Facial Schwannoma

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Original Editor - Wendy Walker

Lead Editors  

Introduction

Facial Schwannoma is a very rare tumour which grows on the 7th Cranial Nerve, the Facial Nerve.

It is also known as a Facial Neuroma.

Clinically Relevant Anatomy

Contrast-enhanced T2-weighted magnetic resonance imaging reveals an intracanalicular tumor in the region of the cerebellopontine angle (shown by the arrow).

For details of the path of the Cranial Nerve 7, please see the Facial Nerve page.

Location of Tumour

The majority of tumours are found on the segment of the nerve within the internal auditory canal, with one UK study[1] of a cohort of 28 Facial Schwannoma patients reporting 68% incidence in this section of the nerve.

The same study also found multi-segmental lesions in 46% of the patients.

Facial weakness was most commonly associated with involvement of the labyrinthine segment (89%).

Mechanism of Injury / Pathological Process

Schwannomas are extremely slow growing tumours, the majority of which are benign[2].
They originate from the Schwann cells which surround the nerve axons.

Clinical Presentation

The presentation frequently comprises hearing loss and facial weakness or paralysis[3]:

Facial Palsy/Paralysis

In Facial Schwannoma, the patient often reports a very slow onset unilateral facial palsy, ie. paralysis or weakness of the facial muscles. It is a lower motor neuron palsy.

There are more details on the Facial Palsy page.

Hearing Loss

The Auditory or Acoustic Nerve, 8th Cranial Nerve, travels next to the facial nerve in the Internal Auditory Canal. A growing tumour on the portion of the Facial Nerve within the Internal Auditory Canal can therefore cause compression on the Acoustic Nerve, which results in hearing loss.

Other symptoms

These can include pain, balance difficulties, vertigo and tinnitus.

Incidence of Symptoms

A 2006 study[4] examined 24 patients with Facial Schwannoma and reported the following incidence of symptoms:

Peripheral facial nerve neuropathy in 10 cases, ie. 42% of patients. This encompassed weakness, focal twitch, and/or full hemifacial spasm.

Sensorineural hearing loss occurred in 7 cases (29%),

Conductive hearing loss in 4 cases (17%)

Clinical presentation with a middle ear mass in 3 cases (13%)

Vestibular symptoms in 3 cases (13%)

Diagnostic Procedures

In the majority of centres, a brain MRI is used as part of the evaluation of facial paralysis[5][4][6]; however, this often misses a Facial Schwannoma because of the very small diameter of the facial nerve - approx 1 mm - and the thickness of the image slices - 5 mm.

The optimal imaging technique is an MRI of the internal auditory canals, with and without the contrast agent gadolinium. This imaging technique allows thinner slices through the temporal bone, it is much more likely to show the tumour[7].

Outcome Measures

  • Sunnybrook Facial Grading System
  • House-Brackmann facial nerve grading scale
  • Linear Measurement Index
  • Facial Disability Index

Management / Interventions

Surgical Intervention

Facial Schwannomas are frequently resected surgically, although if the tumour is not causing any problems it will generally just be monitored and no surgical intervention undertaken[8]. One study[9] states "for patients with mild or no facial dysfunction, a conservative attitude with observation is preferred."

Radiosurgery/Gamma Knife

In recent years, a number of studies have evaluated Gamma Knife radiosurgery, and other forms of stereotactic radiosurgery, for management of Facial Schwannomas. The results have been promising with one study[10] concluding " GKS is a safe alternative to resection"; another[11] concludes: "study demonstrates that radiosurgery allows treatment of these patients while preserving normal motor facial function. Such an advantage should lead to the consideration of radiosurgery as a first treatment option for small- to medium-size facial nerve schwannomas."

Oculoplastic Surgery

Patients at high risk of a corneal ulcer may be offered oculoplastic surgery to protect the eye.

For patients with dense facial palsy and no nerve function, a number of surgical interventions may be used. These fall into the following categories:

  1. Facial reanimation surgeries which involve nerve graft or anastomosis
  2. Facial reanimation surgeries which involve muscle transposition
  3. Static surgeries, ie. plastic surgery to improve symmetry at rest but no improvement in movement

Differential Diagnosis

Acoustic Neuroma - due to the difficulties in imaging this region, and also as a number of patients with Facial Schwannoma present with no facial neuropathy at all, but do present with hearing loss, the lesion may easily be mis-diagnosed as an Acoustic Neuroma/Schwannoma, and only on performing surgery does it become apparent that the tumour is not on the Acoustic Nerve but on the Facial Nerve. One study[4] found that out of 24 patients with Facial Schwannoma 5 cases were misdiagnosed preoperatively as an acoustic schwannoma, ie. 24% of the group.

