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| CASE REPORT |
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| Year : 2017 | Volume
: 23
| Issue : 4 | Page : 267-269 |
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When to operate facial nerve schwannomas?
Rajeshwary Aroor1, Deepika Pratap1, Marina Saldanha1, Vijay Pai2, U Raguraj3
1 Department of ENT, K S Hegde Medical Academy, Mangalore, Karnataka, India
2 Department of Ophthalmology, K S Hegde Medical Academy, Mangalore, Karnataka, India
3 Department of Radiodiagnosis, K S Hegde Medical Academy, Mangalore, Karnataka, India
| Date of Web Publication | 2-May-2018 |
Correspondence Address:
Dr. Rajeshwary Aroor
Department of ENT, K S Hegde Medical Academy, Deralakatte, Mangalore, Karnataka
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/indianjotol.INDIANJOTOL_72_17
Facial nerve schwannomas are rare, benign slow-growing tumors arising from the Schwann cell sheath of the facial nerve. A 60-year-old female presented with a mass in the left parotid region for 6 months. It was associated with Grade 6 left lower motor neuron facial palsy. Malignancy of the parotid gland associated with facial nerve involvement was suspected. However, high-resolution computed tomography temporal bone and magnetic resonance imaging done showed a soft-tissue density along the vertical portion of the facial nerve and into the parotid gland. The lesion was eroding the skull base and was found to be in direct contact with the jugular bulb. She underwent excision of the tumor by a modified Blair incision along with a cortical mastoidectomy. Tumor abutting the jugular bulb was removed through transmastoid approach. Facial nerve was transected during tumor excision. Postoperatively, gold implant was inserted. Facial schwannomas can arise from any segment of the nerve, from the cerebellopontine angle to the extratemporal peripheral portion. About 650 cases have been reported in the world literature. The best timing for surgery depends on facial and hearing function, size, and intracranial mass effect.
Keywords: Extratympanic, facial nerve, schwannoma
How to cite this article:
Aroor R, Pratap D, Saldanha M, Pai V, Raguraj U. When to operate facial nerve schwannomas?. Indian J Otol 2017;23:267-9 |
| Introduction | |  |
Facial nerve schwannomas are rare benign neoplasms of Schwann cells. Only few cases have been reported in the literature.[1] They can arise from any segment of the nerve from the cerebellopontine angle to the extratemporal peripheral portion.[2],[3] Most of the facial nerve schwannomas are localized in the intratemporal region; only 9% of cases involve a portion of the extratemporal segment.[4]
| Case Report | | |
A 60-year-old female presented with a swelling in front of the left ear for 6 months and incomplete eye closure for 3 months. On examination, a single, oval, firm swelling measuring 4 cm × 3 cm was present in the left preauricular region [Figure 1]. It was associated with Grade 6 left lower motor nerve type of facial palsy. Tympanic membrane examination was normal. Magnetic resonance imaging (MRI) scan showed an intensely enhancing altered signal intensity elongated tubular lesion with cystic changes in the mastoid segment of the left facial nerve canal extending across widened stylomastoid foramen into the ipsilateral parotid gland [Figure 2]. Subsequently, high-resolution computed tomography (CT) of the temporal bone was obtained to evaluate facial canal and related structures. It revealed widening of the mastoid segment of the left facial nerve canal and stylomastoid foramen occupied by heterogeneous soft-tissue density contents with extension into the parotid gland. There was an erosion of bony septum between left facial nerve canal and jugular bulb with lesion in direct contact with the jugular bulb. Based on MRI and CT findings, a diagnosis of facial nerve schwannoma was proposed. It was confirmed by fine-needle aspiration cytology. Since the patient had Grade 6 facial nerve palsy with a tumor abutting the jugular bulb, surgical excision was planned. Modified Blair incision was given [Figure 3]. Intratemporal portion of the tumor was removed by transmastoid approach keeping the posterior canal wall intact. The tumor was dissected from the jugular bulb [Figure 4]. The extratemporal portion of the tumor was removed by continuing the dissection along the stylomastoid foramen and parotid gland. The nerve had to be sacrificed as the tumor was engulfing it. Histopathological examination confirmed the tumor as schwannoma. Postoperative facial palsy grading remained the same, and a gold implant was inserted for the treatment of lagophthalmos. Since the middle ear ossicles, posterior canal wall, and labyrinthine structures were untouched, our patient's hearing and balance were unaffected. MRI scan done 6 months following surgery showed no residual tumor. | Figure 1: Preoperative photograph showing extratympanic parotid swelling
