Large facial nerve schwannomas without facial palsy: case reports and review of the literature

Facial nerve schwannoma: Case report and brief review of the literature

Schwannomas are rare nerve sheath tumors that can occur throughout the body, and are symptomatic based on location, size, and impingement on adjacent structures. These tumors are often benign lesions and occur sporadically or from genetic conditions such as neurofibromatosis. Schwannomas may arise from peripheral nerves, gastrointestinal nerves, spinal nerve roots and cranial nerves. Facial nerve schwannomas arise from cranial nerve VII, commonly involving the geniculate ganglion, labyrinthine segment, and internal auditory canal. While small lesions are asymptomatic, larger lesions can cause facial nerve paralysis, and facial spasms. Lesions in the internal auditory canal can cause hearing loss, tinnitus, vertigo, and otalgia. High-resolution CT imaging and MRI imaging are useful for distinguishing between other pathologies that arise from the same region. High-resolution CT scans can show bony degeneration of nearby structures such as the labyrinth or ossicles. MRI imaging shows hypo intensity on T1 imaging, and hyperintensity on T2 imaging. On T1 postcontrast, enhancement can be homogenous or heterogeneous with cystic degeneration if the lesion is large. Nodular enhancement is commonly seen on facial nerve schwannomas within the internal auditory canal. Vestibular schwannomas involving CN VIII are more common, and appear similar to facial nerve schwannomas, but can be distinguished apart due to growth in the geniculate ganglion and/or the labyrinthine segment. Management of asymptomatic or mild lesions is typically conservative with follow up imaging, and surgery for larger lesions. Here, we present a case of a facial nerve schwannoma in a 57-year-old woman.

Middle fossa approach for a facial nerve schwannoma: how I do it

BACKGROUND

Facial nerve schwannomas can extend to the middle fossa or the cerebellopontine angle through the labyrinthine and cisternal segments of the facial nerve. The middle fossa approach (MFA) and its extensions provide a wide approach to deal with a large variety of lesions located in the middle and posterior cranial fossa junction.

METHODS

We describe the MFA along with its advantages and limitations to treat a facial nerve schwannoma involving the middle and posterior cranial fossa.

CONCLUSIONS

The MFA is a well-established route to surgically deal with tumors located in and around the proximal four segments of the facial nerve.

Preoperative Differences in Intracranial Facial Versus Vestibular Schwannomas: A Four Nerve Assessment

OBJECTIVES

Assesses whether preoperative functional testing can distinguish vestibular schwannomas from facial nerve schwannomas medial to the labyrinthine segment.

STUDY DESIGN

Retrospective cohort.

METHODS

Retrospectively review surgically managed intracranial facial and vestibular schwannomas between January 2015 and December 2019 at two tertiary care centers. Patients with neurofibromatosis 2 and surgery for recurrence were excluded. Preoperative functional testing to include House-Brackmann scores, electroneuronography (ENoG), cervical vestibular evoked myogenic potentials (cVEMP), caloric testing, acoustic brainstem responses (ABRs), acoustic reflexes, and audiograms was compared between the two groups of schwannomas.

RESULTS

Twelve facial and 128 vestibular schwannomas met inclusion criteria. In only one case was a facial schwannoma diagnosed preoperatively from imaging. No statistically significant difference was found in preoperative House-Brackmann scores, ENoG, cVEMP, caloric testing, ABRs, or acoustic reflexes. Pure tone average was worse in the vestibular schwannoma group (63 dB [95% CI: 58-68 dB] vs. 46 dB [95% CI: 34-58 dB], P = .01), and the difference was more apparent in the lower frequencies. Word recognition score was better in the facial schwannoma group (66% [95% CI: 45-86%] vs. 41% [95% CI: 34-47%], P = .02).

CONCLUSION

Specialized preoperative functional evaluation of the nerves of the internal auditory canal cannot reliably predict the presence of an intracranial facial schwannoma. Hearing is better in facial schwannomas, particularly in the lower frequencies. This should raise the index of suspicion for an intracranial facial schwannoma, especially in candidates for hearing preservation vestibular schwannoma surgery.

LEVEL OF EVIDENCE

3 Laryngoscope, 131:2098-2105, 2021.

Hypoglossal canal schwannoma causing isolated left 12th cranial nerve palsy

A 40-year-old woman presented with insidious onset, gradually progressive dysarthria and inability to manoeuvre bolus of food in her mouth while eating. The duration of her symptoms was 3 months. On evaluation, the left half of her tongue was wasted. The tongue deviated to the left on protrusion. There were no clinical features suggestive of involvement of the ipsilateral 9th, 10th or 11th cranial nerves. MRI of the brain showed a large, fusiform lesion in the left hypoglossal canal, extending into the jugular canal. The lesion was surgically excised and found to be a schwannoma.

