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Facial Schwannoma

Summary

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  • Rare benign tumour arising from Schwann cells of the facial nerve
  • Presents with facial weakness, hearing loss, or tinnitus
  • Imaging shows a well-defined mass along the course of the facial nerve1

Pathophysiology

  • Originates from Schwann cells of the facial nerve (cranial nerve VII)
  • Slow-growing, encapsulated tumour
  • Can occur anywhere along the course of the facial nerve, from the cerebellopontine angle to the parotid gland
  • May cause compression of adjacent structures

Demographics

  • Rare, accounting for <1% of temporal bone tumours
  • No gender predilection
  • Most common in adults aged 20-50 years
  • Sporadic occurrence, but may be associated with neurofibromatosis type 2

Diagnosis

  • Clinical presentation:
    • Gradual onset of facial weakness or paralysis
    • Hearing loss
    • Tinnitus
    • Vertigo
  • Physical examination:
    • Facial nerve dysfunction (House-Brackmann grading)
    • Otoscopic examination may reveal a mass behind the tympanic membrane
  • Audiometry:
    • Conductive or sensorineural hearing loss
  • Electromyography:
    • May show denervation of facial muscles

Imaging

  • Computed Tomography (CT):
    • Well-defined, soft tissue mass
    • Enlargement of the facial nerve canal
    • Erosion of adjacent bony structures
  • Magnetic Resonance Imaging (MRI):
    • T1: Isointense to hypointense
    • T2: Hyperintense
    • Gadolinium enhancement: Strong, homogeneous enhancement
    • Helps delineate tumour extent and relationship to adjacent structures
  • Diffusion-weighted imaging:
    • Typically shows restricted diffusion
  • MR neurography:
    • May help differentiate schwannoma from other facial nerve lesions

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  • A 40-year-old patient presented with a right sided facial palsy.
  • CT showed erosion of the bone surrounding the facial geniculate ganglion.
  • MRI showed a large enhancing middle cranial fossa lesion that extended along the right internal auditory canal.
  • Following resection, a schwannoma was confirmed.

Treatment

  • Often observed given surgical morbidity to the nerve; resection or radiosurgery for growth or severe symptoms

Differential diagnosis

Differential Diagnosis Differentiating Feature
Acoustic neuroma Originates from vestibular nerve, centered in internal auditory canal
Meningioma Broad dural attachment, "dural tail" sign on MRI
Facial nerve hemangioma Characteristic "honeycomb" appearance on CT
Paraganglioma Salt-and-pepper appearance on MRI, intense enhancement
Facial nerve neuritis Enhancement of facial nerve without mass effect
Cholesteatoma Erosive lesion in temporal bone, restricted diffusion on MRI
Parotid gland tumour Located in parotid gland, spares facial nerve
Metastatic lesion Multiple lesions; perineural spread; irregular margins; bone destruction rather than smooth remodelling
Facial nerve granuloma Enhancing nodular lesion along facial nerve; associated with temporal bone inflammatory changes
Rhabdomyosarcoma Aggressive bone destruction; irregular margins; soft tissue mass; no nerve sheath morphology

  1. Bartindale et al. Facial Schwannoma Management Outcomes: A Systematic Review of the Literature. 2020. Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery - Open in new tab. ↩