NF2 - Sometimes facial nerve schwannoma is bilateral as part of Neurofibromatosis type 2 spectrum. 

Parotid Adenoma[2]

Physiotherapy Management

This is indicated when the person has facial paralysis or weakness. Physiotherapy interventions commonly include:

  • Neuromuscular Retraining (NMR)[12]
  • Electromyography (EMG) and mirror biofeedback[13][14]
  • Trophic Electrical Stimulation (TES)[8][15]
  • Proprioceptive Neuro Muscular Facilitation Techniques[6]

Resources

add appropriate resources here

References

  1. Doshi J, Heyes R, Freeman SR, Potter G, Ward C, Rutherford S, King A, Ramsden R, Lloyd SK. Clinical and Radiological Guidance in Managing Facial Nerve Schwannomas Otology & Neurotology. 36(5):892–895, JUNE 2015
  2. 2.0 2.1 Jayashankar N, Sankhla S. Facial schwannomas: Diagnosis and surgical perspectives. Neurol India [serial online] 2018 [cited 2019 Nov 28];66:144-6. Available from: http://www.neurologyindia.com/text.asp?2018/66/1/144/222821
  3. Lahlou G; Nguyen Y; Russo FY; Ferrary E; Sterkers O; Bernardeschi D Intratemporal facial nerve schwannoma: clinical presentation and management. Eur Arch Otorhinolaryngol.  2016; 273(11):3497-3504 (ISSN: 1434-4726)
  4. 4.0 4.1 4.2 R.H. Wiggins, H.R. Harnsberger, K.L. Salzman, C. Shelton, T.R. Kertesz and C.M. Glastonbury The Many Faces of Facial Nerve Schwannoma American Journal of Neuroradiology March 2006, 27 (3) 694-699;
  5. Chung SY, Kim DI, Lee BH, Yoon PH, Jeon P, Chung TS. Facial nerve schwannomas: CT and MR findings. Yonsei Med J. 1998 Apr;39(2):148-53.
  6. Sherman JD, Dagnew E, Pensak ML, van Loveren HR, Tew JM Jr. Facial nerve neuromas: report of 10 cases and review of the literature. Neurosurgery. 2002 Mar;50(3):450-6.
  7. Djalilian, Hamid R. MD Symptoms: Hearing Loss and Facial Paralysis The Hearing Journal: May 2014 - Volume 67 - Issue 5 - p 11,14
  8. 8.0 8.1 Marzo SJ, Zender CA, Leonetti JP. Facial nerve schwannoma. Curr Opin Otolaryngol Head Neck Surg. 2009 Oct;17(5):346-50. doi: 10.1097/MOO.0b013e32832ea999.
  9. Saumya Mishra*, Haritosh K Velankar, Merin Sara Mathew, Roshni K and Yogesh G Dabholkar Diagnostic Paradox behind Facial Nerve Schwannoma Department of ENT, DY Patil Hospital and Research Centre, Navi Mumbai, India
  10. Hasegawa T, Kato T, Kida Y, Hayashi M, et al. Gamma Knife surgery for patients with facial nerve schwannomas: a multi-institutional retrospective study in Japan. J Neurosurg. 2016 Feb;124(2):403-10. doi: 10.3171/2015.3.JNS142677. Epub 2015 Sep 11.
  11. Litre CF, Gourg GP, Tamura M, Mdarhri D, Touzani A, Roche PH, Régis J. Gamma knife surgery for facial nerve schwannomas. Neurosurgery. 2007 May;60(5):853-9; discussion 853-9.
  12. Manikandan N. Effect of facial neuromuscular re-education on facial symmetry in patients with Bell's palsy: a randomized controlled trial. Clin Rehabil. 2007 Apr;21(4):338-43.
  13. Zhao Y, Feng G, Gao Z. Advances in diagnosis and non-surgical treatment of Bell's palsy. Journal of otology. 2015 Mar 1;10(1):7-12
  14. Bossi D, Buonocore M et al. Usefulness of BFB/EMG in facial palsy rehabilitation. Disabil Rehabil. 2005 Jul 22;27(14):809-15
  15. Targan R S, Alon G, Kay SL. Effect of long-term electrical stimulation on motor recovery and improvement of clinical residuals in patients with unresolved facial nerve palsy Otolaryngol Head Neck Surgery February 2000 vol. 122 no. 2 246-252
This article or area is currently under construction and may only be partially complete. Please come back soon to see the finished work!