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 | Figure 2: Magnetic resonance imaging showing intensely enhancing tubular lesion in the mastoid segment of the left facial nerve canal extending across widened stylomastoid foramen into the ipsilateral parotid gland
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| Discussion | | |
Facial nerve schwannomas are rare benign tumors. Peak incidence is between third and sixth decades. Gender predilection is not seen. The majority of facial nerve schwannomas are intratemporal, with 9% of cases arising from the intraparotid portion.[5] Malignant schwannoma of the facial nerve is extremely rare.[6]
The presentation of facial nerve schwannoma depends on the site and extent of the lesion. These lesions will usually expand along the path of least resistance and can remain asymptomatic until large. Facial weakness and asymmetry is a common presenting complaint.[7] In about 5% of patients diagnosed as Bell's palsy, a facial nerve schwannoma is found to be the cause.[8] However, in 27% of patients, a normal facial nerve function has been reported.[9],[10]
Conductive hearing loss due to facial nerve schwannoma of the tympanic segment may be seen in up to 76% of cases.[11] The other complaints include otalgia, tinnitus, and hemifacial spasm.[12],[13],[14] A schwannoma near the geniculate ganglion can cause dryness of eyes due to the involvement of the greater superficial petrosal nerve.[14]
As the presentations of facial schwannoma can be highly varied, a fine-needle aspiration cytology and radiological investigations aid in the diagnosis and identification of location of the tumor.
Temporal bone CT is particularly useful in the evaluation of the internal auditory canal and bony facial nerve canal. CT aids in surgical planning as it shows the relationship of the facial nerve canal to normal anatomic landmarks such as the ossicles which are not seen on MRI. MRI is useful to identify the soft-tissue facial nerve abnormalities. It can be used to distinguish masses around the facial nerve such as lipoma, hemangioma, and cholesteatoma from tumors arising from the nerve. It can also determine the presence of perineural spread from parotid malignancies.[15]
Electroneurography may help to predict the prognosis of postoperative facial paralysis.[16] Electromyography helps to predict the postoperative recovery of a facial nerve after grafting by evaluating the residual motor function.[3]
A retrospective cohort study and a literature review on 124 patients done by Gross et al. proposed a treatment algorithm based on the location of the tumor. They suggested that for intraparotid tumors with intratemporal extension and good preoperative facial nerve function (House-Brackmann grade [HBG] 1–3), mastoidectomy with wide decompression beginning proximal to the tumor and extending to the extratemporal segment should be done. Decompression surgery is sufficient as schwannoma is a slow-growing tumor. For patients with a combined intratemporal/extratemporal facial nerve schwannoma and poor facial nerve function (HBG 4–6), complete excision of the tumor with no attempts of nerve preservation should be done. An interposition nerve grafting can be done.[4] A middle fossa craniotomy is used for patients with intracanalicular neuromas and useful hearing. The translabyrinthine or transpetrosal route is useful for patients without useful hearing and a facial nerve neuroma in the internal acoustic canal.[3],[16]
In our patient, a surgical intervention was required as the tumor was abutting the jugular bulb. A delay in surgery would have resulted in the lower cranial nerve palsy and intracranial extension. Priority was given for the disease clearance. Since the tumor was involving the vertical portion of the facial nerve, canal wall was preserved. The ossicles and hearing were undisturbed. Nerve grafting was not done as the tumor engulfed the peripheral branches of facial nerve. A gold implant weighing 1 g was inserted to treat the lagophthalmos with good functional outcome.
| Conclusion | | |
Facial nerve schwannomas involving the vertical segment of facial nerve with intraparotid extension are very rare. Complete excision should only be done if the grade of facial palsy is >3. A complete cure is seen following excision. The best timing for surgery depends on facial and hearing function, size, and intracranial mass effect.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for images and other clinical information to be reported in the journal. The patient understands that name and initial will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
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