Management of Facial Nerve Schwannoma: A Multicenter Study of 50 Cases

Objective  In the management of facial nerve schwannoma (FNS), surgical tumor resection is now often being replaced with more conservative approaches, such as observation with serial imaging or stereotactic radiosurgery (SRS). Given the scarcity of these lesions, determining the optimal management of FNS remains challenging and subject of debate with multiple treatment approaches supported in the literature. Methods  A retrospective chart review was performed in two academic centers for patients diagnosed with FNS between 1996 and 2017. The clinical presentation, treatment modalities employed, tumor control rates, and facial nerve function (FNF) outcomes (House-Brackmann system) were assessed and analyzed. Results  The study comprised 50 adult patients. Initial treatment modalities included observation with serial clinicoradiologic review in 27 patients (54%), surgery in 17 patients (34%), and SRS in 6 patients (12%). The FNF were decreased in more than half of the patients who had surgery. Nonetheless, more than 80% of the patients who were initially managed with observation or SRS had stable or improved FNF. Conclusion  A prevailing trend toward more conservative treatment modalities for FNS has evolved over time, providing relatively long-term preservation of FNF. As there are multiple management options available, it is of paramount importance that the treating physician be familiar with all treatment modalities and outcomes and counsel patients appropriately. The surgery should be reserved for large tumors and poor FNF at initial presentation or follow-up while watchful observation with imaging is the treatment of choice for rest of the patients.

Surgical findings to differentiate between facial nerve schwannoma and vestibular schwannoma

Objectives

Facial nerve schwannomas may be misdiagnosed as vestibular schwannomas (VSs) if the tumor is confined to the internal auditory canal (IAC) without involvement the geniculated ganglion or labyrinthine segment of facial nerve. Because facial nerve schwannomas may be misdiagnosed as VSs, we investigated the differences between the two.

Methods

The study included 187 patients with a preoperative diagnosis of VS. Of these, six were diagnosed with facial nerve schwannomas during surgery. We reviewed the preoperative evaluations and surgical findings of facial nerve schwannomas mimicking VSs.

Results

No useful preoperative predictors are available for facial nerve schwannomas mimicking VSs. Facial nerve schwannomas are usually confined to the IAC. After opening the dura of the IAC, a facial nerve schwannoma can be diagnosed after identifying a normal-appearing nerve located lateral to the tumor. When this was the case, we performed facial nerve preservation surgery or decompression.

Conclusion

Facial nerve schwannomas can be differentiated from VSs by identifying specific findings during surgery.

Surgical management of internal auditory canal and cerebellopontine angle facial nerve schwannoma

OBJECTIVE

To investigate the long-term patient outcomes after tumor debulking for internal auditory canal facial schwannoma (FNS).

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary referral center.

PATIENTS

Patients operated on between 1998 and 2010 for a preoperative diagnosis of vestibular schwannoma with the intraoperative identification FNS instead.

INTERVENTION

Diagnostic and therapeutic.

MAIN OUTCOME MEASURES

House-Brackmann facial nerve score immediately and at long-term follow-up (>1 yr); recurrence of tumor.

RESULTS

Sixteen patients were identified who were presumed to have vestibular schwannoma but intraoperatively were diagnosed with facial nerve schwannoma. Eleven underwent debulking surgery (67%-99% tumor removal), 2 underwent decompression only, 2 were diagnosed with nervus intermedius tumors and had total tumor removal with preservation of the motor branch of cranial nerve VII, and 1 had complete tumor removal with facial nerve grafting. Five of 11 debulking patients underwent the middle cranial fossa approach for tumor removal; the remainder had translabyrinthine resections. One debulking patient was lost to follow-up. Nine of 10 patients with long-term follow-up had House-Brackmann Grade I or II facial function. One patient had recurrence of the tumor that required revision surgery with total removal and facial nerve grafting.

CONCLUSION

Tumor debulking for FNS provides an opportunity for tumor removal and excellent facial nerve function. Continuous facial nerve monitoring is vital for successful debulking surgery. FNS debulking is feasible via the middle cranial fossa approach. Serial postoperative imaging is warranted to monitor for recurrence.

Isolated hypoglossal schwannoma in a 9-year-old child

The authors report a case of an isolated schwannoma of left hypoglossal nerve in a 9-year-old girl. To the authors' knowledge, this is the first case report of hypoglossal nerve schwannoma in the pediatric population in the absence of neurofibromatosis Type 2. The patient presented with a 2-month history of morning nausea and vomiting with occasional daytime headaches. Magnetic resonance imaging and subsequent CT scanning revealed a dumbbell tumor with a belly in the lower third of the posterior fossa and head underneath the left jugular foramen. Its neck protruded through an expanded hypoglossal canal. Although the lesion bore radiological characteristics of a hypoglossal schwannoma, the absence of hypoglossal palsy and the apparent lack of such tumors in the pediatric population the preoperative diagnosis was not certain. The tumor was approached via a midline suboccipital craniotomy, and gross-total resection was achieved. Pathological examination confirmed the diagnosis of schwannoma. Blood and tumor tests for mutations in the NF2 gene were negative. Postoperative mild hypoglossal palsy recovered by the 3-month follow-up, and an MRI study obtained at 1 year did not show recurrence.

