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|Year : 2019 | Volume
| Issue : 5 | Page : 1393-1394
“One Soul, Many Faces”: Facial Nerve Schwannoma with Dumbbell Appearance
Jaskaran S Gosal, Shruti Gupta, Kuntal K Das, Sanjay Behari
Department of Neurosurgery, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Rae Bareli Road, Lucknow, Uttar Pradesh, India
|Date of Web Publication||19-Nov-2019|
Dr. Kuntal K Das
Department of Neurosurgery, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Rae Bareli Road, Lucknow - 226 014, Uttar Pradesh
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Gosal JS, Gupta S, Das KK, Behari S. “One Soul, Many Faces”: Facial Nerve Schwannoma with Dumbbell Appearance. Neurol India 2019;67:1393-4
Facial nerve schwannomas (FNS) are rare, benign tumors constituting the third most common type of intracranial schwannoma, after vestibular and trigeminal schwannomas. They may occur sporadically or in association with neurofibromatosis type 2. FNS may arise anywhere along the course of the facial nerve, from its root entry zone at the pons to the extratemporal segment comprising the distal-most branches supplying the muscles of facial expression. The involvement of the geniculate ganglion and the labyrinthine segment is classical of FNS; however, the multisegmental involvement of the facial nerve is not uncommon., Facial weakness is the most common symptom, although tinnitus, hearing loss, facial spasm, headache, or dizziness may also occur.
The relative rarity of these lesions has hampered their proper radiological characterizations. Depending upon the origin of the tumor on the 7th cranial nerve, FNS may take one of the many known radiological patterns. FNSs arising in internal auditory canal-cerebellopontine angle are similar in appearance to the vestibular schwannomas radiologically; tumors arising from the labyrinthine segment and extending to the geniculate fossa (as in our case) have a characteristic dumbbell appearance and third, tumors extending from geniculate fossa along the greater superficial petrosal nerve (GSPN) have a characteristic tubular appearance. Here, we describe one such rare radiological appearance of 7th nerve schwannoma where the tumor arose from the labyrinthine segment and extended into the middle as well as the posterior cranial fossa, giving it a characteristic dumbbell appearance.
A 28-year-old right-handed gentleman presented with a six week history of mild hearing loss associated with tinnitus in the right ear and facial deviation to the left side. He also complained of unsteadiness of gait for the same duration. On examination, he had a House–Brackmann (HB) grade 3 right-sided facial weakness. Pure tone audiometry revealed a mild right-sided sensorineural hearing loss. Magnetic resonance imaging (MRI) revealed an enhancing, bi-lobed, extraaxial lesion having a smaller Cerebellopontine (CP) angle and a sizeable middle fossa component. An apparent connection across the internal auditory meatus was noted between the two components. The middle fossa component was along the geniculate ganglion and along the course of the GSPN. The posterior fossa component was small (1.5 × 1.5 cm) without any brainstem or cerebellar compression [Figure 1]a, [Figure 1]b, [Figure 1]c, [Figure 1]d. The findings were suggestive of a FNS. We had planned a middle fossa approach for this patient with a second stage surgery for the posterior fossa lesion. However, the patient did not undergo surgery due to financial constraints and was lost to follow-up.
|Figure 1: (a) T2 axial magnetic resonance (MR) image showing a well-defined extraaxial mass lesion in right cerebellopontine angle with extension into right temporal bone and middle cranial fossa. Fourth ventricle is not compressed. (b and c) Axial contrast enhanced MR images demonstrate a well-defined homogenously enhancing dumbbell-shaped mass lesion with a small posterior and a sizeable middle fossa component. Also shown is the geniculate ganglion (c, arrow) which neither is seen normally nor in a vestibular schwannoma patient, and is a characteristic radiological feature of facial schwannoma. (d) Coronal contrast MR showing bi-lobed mass with enhancing geniculate ganglion|
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Depending upon the location of the tumor as outlined before, hearing loss may or may not be present. FNS, especially the IAC-cerebellopontine angle type, is difficult to distinguish from vestibular schwannoma. A contrast-enhanced MRI, however, is diagnostic and the lesion typically shows avid, irregular enhancement with characteristic visualization of the geniculate ganglia which neither is visible physiologically nor in a vestibular schwannoma patient [as shown in [Figure 1]c and [Figure 2]]. Dumbbell-shaped lesions are seen if the tumor erodes the bony lamina above the geniculate ganglion and extends into the middle cranial fossa.
|Figure 2: (a and b) shows the axial and coronal schematic diagrams respectively showing the dumbbell-shaped FNS with the geniculate ganglion seen in between the two components which is a characteristic radiological feature of FNS. Contrast this from the typical dumbbell-shaped trigeminal nerve schwannomas|
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Preoperative diagnosis or at least a suspicion is essential as it has management implications. There is a trend now-a-days for preferring conservative management options like watchful waiting and stereotactic radiosurgery over microsurgery in order to preserve facial function, although the ideal treatment still remains elusive. Surgical treatment consists of gross total excision of tumor with facial nerve repair or nerve grafting. Microsurgical resection is preferred mostly in cases with brainstem compression or hydrocephalus as even after successful facial nerve grafting, the reported postoperative facial nerve paresis rarely improves to be better than HB grade 3. The treatment, however, needs to be individualized. Patient preference and finances are to be kept in mind especially in a third world country like India.
Thus, the radiological presentation in 7th nerve schwannoma is protean and needs a closer examination to make a correct diagnosis. Early 7th cranial nerve palsy in cerebellopontine angle tumors may be a clinical pointer although clinical differentiation is not always reliable. Treatment decisions are based on the tumor size, extent, and the status of hearing and include both microsurgery and radiosurgery. In the end, one has to be aware of the variations in the radiological presentation of FNS. The rarity of such lesions only adds to the difficulty in making a correct diagnosis.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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Conflicts of interest
There are no conflicts of interest.
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