomas of the facial nerve presenting as parotid gland tumours. Ann Surg 1956; 144:258-262.
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Figures
[Figure - 1]
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Intraparotid facial nerve schwannoma. What to do? |
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| Kreeft A, Schellekens PPA, Leverstein H | | CLINICAL OTOLARYNGOLOGY. 2007; 32 (2): 125-129 | | [Pubmed] | |
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