Surgical Management of PICA Aneurysm and Incidental Facial Nerve Schwannoma: Case Report

We report a patient with a posterior inferior cerebellar artery (PICA) aneurysm and an incidental facial nerve schwannoma at the cerebellopontine angle (CPA). A 46-year-old woman presented with the sudden onset of a severe headache, nausea, and vomiting. She had no other abnormal neurological symptoms and signs. Computed tomography (CT) showed hemorrhage in the fourth ventricle. Cerebral angiography demonstrated an aneurysm arising from the tonsillomedullary segment of the left PICA. A facial nerve schwannoma was incidentally found as the aneurysm was being clipped. The aneurysm was clipped via a left transcondylar approach. Subsequently, the schwannoma (2 x 3 x 2 mm) was resected from the facial nerve fascicles, and the facial nerve was preserved. Postoperatively, the patient developed mild to moderate dysfunction of the facial nerve (House-Brackmann grade III [H-B III]) but her hearing was intact. Both a facial nerve schwannoma involving the CPA and an aneurysm involving the PICA can be managed through the transcondylar approach. An asymptomatic facial nerve schwannoma can be resected safely with minimal facial nerve dysfunction.

Large cystic hypoglossal schwannoma with fluid-fluid level: a case report

Hypoglossal schwannomas are rare skull base tumors. Furthermore, cystic hypoglossal schwannomas are extremely uncommon. We report the first case of a large cystic hypoglossal schwannoma with a fluid-fluid level. A 36-year-old woman presented with increased intracranial pressure and cerebellar signs without hypoglossal nerve palsy. Magnetic resonance imaging showed a predominantly cystic mass with a fluid-fluid level in the foramen magnum region extending into the hypoglossal canal. The intracranial tumor was largely removed via a midline suboccipital subtonsillar approach, leaving only a tiny residue in the hypoglossal canal. Histology confirmed a schwannoma with relative hypervascularity. Twenty months later, the tumor recurred and presented as a multicystic dumbbell-shaped lesion, extending intra- and extracranially through the enlarged hypoglossal canal. A complete resection of the intracranial and intracanalicular parts of the tumor was achieved with a small extracranial remnant treated by radiosurgery. Histology revealed a focal increased K(i)67 proliferative index. In this report, we discuss the possible reasons for the absence of hypoglossal nerve palsy and the potential mechanism of the formation of the fluid-fluid level, and we consider the treatment of this lesion.

Intradural facial nerve schwannoma: diagnostic and therapeutic problems

OBJECTIVES

To define characteristics of intradural facial schwannoma (FS) and discuss management strategies.

METHOD

Retrospective review of clinical charts.

RESULTS

Six patients were diagnosed, based on surgical findings, as having intradural FS. None of the patients complained initially of facial weakness, but all showed severe disturbance of hearing function assessed on admission. FS was suspected in four of our six patients because of imaging findings or facial palsy caused by a small tumor. Total removal was performed in five cases followed by facial nerve reconstruction, and nearly total removal was performed in one case. Most patients recovered to Grade II or III palsy during the follow-up, and long-lasting palsy before surgery showed poor recovery.

CONCLUSION

Imaging findings such as tumor extension to the middle fossa and clinical findings such as facial palsy caused by a small tumor strongly suggest a diagnosis of FS. Facial function can be restored satisfactorily for most patients after appropriate surgery.

Surgical treatment of patients with facial neuromas--a report of 26 consecutive operations

OBJECTIVE

To analyze surgical treatment and outcome in patients with facial neuromas at a tertiary referral hospital.

STUDY DESIGN

A chart review of 26 patients treated between 1971 and 2006, with questionnaire follow-up ranging from 2 to 19 years. All patients except one were operated with radical tumor removal approaches.

RESULTS

Approximately 54% of the patients presented with symptoms related to the VIIth cranial nerve (facial palsy and facial spasm), 58% with symptoms related to the VIIIth cranial nerve (hearing deficit, tinnitus, and vertigo), and 8% related to the Vth cranial nerve (facial pain and facial sensory deficit). Approximately 39% presented with no facial symptoms. Twenty-one patients received a facial nerve graft from the greater auricular nerve or the sural nerve; 1 patient had an accessory-facial anastomosis. One patient had a subtotal tumor removal preserving the facial nerve. Three patients were not grafted. Most tumors (88%) affect the geniculate ganglion. Approximately 82% of the grafted patients regained a House-Brackmann facial nerve function (HB) grade III; 14% regained HB grades IV to V. No serious morbidity or mortality was reported. No recurrences have been reported where a total tumor removal was performed.

CONCLUSION

Surgical removal of facial neuroma is a safe procedure with a low complication rate and a low recurrence rate. First symptoms are diverse and are predominantly derived from the facial and vestibulocochlear nerve. Facial nerve grafting is reliable, giving the patient an acceptable facial nerve function (HB III).